/src/libbpf/src/libbpf.c

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// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)

/*
 * Common eBPF ELF object loading operations.
 *
 * Copyright (C) 2013-2015 Alexei Starovoitov <ast@kernel.org>
 * Copyright (C) 2015 Wang Nan <wangnan0@huawei.com>
 * Copyright (C) 2015 Huawei Inc.
 * Copyright (C) 2017 Nicira, Inc.
 * Copyright (C) 2019 Isovalent, Inc.
 */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <libgen.h>
#include <inttypes.h>
#include <limits.h>
#include <string.h>
#include <unistd.h>
#include <endian.h>
#include <fcntl.h>
#include <errno.h>
#include <ctype.h>
#include <asm/unistd.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/bpf.h>
#include <linux/btf.h>
#include <linux/filter.h>
#include <linux/limits.h>
#include <linux/perf_event.h>
#include <linux/bpf_perf_event.h>
#include <linux/ring_buffer.h>
#include <sys/epoll.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/vfs.h>
#include <sys/utsname.h>
#include <sys/resource.h>
#include <libelf.h>
#include <gelf.h>
#include <zlib.h>

#include "libbpf.h"
#include "bpf.h"
#include "btf.h"
#include "str_error.h"
#include "libbpf_internal.h"
#include "hashmap.h"
#include "bpf_gen_internal.h"
#include "zip.h"

#ifndef BPF_FS_MAGIC
#define BPF_FS_MAGIC    0xcafe4a11
#endif

#define BPF_FS_DEFAULT_PATH "/sys/fs/bpf"

#define BPF_INSN_SZ (sizeof(struct bpf_insn))

/* vsprintf() in __base_pr() uses nonliteral format string. It may break
 * compilation if user enables corresponding warning. Disable it explicitly.
 */
#pragma GCC diagnostic ignored "-Wformat-nonliteral"

#define __printf(a, b)  __attribute__((format(printf, a, b)))

static struct bpf_map *bpf_object__add_map(struct bpf_object *obj);
static bool prog_is_subprog(const struct bpf_object *obj, const struct bpf_program *prog);
static int map_set_def_max_entries(struct bpf_map *map);

static const char * const attach_type_name[] = {
  [BPF_CGROUP_INET_INGRESS] = "cgroup_inet_ingress",
  [BPF_CGROUP_INET_EGRESS]  = "cgroup_inet_egress",
  [BPF_CGROUP_INET_SOCK_CREATE] = "cgroup_inet_sock_create",
  [BPF_CGROUP_INET_SOCK_RELEASE]  = "cgroup_inet_sock_release",
  [BPF_CGROUP_SOCK_OPS]   = "cgroup_sock_ops",
  [BPF_CGROUP_DEVICE]   = "cgroup_device",
  [BPF_CGROUP_INET4_BIND]   = "cgroup_inet4_bind",
  [BPF_CGROUP_INET6_BIND]   = "cgroup_inet6_bind",
  [BPF_CGROUP_INET4_CONNECT]  = "cgroup_inet4_connect",
  [BPF_CGROUP_INET6_CONNECT]  = "cgroup_inet6_connect",
  [BPF_CGROUP_UNIX_CONNECT]       = "cgroup_unix_connect",
  [BPF_CGROUP_INET4_POST_BIND]  = "cgroup_inet4_post_bind",
  [BPF_CGROUP_INET6_POST_BIND]  = "cgroup_inet6_post_bind",
  [BPF_CGROUP_INET4_GETPEERNAME]  = "cgroup_inet4_getpeername",
  [BPF_CGROUP_INET6_GETPEERNAME]  = "cgroup_inet6_getpeername",
  [BPF_CGROUP_UNIX_GETPEERNAME] = "cgroup_unix_getpeername",
  [BPF_CGROUP_INET4_GETSOCKNAME]  = "cgroup_inet4_getsockname",
  [BPF_CGROUP_INET6_GETSOCKNAME]  = "cgroup_inet6_getsockname",
  [BPF_CGROUP_UNIX_GETSOCKNAME] = "cgroup_unix_getsockname",
  [BPF_CGROUP_UDP4_SENDMSG] = "cgroup_udp4_sendmsg",
  [BPF_CGROUP_UDP6_SENDMSG] = "cgroup_udp6_sendmsg",
  [BPF_CGROUP_UNIX_SENDMSG] = "cgroup_unix_sendmsg",
  [BPF_CGROUP_SYSCTL]   = "cgroup_sysctl",
  [BPF_CGROUP_UDP4_RECVMSG] = "cgroup_udp4_recvmsg",
  [BPF_CGROUP_UDP6_RECVMSG] = "cgroup_udp6_recvmsg",
  [BPF_CGROUP_UNIX_RECVMSG] = "cgroup_unix_recvmsg",
  [BPF_CGROUP_GETSOCKOPT]   = "cgroup_getsockopt",
  [BPF_CGROUP_SETSOCKOPT]   = "cgroup_setsockopt",
  [BPF_SK_SKB_STREAM_PARSER]  = "sk_skb_stream_parser",
  [BPF_SK_SKB_STREAM_VERDICT] = "sk_skb_stream_verdict",
  [BPF_SK_SKB_VERDICT]    = "sk_skb_verdict",
  [BPF_SK_MSG_VERDICT]    = "sk_msg_verdict",
  [BPF_LIRC_MODE2]    = "lirc_mode2",
  [BPF_FLOW_DISSECTOR]    = "flow_dissector",
  [BPF_TRACE_RAW_TP]    = "trace_raw_tp",
  [BPF_TRACE_FENTRY]    = "trace_fentry",
  [BPF_TRACE_FEXIT]   = "trace_fexit",
  [BPF_MODIFY_RETURN]   = "modify_return",
  [BPF_LSM_MAC]     = "lsm_mac",
  [BPF_LSM_CGROUP]    = "lsm_cgroup",
  [BPF_SK_LOOKUP]     = "sk_lookup",
  [BPF_TRACE_ITER]    = "trace_iter",
  [BPF_XDP_DEVMAP]    = "xdp_devmap",
  [BPF_XDP_CPUMAP]    = "xdp_cpumap",
  [BPF_XDP]     = "xdp",
  [BPF_SK_REUSEPORT_SELECT] = "sk_reuseport_select",
  [BPF_SK_REUSEPORT_SELECT_OR_MIGRATE]  = "sk_reuseport_select_or_migrate",
  [BPF_PERF_EVENT]    = "perf_event",
  [BPF_TRACE_KPROBE_MULTI]  = "trace_kprobe_multi",
  [BPF_STRUCT_OPS]    = "struct_ops",
  [BPF_NETFILTER]     = "netfilter",
  [BPF_TCX_INGRESS]   = "tcx_ingress",
  [BPF_TCX_EGRESS]    = "tcx_egress",
  [BPF_TRACE_UPROBE_MULTI]  = "trace_uprobe_multi",
  [BPF_NETKIT_PRIMARY]    = "netkit_primary",
  [BPF_NETKIT_PEER]   = "netkit_peer",
  [BPF_TRACE_KPROBE_SESSION]  = "trace_kprobe_session",
};

static const char * const link_type_name[] = {
  [BPF_LINK_TYPE_UNSPEC]      = "unspec",
  [BPF_LINK_TYPE_RAW_TRACEPOINT]    = "raw_tracepoint",
  [BPF_LINK_TYPE_TRACING]     = "tracing",
  [BPF_LINK_TYPE_CGROUP]      = "cgroup",
  [BPF_LINK_TYPE_ITER]      = "iter",
  [BPF_LINK_TYPE_NETNS]     = "netns",
  [BPF_LINK_TYPE_XDP]     = "xdp",
  [BPF_LINK_TYPE_PERF_EVENT]    = "perf_event",
  [BPF_LINK_TYPE_KPROBE_MULTI]    = "kprobe_multi",
  [BPF_LINK_TYPE_STRUCT_OPS]    = "struct_ops",
  [BPF_LINK_TYPE_NETFILTER]   = "netfilter",
  [BPF_LINK_TYPE_TCX]     = "tcx",
  [BPF_LINK_TYPE_UPROBE_MULTI]    = "uprobe_multi",
  [BPF_LINK_TYPE_NETKIT]      = "netkit",
  [BPF_LINK_TYPE_SOCKMAP]     = "sockmap",
};

static const char * const map_type_name[] = {
  [BPF_MAP_TYPE_UNSPEC]     = "unspec",
  [BPF_MAP_TYPE_HASH]     = "hash",
  [BPF_MAP_TYPE_ARRAY]      = "array",
  [BPF_MAP_TYPE_PROG_ARRAY]   = "prog_array",
  [BPF_MAP_TYPE_PERF_EVENT_ARRAY]   = "perf_event_array",
  [BPF_MAP_TYPE_PERCPU_HASH]    = "percpu_hash",
  [BPF_MAP_TYPE_PERCPU_ARRAY]   = "percpu_array",
  [BPF_MAP_TYPE_STACK_TRACE]    = "stack_trace",
  [BPF_MAP_TYPE_CGROUP_ARRAY]   = "cgroup_array",
  [BPF_MAP_TYPE_LRU_HASH]     = "lru_hash",
  [BPF_MAP_TYPE_LRU_PERCPU_HASH]    = "lru_percpu_hash",
  [BPF_MAP_TYPE_LPM_TRIE]     = "lpm_trie",
  [BPF_MAP_TYPE_ARRAY_OF_MAPS]    = "array_of_maps",
  [BPF_MAP_TYPE_HASH_OF_MAPS]   = "hash_of_maps",
  [BPF_MAP_TYPE_DEVMAP]     = "devmap",
  [BPF_MAP_TYPE_DEVMAP_HASH]    = "devmap_hash",
  [BPF_MAP_TYPE_SOCKMAP]      = "sockmap",
  [BPF_MAP_TYPE_CPUMAP]     = "cpumap",
  [BPF_MAP_TYPE_XSKMAP]     = "xskmap",
  [BPF_MAP_TYPE_SOCKHASH]     = "sockhash",
  [BPF_MAP_TYPE_CGROUP_STORAGE]   = "cgroup_storage",
  [BPF_MAP_TYPE_REUSEPORT_SOCKARRAY]  = "reuseport_sockarray",
  [BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE]  = "percpu_cgroup_storage",
  [BPF_MAP_TYPE_QUEUE]      = "queue",
  [BPF_MAP_TYPE_STACK]      = "stack",
  [BPF_MAP_TYPE_SK_STORAGE]   = "sk_storage",
  [BPF_MAP_TYPE_STRUCT_OPS]   = "struct_ops",
  [BPF_MAP_TYPE_RINGBUF]      = "ringbuf",
  [BPF_MAP_TYPE_INODE_STORAGE]    = "inode_storage",
  [BPF_MAP_TYPE_TASK_STORAGE]   = "task_storage",
  [BPF_MAP_TYPE_BLOOM_FILTER]   = "bloom_filter",
  [BPF_MAP_TYPE_USER_RINGBUF]             = "user_ringbuf",
  [BPF_MAP_TYPE_CGRP_STORAGE]   = "cgrp_storage",
  [BPF_MAP_TYPE_ARENA]      = "arena",
};

static const char * const prog_type_name[] = {
  [BPF_PROG_TYPE_UNSPEC]      = "unspec",
  [BPF_PROG_TYPE_SOCKET_FILTER]   = "socket_filter",
  [BPF_PROG_TYPE_KPROBE]      = "kprobe",
  [BPF_PROG_TYPE_SCHED_CLS]   = "sched_cls",
  [BPF_PROG_TYPE_SCHED_ACT]   = "sched_act",
  [BPF_PROG_TYPE_TRACEPOINT]    = "tracepoint",
  [BPF_PROG_TYPE_XDP]     = "xdp",
  [BPF_PROG_TYPE_PERF_EVENT]    = "perf_event",
  [BPF_PROG_TYPE_CGROUP_SKB]    = "cgroup_skb",
  [BPF_PROG_TYPE_CGROUP_SOCK]   = "cgroup_sock",
  [BPF_PROG_TYPE_LWT_IN]      = "lwt_in",
  [BPF_PROG_TYPE_LWT_OUT]     = "lwt_out",
  [BPF_PROG_TYPE_LWT_XMIT]    = "lwt_xmit",
  [BPF_PROG_TYPE_SOCK_OPS]    = "sock_ops",
  [BPF_PROG_TYPE_SK_SKB]      = "sk_skb",
  [BPF_PROG_TYPE_CGROUP_DEVICE]   = "cgroup_device",
  [BPF_PROG_TYPE_SK_MSG]      = "sk_msg",
  [BPF_PROG_TYPE_RAW_TRACEPOINT]    = "raw_tracepoint",
  [BPF_PROG_TYPE_CGROUP_SOCK_ADDR]  = "cgroup_sock_addr",
  [BPF_PROG_TYPE_LWT_SEG6LOCAL]   = "lwt_seg6local",
  [BPF_PROG_TYPE_LIRC_MODE2]    = "lirc_mode2",
  [BPF_PROG_TYPE_SK_REUSEPORT]    = "sk_reuseport",
  [BPF_PROG_TYPE_FLOW_DISSECTOR]    = "flow_dissector",
  [BPF_PROG_TYPE_CGROUP_SYSCTL]   = "cgroup_sysctl",
  [BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE] = "raw_tracepoint_writable",
  [BPF_PROG_TYPE_CGROUP_SOCKOPT]    = "cgroup_sockopt",
  [BPF_PROG_TYPE_TRACING]     = "tracing",
  [BPF_PROG_TYPE_STRUCT_OPS]    = "struct_ops",
  [BPF_PROG_TYPE_EXT]     = "ext",
  [BPF_PROG_TYPE_LSM]     = "lsm",
  [BPF_PROG_TYPE_SK_LOOKUP]   = "sk_lookup",
  [BPF_PROG_TYPE_SYSCALL]     = "syscall",
  [BPF_PROG_TYPE_NETFILTER]   = "netfilter",
};

static int __base_pr(enum libbpf_print_level level, const char *format,
         va_list args)
{
  const char *env_var = "LIBBPF_LOG_LEVEL";
  static enum libbpf_print_level min_level = LIBBPF_INFO;
  static bool initialized;

  if (!initialized) {
    char *verbosity;

    initialized = true;
    verbosity = getenv(env_var);
    if (verbosity) {
      if (strcasecmp(verbosity, "warn") == 0)
        min_level = LIBBPF_WARN;
      else if (strcasecmp(verbosity, "debug") == 0)
        min_level = LIBBPF_DEBUG;
      else if (strcasecmp(verbosity, "info") == 0)
        min_level = LIBBPF_INFO;
      else
        fprintf(stderr, "libbpf: unrecognized '%s' envvar value: '%s', should be one of 'warn', 'debug', or 'info'.\n",
          env_var, verbosity);
    }
  }

  /* if too verbose, skip logging  */
  if (level > min_level)
    return 0;

  return vfprintf(stderr, format, args);
}

static libbpf_print_fn_t __libbpf_pr = __base_pr;

libbpf_print_fn_t libbpf_set_print(libbpf_print_fn_t fn)
{
  libbpf_print_fn_t old_print_fn;

  old_print_fn = __atomic_exchange_n(&__libbpf_pr, fn, __ATOMIC_RELAXED);

  return old_print_fn;
}

__printf(2, 3)
void libbpf_print(enum libbpf_print_level level, const char *format, ...)
{
  va_list args;
  int old_errno;
  libbpf_print_fn_t print_fn;

  print_fn = __atomic_load_n(&__libbpf_pr, __ATOMIC_RELAXED);
  if (!print_fn)
    return;

  old_errno = errno;

  va_start(args, format);
  __libbpf_pr(level, format, args);
  va_end(args);

  errno = old_errno;
}

static void pr_perm_msg(int err)
{
  struct rlimit limit;
  char buf[100];

  if (err != -EPERM || geteuid() != 0)
    return;

  err = getrlimit(RLIMIT_MEMLOCK, &limit);
  if (err)
    return;

  if (limit.rlim_cur == RLIM_INFINITY)
    return;

  if (limit.rlim_cur < 1024)
    snprintf(buf, sizeof(buf), "%zu bytes", (size_t)limit.rlim_cur);
  else if (limit.rlim_cur < 1024*1024)
    snprintf(buf, sizeof(buf), "%.1f KiB", (double)limit.rlim_cur / 1024);
  else
    snprintf(buf, sizeof(buf), "%.1f MiB", (double)limit.rlim_cur / (1024*1024));

  pr_warn("permission error while running as root; try raising 'ulimit -l'? current value: %s\n",
    buf);
}

#define STRERR_BUFSIZE  128

/* Copied from tools/perf/util/util.h */
#ifndef zfree
# define zfree(ptr) ({ free(*ptr); *ptr = NULL; })
#endif

#ifndef zclose
# define zclose(fd) ({      \
  int ___err = 0;     \
  if ((fd) >= 0)     \
    ___err = close((fd)); \
  fd = -1;      \
  ___err; })
#endif

static inline __u64 ptr_to_u64(const void *ptr)
{
  return (__u64) (unsigned long) ptr;
}

int libbpf_set_strict_mode(enum libbpf_strict_mode mode)
{
  /* as of v1.0 libbpf_set_strict_mode() is a no-op */
  return 0;
}

__u32 libbpf_major_version(void)
{
  return LIBBPF_MAJOR_VERSION;
}

__u32 libbpf_minor_version(void)
{
  return LIBBPF_MINOR_VERSION;
}

const char *libbpf_version_string(void)
{
#define __S(X) #X
#define _S(X) __S(X)
  return  "v" _S(LIBBPF_MAJOR_VERSION) "." _S(LIBBPF_MINOR_VERSION);
#undef _S
#undef __S
}

enum reloc_type {
  RELO_LD64,
  RELO_CALL,
  RELO_DATA,
  RELO_EXTERN_LD64,
  RELO_EXTERN_CALL,
  RELO_SUBPROG_ADDR,
  RELO_CORE,
};

struct reloc_desc {
  enum reloc_type type;
  int insn_idx;
  union {
    const struct bpf_core_relo *core_relo; /* used when type == RELO_CORE */
    struct {
      int map_idx;
      int sym_off;
      int ext_idx;
    };
  };
};

/* stored as sec_def->cookie for all libbpf-supported SEC()s */
enum sec_def_flags {
  SEC_NONE = 0,
  /* expected_attach_type is optional, if kernel doesn't support that */
  SEC_EXP_ATTACH_OPT = 1,
  /* legacy, only used by libbpf_get_type_names() and
   * libbpf_attach_type_by_name(), not used by libbpf itself at all.
   * This used to be associated with cgroup (and few other) BPF programs
   * that were attachable through BPF_PROG_ATTACH command. Pretty
   * meaningless nowadays, though.
   */
  SEC_ATTACHABLE = 2,
  SEC_ATTACHABLE_OPT = SEC_ATTACHABLE | SEC_EXP_ATTACH_OPT,
  /* attachment target is specified through BTF ID in either kernel or
   * other BPF program's BTF object
   */
  SEC_ATTACH_BTF = 4,
  /* BPF program type allows sleeping/blocking in kernel */
  SEC_SLEEPABLE = 8,
  /* BPF program support non-linear XDP buffer */
  SEC_XDP_FRAGS = 16,
  /* Setup proper attach type for usdt probes. */
  SEC_USDT = 32,
};

struct bpf_sec_def {
  char *sec;
  enum bpf_prog_type prog_type;
  enum bpf_attach_type expected_attach_type;
  long cookie;
  int handler_id;

  libbpf_prog_setup_fn_t prog_setup_fn;
  libbpf_prog_prepare_load_fn_t prog_prepare_load_fn;
  libbpf_prog_attach_fn_t prog_attach_fn;
};

/*
 * bpf_prog should be a better name but it has been used in
 * linux/filter.h.
 */
struct bpf_program {
  char *name;
  char *sec_name;
  size_t sec_idx;
  const struct bpf_sec_def *sec_def;
  /* this program's instruction offset (in number of instructions)
   * within its containing ELF section
   */
  size_t sec_insn_off;
  /* number of original instructions in ELF section belonging to this
   * program, not taking into account subprogram instructions possible
   * appended later during relocation
   */
  size_t sec_insn_cnt;
  /* Offset (in number of instructions) of the start of instruction
   * belonging to this BPF program  within its containing main BPF
   * program. For the entry-point (main) BPF program, this is always
   * zero. For a sub-program, this gets reset before each of main BPF
   * programs are processed and relocated and is used to determined
   * whether sub-program was already appended to the main program, and
   * if yes, at which instruction offset.
   */
  size_t sub_insn_off;

  /* instructions that belong to BPF program; insns[0] is located at
   * sec_insn_off instruction within its ELF section in ELF file, so
   * when mapping ELF file instruction index to the local instruction,
   * one needs to subtract sec_insn_off; and vice versa.
   */
  struct bpf_insn *insns;
  /* actual number of instruction in this BPF program's image; for
   * entry-point BPF programs this includes the size of main program
   * itself plus all the used sub-programs, appended at the end
   */
  size_t insns_cnt;

  struct reloc_desc *reloc_desc;
  int nr_reloc;

  /* BPF verifier log settings */
  char *log_buf;
  size_t log_size;
  __u32 log_level;

  struct bpf_object *obj;

  int fd;
  bool autoload;
  bool autoattach;
  bool sym_global;
  bool mark_btf_static;
  enum bpf_prog_type type;
  enum bpf_attach_type expected_attach_type;
  int exception_cb_idx;

  int prog_ifindex;
  __u32 attach_btf_obj_fd;
  __u32 attach_btf_id;
  __u32 attach_prog_fd;

  void *func_info;
  __u32 func_info_rec_size;
  __u32 func_info_cnt;

  void *line_info;
  __u32 line_info_rec_size;
  __u32 line_info_cnt;
  __u32 prog_flags;
};

struct bpf_struct_ops {
  struct bpf_program **progs;
  __u32 *kern_func_off;
  /* e.g. struct tcp_congestion_ops in bpf_prog's btf format */
  void *data;
  /* e.g. struct bpf_struct_ops_tcp_congestion_ops in
   *      btf_vmlinux's format.
   * struct bpf_struct_ops_tcp_congestion_ops {
   *  [... some other kernel fields ...]
   *  struct tcp_congestion_ops data;
   * }
   * kern_vdata-size == sizeof(struct bpf_struct_ops_tcp_congestion_ops)
   * bpf_map__init_kern_struct_ops() will populate the "kern_vdata"
   * from "data".
   */
  void *kern_vdata;
  __u32 type_id;
};

#define DATA_SEC ".data"
#define BSS_SEC ".bss"
#define RODATA_SEC ".rodata"
#define KCONFIG_SEC ".kconfig"
#define KSYMS_SEC ".ksyms"
#define STRUCT_OPS_SEC ".struct_ops"
#define STRUCT_OPS_LINK_SEC ".struct_ops.link"
#define ARENA_SEC ".addr_space.1"

enum libbpf_map_type {
  LIBBPF_MAP_UNSPEC,
  LIBBPF_MAP_DATA,
  LIBBPF_MAP_BSS,
  LIBBPF_MAP_RODATA,
  LIBBPF_MAP_KCONFIG,
};

struct bpf_map_def {
  unsigned int type;
  unsigned int key_size;
  unsigned int value_size;
  unsigned int max_entries;
  unsigned int map_flags;
};

struct bpf_map {
  struct bpf_object *obj;
  char *name;
  /* real_name is defined for special internal maps (.rodata*,
   * .data*, .bss, .kconfig) and preserves their original ELF section
   * name. This is important to be able to find corresponding BTF
   * DATASEC information.
   */
  char *real_name;
  int fd;
  int sec_idx;
  size_t sec_offset;
  int map_ifindex;
  int inner_map_fd;
  struct bpf_map_def def;
  __u32 numa_node;
  __u32 btf_var_idx;
  int mod_btf_fd;
  __u32 btf_key_type_id;
  __u32 btf_value_type_id;
  __u32 btf_vmlinux_value_type_id;
  enum libbpf_map_type libbpf_type;
  void *mmaped;
  struct bpf_struct_ops *st_ops;
  struct bpf_map *inner_map;
  void **init_slots;
  int init_slots_sz;
  char *pin_path;
  bool pinned;
  bool reused;
  bool autocreate;
  bool autoattach;
  __u64 map_extra;
};

enum extern_type {
  EXT_UNKNOWN,
  EXT_KCFG,
  EXT_KSYM,
};

enum kcfg_type {
  KCFG_UNKNOWN,
  KCFG_CHAR,
  KCFG_BOOL,
  KCFG_INT,
  KCFG_TRISTATE,
  KCFG_CHAR_ARR,
};

struct extern_desc {
  enum extern_type type;
  int sym_idx;
  int btf_id;
  int sec_btf_id;
  const char *name;
  char *essent_name;
  bool is_set;
  bool is_weak;
  union {
    struct {
      enum kcfg_type type;
      int sz;
      int align;
      int data_off;
      bool is_signed;
    } kcfg;
    struct {
      unsigned long long addr;

      /* target btf_id of the corresponding kernel var. */
      int kernel_btf_obj_fd;
      int kernel_btf_id;

      /* local btf_id of the ksym extern's type. */
      __u32 type_id;
      /* BTF fd index to be patched in for insn->off, this is
       * 0 for vmlinux BTF, index in obj->fd_array for module
       * BTF
       */
      __s16 btf_fd_idx;
    } ksym;
  };
};

struct module_btf {
  struct btf *btf;
  char *name;
  __u32 id;
  int fd;
  int fd_array_idx;
};

enum sec_type {
  SEC_UNUSED = 0,
  SEC_RELO,
  SEC_BSS,
  SEC_DATA,
  SEC_RODATA,
  SEC_ST_OPS,
};

struct elf_sec_desc {
  enum sec_type sec_type;
  Elf64_Shdr *shdr;
  Elf_Data *data;
};

struct elf_state {
  int fd;
  const void *obj_buf;
  size_t obj_buf_sz;
  Elf *elf;
  Elf64_Ehdr *ehdr;
  Elf_Data *symbols;
  Elf_Data *arena_data;
  size_t shstrndx; /* section index for section name strings */
  size_t strtabidx;
  struct elf_sec_desc *secs;
  size_t sec_cnt;
  int btf_maps_shndx;
  __u32 btf_maps_sec_btf_id;
  int text_shndx;
  int symbols_shndx;
  bool has_st_ops;
  int arena_data_shndx;
};

struct usdt_manager;

struct bpf_object {
  char name[BPF_OBJ_NAME_LEN];
  char license[64];
  __u32 kern_version;

  struct bpf_program *programs;
  size_t nr_programs;
  struct bpf_map *maps;
  size_t nr_maps;
  size_t maps_cap;

  char *kconfig;
  struct extern_desc *externs;
  int nr_extern;
  int kconfig_map_idx;

  bool loaded;
  bool has_subcalls;
  bool has_rodata;

  struct bpf_gen *gen_loader;

  /* Information when doing ELF related work. Only valid if efile.elf is not NULL */
  struct elf_state efile;

  struct btf *btf;
  struct btf_ext *btf_ext;

  /* Parse and load BTF vmlinux if any of the programs in the object need
   * it at load time.
   */
  struct btf *btf_vmlinux;
  /* Path to the custom BTF to be used for BPF CO-RE relocations as an
   * override for vmlinux BTF.
   */
  char *btf_custom_path;
  /* vmlinux BTF override for CO-RE relocations */
  struct btf *btf_vmlinux_override;
  /* Lazily initialized kernel module BTFs */
  struct module_btf *btf_modules;
  bool btf_modules_loaded;
  size_t btf_module_cnt;
  size_t btf_module_cap;

  /* optional log settings passed to BPF_BTF_LOAD and BPF_PROG_LOAD commands */
  char *log_buf;
  size_t log_size;
  __u32 log_level;

  int *fd_array;
  size_t fd_array_cap;
  size_t fd_array_cnt;

  struct usdt_manager *usdt_man;

  struct bpf_map *arena_map;
  void *arena_data;
  size_t arena_data_sz;

  struct kern_feature_cache *feat_cache;
  char *token_path;
  int token_fd;

  char path[];
};

static const char *elf_sym_str(const struct bpf_object *obj, size_t off);
static const char *elf_sec_str(const struct bpf_object *obj, size_t off);
static Elf_Scn *elf_sec_by_idx(const struct bpf_object *obj, size_t idx);
static Elf_Scn *elf_sec_by_name(const struct bpf_object *obj, const char *name);
static Elf64_Shdr *elf_sec_hdr(const struct bpf_object *obj, Elf_Scn *scn);
static const char *elf_sec_name(const struct bpf_object *obj, Elf_Scn *scn);
static Elf_Data *elf_sec_data(const struct bpf_object *obj, Elf_Scn *scn);
static Elf64_Sym *elf_sym_by_idx(const struct bpf_object *obj, size_t idx);
static Elf64_Rel *elf_rel_by_idx(Elf_Data *data, size_t idx);

void bpf_program__unload(struct bpf_program *prog)
{
  if (!prog)
    return;

  zclose(prog->fd);

  zfree(&prog->func_info);
  zfree(&prog->line_info);
}

static void bpf_program__exit(struct bpf_program *prog)
{
  if (!prog)
    return;

  bpf_program__unload(prog);
  zfree(&prog->name);
  zfree(&prog->sec_name);
  zfree(&prog->insns);
  zfree(&prog->reloc_desc);

  prog->nr_reloc = 0;
  prog->insns_cnt = 0;
  prog->sec_idx = -1;
}

static bool insn_is_subprog_call(const struct bpf_insn *insn)
{
  return BPF_CLASS(insn->code) == BPF_JMP &&
         BPF_OP(insn->code) == BPF_CALL &&
         BPF_SRC(insn->code) == BPF_K &&
         insn->src_reg == BPF_PSEUDO_CALL &&
         insn->dst_reg == 0 &&
         insn->off == 0;
}

static bool is_call_insn(const struct bpf_insn *insn)
{
  return insn->code == (BPF_JMP | BPF_CALL);
}

static bool insn_is_pseudo_func(struct bpf_insn *insn)
{
  return is_ldimm64_insn(insn) && insn->src_reg == BPF_PSEUDO_FUNC;
}

static int
bpf_object__init_prog(struct bpf_object *obj, struct bpf_program *prog,
          const char *name, size_t sec_idx, const char *sec_name,
          size_t sec_off, void *insn_data, size_t insn_data_sz)
{
  if (insn_data_sz == 0 || insn_data_sz % BPF_INSN_SZ || sec_off % BPF_INSN_SZ) {
    pr_warn("sec '%s': corrupted program '%s', offset %zu, size %zu\n",
      sec_name, name, sec_off, insn_data_sz);
    return -EINVAL;
  }

  memset(prog, 0, sizeof(*prog));
  prog->obj = obj;

  prog->sec_idx = sec_idx;
  prog->sec_insn_off = sec_off / BPF_INSN_SZ;
  prog->sec_insn_cnt = insn_data_sz / BPF_INSN_SZ;
  /* insns_cnt can later be increased by appending used subprograms */
  prog->insns_cnt = prog->sec_insn_cnt;

  prog->type = BPF_PROG_TYPE_UNSPEC;
  prog->fd = -1;
  prog->exception_cb_idx = -1;

  /* libbpf's convention for SEC("?abc...") is that it's just like
   * SEC("abc...") but the corresponding bpf_program starts out with
   * autoload set to false.
   */
  if (sec_name[0] == '?') {
    prog->autoload = false;
    /* from now on forget there was ? in section name */
    sec_name++;
  } else {
    prog->autoload = true;
  }

  prog->autoattach = true;

  /* inherit object's log_level */
  prog->log_level = obj->log_level;

  prog->sec_name = strdup(sec_name);
  if (!prog->sec_name)
    goto errout;

  prog->name = strdup(name);
  if (!prog->name)
    goto errout;

  prog->insns = malloc(insn_data_sz);
  if (!prog->insns)
    goto errout;
  memcpy(prog->insns, insn_data, insn_data_sz);

  return 0;
errout:
  pr_warn("sec '%s': failed to allocate memory for prog '%s'\n", sec_name, name);
  bpf_program__exit(prog);
  return -ENOMEM;
}

static int
bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data,
       const char *sec_name, int sec_idx)
{
  Elf_Data *symbols = obj->efile.symbols;
  struct bpf_program *prog, *progs;
  void *data = sec_data->d_buf;
  size_t sec_sz = sec_data->d_size, sec_off, prog_sz, nr_syms;
  int nr_progs, err, i;
  const char *name;
  Elf64_Sym *sym;

  progs = obj->programs;
  nr_progs = obj->nr_programs;
  nr_syms = symbols->d_size / sizeof(Elf64_Sym);

  for (i = 0; i < nr_syms; i++) {
    sym = elf_sym_by_idx(obj, i);

    if (sym->st_shndx != sec_idx)
      continue;
    if (ELF64_ST_TYPE(sym->st_info) != STT_FUNC)
      continue;

    prog_sz = sym->st_size;
    sec_off = sym->st_value;

    name = elf_sym_str(obj, sym->st_name);
    if (!name) {
      pr_warn("sec '%s': failed to get symbol name for offset %zu\n",
        sec_name, sec_off);
      return -LIBBPF_ERRNO__FORMAT;
    }

    if (sec_off + prog_sz > sec_sz) {
      pr_warn("sec '%s': program at offset %zu crosses section boundary\n",
        sec_name, sec_off);
      return -LIBBPF_ERRNO__FORMAT;
    }

    if (sec_idx != obj->efile.text_shndx && ELF64_ST_BIND(sym->st_info) == STB_LOCAL) {
      pr_warn("sec '%s': program '%s' is static and not supported\n", sec_name, name);
      return -ENOTSUP;
    }

    pr_debug("sec '%s': found program '%s' at insn offset %zu (%zu bytes), code size %zu insns (%zu bytes)\n",
       sec_name, name, sec_off / BPF_INSN_SZ, sec_off, prog_sz / BPF_INSN_SZ, prog_sz);

    progs = libbpf_reallocarray(progs, nr_progs + 1, sizeof(*progs));
    if (!progs) {
      /*
       * In this case the original obj->programs
       * is still valid, so don't need special treat for
       * bpf_close_object().
       */
      pr_warn("sec '%s': failed to alloc memory for new program '%s'\n",
        sec_name, name);
      return -ENOMEM;
    }
    obj->programs = progs;

    prog = &progs[nr_progs];

    err = bpf_object__init_prog(obj, prog, name, sec_idx, sec_name,
              sec_off, data + sec_off, prog_sz);
    if (err)
      return err;

    if (ELF64_ST_BIND(sym->st_info) != STB_LOCAL)
      prog->sym_global = true;

    /* if function is a global/weak symbol, but has restricted
     * (STV_HIDDEN or STV_INTERNAL) visibility, mark its BTF FUNC
     * as static to enable more permissive BPF verification mode
     * with more outside context available to BPF verifier
     */
    if (prog->sym_global && (ELF64_ST_VISIBILITY(sym->st_other) == STV_HIDDEN
        || ELF64_ST_VISIBILITY(sym->st_other) == STV_INTERNAL))
      prog->mark_btf_static = true;

    nr_progs++;
    obj->nr_programs = nr_progs;
  }

  return 0;
}

static const struct btf_member *
find_member_by_offset(const struct btf_type *t, __u32 bit_offset)
{
  struct btf_member *m;
  int i;

  for (i = 0, m = btf_members(t); i < btf_vlen(t); i++, m++) {
    if (btf_member_bit_offset(t, i) == bit_offset)
      return m;
  }

  return NULL;
}

static const struct btf_member *
find_member_by_name(const struct btf *btf, const struct btf_type *t,
        const char *name)
{
  struct btf_member *m;
  int i;

  for (i = 0, m = btf_members(t); i < btf_vlen(t); i++, m++) {
    if (!strcmp(btf__name_by_offset(btf, m->name_off), name))
      return m;
  }

  return NULL;
}

static int find_ksym_btf_id(struct bpf_object *obj, const char *ksym_name,
          __u16 kind, struct btf **res_btf,
          struct module_btf **res_mod_btf);

#define STRUCT_OPS_VALUE_PREFIX "bpf_struct_ops_"
static int find_btf_by_prefix_kind(const struct btf *btf, const char *prefix,
           const char *name, __u32 kind);

static int
find_struct_ops_kern_types(struct bpf_object *obj, const char *tname_raw,
         struct module_btf **mod_btf,
         const struct btf_type **type, __u32 *type_id,
         const struct btf_type **vtype, __u32 *vtype_id,
         const struct btf_member **data_member)
{
  const struct btf_type *kern_type, *kern_vtype;
  const struct btf_member *kern_data_member;
  struct btf *btf;
  __s32 kern_vtype_id, kern_type_id;
  char tname[256];
  __u32 i;

  snprintf(tname, sizeof(tname), "%.*s",
     (int)bpf_core_essential_name_len(tname_raw), tname_raw);

  kern_type_id = find_ksym_btf_id(obj, tname, BTF_KIND_STRUCT,
          &btf, mod_btf);
  if (kern_type_id < 0) {
    pr_warn("struct_ops init_kern: struct %s is not found in kernel BTF\n",
      tname);
    return kern_type_id;
  }
  kern_type = btf__type_by_id(btf, kern_type_id);

  /* Find the corresponding "map_value" type that will be used
   * in map_update(BPF_MAP_TYPE_STRUCT_OPS).  For example,
   * find "struct bpf_struct_ops_tcp_congestion_ops" from the
   * btf_vmlinux.
   */
  kern_vtype_id = find_btf_by_prefix_kind(btf, STRUCT_OPS_VALUE_PREFIX,
            tname, BTF_KIND_STRUCT);
  if (kern_vtype_id < 0) {
    pr_warn("struct_ops init_kern: struct %s%s is not found in kernel BTF\n",
      STRUCT_OPS_VALUE_PREFIX, tname);
    return kern_vtype_id;
  }
  kern_vtype = btf__type_by_id(btf, kern_vtype_id);

  /* Find "struct tcp_congestion_ops" from
   * struct bpf_struct_ops_tcp_congestion_ops {
   *  [ ... ]
   *  struct tcp_congestion_ops data;
   * }
   */
  kern_data_member = btf_members(kern_vtype);
  for (i = 0; i < btf_vlen(kern_vtype); i++, kern_data_member++) {
    if (kern_data_member->type == kern_type_id)
      break;
  }
  if (i == btf_vlen(kern_vtype)) {
    pr_warn("struct_ops init_kern: struct %s data is not found in struct %s%s\n",
      tname, STRUCT_OPS_VALUE_PREFIX, tname);
    return -EINVAL;
  }

  *type = kern_type;
  *type_id = kern_type_id;
  *vtype = kern_vtype;
  *vtype_id = kern_vtype_id;
  *data_member = kern_data_member;

  return 0;
}

static bool bpf_map__is_struct_ops(const struct bpf_map *map)
{
  return map->def.type == BPF_MAP_TYPE_STRUCT_OPS;
}

static bool is_valid_st_ops_program(struct bpf_object *obj,
            const struct bpf_program *prog)
{
  int i;

  for (i = 0; i < obj->nr_programs; i++) {
    if (&obj->programs[i] == prog)
      return prog->type == BPF_PROG_TYPE_STRUCT_OPS;
  }

  return false;
}

/* For each struct_ops program P, referenced from some struct_ops map M,
 * enable P.autoload if there are Ms for which M.autocreate is true,
 * disable P.autoload if for all Ms M.autocreate is false.
 * Don't change P.autoload for programs that are not referenced from any maps.
 */
static int bpf_object_adjust_struct_ops_autoload(struct bpf_object *obj)
{
  struct bpf_program *prog, *slot_prog;
  struct bpf_map *map;
  int i, j, k, vlen;

  for (i = 0; i < obj->nr_programs; ++i) {
    int should_load = false;
    int use_cnt = 0;

    prog = &obj->programs[i];
    if (prog->type != BPF_PROG_TYPE_STRUCT_OPS)
      continue;

    for (j = 0; j < obj->nr_maps; ++j) {
      const struct btf_type *type;

      map = &obj->maps[j];
      if (!bpf_map__is_struct_ops(map))
        continue;

      type = btf__type_by_id(obj->btf, map->st_ops->type_id);
      vlen = btf_vlen(type);
      for (k = 0; k < vlen; ++k) {
        slot_prog = map->st_ops->progs[k];
        if (prog != slot_prog)
          continue;

        use_cnt++;
        if (map->autocreate)
          should_load = true;
      }
    }
    if (use_cnt)
      prog->autoload = should_load;
  }

  return 0;
}

/* Init the map's fields that depend on kern_btf */
static int bpf_map__init_kern_struct_ops(struct bpf_map *map)
{
  const struct btf_member *member, *kern_member, *kern_data_member;
  const struct btf_type *type, *kern_type, *kern_vtype;
  __u32 i, kern_type_id, kern_vtype_id, kern_data_off;
  struct bpf_object *obj = map->obj;
  const struct btf *btf = obj->btf;
  struct bpf_struct_ops *st_ops;
  const struct btf *kern_btf;
  struct module_btf *mod_btf;
  void *data, *kern_data;
  const char *tname;
  int err;

  st_ops = map->st_ops;
  type = btf__type_by_id(btf, st_ops->type_id);
  tname = btf__name_by_offset(btf, type->name_off);
  err = find_struct_ops_kern_types(obj, tname, &mod_btf,
           &kern_type, &kern_type_id,
           &kern_vtype, &kern_vtype_id,
           &kern_data_member);
  if (err)
    return err;

  kern_btf = mod_btf ? mod_btf->btf : obj->btf_vmlinux;

  pr_debug("struct_ops init_kern %s: type_id:%u kern_type_id:%u kern_vtype_id:%u\n",
     map->name, st_ops->type_id, kern_type_id, kern_vtype_id);

  map->mod_btf_fd = mod_btf ? mod_btf->fd : -1;
  map->def.value_size = kern_vtype->size;
  map->btf_vmlinux_value_type_id = kern_vtype_id;

  st_ops->kern_vdata = calloc(1, kern_vtype->size);
  if (!st_ops->kern_vdata)
    return -ENOMEM;

  data = st_ops->data;
  kern_data_off = kern_data_member->offset / 8;
  kern_data = st_ops->kern_vdata + kern_data_off;

  member = btf_members(type);
  for (i = 0; i < btf_vlen(type); i++, member++) {
    const struct btf_type *mtype, *kern_mtype;
    __u32 mtype_id, kern_mtype_id;
    void *mdata, *kern_mdata;
    struct bpf_program *prog;
    __s64 msize, kern_msize;
    __u32 moff, kern_moff;
    __u32 kern_member_idx;
    const char *mname;

    mname = btf__name_by_offset(btf, member->name_off);
    moff = member->offset / 8;
    mdata = data + moff;
    msize = btf__resolve_size(btf, member->type);
    if (msize < 0) {
      pr_warn("struct_ops init_kern %s: failed to resolve the size of member %s\n",
        map->name, mname);
      return msize;
    }

    kern_member = find_member_by_name(kern_btf, kern_type, mname);
    if (!kern_member) {
      if (!libbpf_is_mem_zeroed(mdata, msize)) {
        pr_warn("struct_ops init_kern %s: Cannot find member %s in kernel BTF\n",
          map->name, mname);
        return -ENOTSUP;
      }

      if (st_ops->progs[i]) {
        /* If we had declaratively set struct_ops callback, we need to
         * force its autoload to false, because it doesn't have
         * a chance of succeeding from POV of the current struct_ops map.
         * If this program is still referenced somewhere else, though,
         * then bpf_object_adjust_struct_ops_autoload() will update its
         * autoload accordingly.
         */
        st_ops->progs[i]->autoload = false;
        st_ops->progs[i] = NULL;
      }

      /* Skip all-zero/NULL fields if they are not present in the kernel BTF */
      pr_info("struct_ops %s: member %s not found in kernel, skipping it as it's set to zero\n",
        map->name, mname);
      continue;
    }

    kern_member_idx = kern_member - btf_members(kern_type);
    if (btf_member_bitfield_size(type, i) ||
        btf_member_bitfield_size(kern_type, kern_member_idx)) {
      pr_warn("struct_ops init_kern %s: bitfield %s is not supported\n",
        map->name, mname);
      return -ENOTSUP;
    }

    kern_moff = kern_member->offset / 8;
    kern_mdata = kern_data + kern_moff;

    mtype = skip_mods_and_typedefs(btf, member->type, &mtype_id);
    kern_mtype = skip_mods_and_typedefs(kern_btf, kern_member->type,
                &kern_mtype_id);
    if (BTF_INFO_KIND(mtype->info) !=
        BTF_INFO_KIND(kern_mtype->info)) {
      pr_warn("struct_ops init_kern %s: Unmatched member type %s %u != %u(kernel)\n",
        map->name, mname, BTF_INFO_KIND(mtype->info),
        BTF_INFO_KIND(kern_mtype->info));
      return -ENOTSUP;
    }

    if (btf_is_ptr(mtype)) {
      prog = *(void **)mdata;
      /* just like for !kern_member case above, reset declaratively
       * set (at compile time) program's autload to false,
       * if user replaced it with another program or NULL
       */
      if (st_ops->progs[i] && st_ops->progs[i] != prog)
        st_ops->progs[i]->autoload = false;

      /* Update the value from the shadow type */
      st_ops->progs[i] = prog;
      if (!prog)
        continue;

      if (!is_valid_st_ops_program(obj, prog)) {
        pr_warn("struct_ops init_kern %s: member %s is not a struct_ops program\n",
          map->name, mname);
        return -ENOTSUP;
      }

      kern_mtype = skip_mods_and_typedefs(kern_btf,
                  kern_mtype->type,
                  &kern_mtype_id);

      /* mtype->type must be a func_proto which was
       * guaranteed in bpf_object__collect_st_ops_relos(),
       * so only check kern_mtype for func_proto here.
       */
      if (!btf_is_func_proto(kern_mtype)) {
        pr_warn("struct_ops init_kern %s: kernel member %s is not a func ptr\n",
          map->name, mname);
        return -ENOTSUP;
      }

      if (mod_btf)
        prog->attach_btf_obj_fd = mod_btf->fd;

      /* if we haven't yet processed this BPF program, record proper
       * attach_btf_id and member_idx
       */
      if (!prog->attach_btf_id) {
        prog->attach_btf_id = kern_type_id;
        prog->expected_attach_type = kern_member_idx;
      }

      /* struct_ops BPF prog can be re-used between multiple
       * .struct_ops & .struct_ops.link as long as it's the
       * same struct_ops struct definition and the same
       * function pointer field
       */
      if (prog->attach_btf_id != kern_type_id) {
        pr_warn("struct_ops init_kern %s func ptr %s: invalid reuse of prog %s in sec %s with type %u: attach_btf_id %u != kern_type_id %u\n",
          map->name, mname, prog->name, prog->sec_name, prog->type,
          prog->attach_btf_id, kern_type_id);
        return -EINVAL;
      }
      if (prog->expected_attach_type != kern_member_idx) {
        pr_warn("struct_ops init_kern %s func ptr %s: invalid reuse of prog %s in sec %s with type %u: expected_attach_type %u != kern_member_idx %u\n",
          map->name, mname, prog->name, prog->sec_name, prog->type,
          prog->expected_attach_type, kern_member_idx);
        return -EINVAL;
      }

      st_ops->kern_func_off[i] = kern_data_off + kern_moff;

      pr_debug("struct_ops init_kern %s: func ptr %s is set to prog %s from data(+%u) to kern_data(+%u)\n",
         map->name, mname, prog->name, moff,
         kern_moff);

      continue;
    }

    kern_msize = btf__resolve_size(kern_btf, kern_mtype_id);
    if (kern_msize < 0 || msize != kern_msize) {
      pr_warn("struct_ops init_kern %s: Error in size of member %s: %zd != %zd(kernel)\n",
        map->name, mname, (ssize_t)msize,
        (ssize_t)kern_msize);
      return -ENOTSUP;
    }

    pr_debug("struct_ops init_kern %s: copy %s %u bytes from data(+%u) to kern_data(+%u)\n",
       map->name, mname, (unsigned int)msize,
       moff, kern_moff);
    memcpy(kern_mdata, mdata, msize);
  }

  return 0;
}

static int bpf_object__init_kern_struct_ops_maps(struct bpf_object *obj)
{
  struct bpf_map *map;
  size_t i;
  int err;

  for (i = 0; i < obj->nr_maps; i++) {
    map = &obj->maps[i];

    if (!bpf_map__is_struct_ops(map))
      continue;

    if (!map->autocreate)
      continue;

    err = bpf_map__init_kern_struct_ops(map);
    if (err)
      return err;
  }

  return 0;
}

static int init_struct_ops_maps(struct bpf_object *obj, const char *sec_name,
        int shndx, Elf_Data *data)
{
  const struct btf_type *type, *datasec;
  const struct btf_var_secinfo *vsi;
  struct bpf_struct_ops *st_ops;
  const char *tname, *var_name;
  __s32 type_id, datasec_id;
  const struct btf *btf;
  struct bpf_map *map;
  __u32 i;

  if (shndx == -1)
    return 0;

  btf = obj->btf;
  datasec_id = btf__find_by_name_kind(btf, sec_name,
              BTF_KIND_DATASEC);
  if (datasec_id < 0) {
    pr_warn("struct_ops init: DATASEC %s not found\n",
      sec_name);
    return -EINVAL;
  }

  datasec = btf__type_by_id(btf, datasec_id);
  vsi = btf_var_secinfos(datasec);
  for (i = 0; i < btf_vlen(datasec); i++, vsi++) {
    type = btf__type_by_id(obj->btf, vsi->type);
    var_name = btf__name_by_offset(obj->btf, type->name_off);

    type_id = btf__resolve_type(obj->btf, vsi->type);
    if (type_id < 0) {
      pr_warn("struct_ops init: Cannot resolve var type_id %u in DATASEC %s\n",
        vsi->type, sec_name);
      return -EINVAL;
    }

    type = btf__type_by_id(obj->btf, type_id);
    tname = btf__name_by_offset(obj->btf, type->name_off);
    if (!tname[0]) {
      pr_warn("struct_ops init: anonymous type is not supported\n");
      return -ENOTSUP;
    }
    if (!btf_is_struct(type)) {
      pr_warn("struct_ops init: %s is not a struct\n", tname);
      return -EINVAL;
    }

    map = bpf_object__add_map(obj);
    if (IS_ERR(map))
      return PTR_ERR(map);

    map->sec_idx = shndx;
    map->sec_offset = vsi->offset;
    map->name = strdup(var_name);
    if (!map->name)
      return -ENOMEM;
    map->btf_value_type_id = type_id;

    /* Follow same convention as for programs autoload:
     * SEC("?.struct_ops") means map is not created by default.
     */
    if (sec_name[0] == '?') {
      map->autocreate = false;
      /* from now on forget there was ? in section name */
      sec_name++;
    }

    map->def.type = BPF_MAP_TYPE_STRUCT_OPS;
    map->def.key_size = sizeof(int);
    map->def.value_size = type->size;
    map->def.max_entries = 1;
    map->def.map_flags = strcmp(sec_name, STRUCT_OPS_LINK_SEC) == 0 ? BPF_F_LINK : 0;
    map->autoattach = true;

    map->st_ops = calloc(1, sizeof(*map->st_ops));
    if (!map->st_ops)
      return -ENOMEM;
    st_ops = map->st_ops;
    st_ops->data = malloc(type->size);
    st_ops->progs = calloc(btf_vlen(type), sizeof(*st_ops->progs));
    st_ops->kern_func_off = malloc(btf_vlen(type) *
                 sizeof(*st_ops->kern_func_off));
    if (!st_ops->data || !st_ops->progs || !st_ops->kern_func_off)
      return -ENOMEM;

    if (vsi->offset + type->size > data->d_size) {
      pr_warn("struct_ops init: var %s is beyond the end of DATASEC %s\n",
        var_name, sec_name);
      return -EINVAL;
    }

    memcpy(st_ops->data,
           data->d_buf + vsi->offset,
           type->size);
    st_ops->type_id = type_id;

    pr_debug("struct_ops init: struct %s(type_id=%u) %s found at offset %u\n",
       tname, type_id, var_name, vsi->offset);
  }

  return 0;
}

static int bpf_object_init_struct_ops(struct bpf_object *obj)
{
  const char *sec_name;
  int sec_idx, err;

  for (sec_idx = 0; sec_idx < obj->efile.sec_cnt; ++sec_idx) {
    struct elf_sec_desc *desc = &obj->efile.secs[sec_idx];

    if (desc->sec_type != SEC_ST_OPS)
      continue;

    sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx));
    if (!sec_name)
      return -LIBBPF_ERRNO__FORMAT;

    err = init_struct_ops_maps(obj, sec_name, sec_idx, desc->data);
    if (err)
      return err;
  }

  return 0;
}

static struct bpf_object *bpf_object__new(const char *path,
            const void *obj_buf,
            size_t obj_buf_sz,
            const char *obj_name)
{
  struct bpf_object *obj;
  char *end;

  obj = calloc(1, sizeof(struct bpf_object) + strlen(path) + 1);
  if (!obj) {
    pr_warn("alloc memory failed for %s\n", path);
    return ERR_PTR(-ENOMEM);
  }

  strcpy(obj->path, path);
  if (obj_name) {
    libbpf_strlcpy(obj->name, obj_name, sizeof(obj->name));
  } else {
    /* Using basename() GNU version which doesn't modify arg. */
    libbpf_strlcpy(obj->name, basename((void *)path), sizeof(obj->name));
    end = strchr(obj->name, '.');
    if (end)
      *end = 0;
  }

  obj->efile.fd = -1;
  /*
   * Caller of this function should also call
   * bpf_object__elf_finish() after data collection to return
   * obj_buf to user. If not, we should duplicate the buffer to
   * avoid user freeing them before elf finish.
   */
  obj->efile.obj_buf = obj_buf;
  obj->efile.obj_buf_sz = obj_buf_sz;
  obj->efile.btf_maps_shndx = -1;
  obj->kconfig_map_idx = -1;

  obj->kern_version = get_kernel_version();
  obj->loaded = false;

  return obj;
}

static void bpf_object__elf_finish(struct bpf_object *obj)
{
  if (!obj->efile.elf)
    return;

  elf_end(obj->efile.elf);
  obj->efile.elf = NULL;
  obj->efile.symbols = NULL;
  obj->efile.arena_data = NULL;

  zfree(&obj->efile.secs);
  obj->efile.sec_cnt = 0;
  zclose(obj->efile.fd);
  obj->efile.obj_buf = NULL;
  obj->efile.obj_buf_sz = 0;
}

static int bpf_object__elf_init(struct bpf_object *obj)
{
  Elf64_Ehdr *ehdr;
  int err = 0;
  Elf *elf;

  if (obj->efile.elf) {
    pr_warn("elf: init internal error\n");
    return -LIBBPF_ERRNO__LIBELF;
  }

  if (obj->efile.obj_buf_sz > 0) {
    /* obj_buf should have been validated by bpf_object__open_mem(). */
    elf = elf_memory((char *)obj->efile.obj_buf, obj->efile.obj_buf_sz);
  } else {
    obj->efile.fd = open(obj->path, O_RDONLY | O_CLOEXEC);
    if (obj->efile.fd < 0) {
      char errmsg[STRERR_BUFSIZE], *cp;

      err = -errno;
      cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
      pr_warn("elf: failed to open %s: %s\n", obj->path, cp);
      return err;
    }

    elf = elf_begin(obj->efile.fd, ELF_C_READ_MMAP, NULL);
  }

  if (!elf) {
    pr_warn("elf: failed to open %s as ELF file: %s\n", obj->path, elf_errmsg(-1));
    err = -LIBBPF_ERRNO__LIBELF;
    goto errout;
  }

  obj->efile.elf = elf;

  if (elf_kind(elf) != ELF_K_ELF) {
    err = -LIBBPF_ERRNO__FORMAT;
    pr_warn("elf: '%s' is not a proper ELF object\n", obj->path);
    goto errout;
  }

  if (gelf_getclass(elf) != ELFCLASS64) {
    err = -LIBBPF_ERRNO__FORMAT;
    pr_warn("elf: '%s' is not a 64-bit ELF object\n", obj->path);
    goto errout;
  }

  obj->efile.ehdr = ehdr = elf64_getehdr(elf);
  if (!obj->efile.ehdr) {
    pr_warn("elf: failed to get ELF header from %s: %s\n", obj->path, elf_errmsg(-1));
    err = -LIBBPF_ERRNO__FORMAT;
    goto errout;
  }

  if (elf_getshdrstrndx(elf, &obj->efile.shstrndx)) {
    pr_warn("elf: failed to get section names section index for %s: %s\n",
      obj->path, elf_errmsg(-1));
    err = -LIBBPF_ERRNO__FORMAT;
    goto errout;
  }

  /* ELF is corrupted/truncated, avoid calling elf_strptr. */
  if (!elf_rawdata(elf_getscn(elf, obj->efile.shstrndx), NULL)) {
    pr_warn("elf: failed to get section names strings from %s: %s\n",
      obj->path, elf_errmsg(-1));
    err = -LIBBPF_ERRNO__FORMAT;
    goto errout;
  }

  /* Old LLVM set e_machine to EM_NONE */
  if (ehdr->e_type != ET_REL || (ehdr->e_machine && ehdr->e_machine != EM_BPF)) {
    pr_warn("elf: %s is not a valid eBPF object file\n", obj->path);
    err = -LIBBPF_ERRNO__FORMAT;
    goto errout;
  }

  return 0;
errout:
  bpf_object__elf_finish(obj);
  return err;
}

static int bpf_object__check_endianness(struct bpf_object *obj)
{
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
  if (obj->efile.ehdr->e_ident[EI_DATA] == ELFDATA2LSB)
    return 0;
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
  if (obj->efile.ehdr->e_ident[EI_DATA] == ELFDATA2MSB)
    return 0;
#else
# error "Unrecognized __BYTE_ORDER__"
#endif
  pr_warn("elf: endianness mismatch in %s.\n", obj->path);
  return -LIBBPF_ERRNO__ENDIAN;
}

static int
bpf_object__init_license(struct bpf_object *obj, void *data, size_t size)
{
  if (!data) {
    pr_warn("invalid license section in %s\n", obj->path);
    return -LIBBPF_ERRNO__FORMAT;
  }
  /* libbpf_strlcpy() only copies first N - 1 bytes, so size + 1 won't
   * go over allowed ELF data section buffer
   */
  libbpf_strlcpy(obj->license, data, min(size + 1, sizeof(obj->license)));
  pr_debug("license of %s is %s\n", obj->path, obj->license);
  return 0;
}

static int
bpf_object__init_kversion(struct bpf_object *obj, void *data, size_t size)
{
  __u32 kver;

  if (!data || size != sizeof(kver)) {
    pr_warn("invalid kver section in %s\n", obj->path);
    return -LIBBPF_ERRNO__FORMAT;
  }
  memcpy(&kver, data, sizeof(kver));
  obj->kern_version = kver;
  pr_debug("kernel version of %s is %x\n", obj->path, obj->kern_version);
  return 0;
}

static bool bpf_map_type__is_map_in_map(enum bpf_map_type type)
{
  if (type == BPF_MAP_TYPE_ARRAY_OF_MAPS ||
      type == BPF_MAP_TYPE_HASH_OF_MAPS)
    return true;
  return false;
}

static int find_elf_sec_sz(const struct bpf_object *obj, const char *name, __u32 *size)
{
  Elf_Data *data;
  Elf_Scn *scn;

  if (!name)
    return -EINVAL;

  scn = elf_sec_by_name(obj, name);
  data = elf_sec_data(obj, scn);
  if (data) {
    *size = data->d_size;
    return 0; /* found it */
  }

  return -ENOENT;
}

static Elf64_Sym *find_elf_var_sym(const struct bpf_object *obj, const char *name)
{
  Elf_Data *symbols = obj->efile.symbols;
  const char *sname;
  size_t si;

  for (si = 0; si < symbols->d_size / sizeof(Elf64_Sym); si++) {
    Elf64_Sym *sym = elf_sym_by_idx(obj, si);

    if (ELF64_ST_TYPE(sym->st_info) != STT_OBJECT)
      continue;

    if (ELF64_ST_BIND(sym->st_info) != STB_GLOBAL &&
        ELF64_ST_BIND(sym->st_info) != STB_WEAK)
      continue;

    sname = elf_sym_str(obj, sym->st_name);
    if (!sname) {
      pr_warn("failed to get sym name string for var %s\n", name);
      return ERR_PTR(-EIO);
    }
    if (strcmp(name, sname) == 0)
      return sym;
  }

  return ERR_PTR(-ENOENT);
}

/* Some versions of Android don't provide memfd_create() in their libc
 * implementation, so avoid complications and just go straight to Linux
 * syscall.
 */
static int sys_memfd_create(const char *name, unsigned flags)
{
  return syscall(__NR_memfd_create, name, flags);
}

#ifndef MFD_CLOEXEC
#define MFD_CLOEXEC 0x0001U
#endif

static int create_placeholder_fd(void)
{
  int fd;

  fd = ensure_good_fd(sys_memfd_create("libbpf-placeholder-fd", MFD_CLOEXEC));
  if (fd < 0)
    return -errno;
  return fd;
}

static struct bpf_map *bpf_object__add_map(struct bpf_object *obj)
{
  struct bpf_map *map;
  int err;

  err = libbpf_ensure_mem((void **)&obj->maps, &obj->maps_cap,
        sizeof(*obj->maps), obj->nr_maps + 1);
  if (err)
    return ERR_PTR(err);

  map = &obj->maps[obj->nr_maps++];
  map->obj = obj;
  /* Preallocate map FD without actually creating BPF map just yet.
   * These map FD "placeholders" will be reused later without changing
   * FD value when map is actually created in the kernel.
   *
   * This is useful to be able to perform BPF program relocations
   * without having to create BPF maps before that step. This allows us
   * to finalize and load BTF very late in BPF object's loading phase,
   * right before BPF maps have to be created and BPF programs have to
   * be loaded. By having these map FD placeholders we can perform all
   * the sanitizations, relocations, and any other adjustments before we
   * start creating actual BPF kernel objects (BTF, maps, progs).
   */
  map->fd = create_placeholder_fd();
  if (map->fd < 0)
    return ERR_PTR(map->fd);
  map->inner_map_fd = -1;
  map->autocreate = true;

  return map;
}

static size_t array_map_mmap_sz(unsigned int value_sz, unsigned int max_entries)
{
  const long page_sz = sysconf(_SC_PAGE_SIZE);
  size_t map_sz;

  map_sz = (size_t)roundup(value_sz, 8) * max_entries;
  map_sz = roundup(map_sz, page_sz);
  return map_sz;
}

static size_t bpf_map_mmap_sz(const struct bpf_map *map)
{
  const long page_sz = sysconf(_SC_PAGE_SIZE);

  switch (map->def.type) {
  case BPF_MAP_TYPE_ARRAY:
    return array_map_mmap_sz(map->def.value_size, map->def.max_entries);
  case BPF_MAP_TYPE_ARENA:
    return page_sz * map->def.max_entries;
  default:
    return 0; /* not supported */
  }
}

static int bpf_map_mmap_resize(struct bpf_map *map, size_t old_sz, size_t new_sz)
{
  void *mmaped;

  if (!map->mmaped)
    return -EINVAL;

  if (old_sz == new_sz)
    return 0;

  mmaped = mmap(NULL, new_sz, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
  if (mmaped == MAP_FAILED)
    return -errno;

  memcpy(mmaped, map->mmaped, min(old_sz, new_sz));
  munmap(map->mmaped, old_sz);
  map->mmaped = mmaped;
  return 0;
}

static char *internal_map_name(struct bpf_object *obj, const char *real_name)
{
  char map_name[BPF_OBJ_NAME_LEN], *p;
  int pfx_len, sfx_len = max((size_t)7, strlen(real_name));

  /* This is one of the more confusing parts of libbpf for various
   * reasons, some of which are historical. The original idea for naming
   * internal names was to include as much of BPF object name prefix as
   * possible, so that it can be distinguished from similar internal
   * maps of a different BPF object.
   * As an example, let's say we have bpf_object named 'my_object_name'
   * and internal map corresponding to '.rodata' ELF section. The final
   * map name advertised to user and to the kernel will be
   * 'my_objec.rodata', taking first 8 characters of object name and
   * entire 7 characters of '.rodata'.
   * Somewhat confusingly, if internal map ELF section name is shorter
   * than 7 characters, e.g., '.bss', we still reserve 7 characters
   * for the suffix, even though we only have 4 actual characters, and
   * resulting map will be called 'my_objec.bss', not even using all 15
   * characters allowed by the kernel. Oh well, at least the truncated
   * object name is somewhat consistent in this case. But if the map
   * name is '.kconfig', we'll still have entirety of '.kconfig' added
   * (8 chars) and thus will be left with only first 7 characters of the
   * object name ('my_obje'). Happy guessing, user, that the final map
   * name will be "my_obje.kconfig".
   * Now, with libbpf starting to support arbitrarily named .rodata.*
   * and .data.* data sections, it's possible that ELF section name is
   * longer than allowed 15 chars, so we now need to be careful to take
   * only up to 15 first characters of ELF name, taking no BPF object
   * name characters at all. So '.rodata.abracadabra' will result in
   * '.rodata.abracad' kernel and user-visible name.
   * We need to keep this convoluted logic intact for .data, .bss and
   * .rodata maps, but for new custom .data.custom and .rodata.custom
   * maps we use their ELF names as is, not prepending bpf_object name
   * in front. We still need to truncate them to 15 characters for the
   * kernel. Full name can be recovered for such maps by using DATASEC
   * BTF type associated with such map's value type, though.
   */
  if (sfx_len >= BPF_OBJ_NAME_LEN)
    sfx_len = BPF_OBJ_NAME_LEN - 1;

  /* if there are two or more dots in map name, it's a custom dot map */
  if (strchr(real_name + 1, '.') != NULL)
    pfx_len = 0;
  else
    pfx_len = min((size_t)BPF_OBJ_NAME_LEN - sfx_len - 1, strlen(obj->name));

  snprintf(map_name, sizeof(map_name), "%.*s%.*s", pfx_len, obj->name,
     sfx_len, real_name);

  /* sanitise map name to characters allowed by kernel */
  for (p = map_name; *p && p < map_name + sizeof(map_name); p++)
    if (!isalnum(*p) && *p != '_' && *p != '.')
      *p = '_';

  return strdup(map_name);
}

static int
map_fill_btf_type_info(struct bpf_object *obj, struct bpf_map *map);

/* Internal BPF map is mmap()'able only if at least one of corresponding
 * DATASEC's VARs are to be exposed through BPF skeleton. I.e., it's a GLOBAL
 * variable and it's not marked as __hidden (which turns it into, effectively,
 * a STATIC variable).
 */
static bool map_is_mmapable(struct bpf_object *obj, struct bpf_map *map)
{
  const struct btf_type *t, *vt;
  struct btf_var_secinfo *vsi;
  int i, n;

  if (!map->btf_value_type_id)
    return false;

  t = btf__type_by_id(obj->btf, map->btf_value_type_id);
  if (!btf_is_datasec(t))
    return false;

  vsi = btf_var_secinfos(t);
  for (i = 0, n = btf_vlen(t); i < n; i++, vsi++) {
    vt = btf__type_by_id(obj->btf, vsi->type);
    if (!btf_is_var(vt))
      continue;

    if (btf_var(vt)->linkage != BTF_VAR_STATIC)
      return true;
  }

  return false;
}

static int
bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type,
            const char *real_name, int sec_idx, void *data, size_t data_sz)
{
  struct bpf_map_def *def;
  struct bpf_map *map;
  size_t mmap_sz;
  int err;

  map = bpf_object__add_map(obj);
  if (IS_ERR(map))
    return PTR_ERR(map);

  map->libbpf_type = type;
  map->sec_idx = sec_idx;
  map->sec_offset = 0;
  map->real_name = strdup(real_name);
  map->name = internal_map_name(obj, real_name);
  if (!map->real_name || !map->name) {
    zfree(&map->real_name);
    zfree(&map->name);
    return -ENOMEM;
  }

  def = &map->def;
  def->type = BPF_MAP_TYPE_ARRAY;
  def->key_size = sizeof(int);
  def->value_size = data_sz;
  def->max_entries = 1;
  def->map_flags = type == LIBBPF_MAP_RODATA || type == LIBBPF_MAP_KCONFIG
    ? BPF_F_RDONLY_PROG : 0;

  /* failures are fine because of maps like .rodata.str1.1 */
  (void) map_fill_btf_type_info(obj, map);

  if (map_is_mmapable(obj, map))
    def->map_flags |= BPF_F_MMAPABLE;

  pr_debug("map '%s' (global data): at sec_idx %d, offset %zu, flags %x.\n",
     map->name, map->sec_idx, map->sec_offset, def->map_flags);

  mmap_sz = bpf_map_mmap_sz(map);
  map->mmaped = mmap(NULL, mmap_sz, PROT_READ | PROT_WRITE,
         MAP_SHARED | MAP_ANONYMOUS, -1, 0);
  if (map->mmaped == MAP_FAILED) {
    err = -errno;
    map->mmaped = NULL;
    pr_warn("failed to alloc map '%s' content buffer: %d\n",
      map->name, err);
    zfree(&map->real_name);
    zfree(&map->name);
    return err;
  }

  if (data)
    memcpy(map->mmaped, data, data_sz);

  pr_debug("map %td is \"%s\"\n", map - obj->maps, map->name);
  return 0;
}

static int bpf_object__init_global_data_maps(struct bpf_object *obj)
{
  struct elf_sec_desc *sec_desc;
  const char *sec_name;
  int err = 0, sec_idx;

  /*
   * Populate obj->maps with libbpf internal maps.
   */
  for (sec_idx = 1; sec_idx < obj->efile.sec_cnt; sec_idx++) {
    sec_desc = &obj->efile.secs[sec_idx];

    /* Skip recognized sections with size 0. */
    if (!sec_desc->data || sec_desc->data->d_size == 0)
      continue;

    switch (sec_desc->sec_type) {
    case SEC_DATA:
      sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx));
      err = bpf_object__init_internal_map(obj, LIBBPF_MAP_DATA,
                  sec_name, sec_idx,
                  sec_desc->data->d_buf,
                  sec_desc->data->d_size);
      break;
    case SEC_RODATA:
      obj->has_rodata = true;
      sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx));
      err = bpf_object__init_internal_map(obj, LIBBPF_MAP_RODATA,
                  sec_name, sec_idx,
                  sec_desc->data->d_buf,
                  sec_desc->data->d_size);
      break;
    case SEC_BSS:
      sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx));
      err = bpf_object__init_internal_map(obj, LIBBPF_MAP_BSS,
                  sec_name, sec_idx,
                  NULL,
                  sec_desc->data->d_size);
      break;
    default:
      /* skip */
      break;
    }
    if (err)
      return err;
  }
  return 0;
}


static struct extern_desc *find_extern_by_name(const struct bpf_object *obj,
                 const void *name)
{
  int i;

  for (i = 0; i < obj->nr_extern; i++) {
    if (strcmp(obj->externs[i].name, name) == 0)
      return &obj->externs[i];
  }
  return NULL;
}

static struct extern_desc *find_extern_by_name_with_len(const struct bpf_object *obj,
              const void *name, int len)
{
  const char *ext_name;
  int i;

  for (i = 0; i < obj->nr_extern; i++) {
    ext_name = obj->externs[i].name;
    if (strlen(ext_name) == len && strncmp(ext_name, name, len) == 0)
      return &obj->externs[i];
  }
  return NULL;
}

static int set_kcfg_value_tri(struct extern_desc *ext, void *ext_val,
            char value)
{
  switch (ext->kcfg.type) {
  case KCFG_BOOL:
    if (value == 'm') {
      pr_warn("extern (kcfg) '%s': value '%c' implies tristate or char type\n",
        ext->name, value);
      return -EINVAL;
    }
    *(bool *)ext_val = value == 'y' ? true : false;
    break;
  case KCFG_TRISTATE:
    if (value == 'y')
      *(enum libbpf_tristate *)ext_val = TRI_YES;
    else if (value == 'm')
      *(enum libbpf_tristate *)ext_val = TRI_MODULE;
    else /* value == 'n' */
      *(enum libbpf_tristate *)ext_val = TRI_NO;
    break;
  case KCFG_CHAR:
    *(char *)ext_val = value;
    break;
  case KCFG_UNKNOWN:
  case KCFG_INT:
  case KCFG_CHAR_ARR:
  default:
    pr_warn("extern (kcfg) '%s': value '%c' implies bool, tristate, or char type\n",
      ext->name, value);
    return -EINVAL;
  }
  ext->is_set = true;
  return 0;
}

static int set_kcfg_value_str(struct extern_desc *ext, char *ext_val,
            const char *value)
{
  size_t len;

  if (ext->kcfg.type != KCFG_CHAR_ARR) {
    pr_warn("extern (kcfg) '%s': value '%s' implies char array type\n",
      ext->name, value);
    return -EINVAL;
  }

  len = strlen(value);
  if (value[len - 1] != '"') {
    pr_warn("extern (kcfg) '%s': invalid string config '%s'\n",
      ext->name, value);
    return -EINVAL;
  }

  /* strip quotes */
  len -= 2;
  if (len >= ext->kcfg.sz) {
    pr_warn("extern (kcfg) '%s': long string '%s' of (%zu bytes) truncated to %d bytes\n",
      ext->name, value, len, ext->kcfg.sz - 1);
    len = ext->kcfg.sz - 1;
  }
  memcpy(ext_val, value + 1, len);
  ext_val[len] = '\0';
  ext->is_set = true;
  return 0;
}

static int parse_u64(const char *value, __u64 *res)
{
  char *value_end;
  int err;

  errno = 0;
  *res = strtoull(value, &value_end, 0);
  if (errno) {
    err = -errno;
    pr_warn("failed to parse '%s' as integer: %d\n", value, err);
    return err;
  }
  if (*value_end) {
    pr_warn("failed to parse '%s' as integer completely\n", value);
    return -EINVAL;
  }
  return 0;
}

static bool is_kcfg_value_in_range(const struct extern_desc *ext, __u64 v)
{
  int bit_sz = ext->kcfg.sz * 8;

  if (ext->kcfg.sz == 8)
    return true;

  /* Validate that value stored in u64 fits in integer of `ext->sz`
   * bytes size without any loss of information. If the target integer
   * is signed, we rely on the following limits of integer type of
   * Y bits and subsequent transformation:
   *
   *     -2^(Y-1) <= X           <= 2^(Y-1) - 1
   *            0 <= X + 2^(Y-1) <= 2^Y - 1
   *            0 <= X + 2^(Y-1) <  2^Y
   *
   *  For unsigned target integer, check that all the (64 - Y) bits are
   *  zero.
   */
  if (ext->kcfg.is_signed)
    return v + (1ULL << (bit_sz - 1)) < (1ULL << bit_sz);
  else
    return (v >> bit_sz) == 0;
}

static int set_kcfg_value_num(struct extern_desc *ext, void *ext_val,
            __u64 value)
{
  if (ext->kcfg.type != KCFG_INT && ext->kcfg.type != KCFG_CHAR &&
      ext->kcfg.type != KCFG_BOOL) {
    pr_warn("extern (kcfg) '%s': value '%llu' implies integer, char, or boolean type\n",
      ext->name, (unsigned long long)value);
    return -EINVAL;
  }
  if (ext->kcfg.type == KCFG_BOOL && value > 1) {
    pr_warn("extern (kcfg) '%s': value '%llu' isn't boolean compatible\n",
      ext->name, (unsigned long long)value);
    return -EINVAL;

  }
  if (!is_kcfg_value_in_range(ext, value)) {
    pr_warn("extern (kcfg) '%s': value '%llu' doesn't fit in %d bytes\n",
      ext->name, (unsigned long long)value, ext->kcfg.sz);
    return -ERANGE;
  }
  switch (ext->kcfg.sz) {
  case 1:
    *(__u8 *)ext_val = value;
    break;
  case 2:
    *(__u16 *)ext_val = value;
    break;
  case 4:
    *(__u32 *)ext_val = value;
    break;
  case 8:
    *(__u64 *)ext_val = value;
    break;
  default:
    return -EINVAL;
  }
  ext->is_set = true;
  return 0;
}

static int bpf_object__process_kconfig_line(struct bpf_object *obj,
              char *buf, void *data)
{
  struct extern_desc *ext;
  char *sep, *value;
  int len, err = 0;
  void *ext_val;
  __u64 num;

  if (!str_has_pfx(buf, "CONFIG_"))
    return 0;

  sep = strchr(buf, '=');
  if (!sep) {
    pr_warn("failed to parse '%s': no separator\n", buf);
    return -EINVAL;
  }

  /* Trim ending '\n' */
  len = strlen(buf);
  if (buf[len - 1] == '\n')
    buf[len - 1] = '\0';
  /* Split on '=' and ensure that a value is present. */
  *sep = '\0';
  if (!sep[1]) {
    *sep = '=';
    pr_warn("failed to parse '%s': no value\n", buf);
    return -EINVAL;
  }

  ext = find_extern_by_name(obj, buf);
  if (!ext || ext->is_set)
    return 0;

  ext_val = data + ext->kcfg.data_off;
  value = sep + 1;

  switch (*value) {
  case 'y': case 'n': case 'm':
    err = set_kcfg_value_tri(ext, ext_val, *value);
    break;
  case '"':
    err = set_kcfg_value_str(ext, ext_val, value);
    break;
  default:
    /* assume integer */
    err = parse_u64(value, &num);
    if (err) {
      pr_warn("extern (kcfg) '%s': value '%s' isn't a valid integer\n", ext->name, value);
      return err;
    }
    if (ext->kcfg.type != KCFG_INT && ext->kcfg.type != KCFG_CHAR) {
      pr_warn("extern (kcfg) '%s': value '%s' implies integer type\n", ext->name, value);
      return -EINVAL;
    }
    err = set_kcfg_value_num(ext, ext_val, num);
    break;
  }
  if (err)
    return err;
  pr_debug("extern (kcfg) '%s': set to %s\n", ext->name, value);
  return 0;
}

static int bpf_object__read_kconfig_file(struct bpf_object *obj, void *data)
{
  char buf[PATH_MAX];
  struct utsname uts;
  int len, err = 0;
  gzFile file;

  uname(&uts);
  len = snprintf(buf, PATH_MAX, "/boot/config-%s", uts.release);
  if (len < 0)
    return -EINVAL;
  else if (len >= PATH_MAX)
    return -ENAMETOOLONG;

  /* gzopen also accepts uncompressed files. */
  file = gzopen(buf, "re");
  if (!file)
    file = gzopen("/proc/config.gz", "re");

  if (!file) {
    pr_warn("failed to open system Kconfig\n");
    return -ENOENT;
  }

  while (gzgets(file, buf, sizeof(buf))) {
    err = bpf_object__process_kconfig_line(obj, buf, data);
    if (err) {
      pr_warn("error parsing system Kconfig line '%s': %d\n",
        buf, err);
      goto out;
    }
  }

out:
  gzclose(file);
  return err;
}

static int bpf_object__read_kconfig_mem(struct bpf_object *obj,
          const char *config, void *data)
{
  char buf[PATH_MAX];
  int err = 0;
  FILE *file;

  file = fmemopen((void *)config, strlen(config), "r");
  if (!file) {
    err = -errno;
    pr_warn("failed to open in-memory Kconfig: %d\n", err);
    return err;
  }

  while (fgets(buf, sizeof(buf), file)) {
    err = bpf_object__process_kconfig_line(obj, buf, data);
    if (err) {
      pr_warn("error parsing in-memory Kconfig line '%s': %d\n",
        buf, err);
      break;
    }
  }

  fclose(file);
  return err;
}

static int bpf_object__init_kconfig_map(struct bpf_object *obj)
{
  struct extern_desc *last_ext = NULL, *ext;
  size_t map_sz;
  int i, err;

  for (i = 0; i < obj->nr_extern; i++) {
    ext = &obj->externs[i];
    if (ext->type == EXT_KCFG)
      last_ext = ext;
  }

  if (!last_ext)
    return 0;

  map_sz = last_ext->kcfg.data_off + last_ext->kcfg.sz;
  err = bpf_object__init_internal_map(obj, LIBBPF_MAP_KCONFIG,
              ".kconfig", obj->efile.symbols_shndx,
              NULL, map_sz);
  if (err)
    return err;

  obj->kconfig_map_idx = obj->nr_maps - 1;

  return 0;
}

const struct btf_type *
skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id)
{
  const struct btf_type *t = btf__type_by_id(btf, id);

  if (res_id)
    *res_id = id;

  while (btf_is_mod(t) || btf_is_typedef(t)) {
    if (res_id)
      *res_id = t->type;
    t = btf__type_by_id(btf, t->type);
  }

  return t;
}

static const struct btf_type *
resolve_func_ptr(const struct btf *btf, __u32 id, __u32 *res_id)
{
  const struct btf_type *t;

  t = skip_mods_and_typedefs(btf, id, NULL);
  if (!btf_is_ptr(t))
    return NULL;

  t = skip_mods_and_typedefs(btf, t->type, res_id);

  return btf_is_func_proto(t) ? t : NULL;
}

static const char *__btf_kind_str(__u16 kind)
{
  switch (kind) {
  case BTF_KIND_UNKN: return "void";
  case BTF_KIND_INT: return "int";
  case BTF_KIND_PTR: return "ptr";
  case BTF_KIND_ARRAY: return "array";
  case BTF_KIND_STRUCT: return "struct";
  case BTF_KIND_UNION: return "union";
  case BTF_KIND_ENUM: return "enum";
  case BTF_KIND_FWD: return "fwd";
  case BTF_KIND_TYPEDEF: return "typedef";
  case BTF_KIND_VOLATILE: return "volatile";
  case BTF_KIND_CONST: return "const";
  case BTF_KIND_RESTRICT: return "restrict";
  case BTF_KIND_FUNC: return "func";
  case BTF_KIND_FUNC_PROTO: return "func_proto";
  case BTF_KIND_VAR: return "var";
  case BTF_KIND_DATASEC: return "datasec";
  case BTF_KIND_FLOAT: return "float";
  case BTF_KIND_DECL_TAG: return "decl_tag";
  case BTF_KIND_TYPE_TAG: return "type_tag";
  case BTF_KIND_ENUM64: return "enum64";
  default: return "unknown";
  }
}

const char *btf_kind_str(const struct btf_type *t)
{
  return __btf_kind_str(btf_kind(t));
}

/*
 * Fetch integer attribute of BTF map definition. Such attributes are
 * represented using a pointer to an array, in which dimensionality of array
 * encodes specified integer value. E.g., int (*type)[BPF_MAP_TYPE_ARRAY];
 * encodes `type => BPF_MAP_TYPE_ARRAY` key/value pair completely using BTF
 * type definition, while using only sizeof(void *) space in ELF data section.
 */
static bool get_map_field_int(const char *map_name, const struct btf *btf,
            const struct btf_member *m, __u32 *res)
{
  const struct btf_type *t = skip_mods_and_typedefs(btf, m->type, NULL);
  const char *name = btf__name_by_offset(btf, m->name_off);
  const struct btf_array *arr_info;
  const struct btf_type *arr_t;

  if (!btf_is_ptr(t)) {
    pr_warn("map '%s': attr '%s': expected PTR, got %s.\n",
      map_name, name, btf_kind_str(t));
    return false;
  }

  arr_t = btf__type_by_id(btf, t->type);
  if (!arr_t) {
    pr_warn("map '%s': attr '%s': type [%u] not found.\n",
      map_name, name, t->type);
    return false;
  }
  if (!btf_is_array(arr_t)) {
    pr_warn("map '%s': attr '%s': expected ARRAY, got %s.\n",
      map_name, name, btf_kind_str(arr_t));
    return false;
  }
  arr_info = btf_array(arr_t);
  *res = arr_info->nelems;
  return true;
}

static bool get_map_field_long(const char *map_name, const struct btf *btf,
             const struct btf_member *m, __u64 *res)
{
  const struct btf_type *t = skip_mods_and_typedefs(btf, m->type, NULL);
  const char *name = btf__name_by_offset(btf, m->name_off);

  if (btf_is_ptr(t)) {
    __u32 res32;
    bool ret;

    ret = get_map_field_int(map_name, btf, m, &res32);
    if (ret)
      *res = (__u64)res32;
    return ret;
  }

  if (!btf_is_enum(t) && !btf_is_enum64(t)) {
    pr_warn("map '%s': attr '%s': expected ENUM or ENUM64, got %s.\n",
      map_name, name, btf_kind_str(t));
    return false;
  }

  if (btf_vlen(t) != 1) {
    pr_warn("map '%s': attr '%s': invalid __ulong\n",
      map_name, name);
    return false;
  }

  if (btf_is_enum(t)) {
    const struct btf_enum *e = btf_enum(t);

    *res = e->val;
  } else {
    const struct btf_enum64 *e = btf_enum64(t);

    *res = btf_enum64_value(e);
  }
  return true;
}

static int pathname_concat(char *buf, size_t buf_sz, const char *path, const char *name)
{
  int len;

  len = snprintf(buf, buf_sz, "%s/%s", path, name);
  if (len < 0)
    return -EINVAL;
  if (len >= buf_sz)
    return -ENAMETOOLONG;

  return 0;
}

static int build_map_pin_path(struct bpf_map *map, const char *path)
{
  char buf[PATH_MAX];
  int err;

  if (!path)
    path = BPF_FS_DEFAULT_PATH;

  err = pathname_concat(buf, sizeof(buf), path, bpf_map__name(map));
  if (err)
    return err;

  return bpf_map__set_pin_path(map, buf);
}

/* should match definition in bpf_helpers.h */
enum libbpf_pin_type {
  LIBBPF_PIN_NONE,
  /* PIN_BY_NAME: pin maps by name (in /sys/fs/bpf by default) */
  LIBBPF_PIN_BY_NAME,
};

int parse_btf_map_def(const char *map_name, struct btf *btf,
          const struct btf_type *def_t, bool strict,
          struct btf_map_def *map_def, struct btf_map_def *inner_def)
{
  const struct btf_type *t;
  const struct btf_member *m;
  bool is_inner = inner_def == NULL;
  int vlen, i;

  vlen = btf_vlen(def_t);
  m = btf_members(def_t);
  for (i = 0; i < vlen; i++, m++) {
    const char *name = btf__name_by_offset(btf, m->name_off);

    if (!name) {
      pr_warn("map '%s': invalid field #%d.\n", map_name, i);
      return -EINVAL;
    }
    if (strcmp(name, "type") == 0) {
      if (!get_map_field_int(map_name, btf, m, &map_def->map_type))
        return -EINVAL;
      map_def->parts |= MAP_DEF_MAP_TYPE;
    } else if (strcmp(name, "max_entries") == 0) {
      if (!get_map_field_int(map_name, btf, m, &map_def->max_entries))
        return -EINVAL;
      map_def->parts |= MAP_DEF_MAX_ENTRIES;
    } else if (strcmp(name, "map_flags") == 0) {
      if (!get_map_field_int(map_name, btf, m, &map_def->map_flags))
        return -EINVAL;
      map_def->parts |= MAP_DEF_MAP_FLAGS;
    } else if (strcmp(name, "numa_node") == 0) {
      if (!get_map_field_int(map_name, btf, m, &map_def->numa_node))
        return -EINVAL;
      map_def->parts |= MAP_DEF_NUMA_NODE;
    } else if (strcmp(name, "key_size") == 0) {
      __u32 sz;

      if (!get_map_field_int(map_name, btf, m, &sz))
        return -EINVAL;
      if (map_def->key_size && map_def->key_size != sz) {
        pr_warn("map '%s': conflicting key size %u != %u.\n",
          map_name, map_def->key_size, sz);
        return -EINVAL;
      }
      map_def->key_size = sz;
      map_def->parts |= MAP_DEF_KEY_SIZE;
    } else if (strcmp(name, "key") == 0) {
      __s64 sz;

      t = btf__type_by_id(btf, m->type);
      if (!t) {
        pr_warn("map '%s': key type [%d] not found.\n",
          map_name, m->type);
        return -EINVAL;
      }
      if (!btf_is_ptr(t)) {
        pr_warn("map '%s': key spec is not PTR: %s.\n",
          map_name, btf_kind_str(t));
        return -EINVAL;
      }
      sz = btf__resolve_size(btf, t->type);
      if (sz < 0) {
        pr_warn("map '%s': can't determine key size for type [%u]: %zd.\n",
          map_name, t->type, (ssize_t)sz);
        return sz;
      }
      if (map_def->key_size && map_def->key_size != sz) {
        pr_warn("map '%s': conflicting key size %u != %zd.\n",
          map_name, map_def->key_size, (ssize_t)sz);
        return -EINVAL;
      }
      map_def->key_size = sz;
      map_def->key_type_id = t->type;
      map_def->parts |= MAP_DEF_KEY_SIZE | MAP_DEF_KEY_TYPE;
    } else if (strcmp(name, "value_size") == 0) {
      __u32 sz;

      if (!get_map_field_int(map_name, btf, m, &sz))
        return -EINVAL;
      if (map_def->value_size && map_def->value_size != sz) {
        pr_warn("map '%s': conflicting value size %u != %u.\n",
          map_name, map_def->value_size, sz);
        return -EINVAL;
      }
      map_def->value_size = sz;
      map_def->parts |= MAP_DEF_VALUE_SIZE;
    } else if (strcmp(name, "value") == 0) {
      __s64 sz;

      t = btf__type_by_id(btf, m->type);
      if (!t) {
        pr_warn("map '%s': value type [%d] not found.\n",
          map_name, m->type);
        return -EINVAL;
      }
      if (!btf_is_ptr(t)) {
        pr_warn("map '%s': value spec is not PTR: %s.\n",
          map_name, btf_kind_str(t));
        return -EINVAL;
      }
      sz = btf__resolve_size(btf, t->type);
      if (sz < 0) {
        pr_warn("map '%s': can't determine value size for type [%u]: %zd.\n",
          map_name, t->type, (ssize_t)sz);
        return sz;
      }
      if (map_def->value_size && map_def->value_size != sz) {
        pr_warn("map '%s': conflicting value size %u != %zd.\n",
          map_name, map_def->value_size, (ssize_t)sz);
        return -EINVAL;
      }
      map_def->value_size = sz;
      map_def->value_type_id = t->type;
      map_def->parts |= MAP_DEF_VALUE_SIZE | MAP_DEF_VALUE_TYPE;
    }
    else if (strcmp(name, "values") == 0) {
      bool is_map_in_map = bpf_map_type__is_map_in_map(map_def->map_type);
      bool is_prog_array = map_def->map_type == BPF_MAP_TYPE_PROG_ARRAY;
      const char *desc = is_map_in_map ? "map-in-map inner" : "prog-array value";
      char inner_map_name[128];
      int err;

      if (is_inner) {
        pr_warn("map '%s': multi-level inner maps not supported.\n",
          map_name);
        return -ENOTSUP;
      }
      if (i != vlen - 1) {
        pr_warn("map '%s': '%s' member should be last.\n",
          map_name, name);
        return -EINVAL;
      }
      if (!is_map_in_map && !is_prog_array) {
        pr_warn("map '%s': should be map-in-map or prog-array.\n",
          map_name);
        return -ENOTSUP;
      }
      if (map_def->value_size && map_def->value_size != 4) {
        pr_warn("map '%s': conflicting value size %u != 4.\n",
          map_name, map_def->value_size);
        return -EINVAL;
      }
      map_def->value_size = 4;
      t = btf__type_by_id(btf, m->type);
      if (!t) {
        pr_warn("map '%s': %s type [%d] not found.\n",
          map_name, desc, m->type);
        return -EINVAL;
      }
      if (!btf_is_array(t) || btf_array(t)->nelems) {
        pr_warn("map '%s': %s spec is not a zero-sized array.\n",
          map_name, desc);
        return -EINVAL;
      }
      t = skip_mods_and_typedefs(btf, btf_array(t)->type, NULL);
      if (!btf_is_ptr(t)) {
        pr_warn("map '%s': %s def is of unexpected kind %s.\n",
          map_name, desc, btf_kind_str(t));
        return -EINVAL;
      }
      t = skip_mods_and_typedefs(btf, t->type, NULL);
      if (is_prog_array) {
        if (!btf_is_func_proto(t)) {
          pr_warn("map '%s': prog-array value def is of unexpected kind %s.\n",
            map_name, btf_kind_str(t));
          return -EINVAL;
        }
        continue;
      }
      if (!btf_is_struct(t)) {
        pr_warn("map '%s': map-in-map inner def is of unexpected kind %s.\n",
          map_name, btf_kind_str(t));
        return -EINVAL;
      }

      snprintf(inner_map_name, sizeof(inner_map_name), "%s.inner", map_name);
      err = parse_btf_map_def(inner_map_name, btf, t, strict, inner_def, NULL);
      if (err)
        return err;

      map_def->parts |= MAP_DEF_INNER_MAP;
    } else if (strcmp(name, "pinning") == 0) {
      __u32 val;

      if (is_inner) {
        pr_warn("map '%s': inner def can't be pinned.\n", map_name);
        return -EINVAL;
      }
      if (!get_map_field_int(map_name, btf, m, &val))
        return -EINVAL;
      if (val != LIBBPF_PIN_NONE && val != LIBBPF_PIN_BY_NAME) {
        pr_warn("map '%s': invalid pinning value %u.\n",
          map_name, val);
        return -EINVAL;
      }
      map_def->pinning = val;
      map_def->parts |= MAP_DEF_PINNING;
    } else if (strcmp(name, "map_extra") == 0) {
      __u64 map_extra;

      if (!get_map_field_long(map_name, btf, m, &map_extra))
        return -EINVAL;
      map_def->map_extra = map_extra;
      map_def->parts |= MAP_DEF_MAP_EXTRA;
    } else {
      if (strict) {
        pr_warn("map '%s': unknown field '%s'.\n", map_name, name);
        return -ENOTSUP;
      }
      pr_debug("map '%s': ignoring unknown field '%s'.\n", map_name, name);
    }
  }

  if (map_def->map_type == BPF_MAP_TYPE_UNSPEC) {
    pr_warn("map '%s': map type isn't specified.\n", map_name);
    return -EINVAL;
  }

  return 0;
}

static size_t adjust_ringbuf_sz(size_t sz)
{
  __u32 page_sz = sysconf(_SC_PAGE_SIZE);
  __u32 mul;

  /* if user forgot to set any size, make sure they see error */
  if (sz == 0)
    return 0;
  /* Kernel expects BPF_MAP_TYPE_RINGBUF's max_entries to be
   * a power-of-2 multiple of kernel's page size. If user diligently
   * satisified these conditions, pass the size through.
   */
  if ((sz % page_sz) == 0 && is_pow_of_2(sz / page_sz))
    return sz;

  /* Otherwise find closest (page_sz * power_of_2) product bigger than
   * user-set size to satisfy both user size request and kernel
   * requirements and substitute correct max_entries for map creation.
   */
  for (mul = 1; mul <= UINT_MAX / page_sz; mul <<= 1) {
    if (mul * page_sz > sz)
      return mul * page_sz;
  }

  /* if it's impossible to satisfy the conditions (i.e., user size is
   * very close to UINT_MAX but is not a power-of-2 multiple of
   * page_size) then just return original size and let kernel reject it
   */
  return sz;
}

static bool map_is_ringbuf(const struct bpf_map *map)
{
  return map->def.type == BPF_MAP_TYPE_RINGBUF ||
         map->def.type == BPF_MAP_TYPE_USER_RINGBUF;
}

static void fill_map_from_def(struct bpf_map *map, const struct btf_map_def *def)
{
  map->def.type = def->map_type;
  map->def.key_size = def->key_size;
  map->def.value_size = def->value_size;
  map->def.max_entries = def->max_entries;
  map->def.map_flags = def->map_flags;
  map->map_extra = def->map_extra;

  map->numa_node = def->numa_node;
  map->btf_key_type_id = def->key_type_id;
  map->btf_value_type_id = def->value_type_id;

  /* auto-adjust BPF ringbuf map max_entries to be a multiple of page size */
  if (map_is_ringbuf(map))
    map->def.max_entries = adjust_ringbuf_sz(map->def.max_entries);

  if (def->parts & MAP_DEF_MAP_TYPE)
    pr_debug("map '%s': found type = %u.\n", map->name, def->map_type);

  if (def->parts & MAP_DEF_KEY_TYPE)
    pr_debug("map '%s': found key [%u], sz = %u.\n",
       map->name, def->key_type_id, def->key_size);
  else if (def->parts & MAP_DEF_KEY_SIZE)
    pr_debug("map '%s': found key_size = %u.\n", map->name, def->key_size);

  if (def->parts & MAP_DEF_VALUE_TYPE)
    pr_debug("map '%s': found value [%u], sz = %u.\n",
       map->name, def->value_type_id, def->value_size);
  else if (def->parts & MAP_DEF_VALUE_SIZE)
    pr_debug("map '%s': found value_size = %u.\n", map->name, def->value_size);

  if (def->parts & MAP_DEF_MAX_ENTRIES)
    pr_debug("map '%s': found max_entries = %u.\n", map->name, def->max_entries);
  if (def->parts & MAP_DEF_MAP_FLAGS)
    pr_debug("map '%s': found map_flags = 0x%x.\n", map->name, def->map_flags);
  if (def->parts & MAP_DEF_MAP_EXTRA)
    pr_debug("map '%s': found map_extra = 0x%llx.\n", map->name,
       (unsigned long long)def->map_extra);
  if (def->parts & MAP_DEF_PINNING)
    pr_debug("map '%s': found pinning = %u.\n", map->name, def->pinning);
  if (def->parts & MAP_DEF_NUMA_NODE)
    pr_debug("map '%s': found numa_node = %u.\n", map->name, def->numa_node);

  if (def->parts & MAP_DEF_INNER_MAP)
    pr_debug("map '%s': found inner map definition.\n", map->name);
}

static const char *btf_var_linkage_str(__u32 linkage)
{
  switch (linkage) {
  case BTF_VAR_STATIC: return "static";
  case BTF_VAR_GLOBAL_ALLOCATED: return "global";
  case BTF_VAR_GLOBAL_EXTERN: return "extern";
  default: return "unknown";
  }
}

static int bpf_object__init_user_btf_map(struct bpf_object *obj,
           const struct btf_type *sec,
           int var_idx, int sec_idx,
           const Elf_Data *data, bool strict,
           const char *pin_root_path)
{
  struct btf_map_def map_def = {}, inner_def = {};
  const struct btf_type *var, *def;
  const struct btf_var_secinfo *vi;
  const struct btf_var *var_extra;
  const char *map_name;
  struct bpf_map *map;
  int err;

  vi = btf_var_secinfos(sec) + var_idx;
  var = btf__type_by_id(obj->btf, vi->type);
  var_extra = btf_var(var);
  map_name = btf__name_by_offset(obj->btf, var->name_off);

  if (map_name == NULL || map_name[0] == '\0') {
    pr_warn("map #%d: empty name.\n", var_idx);
    return -EINVAL;
  }
  if ((__u64)vi->offset + vi->size > data->d_size) {
    pr_warn("map '%s' BTF data is corrupted.\n", map_name);
    return -EINVAL;
  }
  if (!btf_is_var(var)) {
    pr_warn("map '%s': unexpected var kind %s.\n",
      map_name, btf_kind_str(var));
    return -EINVAL;
  }
  if (var_extra->linkage != BTF_VAR_GLOBAL_ALLOCATED) {
    pr_warn("map '%s': unsupported map linkage %s.\n",
      map_name, btf_var_linkage_str(var_extra->linkage));
    return -EOPNOTSUPP;
  }

  def = skip_mods_and_typedefs(obj->btf, var->type, NULL);
  if (!btf_is_struct(def)) {
    pr_warn("map '%s': unexpected def kind %s.\n",
      map_name, btf_kind_str(var));
    return -EINVAL;
  }
  if (def->size > vi->size) {
    pr_warn("map '%s': invalid def size.\n", map_name);
    return -EINVAL;
  }

  map = bpf_object__add_map(obj);
  if (IS_ERR(map))
    return PTR_ERR(map);
  map->name = strdup(map_name);
  if (!map->name) {
    pr_warn("map '%s': failed to alloc map name.\n", map_name);
    return -ENOMEM;
  }
  map->libbpf_type = LIBBPF_MAP_UNSPEC;
  map->def.type = BPF_MAP_TYPE_UNSPEC;
  map->sec_idx = sec_idx;
  map->sec_offset = vi->offset;
  map->btf_var_idx = var_idx;
  pr_debug("map '%s': at sec_idx %d, offset %zu.\n",
     map_name, map->sec_idx, map->sec_offset);

  err = parse_btf_map_def(map->name, obj->btf, def, strict, &map_def, &inner_def);
  if (err)
    return err;

  fill_map_from_def(map, &map_def);

  if (map_def.pinning == LIBBPF_PIN_BY_NAME) {
    err = build_map_pin_path(map, pin_root_path);
    if (err) {
      pr_warn("map '%s': couldn't build pin path.\n", map->name);
      return err;
    }
  }

  if (map_def.parts & MAP_DEF_INNER_MAP) {
    map->inner_map = calloc(1, sizeof(*map->inner_map));
    if (!map->inner_map)
      return -ENOMEM;
    map->inner_map->fd = create_placeholder_fd();
    if (map->inner_map->fd < 0)
      return map->inner_map->fd;
    map->inner_map->sec_idx = sec_idx;
    map->inner_map->name = malloc(strlen(map_name) + sizeof(".inner") + 1);
    if (!map->inner_map->name)
      return -ENOMEM;
    sprintf(map->inner_map->name, "%s.inner", map_name);

    fill_map_from_def(map->inner_map, &inner_def);
  }

  err = map_fill_btf_type_info(obj, map);
  if (err)
    return err;

  return 0;
}

static int init_arena_map_data(struct bpf_object *obj, struct bpf_map *map,
             const char *sec_name, int sec_idx,
             void *data, size_t data_sz)
{
  const long page_sz = sysconf(_SC_PAGE_SIZE);
  size_t mmap_sz;

  mmap_sz = bpf_map_mmap_sz(obj->arena_map);
  if (roundup(data_sz, page_sz) > mmap_sz) {
    pr_warn("elf: sec '%s': declared ARENA map size (%zu) is too small to hold global __arena variables of size %zu\n",
      sec_name, mmap_sz, data_sz);
    return -E2BIG;
  }

  obj->arena_data = malloc(data_sz);
  if (!obj->arena_data)
    return -ENOMEM;
  memcpy(obj->arena_data, data, data_sz);
  obj->arena_data_sz = data_sz;

  /* make bpf_map__init_value() work for ARENA maps */
  map->mmaped = obj->arena_data;

  return 0;
}

static int bpf_object__init_user_btf_maps(struct bpf_object *obj, bool strict,
            const char *pin_root_path)
{
  const struct btf_type *sec = NULL;
  int nr_types, i, vlen, err;
  const struct btf_type *t;
  const char *name;
  Elf_Data *data;
  Elf_Scn *scn;

  if (obj->efile.btf_maps_shndx < 0)
    return 0;

  scn = elf_sec_by_idx(obj, obj->efile.btf_maps_shndx);
  data = elf_sec_data(obj, scn);
  if (!scn || !data) {
    pr_warn("elf: failed to get %s map definitions for %s\n",
      MAPS_ELF_SEC, obj->path);
    return -EINVAL;
  }

  nr_types = btf__type_cnt(obj->btf);
  for (i = 1; i < nr_types; i++) {
    t = btf__type_by_id(obj->btf, i);
    if (!btf_is_datasec(t))
      continue;
    name = btf__name_by_offset(obj->btf, t->name_off);
    if (strcmp(name, MAPS_ELF_SEC) == 0) {
      sec = t;
      obj->efile.btf_maps_sec_btf_id = i;
      break;
    }
  }

  if (!sec) {
    pr_warn("DATASEC '%s' not found.\n", MAPS_ELF_SEC);
    return -ENOENT;
  }

  vlen = btf_vlen(sec);
  for (i = 0; i < vlen; i++) {
    err = bpf_object__init_user_btf_map(obj, sec, i,
                obj->efile.btf_maps_shndx,
                data, strict,
                pin_root_path);
    if (err)
      return err;
  }

  for (i = 0; i < obj->nr_maps; i++) {
    struct bpf_map *map = &obj->maps[i];

    if (map->def.type != BPF_MAP_TYPE_ARENA)
      continue;

    if (obj->arena_map) {
      pr_warn("map '%s': only single ARENA map is supported (map '%s' is also ARENA)\n",
        map->name, obj->arena_map->name);
      return -EINVAL;
    }
    obj->arena_map = map;

    if (obj->efile.arena_data) {
      err = init_arena_map_data(obj, map, ARENA_SEC, obj->efile.arena_data_shndx,
              obj->efile.arena_data->d_buf,
              obj->efile.arena_data->d_size);
      if (err)
        return err;
    }
  }
  if (obj->efile.arena_data && !obj->arena_map) {
    pr_warn("elf: sec '%s': to use global __arena variables the ARENA map should be explicitly declared in SEC(\".maps\")\n",
      ARENA_SEC);
    return -ENOENT;
  }

  return 0;
}

static int bpf_object__init_maps(struct bpf_object *obj,
         const struct bpf_object_open_opts *opts)
{
  const char *pin_root_path;
  bool strict;
  int err = 0;

  strict = !OPTS_GET(opts, relaxed_maps, false);
  pin_root_path = OPTS_GET(opts, pin_root_path, NULL);

  err = bpf_object__init_user_btf_maps(obj, strict, pin_root_path);
  err = err ?: bpf_object__init_global_data_maps(obj);
  err = err ?: bpf_object__init_kconfig_map(obj);
  err = err ?: bpf_object_init_struct_ops(obj);

  return err;
}

static bool section_have_execinstr(struct bpf_object *obj, int idx)
{
  Elf64_Shdr *sh;

  sh = elf_sec_hdr(obj, elf_sec_by_idx(obj, idx));
  if (!sh)
    return false;

  return sh->sh_flags & SHF_EXECINSTR;
}

static bool starts_with_qmark(const char *s)
{
  return s && s[0] == '?';
}

static bool btf_needs_sanitization(struct bpf_object *obj)
{
  bool has_func_global = kernel_supports(obj, FEAT_BTF_GLOBAL_FUNC);
  bool has_datasec = kernel_supports(obj, FEAT_BTF_DATASEC);
  bool has_float = kernel_supports(obj, FEAT_BTF_FLOAT);
  bool has_func = kernel_supports(obj, FEAT_BTF_FUNC);
  bool has_decl_tag = kernel_supports(obj, FEAT_BTF_DECL_TAG);
  bool has_type_tag = kernel_supports(obj, FEAT_BTF_TYPE_TAG);
  bool has_enum64 = kernel_supports(obj, FEAT_BTF_ENUM64);
  bool has_qmark_datasec = kernel_supports(obj, FEAT_BTF_QMARK_DATASEC);

  return !has_func || !has_datasec || !has_func_global || !has_float ||
         !has_decl_tag || !has_type_tag || !has_enum64 || !has_qmark_datasec;
}

static int bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
{
  bool has_func_global = kernel_supports(obj, FEAT_BTF_GLOBAL_FUNC);
  bool has_datasec = kernel_supports(obj, FEAT_BTF_DATASEC);
  bool has_float = kernel_supports(obj, FEAT_BTF_FLOAT);
  bool has_func = kernel_supports(obj, FEAT_BTF_FUNC);
  bool has_decl_tag = kernel_supports(obj, FEAT_BTF_DECL_TAG);
  bool has_type_tag = kernel_supports(obj, FEAT_BTF_TYPE_TAG);
  bool has_enum64 = kernel_supports(obj, FEAT_BTF_ENUM64);
  bool has_qmark_datasec = kernel_supports(obj, FEAT_BTF_QMARK_DATASEC);
  int enum64_placeholder_id = 0;
  struct btf_type *t;
  int i, j, vlen;

  for (i = 1; i < btf__type_cnt(btf); i++) {
    t = (struct btf_type *)btf__type_by_id(btf, i);

    if ((!has_datasec && btf_is_var(t)) || (!has_decl_tag && btf_is_decl_tag(t))) {
      /* replace VAR/DECL_TAG with INT */
      t->info = BTF_INFO_ENC(BTF_KIND_INT, 0, 0);
      /*
       * using size = 1 is the safest choice, 4 will be too
       * big and cause kernel BTF validation failure if
       * original variable took less than 4 bytes
       */
      t->size = 1;
      *(int *)(t + 1) = BTF_INT_ENC(0, 0, 8);
    } else if (!has_datasec && btf_is_datasec(t)) {
      /* replace DATASEC with STRUCT */
      const struct btf_var_secinfo *v = btf_var_secinfos(t);
      struct btf_member *m = btf_members(t);
      struct btf_type *vt;
      char *name;

      name = (char *)btf__name_by_offset(btf, t->name_off);
      while (*name) {
        if (*name == '.' || *name == '?')
          *name = '_';
        name++;
      }

      vlen = btf_vlen(t);
      t->info = BTF_INFO_ENC(BTF_KIND_STRUCT, 0, vlen);
      for (j = 0; j < vlen; j++, v++, m++) {
        /* order of field assignments is important */
        m->offset = v->offset * 8;
        m->type = v->type;
        /* preserve variable name as member name */
        vt = (void *)btf__type_by_id(btf, v->type);
        m->name_off = vt->name_off;
      }
    } else if (!has_qmark_datasec && btf_is_datasec(t) &&
         starts_with_qmark(btf__name_by_offset(btf, t->name_off))) {
      /* replace '?' prefix with '_' for DATASEC names */
      char *name;

      name = (char *)btf__name_by_offset(btf, t->name_off);
      if (name[0] == '?')
        name[0] = '_';
    } else if (!has_func && btf_is_func_proto(t)) {
      /* replace FUNC_PROTO with ENUM */
      vlen = btf_vlen(t);
      t->info = BTF_INFO_ENC(BTF_KIND_ENUM, 0, vlen);
      t->size = sizeof(__u32); /* kernel enforced */
    } else if (!has_func && btf_is_func(t)) {
      /* replace FUNC with TYPEDEF */
      t->info = BTF_INFO_ENC(BTF_KIND_TYPEDEF, 0, 0);
    } else if (!has_func_global && btf_is_func(t)) {
      /* replace BTF_FUNC_GLOBAL with BTF_FUNC_STATIC */
      t->info = BTF_INFO_ENC(BTF_KIND_FUNC, 0, 0);
    } else if (!has_float && btf_is_float(t)) {
      /* replace FLOAT with an equally-sized empty STRUCT;
       * since C compilers do not accept e.g. "float" as a
       * valid struct name, make it anonymous
       */
      t->name_off = 0;
      t->info = BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 0);
    } else if (!has_type_tag && btf_is_type_tag(t)) {
      /* replace TYPE_TAG with a CONST */
      t->name_off = 0;
      t->info = BTF_INFO_ENC(BTF_KIND_CONST, 0, 0);
    } else if (!has_enum64 && btf_is_enum(t)) {
      /* clear the kflag */
      t->info = btf_type_info(btf_kind(t), btf_vlen(t), false);
    } else if (!has_enum64 && btf_is_enum64(t)) {
      /* replace ENUM64 with a union */
      struct btf_member *m;

      if (enum64_placeholder_id == 0) {
        enum64_placeholder_id = btf__add_int(btf, "enum64_placeholder", 1, 0);
        if (enum64_placeholder_id < 0)
          return enum64_placeholder_id;

        t = (struct btf_type *)btf__type_by_id(btf, i);
      }

      m = btf_members(t);
      vlen = btf_vlen(t);
      t->info = BTF_INFO_ENC(BTF_KIND_UNION, 0, vlen);
      for (j = 0; j < vlen; j++, m++) {
        m->type = enum64_placeholder_id;
        m->offset = 0;
      }
    }
  }

  return 0;
}

static bool libbpf_needs_btf(const struct bpf_object *obj)
{
  return obj->efile.btf_maps_shndx >= 0 ||
         obj->efile.has_st_ops ||
         obj->nr_extern > 0;
}

static bool kernel_needs_btf(const struct bpf_object *obj)
{
  return obj->efile.has_st_ops;
}

static int bpf_object__init_btf(struct bpf_object *obj,
        Elf_Data *btf_data,
        Elf_Data *btf_ext_data)
{
  int err = -ENOENT;

  if (btf_data) {
    obj->btf = btf__new(btf_data->d_buf, btf_data->d_size);
    err = libbpf_get_error(obj->btf);
    if (err) {
      obj->btf = NULL;
      pr_warn("Error loading ELF section %s: %d.\n", BTF_ELF_SEC, err);
      goto out;
    }
    /* enforce 8-byte pointers for BPF-targeted BTFs */
    btf__set_pointer_size(obj->btf, 8);
  }
  if (btf_ext_data) {
    struct btf_ext_info *ext_segs[3];
    int seg_num, sec_num;

    if (!obj->btf) {
      pr_debug("Ignore ELF section %s because its depending ELF section %s is not found.\n",
         BTF_EXT_ELF_SEC, BTF_ELF_SEC);
      goto out;
    }
    obj->btf_ext = btf_ext__new(btf_ext_data->d_buf, btf_ext_data->d_size);
    err = libbpf_get_error(obj->btf_ext);
    if (err) {
      pr_warn("Error loading ELF section %s: %d. Ignored and continue.\n",
        BTF_EXT_ELF_SEC, err);
      obj->btf_ext = NULL;
      goto out;
    }

    /* setup .BTF.ext to ELF section mapping */
    ext_segs[0] = &obj->btf_ext->func_info;
    ext_segs[1] = &obj->btf_ext->line_info;
    ext_segs[2] = &obj->btf_ext->core_relo_info;
    for (seg_num = 0; seg_num < ARRAY_SIZE(ext_segs); seg_num++) {
      struct btf_ext_info *seg = ext_segs[seg_num];
      const struct btf_ext_info_sec *sec;
      const char *sec_name;
      Elf_Scn *scn;

      if (seg->sec_cnt == 0)
        continue;

      seg->sec_idxs = calloc(seg->sec_cnt, sizeof(*seg->sec_idxs));
      if (!seg->sec_idxs) {
        err = -ENOMEM;
        goto out;
      }

      sec_num = 0;
      for_each_btf_ext_sec(seg, sec) {
        /* preventively increment index to avoid doing
         * this before every continue below
         */
        sec_num++;

        sec_name = btf__name_by_offset(obj->btf, sec->sec_name_off);
        if (str_is_empty(sec_name))
          continue;
        scn = elf_sec_by_name(obj, sec_name);
        if (!scn)
          continue;

        seg->sec_idxs[sec_num - 1] = elf_ndxscn(scn);
      }
    }
  }
out:
  if (err && libbpf_needs_btf(obj)) {
    pr_warn("BTF is required, but is missing or corrupted.\n");
    return err;
  }
  return 0;
}

static int compare_vsi_off(const void *_a, const void *_b)
{
  const struct btf_var_secinfo *a = _a;
  const struct btf_var_secinfo *b = _b;

  return a->offset - b->offset;
}

static int btf_fixup_datasec(struct bpf_object *obj, struct btf *btf,
           struct btf_type *t)
{
  __u32 size = 0, i, vars = btf_vlen(t);
  const char *sec_name = btf__name_by_offset(btf, t->name_off);
  struct btf_var_secinfo *vsi;
  bool fixup_offsets = false;
  int err;

  if (!sec_name) {
    pr_debug("No name found in string section for DATASEC kind.\n");
    return -ENOENT;
  }

  /* Extern-backing datasecs (.ksyms, .kconfig) have their size and
   * variable offsets set at the previous step. Further, not every
   * extern BTF VAR has corresponding ELF symbol preserved, so we skip
   * all fixups altogether for such sections and go straight to sorting
   * VARs within their DATASEC.
   */
  if (strcmp(sec_name, KCONFIG_SEC) == 0 || strcmp(sec_name, KSYMS_SEC) == 0)
    goto sort_vars;

  /* Clang leaves DATASEC size and VAR offsets as zeroes, so we need to
   * fix this up. But BPF static linker already fixes this up and fills
   * all the sizes and offsets during static linking. So this step has
   * to be optional. But the STV_HIDDEN handling is non-optional for any
   * non-extern DATASEC, so the variable fixup loop below handles both
   * functions at the same time, paying the cost of BTF VAR <-> ELF
   * symbol matching just once.
   */
  if (t->size == 0) {
    err = find_elf_sec_sz(obj, sec_name, &size);
    if (err || !size) {
      pr_debug("sec '%s': failed to determine size from ELF: size %u, err %d\n",
         sec_name, size, err);
      return -ENOENT;
    }

    t->size = size;
    fixup_offsets = true;
  }

  for (i = 0, vsi = btf_var_secinfos(t); i < vars; i++, vsi++) {
    const struct btf_type *t_var;
    struct btf_var *var;
    const char *var_name;
    Elf64_Sym *sym;

    t_var = btf__type_by_id(btf, vsi->type);
    if (!t_var || !btf_is_var(t_var)) {
      pr_debug("sec '%s': unexpected non-VAR type found\n", sec_name);
      return -EINVAL;
    }

    var = btf_var(t_var);
    if (var->linkage == BTF_VAR_STATIC || var->linkage == BTF_VAR_GLOBAL_EXTERN)
      continue;

    var_name = btf__name_by_offset(btf, t_var->name_off);
    if (!var_name) {
      pr_debug("sec '%s': failed to find name of DATASEC's member #%d\n",
         sec_name, i);
      return -ENOENT;
    }

    sym = find_elf_var_sym(obj, var_name);
    if (IS_ERR(sym)) {
      pr_debug("sec '%s': failed to find ELF symbol for VAR '%s'\n",
         sec_name, var_name);
      return -ENOENT;
    }

    if (fixup_offsets)
      vsi->offset = sym->st_value;

    /* if variable is a global/weak symbol, but has restricted
     * (STV_HIDDEN or STV_INTERNAL) visibility, mark its BTF VAR
     * as static. This follows similar logic for functions (BPF
     * subprogs) and influences libbpf's further decisions about
     * whether to make global data BPF array maps as
     * BPF_F_MMAPABLE.
     */
    if (ELF64_ST_VISIBILITY(sym->st_other) == STV_HIDDEN
        || ELF64_ST_VISIBILITY(sym->st_other) == STV_INTERNAL)
      var->linkage = BTF_VAR_STATIC;
  }

sort_vars:
  qsort(btf_var_secinfos(t), vars, sizeof(*vsi), compare_vsi_off);
  return 0;
}

static int bpf_object_fixup_btf(struct bpf_object *obj)
{
  int i, n, err = 0;

  if (!obj->btf)
    return 0;

  n = btf__type_cnt(obj->btf);
  for (i = 1; i < n; i++) {
    struct btf_type *t = btf_type_by_id(obj->btf, i);

    /* Loader needs to fix up some of the things compiler
     * couldn't get its hands on while emitting BTF. This
     * is section size and global variable offset. We use
     * the info from the ELF itself for this purpose.
     */
    if (btf_is_datasec(t)) {
      err = btf_fixup_datasec(obj, obj->btf, t);
      if (err)
        return err;
    }
  }

  return 0;
}

static bool prog_needs_vmlinux_btf(struct bpf_program *prog)
{
  if (prog->type == BPF_PROG_TYPE_STRUCT_OPS ||
      prog->type == BPF_PROG_TYPE_LSM)
    return true;

  /* BPF_PROG_TYPE_TRACING programs which do not attach to other programs
   * also need vmlinux BTF
   */
  if (prog->type == BPF_PROG_TYPE_TRACING && !prog->attach_prog_fd)
    return true;

  return false;
}

static bool map_needs_vmlinux_btf(struct bpf_map *map)
{
  return bpf_map__is_struct_ops(map);
}

static bool obj_needs_vmlinux_btf(const struct bpf_object *obj)
{
  struct bpf_program *prog;
  struct bpf_map *map;
  int i;

  /* CO-RE relocations need kernel BTF, only when btf_custom_path
   * is not specified
   */
  if (obj->btf_ext && obj->btf_ext->core_relo_info.len && !obj->btf_custom_path)
    return true;

  /* Support for typed ksyms needs kernel BTF */
  for (i = 0; i < obj->nr_extern; i++) {
    const struct extern_desc *ext;

    ext = &obj->externs[i];
    if (ext->type == EXT_KSYM && ext->ksym.type_id)
      return true;
  }

  bpf_object__for_each_program(prog, obj) {
    if (!prog->autoload)
      continue;
    if (prog_needs_vmlinux_btf(prog))
      return true;
  }

  bpf_object__for_each_map(map, obj) {
    if (map_needs_vmlinux_btf(map))
      return true;
  }

  return false;
}

static int bpf_object__load_vmlinux_btf(struct bpf_object *obj, bool force)
{
  int err;

  /* btf_vmlinux could be loaded earlier */
  if (obj->btf_vmlinux || obj->gen_loader)
    return 0;

  if (!force && !obj_needs_vmlinux_btf(obj))
    return 0;

  obj->btf_vmlinux = btf__load_vmlinux_btf();
  err = libbpf_get_error(obj->btf_vmlinux);
  if (err) {
    pr_warn("Error loading vmlinux BTF: %d\n", err);
    obj->btf_vmlinux = NULL;
    return err;
  }
  return 0;
}

static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
{
  struct btf *kern_btf = obj->btf;
  bool btf_mandatory, sanitize;
  int i, err = 0;

  if (!obj->btf)
    return 0;

  if (!kernel_supports(obj, FEAT_BTF)) {
    if (kernel_needs_btf(obj)) {
      err = -EOPNOTSUPP;
      goto report;
    }
    pr_debug("Kernel doesn't support BTF, skipping uploading it.\n");
    return 0;
  }

  /* Even though some subprogs are global/weak, user might prefer more
   * permissive BPF verification process that BPF verifier performs for
   * static functions, taking into account more context from the caller
   * functions. In such case, they need to mark such subprogs with
   * __attribute__((visibility("hidden"))) and libbpf will adjust
   * corresponding FUNC BTF type to be marked as static and trigger more
   * involved BPF verification process.
   */
  for (i = 0; i < obj->nr_programs; i++) {
    struct bpf_program *prog = &obj->programs[i];
    struct btf_type *t;
    const char *name;
    int j, n;

    if (!prog->mark_btf_static || !prog_is_subprog(obj, prog))
      continue;

    n = btf__type_cnt(obj->btf);
    for (j = 1; j < n; j++) {
      t = btf_type_by_id(obj->btf, j);
      if (!btf_is_func(t) || btf_func_linkage(t) != BTF_FUNC_GLOBAL)
        continue;

      name = btf__str_by_offset(obj->btf, t->name_off);
      if (strcmp(name, prog->name) != 0)
        continue;

      t->info = btf_type_info(BTF_KIND_FUNC, BTF_FUNC_STATIC, 0);
      break;
    }
  }

  sanitize = btf_needs_sanitization(obj);
  if (sanitize) {
    const void *raw_data;
    __u32 sz;

    /* clone BTF to sanitize a copy and leave the original intact */
    raw_data = btf__raw_data(obj->btf, &sz);
    kern_btf = btf__new(raw_data, sz);
    err = libbpf_get_error(kern_btf);
    if (err)
      return err;

    /* enforce 8-byte pointers for BPF-targeted BTFs */
    btf__set_pointer_size(obj->btf, 8);
    err = bpf_object__sanitize_btf(obj, kern_btf);
    if (err)
      return err;
  }

  if (obj->gen_loader) {
    __u32 raw_size = 0;
    const void *raw_data = btf__raw_data(kern_btf, &raw_size);

    if (!raw_data)
      return -ENOMEM;
    bpf_gen__load_btf(obj->gen_loader, raw_data, raw_size);
    /* Pretend to have valid FD to pass various fd >= 0 checks.
     * This fd == 0 will not be used with any syscall and will be reset to -1 eventually.
     */
    btf__set_fd(kern_btf, 0);
  } else {
    /* currently BPF_BTF_LOAD only supports log_level 1 */
    err = btf_load_into_kernel(kern_btf, obj->log_buf, obj->log_size,
             obj->log_level ? 1 : 0, obj->token_fd);
  }
  if (sanitize) {
    if (!err) {
      /* move fd to libbpf's BTF */
      btf__set_fd(obj->btf, btf__fd(kern_btf));
      btf__set_fd(kern_btf, -1);
    }
    btf__free(kern_btf);
  }
report:
  if (err) {
    btf_mandatory = kernel_needs_btf(obj);
    pr_warn("Error loading .BTF into kernel: %d. %s\n", err,
      btf_mandatory ? "BTF is mandatory, can't proceed."
              : "BTF is optional, ignoring.");
    if (!btf_mandatory)
      err = 0;
  }
  return err;
}

static const char *elf_sym_str(const struct bpf_object *obj, size_t off)
{
  const char *name;

  name = elf_strptr(obj->efile.elf, obj->efile.strtabidx, off);
  if (!name) {
    pr_warn("elf: failed to get section name string at offset %zu from %s: %s\n",
      off, obj->path, elf_errmsg(-1));
    return NULL;
  }

  return name;
}

static const char *elf_sec_str(const struct bpf_object *obj, size_t off)
{
  const char *name;

  name = elf_strptr(obj->efile.elf, obj->efile.shstrndx, off);
  if (!name) {
    pr_warn("elf: failed to get section name string at offset %zu from %s: %s\n",
      off, obj->path, elf_errmsg(-1));
    return NULL;
  }

  return name;
}

static Elf_Scn *elf_sec_by_idx(const struct bpf_object *obj, size_t idx)
{
  Elf_Scn *scn;

  scn = elf_getscn(obj->efile.elf, idx);
  if (!scn) {
    pr_warn("elf: failed to get section(%zu) from %s: %s\n",
      idx, obj->path, elf_errmsg(-1));
    return NULL;
  }
  return scn;
}

static Elf_Scn *elf_sec_by_name(const struct bpf_object *obj, const char *name)
{
  Elf_Scn *scn = NULL;
  Elf *elf = obj->efile.elf;
  const char *sec_name;

  while ((scn = elf_nextscn(elf, scn)) != NULL) {
    sec_name = elf_sec_name(obj, scn);
    if (!sec_name)
      return NULL;

    if (strcmp(sec_name, name) != 0)
      continue;

    return scn;
  }
  return NULL;
}

static Elf64_Shdr *elf_sec_hdr(const struct bpf_object *obj, Elf_Scn *scn)
{
  Elf64_Shdr *shdr;

  if (!scn)
    return NULL;

  shdr = elf64_getshdr(scn);
  if (!shdr) {
    pr_warn("elf: failed to get section(%zu) header from %s: %s\n",
      elf_ndxscn(scn), obj->path, elf_errmsg(-1));
    return NULL;
  }

  return shdr;
}

static const char *elf_sec_name(const struct bpf_object *obj, Elf_Scn *scn)
{
  const char *name;
  Elf64_Shdr *sh;

  if (!scn)
    return NULL;

  sh = elf_sec_hdr(obj, scn);
  if (!sh)
    return NULL;

  name = elf_sec_str(obj, sh->sh_name);
  if (!name) {
    pr_warn("elf: failed to get section(%zu) name from %s: %s\n",
      elf_ndxscn(scn), obj->path, elf_errmsg(-1));
    return NULL;
  }

  return name;
}

static Elf_Data *elf_sec_data(const struct bpf_object *obj, Elf_Scn *scn)
{
  Elf_Data *data;

  if (!scn)
    return NULL;

  data = elf_getdata(scn, 0);
  if (!data) {
    pr_warn("elf: failed to get section(%zu) %s data from %s: %s\n",
      elf_ndxscn(scn), elf_sec_name(obj, scn) ?: "<?>",
      obj->path, elf_errmsg(-1));
    return NULL;
  }

  return data;
}

static Elf64_Sym *elf_sym_by_idx(const struct bpf_object *obj, size_t idx)
{
  if (idx >= obj->efile.symbols->d_size / sizeof(Elf64_Sym))
    return NULL;

  return (Elf64_Sym *)obj->efile.symbols->d_buf + idx;
}

static Elf64_Rel *elf_rel_by_idx(Elf_Data *data, size_t idx)
{
  if (idx >= data->d_size / sizeof(Elf64_Rel))
    return NULL;

  return (Elf64_Rel *)data->d_buf + idx;
}

static bool is_sec_name_dwarf(const char *name)
{
  /* approximation, but the actual list is too long */
  return str_has_pfx(name, ".debug_");
}

static bool ignore_elf_section(Elf64_Shdr *hdr, const char *name)
{
  /* no special handling of .strtab */
  if (hdr->sh_type == SHT_STRTAB)
    return true;

  /* ignore .llvm_addrsig section as well */
  if (hdr->sh_type == SHT_LLVM_ADDRSIG)
    return true;

  /* no subprograms will lead to an empty .text section, ignore it */
  if (hdr->sh_type == SHT_PROGBITS && hdr->sh_size == 0 &&
      strcmp(name, ".text") == 0)
    return true;

  /* DWARF sections */
  if (is_sec_name_dwarf(name))
    return true;

  if (str_has_pfx(name, ".rel")) {
    name += sizeof(".rel") - 1;
    /* DWARF section relocations */
    if (is_sec_name_dwarf(name))
      return true;

    /* .BTF and .BTF.ext don't need relocations */
    if (strcmp(name, BTF_ELF_SEC) == 0 ||
        strcmp(name, BTF_EXT_ELF_SEC) == 0)
      return true;
  }

  return false;
}

static int cmp_progs(const void *_a, const void *_b)
{
  const struct bpf_program *a = _a;
  const struct bpf_program *b = _b;

  if (a->sec_idx != b->sec_idx)
    return a->sec_idx < b->sec_idx ? -1 : 1;

  /* sec_insn_off can't be the same within the section */
  return a->sec_insn_off < b->sec_insn_off ? -1 : 1;
}

static int bpf_object__elf_collect(struct bpf_object *obj)
{
  struct elf_sec_desc *sec_desc;
  Elf *elf = obj->efile.elf;
  Elf_Data *btf_ext_data = NULL;
  Elf_Data *btf_data = NULL;
  int idx = 0, err = 0;
  const char *name;
  Elf_Data *data;
  Elf_Scn *scn;
  Elf64_Shdr *sh;

  /* ELF section indices are 0-based, but sec #0 is special "invalid"
   * section. Since section count retrieved by elf_getshdrnum() does
   * include sec #0, it is already the necessary size of an array to keep
   * all the sections.
   */
  if (elf_getshdrnum(obj->efile.elf, &obj->efile.sec_cnt)) {
    pr_warn("elf: failed to get the number of sections for %s: %s\n",
      obj->path, elf_errmsg(-1));
    return -LIBBPF_ERRNO__FORMAT;
  }
  obj->efile.secs = calloc(obj->efile.sec_cnt, sizeof(*obj->efile.secs));
  if (!obj->efile.secs)
    return -ENOMEM;

  /* a bunch of ELF parsing functionality depends on processing symbols,
   * so do the first pass and find the symbol table
   */
  scn = NULL;
  while ((scn = elf_nextscn(elf, scn)) != NULL) {
    sh = elf_sec_hdr(obj, scn);
    if (!sh)
      return -LIBBPF_ERRNO__FORMAT;

    if (sh->sh_type == SHT_SYMTAB) {
      if (obj->efile.symbols) {
        pr_warn("elf: multiple symbol tables in %s\n", obj->path);
        return -LIBBPF_ERRNO__FORMAT;
      }

      data = elf_sec_data(obj, scn);
      if (!data)
        return -LIBBPF_ERRNO__FORMAT;

      idx = elf_ndxscn(scn);

      obj->efile.symbols = data;
      obj->efile.symbols_shndx = idx;
      obj->efile.strtabidx = sh->sh_link;
    }
  }

  if (!obj->efile.symbols) {
    pr_warn("elf: couldn't find symbol table in %s, stripped object file?\n",
      obj->path);
    return -ENOENT;
  }

  scn = NULL;
  while ((scn = elf_nextscn(elf, scn)) != NULL) {
    idx = elf_ndxscn(scn);
    sec_desc = &obj->efile.secs[idx];

    sh = elf_sec_hdr(obj, scn);
    if (!sh)
      return -LIBBPF_ERRNO__FORMAT;

    name = elf_sec_str(obj, sh->sh_name);
    if (!name)
      return -LIBBPF_ERRNO__FORMAT;

    if (ignore_elf_section(sh, name))
      continue;

    data = elf_sec_data(obj, scn);
    if (!data)
      return -LIBBPF_ERRNO__FORMAT;

    pr_debug("elf: section(%d) %s, size %ld, link %d, flags %lx, type=%d\n",
       idx, name, (unsigned long)data->d_size,
       (int)sh->sh_link, (unsigned long)sh->sh_flags,
       (int)sh->sh_type);

    if (strcmp(name, "license") == 0) {
      err = bpf_object__init_license(obj, data->d_buf, data->d_size);
      if (err)
        return err;
    } else if (strcmp(name, "version") == 0) {
      err = bpf_object__init_kversion(obj, data->d_buf, data->d_size);
      if (err)
        return err;
    } else if (strcmp(name, "maps") == 0) {
      pr_warn("elf: legacy map definitions in 'maps' section are not supported by libbpf v1.0+\n");
      return -ENOTSUP;
    } else if (strcmp(name, MAPS_ELF_SEC) == 0) {
      obj->efile.btf_maps_shndx = idx;
    } else if (strcmp(name, BTF_ELF_SEC) == 0) {
      if (sh->sh_type != SHT_PROGBITS)
        return -LIBBPF_ERRNO__FORMAT;
      btf_data = data;
    } else if (strcmp(name, BTF_EXT_ELF_SEC) == 0) {
      if (sh->sh_type != SHT_PROGBITS)
        return -LIBBPF_ERRNO__FORMAT;
      btf_ext_data = data;
    } else if (sh->sh_type == SHT_SYMTAB) {
      /* already processed during the first pass above */
    } else if (sh->sh_type == SHT_PROGBITS && data->d_size > 0) {
      if (sh->sh_flags & SHF_EXECINSTR) {
        if (strcmp(name, ".text") == 0)
          obj->efile.text_shndx = idx;
        err = bpf_object__add_programs(obj, data, name, idx);
        if (err)
          return err;
      } else if (strcmp(name, DATA_SEC) == 0 ||
           str_has_pfx(name, DATA_SEC ".")) {
        sec_desc->sec_type = SEC_DATA;
        sec_desc->shdr = sh;
        sec_desc->data = data;
      } else if (strcmp(name, RODATA_SEC) == 0 ||
           str_has_pfx(name, RODATA_SEC ".")) {
        sec_desc->sec_type = SEC_RODATA;
        sec_desc->shdr = sh;
        sec_desc->data = data;
      } else if (strcmp(name, STRUCT_OPS_SEC) == 0 ||
           strcmp(name, STRUCT_OPS_LINK_SEC) == 0 ||
           strcmp(name, "?" STRUCT_OPS_SEC) == 0 ||
           strcmp(name, "?" STRUCT_OPS_LINK_SEC) == 0) {
        sec_desc->sec_type = SEC_ST_OPS;
        sec_desc->shdr = sh;
        sec_desc->data = data;
        obj->efile.has_st_ops = true;
      } else if (strcmp(name, ARENA_SEC) == 0) {
        obj->efile.arena_data = data;
        obj->efile.arena_data_shndx = idx;
      } else {
        pr_info("elf: skipping unrecognized data section(%d) %s\n",
          idx, name);
      }
    } else if (sh->sh_type == SHT_REL) {
      int targ_sec_idx = sh->sh_info; /* points to other section */

      if (sh->sh_entsize != sizeof(Elf64_Rel) ||
          targ_sec_idx >= obj->efile.sec_cnt)
        return -LIBBPF_ERRNO__FORMAT;

      /* Only do relo for section with exec instructions */
      if (!section_have_execinstr(obj, targ_sec_idx) &&
          strcmp(name, ".rel" STRUCT_OPS_SEC) &&
          strcmp(name, ".rel" STRUCT_OPS_LINK_SEC) &&
          strcmp(name, ".rel?" STRUCT_OPS_SEC) &&
          strcmp(name, ".rel?" STRUCT_OPS_LINK_SEC) &&
          strcmp(name, ".rel" MAPS_ELF_SEC)) {
        pr_info("elf: skipping relo section(%d) %s for section(%d) %s\n",
          idx, name, targ_sec_idx,
          elf_sec_name(obj, elf_sec_by_idx(obj, targ_sec_idx)) ?: "<?>");
        continue;
      }

      sec_desc->sec_type = SEC_RELO;
      sec_desc->shdr = sh;
      sec_desc->data = data;
    } else if (sh->sh_type == SHT_NOBITS && (strcmp(name, BSS_SEC) == 0 ||
               str_has_pfx(name, BSS_SEC "."))) {
      sec_desc->sec_type = SEC_BSS;
      sec_desc->shdr = sh;
      sec_desc->data = data;
    } else {
      pr_info("elf: skipping section(%d) %s (size %zu)\n", idx, name,
        (size_t)sh->sh_size);
    }
  }

  if (!obj->efile.strtabidx || obj->efile.strtabidx > idx) {
    pr_warn("elf: symbol strings section missing or invalid in %s\n", obj->path);
    return -LIBBPF_ERRNO__FORMAT;
  }

  /* sort BPF programs by section name and in-section instruction offset
   * for faster search
   */
  if (obj->nr_programs)
    qsort(obj->programs, obj->nr_programs, sizeof(*obj->programs), cmp_progs);

  return bpf_object__init_btf(obj, btf_data, btf_ext_data);
}

static bool sym_is_extern(const Elf64_Sym *sym)
{
  int bind = ELF64_ST_BIND(sym->st_info);
  /* externs are symbols w/ type=NOTYPE, bind=GLOBAL|WEAK, section=UND */
  return sym->st_shndx == SHN_UNDEF &&
         (bind == STB_GLOBAL || bind == STB_WEAK) &&
         ELF64_ST_TYPE(sym->st_info) == STT_NOTYPE;
}

static bool sym_is_subprog(const Elf64_Sym *sym, int text_shndx)
{
  int bind = ELF64_ST_BIND(sym->st_info);
  int type = ELF64_ST_TYPE(sym->st_info);

  /* in .text section */
  if (sym->st_shndx != text_shndx)
    return false;

  /* local function */
  if (bind == STB_LOCAL && type == STT_SECTION)
    return true;

  /* global function */
  return bind == STB_GLOBAL && type == STT_FUNC;
}

static int find_extern_btf_id(const struct btf *btf, const char *ext_name)
{
  const struct btf_type *t;
  const char *tname;
  int i, n;

  if (!btf)
    return -ESRCH;

  n = btf__type_cnt(btf);
  for (i = 1; i < n; i++) {
    t = btf__type_by_id(btf, i);

    if (!btf_is_var(t) && !btf_is_func(t))
      continue;

    tname = btf__name_by_offset(btf, t->name_off);
    if (strcmp(tname, ext_name))
      continue;

    if (btf_is_var(t) &&
        btf_var(t)->linkage != BTF_VAR_GLOBAL_EXTERN)
      return -EINVAL;

    if (btf_is_func(t) && btf_func_linkage(t) != BTF_FUNC_EXTERN)
      return -EINVAL;

    return i;
  }

  return -ENOENT;
}

static int find_extern_sec_btf_id(struct btf *btf, int ext_btf_id) {
  const struct btf_var_secinfo *vs;
  const struct btf_type *t;
  int i, j, n;

  if (!btf)
    return -ESRCH;

  n = btf__type_cnt(btf);
  for (i = 1; i < n; i++) {
    t = btf__type_by_id(btf, i);

    if (!btf_is_datasec(t))
      continue;

    vs = btf_var_secinfos(t);
    for (j = 0; j < btf_vlen(t); j++, vs++) {
      if (vs->type == ext_btf_id)
        return i;
    }
  }

  return -ENOENT;
}

static enum kcfg_type find_kcfg_type(const struct btf *btf, int id,
             bool *is_signed)
{
  const struct btf_type *t;
  const char *name;

  t = skip_mods_and_typedefs(btf, id, NULL);
  name = btf__name_by_offset(btf, t->name_off);

  if (is_signed)
    *is_signed = false;
  switch (btf_kind(t)) {
  case BTF_KIND_INT: {
    int enc = btf_int_encoding(t);

    if (enc & BTF_INT_BOOL)
      return t->size == 1 ? KCFG_BOOL : KCFG_UNKNOWN;
    if (is_signed)
      *is_signed = enc & BTF_INT_SIGNED;
    if (t->size == 1)
      return KCFG_CHAR;
    if (t->size < 1 || t->size > 8 || (t->size & (t->size - 1)))
      return KCFG_UNKNOWN;
    return KCFG_INT;
  }
  case BTF_KIND_ENUM:
    if (t->size != 4)
      return KCFG_UNKNOWN;
    if (strcmp(name, "libbpf_tristate"))
      return KCFG_UNKNOWN;
    return KCFG_TRISTATE;
  case BTF_KIND_ENUM64:
    if (strcmp(name, "libbpf_tristate"))
      return KCFG_UNKNOWN;
    return KCFG_TRISTATE;
  case BTF_KIND_ARRAY:
    if (btf_array(t)->nelems == 0)
      return KCFG_UNKNOWN;
    if (find_kcfg_type(btf, btf_array(t)->type, NULL) != KCFG_CHAR)
      return KCFG_UNKNOWN;
    return KCFG_CHAR_ARR;
  default:
    return KCFG_UNKNOWN;
  }
}

static int cmp_externs(const void *_a, const void *_b)
{
  const struct extern_desc *a = _a;
  const struct extern_desc *b = _b;

  if (a->type != b->type)
    return a->type < b->type ? -1 : 1;

  if (a->type == EXT_KCFG) {
    /* descending order by alignment requirements */
    if (a->kcfg.align != b->kcfg.align)
      return a->kcfg.align > b->kcfg.align ? -1 : 1;
    /* ascending order by size, within same alignment class */
    if (a->kcfg.sz != b->kcfg.sz)
      return a->kcfg.sz < b->kcfg.sz ? -1 : 1;
  }

  /* resolve ties by name */
  return strcmp(a->name, b->name);
}

static int find_int_btf_id(const struct btf *btf)
{
  const struct btf_type *t;
  int i, n;

  n = btf__type_cnt(btf);
  for (i = 1; i < n; i++) {
    t = btf__type_by_id(btf, i);

    if (btf_is_int(t) && btf_int_bits(t) == 32)
      return i;
  }

  return 0;
}

static int add_dummy_ksym_var(struct btf *btf)
{
  int i, int_btf_id, sec_btf_id, dummy_var_btf_id;
  const struct btf_var_secinfo *vs;
  const struct btf_type *sec;

  if (!btf)
    return 0;

  sec_btf_id = btf__find_by_name_kind(btf, KSYMS_SEC,
              BTF_KIND_DATASEC);
  if (sec_btf_id < 0)
    return 0;

  sec = btf__type_by_id(btf, sec_btf_id);
  vs = btf_var_secinfos(sec);
  for (i = 0; i < btf_vlen(sec); i++, vs++) {
    const struct btf_type *vt;

    vt = btf__type_by_id(btf, vs->type);
    if (btf_is_func(vt))
      break;
  }

  /* No func in ksyms sec.  No need to add dummy var. */
  if (i == btf_vlen(sec))
    return 0;

  int_btf_id = find_int_btf_id(btf);
  dummy_var_btf_id = btf__add_var(btf,
          "dummy_ksym",
          BTF_VAR_GLOBAL_ALLOCATED,
          int_btf_id);
  if (dummy_var_btf_id < 0)
    pr_warn("cannot create a dummy_ksym var\n");

  return dummy_var_btf_id;
}

static int bpf_object__collect_externs(struct bpf_object *obj)
{
  struct btf_type *sec, *kcfg_sec = NULL, *ksym_sec = NULL;
  const struct btf_type *t;
  struct extern_desc *ext;
  int i, n, off, dummy_var_btf_id;
  const char *ext_name, *sec_name;
  size_t ext_essent_len;
  Elf_Scn *scn;
  Elf64_Shdr *sh;

  if (!obj->efile.symbols)
    return 0;

  scn = elf_sec_by_idx(obj, obj->efile.symbols_shndx);
  sh = elf_sec_hdr(obj, scn);
  if (!sh || sh->sh_entsize != sizeof(Elf64_Sym))
    return -LIBBPF_ERRNO__FORMAT;

  dummy_var_btf_id = add_dummy_ksym_var(obj->btf);
  if (dummy_var_btf_id < 0)
    return dummy_var_btf_id;

  n = sh->sh_size / sh->sh_entsize;
  pr_debug("looking for externs among %d symbols...\n", n);

  for (i = 0; i < n; i++) {
    Elf64_Sym *sym = elf_sym_by_idx(obj, i);

    if (!sym)
      return -LIBBPF_ERRNO__FORMAT;
    if (!sym_is_extern(sym))
      continue;
    ext_name = elf_sym_str(obj, sym->st_name);
    if (!ext_name || !ext_name[0])
      continue;

    ext = obj->externs;
    ext = libbpf_reallocarray(ext, obj->nr_extern + 1, sizeof(*ext));
    if (!ext)
      return -ENOMEM;
    obj->externs = ext;
    ext = &ext[obj->nr_extern];
    memset(ext, 0, sizeof(*ext));
    obj->nr_extern++;

    ext->btf_id = find_extern_btf_id(obj->btf, ext_name);
    if (ext->btf_id <= 0) {
      pr_warn("failed to find BTF for extern '%s': %d\n",
        ext_name, ext->btf_id);
      return ext->btf_id;
    }
    t = btf__type_by_id(obj->btf, ext->btf_id);
    ext->name = btf__name_by_offset(obj->btf, t->name_off);
    ext->sym_idx = i;
    ext->is_weak = ELF64_ST_BIND(sym->st_info) == STB_WEAK;

    ext_essent_len = bpf_core_essential_name_len(ext->name);
    ext->essent_name = NULL;
    if (ext_essent_len != strlen(ext->name)) {
      ext->essent_name = strndup(ext->name, ext_essent_len);
      if (!ext->essent_name)
        return -ENOMEM;
    }

    ext->sec_btf_id = find_extern_sec_btf_id(obj->btf, ext->btf_id);
    if (ext->sec_btf_id <= 0) {
      pr_warn("failed to find BTF for extern '%s' [%d] section: %d\n",
        ext_name, ext->btf_id, ext->sec_btf_id);
      return ext->sec_btf_id;
    }
    sec = (void *)btf__type_by_id(obj->btf, ext->sec_btf_id);
    sec_name = btf__name_by_offset(obj->btf, sec->name_off);

    if (strcmp(sec_name, KCONFIG_SEC) == 0) {
      if (btf_is_func(t)) {
        pr_warn("extern function %s is unsupported under %s section\n",
          ext->name, KCONFIG_SEC);
        return -ENOTSUP;
      }
      kcfg_sec = sec;
      ext->type = EXT_KCFG;
      ext->kcfg.sz = btf__resolve_size(obj->btf, t->type);
      if (ext->kcfg.sz <= 0) {
        pr_warn("failed to resolve size of extern (kcfg) '%s': %d\n",
          ext_name, ext->kcfg.sz);
        return ext->kcfg.sz;
      }
      ext->kcfg.align = btf__align_of(obj->btf, t->type);
      if (ext->kcfg.align <= 0) {
        pr_warn("failed to determine alignment of extern (kcfg) '%s': %d\n",
          ext_name, ext->kcfg.align);
        return -EINVAL;
      }
      ext->kcfg.type = find_kcfg_type(obj->btf, t->type,
              &ext->kcfg.is_signed);
      if (ext->kcfg.type == KCFG_UNKNOWN) {
        pr_warn("extern (kcfg) '%s': type is unsupported\n", ext_name);
        return -ENOTSUP;
      }
    } else if (strcmp(sec_name, KSYMS_SEC) == 0) {
      ksym_sec = sec;
      ext->type = EXT_KSYM;
      skip_mods_and_typedefs(obj->btf, t->type,
                 &ext->ksym.type_id);
    } else {
      pr_warn("unrecognized extern section '%s'\n", sec_name);
      return -ENOTSUP;
    }
  }
  pr_debug("collected %d externs total\n", obj->nr_extern);

  if (!obj->nr_extern)
    return 0;

  /* sort externs by type, for kcfg ones also by (align, size, name) */
  qsort(obj->externs, obj->nr_extern, sizeof(*ext), cmp_externs);

  /* for .ksyms section, we need to turn all externs into allocated
   * variables in BTF to pass kernel verification; we do this by
   * pretending that each extern is a 8-byte variable
   */
  if (ksym_sec) {
    /* find existing 4-byte integer type in BTF to use for fake
     * extern variables in DATASEC
     */
    int int_btf_id = find_int_btf_id(obj->btf);
    /* For extern function, a dummy_var added earlier
     * will be used to replace the vs->type and
     * its name string will be used to refill
     * the missing param's name.
     */
    const struct btf_type *dummy_var;

    dummy_var = btf__type_by_id(obj->btf, dummy_var_btf_id);
    for (i = 0; i < obj->nr_extern; i++) {
      ext = &obj->externs[i];
      if (ext->type != EXT_KSYM)
        continue;
      pr_debug("extern (ksym) #%d: symbol %d, name %s\n",
         i, ext->sym_idx, ext->name);
    }

    sec = ksym_sec;
    n = btf_vlen(sec);
    for (i = 0, off = 0; i < n; i++, off += sizeof(int)) {
      struct btf_var_secinfo *vs = btf_var_secinfos(sec) + i;
      struct btf_type *vt;

      vt = (void *)btf__type_by_id(obj->btf, vs->type);
      ext_name = btf__name_by_offset(obj->btf, vt->name_off);
      ext = find_extern_by_name(obj, ext_name);
      if (!ext) {
        pr_warn("failed to find extern definition for BTF %s '%s'\n",
          btf_kind_str(vt), ext_name);
        return -ESRCH;
      }
      if (btf_is_func(vt)) {
        const struct btf_type *func_proto;
        struct btf_param *param;
        int j;

        func_proto = btf__type_by_id(obj->btf,
                   vt->type);
        param = btf_params(func_proto);
        /* Reuse the dummy_var string if the
         * func proto does not have param name.
         */
        for (j = 0; j < btf_vlen(func_proto); j++)
          if (param[j].type && !param[j].name_off)
            param[j].name_off =
              dummy_var->name_off;
        vs->type = dummy_var_btf_id;
        vt->info &= ~0xffff;
        vt->info |= BTF_FUNC_GLOBAL;
      } else {
        btf_var(vt)->linkage = BTF_VAR_GLOBAL_ALLOCATED;
        vt->type = int_btf_id;
      }
      vs->offset = off;
      vs->size = sizeof(int);
    }
    sec->size = off;
  }

  if (kcfg_sec) {
    sec = kcfg_sec;
    /* for kcfg externs calculate their offsets within a .kconfig map */
    off = 0;
    for (i = 0; i < obj->nr_extern; i++) {
      ext = &obj->externs[i];
      if (ext->type != EXT_KCFG)
        continue;

      ext->kcfg.data_off = roundup(off, ext->kcfg.align);
      off = ext->kcfg.data_off + ext->kcfg.sz;
      pr_debug("extern (kcfg) #%d: symbol %d, off %u, name %s\n",
         i, ext->sym_idx, ext->kcfg.data_off, ext->name);
    }
    sec->size = off;
    n = btf_vlen(sec);
    for (i = 0; i < n; i++) {
      struct btf_var_secinfo *vs = btf_var_secinfos(sec) + i;

      t = btf__type_by_id(obj->btf, vs->type);
      ext_name = btf__name_by_offset(obj->btf, t->name_off);
      ext = find_extern_by_name(obj, ext_name);
      if (!ext) {
        pr_warn("failed to find extern definition for BTF var '%s'\n",
          ext_name);
        return -ESRCH;
      }
      btf_var(t)->linkage = BTF_VAR_GLOBAL_ALLOCATED;
      vs->offset = ext->kcfg.data_off;
    }
  }
  return 0;
}

static bool prog_is_subprog(const struct bpf_object *obj, const struct bpf_program *prog)
{
  return prog->sec_idx == obj->efile.text_shndx && obj->nr_programs > 1;
}

struct bpf_program *
bpf_object__find_program_by_name(const struct bpf_object *obj,
         const char *name)
{
  struct bpf_program *prog;

  bpf_object__for_each_program(prog, obj) {
    if (prog_is_subprog(obj, prog))
      continue;
    if (!strcmp(prog->name, name))
      return prog;
  }
  return errno = ENOENT, NULL;
}

static bool bpf_object__shndx_is_data(const struct bpf_object *obj,
              int shndx)
{
  switch (obj->efile.secs[shndx].sec_type) {
  case SEC_BSS:
  case SEC_DATA:
  case SEC_RODATA:
    return true;
  default:
    return false;
  }
}

static bool bpf_object__shndx_is_maps(const struct bpf_object *obj,
              int shndx)
{
  return shndx == obj->efile.btf_maps_shndx;
}

static enum libbpf_map_type
bpf_object__section_to_libbpf_map_type(const struct bpf_object *obj, int shndx)
{
  if (shndx == obj->efile.symbols_shndx)
    return LIBBPF_MAP_KCONFIG;

  switch (obj->efile.secs[shndx].sec_type) {
  case SEC_BSS:
    return LIBBPF_MAP_BSS;
  case SEC_DATA:
    return LIBBPF_MAP_DATA;
  case SEC_RODATA:
    return LIBBPF_MAP_RODATA;
  default:
    return LIBBPF_MAP_UNSPEC;
  }
}

static int bpf_program__record_reloc(struct bpf_program *prog,
             struct reloc_desc *reloc_desc,
             __u32 insn_idx, const char *sym_name,
             const Elf64_Sym *sym, const Elf64_Rel *rel)
{
  struct bpf_insn *insn = &prog->insns[insn_idx];
  size_t map_idx, nr_maps = prog->obj->nr_maps;
  struct bpf_object *obj = prog->obj;
  __u32 shdr_idx = sym->st_shndx;
  enum libbpf_map_type type;
  const char *sym_sec_name;
  struct bpf_map *map;

  if (!is_call_insn(insn) && !is_ldimm64_insn(insn)) {
    pr_warn("prog '%s': invalid relo against '%s' for insns[%d].code 0x%x\n",
      prog->name, sym_name, insn_idx, insn->code);
    return -LIBBPF_ERRNO__RELOC;
  }

  if (sym_is_extern(sym)) {
    int sym_idx = ELF64_R_SYM(rel->r_info);
    int i, n = obj->nr_extern;
    struct extern_desc *ext;

    for (i = 0; i < n; i++) {
      ext = &obj->externs[i];
      if (ext->sym_idx == sym_idx)
        break;
    }
    if (i >= n) {
      pr_warn("prog '%s': extern relo failed to find extern for '%s' (%d)\n",
        prog->name, sym_name, sym_idx);
      return -LIBBPF_ERRNO__RELOC;
    }
    pr_debug("prog '%s': found extern #%d '%s' (sym %d) for insn #%u\n",
       prog->name, i, ext->name, ext->sym_idx, insn_idx);
    if (insn->code == (BPF_JMP | BPF_CALL))
      reloc_desc->type = RELO_EXTERN_CALL;
    else
      reloc_desc->type = RELO_EXTERN_LD64;
    reloc_desc->insn_idx = insn_idx;
    reloc_desc->ext_idx = i;
    return 0;
  }

  /* sub-program call relocation */
  if (is_call_insn(insn)) {
    if (insn->src_reg != BPF_PSEUDO_CALL) {
      pr_warn("prog '%s': incorrect bpf_call opcode\n", prog->name);
      return -LIBBPF_ERRNO__RELOC;
    }
    /* text_shndx can be 0, if no default "main" program exists */
    if (!shdr_idx || shdr_idx != obj->efile.text_shndx) {
      sym_sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, shdr_idx));
      pr_warn("prog '%s': bad call relo against '%s' in section '%s'\n",
        prog->name, sym_name, sym_sec_name);
      return -LIBBPF_ERRNO__RELOC;
    }
    if (sym->st_value % BPF_INSN_SZ) {
      pr_warn("prog '%s': bad call relo against '%s' at offset %zu\n",
        prog->name, sym_name, (size_t)sym->st_value);
      return -LIBBPF_ERRNO__RELOC;
    }
    reloc_desc->type = RELO_CALL;
    reloc_desc->insn_idx = insn_idx;
    reloc_desc->sym_off = sym->st_value;
    return 0;
  }

  if (!shdr_idx || shdr_idx >= SHN_LORESERVE) {
    pr_warn("prog '%s': invalid relo against '%s' in special section 0x%x; forgot to initialize global var?..\n",
      prog->name, sym_name, shdr_idx);
    return -LIBBPF_ERRNO__RELOC;
  }

  /* loading subprog addresses */
  if (sym_is_subprog(sym, obj->efile.text_shndx)) {
    /* global_func: sym->st_value = offset in the section, insn->imm = 0.
     * local_func: sym->st_value = 0, insn->imm = offset in the section.
     */
    if ((sym->st_value % BPF_INSN_SZ) || (insn->imm % BPF_INSN_SZ)) {
      pr_warn("prog '%s': bad subprog addr relo against '%s' at offset %zu+%d\n",
        prog->name, sym_name, (size_t)sym->st_value, insn->imm);
      return -LIBBPF_ERRNO__RELOC;
    }

    reloc_desc->type = RELO_SUBPROG_ADDR;
    reloc_desc->insn_idx = insn_idx;
    reloc_desc->sym_off = sym->st_value;
    return 0;
  }

  type = bpf_object__section_to_libbpf_map_type(obj, shdr_idx);
  sym_sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, shdr_idx));

  /* arena data relocation */
  if (shdr_idx == obj->efile.arena_data_shndx) {
    reloc_desc->type = RELO_DATA;
    reloc_desc->insn_idx = insn_idx;
    reloc_desc->map_idx = obj->arena_map - obj->maps;
    reloc_desc->sym_off = sym->st_value;
    return 0;
  }

  /* generic map reference relocation */
  if (type == LIBBPF_MAP_UNSPEC) {
    if (!bpf_object__shndx_is_maps(obj, shdr_idx)) {
      pr_warn("prog '%s': bad map relo against '%s' in section '%s'\n",
        prog->name, sym_name, sym_sec_name);
      return -LIBBPF_ERRNO__RELOC;
    }
    for (map_idx = 0; map_idx < nr_maps; map_idx++) {
      map = &obj->maps[map_idx];
      if (map->libbpf_type != type ||
          map->sec_idx != sym->st_shndx ||
          map->sec_offset != sym->st_value)
        continue;
      pr_debug("prog '%s': found map %zd (%s, sec %d, off %zu) for insn #%u\n",
         prog->name, map_idx, map->name, map->sec_idx,
         map->sec_offset, insn_idx);
      break;
    }
    if (map_idx >= nr_maps) {
      pr_warn("prog '%s': map relo failed to find map for section '%s', off %zu\n",
        prog->name, sym_sec_name, (size_t)sym->st_value);
      return -LIBBPF_ERRNO__RELOC;
    }
    reloc_desc->type = RELO_LD64;
    reloc_desc->insn_idx = insn_idx;
    reloc_desc->map_idx = map_idx;
    reloc_desc->sym_off = 0; /* sym->st_value determines map_idx */
    return 0;
  }

  /* global data map relocation */
  if (!bpf_object__shndx_is_data(obj, shdr_idx)) {
    pr_warn("prog '%s': bad data relo against section '%s'\n",
      prog->name, sym_sec_name);
    return -LIBBPF_ERRNO__RELOC;
  }
  for (map_idx = 0; map_idx < nr_maps; map_idx++) {
    map = &obj->maps[map_idx];
    if (map->libbpf_type != type || map->sec_idx != sym->st_shndx)
      continue;
    pr_debug("prog '%s': found data map %zd (%s, sec %d, off %zu) for insn %u\n",
       prog->name, map_idx, map->name, map->sec_idx,
       map->sec_offset, insn_idx);
    break;
  }
  if (map_idx >= nr_maps) {
    pr_warn("prog '%s': data relo failed to find map for section '%s'\n",
      prog->name, sym_sec_name);
    return -LIBBPF_ERRNO__RELOC;
  }

  reloc_desc->type = RELO_DATA;
  reloc_desc->insn_idx = insn_idx;
  reloc_desc->map_idx = map_idx;
  reloc_desc->sym_off = sym->st_value;
  return 0;
}

static bool prog_contains_insn(const struct bpf_program *prog, size_t insn_idx)
{
  return insn_idx >= prog->sec_insn_off &&
         insn_idx < prog->sec_insn_off + prog->sec_insn_cnt;
}

static struct bpf_program *find_prog_by_sec_insn(const struct bpf_object *obj,
             size_t sec_idx, size_t insn_idx)
{
  int l = 0, r = obj->nr_programs - 1, m;
  struct bpf_program *prog;

  if (!obj->nr_programs)
    return NULL;

  while (l < r) {
    m = l + (r - l + 1) / 2;
    prog = &obj->programs[m];

    if (prog->sec_idx < sec_idx ||
        (prog->sec_idx == sec_idx && prog->sec_insn_off <= insn_idx))
      l = m;
    else
      r = m - 1;
  }
  /* matching program could be at index l, but it still might be the
   * wrong one, so we need to double check conditions for the last time
   */
  prog = &obj->programs[l];
  if (prog->sec_idx == sec_idx && prog_contains_insn(prog, insn_idx))
    return prog;
  return NULL;
}

static int
bpf_object__collect_prog_relos(struct bpf_object *obj, Elf64_Shdr *shdr, Elf_Data *data)
{
  const char *relo_sec_name, *sec_name;
  size_t sec_idx = shdr->sh_info, sym_idx;
  struct bpf_program *prog;
  struct reloc_desc *relos;
  int err, i, nrels;
  const char *sym_name;
  __u32 insn_idx;
  Elf_Scn *scn;
  Elf_Data *scn_data;
  Elf64_Sym *sym;
  Elf64_Rel *rel;

  if (sec_idx >= obj->efile.sec_cnt)
    return -EINVAL;

  scn = elf_sec_by_idx(obj, sec_idx);
  scn_data = elf_sec_data(obj, scn);
  if (!scn_data)
    return -LIBBPF_ERRNO__FORMAT;

  relo_sec_name = elf_sec_str(obj, shdr->sh_name);
  sec_name = elf_sec_name(obj, scn);
  if (!relo_sec_name || !sec_name)
    return -EINVAL;

  pr_debug("sec '%s': collecting relocation for section(%zu) '%s'\n",
     relo_sec_name, sec_idx, sec_name);
  nrels = shdr->sh_size / shdr->sh_entsize;

  for (i = 0; i < nrels; i++) {
    rel = elf_rel_by_idx(data, i);
    if (!rel) {
      pr_warn("sec '%s': failed to get relo #%d\n", relo_sec_name, i);
      return -LIBBPF_ERRNO__FORMAT;
    }

    sym_idx = ELF64_R_SYM(rel->r_info);
    sym = elf_sym_by_idx(obj, sym_idx);
    if (!sym) {
      pr_warn("sec '%s': symbol #%zu not found for relo #%d\n",
        relo_sec_name, sym_idx, i);
      return -LIBBPF_ERRNO__FORMAT;
    }

    if (sym->st_shndx >= obj->efile.sec_cnt) {
      pr_warn("sec '%s': corrupted symbol #%zu pointing to invalid section #%zu for relo #%d\n",
        relo_sec_name, sym_idx, (size_t)sym->st_shndx, i);
      return -LIBBPF_ERRNO__FORMAT;
    }

    if (rel->r_offset % BPF_INSN_SZ || rel->r_offset >= scn_data->d_size) {
      pr_warn("sec '%s': invalid offset 0x%zx for relo #%d\n",
        relo_sec_name, (size_t)rel->r_offset, i);
      return -LIBBPF_ERRNO__FORMAT;
    }

    insn_idx = rel->r_offset / BPF_INSN_SZ;
    /* relocations against static functions are recorded as
     * relocations against the section that contains a function;
     * in such case, symbol will be STT_SECTION and sym.st_name
     * will point to empty string (0), so fetch section name
     * instead
     */
    if (ELF64_ST_TYPE(sym->st_info) == STT_SECTION && sym->st_name == 0)
      sym_name = elf_sec_name(obj, elf_sec_by_idx(obj, sym->st_shndx));
    else
      sym_name = elf_sym_str(obj, sym->st_name);
    sym_name = sym_name ?: "<?";

    pr_debug("sec '%s': relo #%d: insn #%u against '%s'\n",
       relo_sec_name, i, insn_idx, sym_name);

    prog = find_prog_by_sec_insn(obj, sec_idx, insn_idx);
    if (!prog) {
      pr_debug("sec '%s': relo #%d: couldn't find program in section '%s' for insn #%u, probably overridden weak function, skipping...\n",
        relo_sec_name, i, sec_name, insn_idx);
      continue;
    }

    relos = libbpf_reallocarray(prog->reloc_desc,
              prog->nr_reloc + 1, sizeof(*relos));
    if (!relos)
      return -ENOMEM;
    prog->reloc_desc = relos;

    /* adjust insn_idx to local BPF program frame of reference */
    insn_idx -= prog->sec_insn_off;
    err = bpf_program__record_reloc(prog, &relos[prog->nr_reloc],
            insn_idx, sym_name, sym, rel);
    if (err)
      return err;

    prog->nr_reloc++;
  }
  return 0;
}

static int map_fill_btf_type_info(struct bpf_object *obj, struct bpf_map *map)
{
  int id;

  if (!obj->btf)
    return -ENOENT;

  /* if it's BTF-defined map, we don't need to search for type IDs.
   * For struct_ops map, it does not need btf_key_type_id and
   * btf_value_type_id.
   */
  if (map->sec_idx == obj->efile.btf_maps_shndx || bpf_map__is_struct_ops(map))
    return 0;

  /*
   * LLVM annotates global data differently in BTF, that is,
   * only as '.data', '.bss' or '.rodata'.
   */
  if (!bpf_map__is_internal(map))
    return -ENOENT;

  id = btf__find_by_name(obj->btf, map->real_name);
  if (id < 0)
    return id;

  map->btf_key_type_id = 0;
  map->btf_value_type_id = id;
  return 0;
}

static int bpf_get_map_info_from_fdinfo(int fd, struct bpf_map_info *info)
{
  char file[PATH_MAX], buff[4096];
  FILE *fp;
  __u32 val;
  int err;

  snprintf(file, sizeof(file), "/proc/%d/fdinfo/%d", getpid(), fd);
  memset(info, 0, sizeof(*info));

  fp = fopen(file, "re");
  if (!fp) {
    err = -errno;
    pr_warn("failed to open %s: %d. No procfs support?\n", file,
      err);
    return err;
  }

  while (fgets(buff, sizeof(buff), fp)) {
    if (sscanf(buff, "map_type:\t%u", &val) == 1)
      info->type = val;
    else if (sscanf(buff, "key_size:\t%u", &val) == 1)
      info->key_size = val;
    else if (sscanf(buff, "value_size:\t%u", &val) == 1)
      info->value_size = val;
    else if (sscanf(buff, "max_entries:\t%u", &val) == 1)
      info->max_entries = val;
    else if (sscanf(buff, "map_flags:\t%i", &val) == 1)
      info->map_flags = val;
  }

  fclose(fp);

  return 0;
}

bool bpf_map__autocreate(const struct bpf_map *map)
{
  return map->autocreate;
}

int bpf_map__set_autocreate(struct bpf_map *map, bool autocreate)
{
  if (map->obj->loaded)
    return libbpf_err(-EBUSY);

  map->autocreate = autocreate;
  return 0;
}

int bpf_map__set_autoattach(struct bpf_map *map, bool autoattach)
{
  if (!bpf_map__is_struct_ops(map))
    return libbpf_err(-EINVAL);

  map->autoattach = autoattach;
  return 0;
}

bool bpf_map__autoattach(const struct bpf_map *map)
{
  return map->autoattach;
}

int bpf_map__reuse_fd(struct bpf_map *map, int fd)
{
  struct bpf_map_info info;
  __u32 len = sizeof(info), name_len;
  int new_fd, err;
  char *new_name;

  memset(&info, 0, len);
  err = bpf_map_get_info_by_fd(fd, &info, &len);
  if (err && errno == EINVAL)
    err = bpf_get_map_info_from_fdinfo(fd, &info);
  if (err)
    return libbpf_err(err);

  name_len = strlen(info.name);
  if (name_len == BPF_OBJ_NAME_LEN - 1 && strncmp(map->name, info.name, name_len) == 0)
    new_name = strdup(map->name);
  else
    new_name = strdup(info.name);

  if (!new_name)
    return libbpf_err(-errno);

  /*
   * Like dup(), but make sure new FD is >= 3 and has O_CLOEXEC set.
   * This is similar to what we do in ensure_good_fd(), but without
   * closing original FD.
   */
  new_fd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
  if (new_fd < 0) {
    err = -errno;
    goto err_free_new_name;
  }

  err = reuse_fd(map->fd, new_fd);
  if (err)
    goto err_free_new_name;

  free(map->name);

  map->name = new_name;
  map->def.type = info.type;
  map->def.key_size = info.key_size;
  map->def.value_size = info.value_size;
  map->def.max_entries = info.max_entries;
  map->def.map_flags = info.map_flags;
  map->btf_key_type_id = info.btf_key_type_id;
  map->btf_value_type_id = info.btf_value_type_id;
  map->reused = true;
  map->map_extra = info.map_extra;

  return 0;

err_free_new_name:
  free(new_name);
  return libbpf_err(err);
}

__u32 bpf_map__max_entries(const struct bpf_map *map)
{
  return map->def.max_entries;
}

struct bpf_map *bpf_map__inner_map(struct bpf_map *map)
{
  if (!bpf_map_type__is_map_in_map(map->def.type))
    return errno = EINVAL, NULL;

  return map->inner_map;
}

int bpf_map__set_max_entries(struct bpf_map *map, __u32 max_entries)
{
  if (map->obj->loaded)
    return libbpf_err(-EBUSY);

  map->def.max_entries = max_entries;

  /* auto-adjust BPF ringbuf map max_entries to be a multiple of page size */
  if (map_is_ringbuf(map))
    map->def.max_entries = adjust_ringbuf_sz(map->def.max_entries);

  return 0;
}

static int bpf_object_prepare_token(struct bpf_object *obj)
{
  const char *bpffs_path;
  int bpffs_fd = -1, token_fd, err;
  bool mandatory;
  enum libbpf_print_level level;

  /* token is explicitly prevented */
  if (obj->token_path && obj->token_path[0] == '\0') {
    pr_debug("object '%s': token is prevented, skipping...\n", obj->name);
    return 0;
  }

  mandatory = obj->token_path != NULL;
  level = mandatory ? LIBBPF_WARN : LIBBPF_DEBUG;

  bpffs_path = obj->token_path ?: BPF_FS_DEFAULT_PATH;
  bpffs_fd = open(bpffs_path, O_DIRECTORY, O_RDWR);
  if (bpffs_fd < 0) {
    err = -errno;
    __pr(level, "object '%s': failed (%d) to open BPF FS mount at '%s'%s\n",
         obj->name, err, bpffs_path,
         mandatory ? "" : ", skipping optional step...");
    return mandatory ? err : 0;
  }

  token_fd = bpf_token_create(bpffs_fd, 0);
  close(bpffs_fd);
  if (token_fd < 0) {
    if (!mandatory && token_fd == -ENOENT) {
      pr_debug("object '%s': BPF FS at '%s' doesn't have BPF token delegation set up, skipping...\n",
         obj->name, bpffs_path);
      return 0;
    }
    __pr(level, "object '%s': failed (%d) to create BPF token from '%s'%s\n",
         obj->name, token_fd, bpffs_path,
         mandatory ? "" : ", skipping optional step...");
    return mandatory ? token_fd : 0;
  }

  obj->feat_cache = calloc(1, sizeof(*obj->feat_cache));
  if (!obj->feat_cache) {
    close(token_fd);
    return -ENOMEM;
  }

  obj->token_fd = token_fd;
  obj->feat_cache->token_fd = token_fd;

  return 0;
}

static int
bpf_object__probe_loading(struct bpf_object *obj)
{
  char *cp, errmsg[STRERR_BUFSIZE];
  struct bpf_insn insns[] = {
    BPF_MOV64_IMM(BPF_REG_0, 0),
    BPF_EXIT_INSN(),
  };
  int ret, insn_cnt = ARRAY_SIZE(insns);
  LIBBPF_OPTS(bpf_prog_load_opts, opts,
    .token_fd = obj->token_fd,
    .prog_flags = obj->token_fd ? BPF_F_TOKEN_FD : 0,
  );

  if (obj->gen_loader)
    return 0;

  ret = bump_rlimit_memlock();
  if (ret)
    pr_warn("Failed to bump RLIMIT_MEMLOCK (err = %d), you might need to do it explicitly!\n", ret);

  /* make sure basic loading works */
  ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL", insns, insn_cnt, &opts);
  if (ret < 0)
    ret = bpf_prog_load(BPF_PROG_TYPE_TRACEPOINT, NULL, "GPL", insns, insn_cnt, &opts);
  if (ret < 0) {
    ret = errno;
    cp = libbpf_strerror_r(ret, errmsg, sizeof(errmsg));
    pr_warn("Error in %s():%s(%d). Couldn't load trivial BPF "
      "program. Make sure your kernel supports BPF "
      "(CONFIG_BPF_SYSCALL=y) and/or that RLIMIT_MEMLOCK is "
      "set to big enough value.\n", __func__, cp, ret);
    return -ret;
  }
  close(ret);

  return 0;
}

bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
{
  if (obj->gen_loader)
    /* To generate loader program assume the latest kernel
     * to avoid doing extra prog_load, map_create syscalls.
     */
    return true;

  if (obj->token_fd)
    return feat_supported(obj->feat_cache, feat_id);

  return feat_supported(NULL, feat_id);
}

static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd)
{
  struct bpf_map_info map_info;
  char msg[STRERR_BUFSIZE];
  __u32 map_info_len = sizeof(map_info);
  int err;

  memset(&map_info, 0, map_info_len);
  err = bpf_map_get_info_by_fd(map_fd, &map_info, &map_info_len);
  if (err && errno == EINVAL)
    err = bpf_get_map_info_from_fdinfo(map_fd, &map_info);
  if (err) {
    pr_warn("failed to get map info for map FD %d: %s\n", map_fd,
      libbpf_strerror_r(errno, msg, sizeof(msg)));
    return false;
  }

  return (map_info.type == map->def.type &&
    map_info.key_size == map->def.key_size &&
    map_info.value_size == map->def.value_size &&
    map_info.max_entries == map->def.max_entries &&
    map_info.map_flags == map->def.map_flags &&
    map_info.map_extra == map->map_extra);
}

static int
bpf_object__reuse_map(struct bpf_map *map)
{
  char *cp, errmsg[STRERR_BUFSIZE];
  int err, pin_fd;

  pin_fd = bpf_obj_get(map->pin_path);
  if (pin_fd < 0) {
    err = -errno;
    if (err == -ENOENT) {
      pr_debug("found no pinned map to reuse at '%s'\n",
         map->pin_path);
      return 0;
    }

    cp = libbpf_strerror_r(-err, errmsg, sizeof(errmsg));
    pr_warn("couldn't retrieve pinned map '%s': %s\n",
      map->pin_path, cp);
    return err;
  }

  if (!map_is_reuse_compat(map, pin_fd)) {
    pr_warn("couldn't reuse pinned map at '%s': parameter mismatch\n",
      map->pin_path);
    close(pin_fd);
    return -EINVAL;
  }

  err = bpf_map__reuse_fd(map, pin_fd);
  close(pin_fd);
  if (err)
    return err;

  map->pinned = true;
  pr_debug("reused pinned map at '%s'\n", map->pin_path);

  return 0;
}

static int
bpf_object__populate_internal_map(struct bpf_object *obj, struct bpf_map *map)
{
  enum libbpf_map_type map_type = map->libbpf_type;
  char *cp, errmsg[STRERR_BUFSIZE];
  int err, zero = 0;

  if (obj->gen_loader) {
    bpf_gen__map_update_elem(obj->gen_loader, map - obj->maps,
           map->mmaped, map->def.value_size);
    if (map_type == LIBBPF_MAP_RODATA || map_type == LIBBPF_MAP_KCONFIG)
      bpf_gen__map_freeze(obj->gen_loader, map - obj->maps);
    return 0;
  }

  err = bpf_map_update_elem(map->fd, &zero, map->mmaped, 0);
  if (err) {
    err = -errno;
    cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
    pr_warn("Error setting initial map(%s) contents: %s\n",
      map->name, cp);
    return err;
  }

  /* Freeze .rodata and .kconfig map as read-only from syscall side. */
  if (map_type == LIBBPF_MAP_RODATA || map_type == LIBBPF_MAP_KCONFIG) {
    err = bpf_map_freeze(map->fd);
    if (err) {
      err = -errno;
      cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
      pr_warn("Error freezing map(%s) as read-only: %s\n",
        map->name, cp);
      return err;
    }
  }
  return 0;
}

static void bpf_map__destroy(struct bpf_map *map);

static bool map_is_created(const struct bpf_map *map)
{
  return map->obj->loaded || map->reused;
}

static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, bool is_inner)
{
  LIBBPF_OPTS(bpf_map_create_opts, create_attr);
  struct bpf_map_def *def = &map->def;
  const char *map_name = NULL;
  int err = 0, map_fd;

  if (kernel_supports(obj, FEAT_PROG_NAME))
    map_name = map->name;
  create_attr.map_ifindex = map->map_ifindex;
  create_attr.map_flags = def->map_flags;
  create_attr.numa_node = map->numa_node;
  create_attr.map_extra = map->map_extra;
  create_attr.token_fd = obj->token_fd;
  if (obj->token_fd)
    create_attr.map_flags |= BPF_F_TOKEN_FD;

  if (bpf_map__is_struct_ops(map)) {
    create_attr.btf_vmlinux_value_type_id = map->btf_vmlinux_value_type_id;
    if (map->mod_btf_fd >= 0) {
      create_attr.value_type_btf_obj_fd = map->mod_btf_fd;
      create_attr.map_flags |= BPF_F_VTYPE_BTF_OBJ_FD;
    }
  }

  if (obj->btf && btf__fd(obj->btf) >= 0) {
    create_attr.btf_fd = btf__fd(obj->btf);
    create_attr.btf_key_type_id = map->btf_key_type_id;
5164

Coverage Report

Created: 2024-09-30 06:44