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

#ifndef _GNU_SOURCE

#define _GNU_SOURCE

#endif

#include <libelf.h>

#include <gelf.h>

#include <fcntl.h>

#include <linux/kernel.h>

#include "libbpf_internal.h"

/* A SHT_GNU_versym section holds 16-bit words. This bit is set if

 * the symbol is hidden and can only be seen when referenced using an

 * explicit version number. This is a GNU extension.

 */

#define VERSYM_HIDDEN 0x8000

/* This is the mask for the rest of the data in a word read from a

 * SHT_GNU_versym section.

 */

#define VERSYM_VERSION  0x7fff

int elf_open(const char *binary_path, struct elf_fd *elf_fd)

{

  int fd, ret;

  Elf *elf;

  elf_fd->elf = NULL;

  elf_fd->fd = -1;

  if (elf_version(EV_CURRENT) == EV_NONE) {

    pr_warn("elf: failed to init libelf for %s\n", binary_path);

    return -LIBBPF_ERRNO__LIBELF;

  }

  fd = open(binary_path, O_RDONLY | O_CLOEXEC);

  if (fd < 0) {

    ret = -errno;

    pr_warn("elf: failed to open %s: %s\n", binary_path, errstr(ret));

    return ret;

  }

  elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);

  if (!elf) {

    pr_warn("elf: could not read elf from %s: %s\n", binary_path, elf_errmsg(-1));

    close(fd);

    return -LIBBPF_ERRNO__FORMAT;

  }

  elf_fd->fd = fd;

  elf_fd->elf = elf;

  return 0;

}

void elf_close(struct elf_fd *elf_fd)

{

  if (!elf_fd)

    return;

  elf_end(elf_fd->elf);

  close(elf_fd->fd);

}

/* Return next ELF section of sh_type after scn, or first of that type if scn is NULL. */

static Elf_Scn *elf_find_next_scn_by_type(Elf *elf, int sh_type, Elf_Scn *scn)

{

  while ((scn = elf_nextscn(elf, scn)) != NULL) {

    GElf_Shdr sh;

    if (!gelf_getshdr(scn, &sh))

      continue;

    if (sh.sh_type == sh_type)

      return scn;

  }

  return NULL;

}

struct elf_sym {

  const char *name;

  GElf_Sym sym;

  GElf_Shdr sh;

  int ver;

  bool hidden;

};

struct elf_sym_iter {

  Elf *elf;

  Elf_Data *syms;

  Elf_Data *versyms;

  Elf_Data *verdefs;

  size_t nr_syms;

  size_t strtabidx;

  size_t verdef_strtabidx;

  size_t next_sym_idx;

  struct elf_sym sym;

  int st_type;

};

static int elf_sym_iter_new(struct elf_sym_iter *iter,

          Elf *elf, const char *binary_path,

          int sh_type, int st_type)

{

  Elf_Scn *scn = NULL;

  GElf_Ehdr ehdr;

  GElf_Shdr sh;

  memset(iter, 0, sizeof(*iter));

  if (!gelf_getehdr(elf, &ehdr)) {

    pr_warn("elf: failed to get ehdr from %s: %s\n", binary_path, elf_errmsg(-1));

    return -EINVAL;

  }

  scn = elf_find_next_scn_by_type(elf, sh_type, NULL);

  if (!scn) {

    pr_debug("elf: failed to find symbol table ELF sections in '%s'\n",

       binary_path);

    return -ENOENT;

  }

  if (!gelf_getshdr(scn, &sh))

    return -EINVAL;

  iter->strtabidx = sh.sh_link;

  iter->syms = elf_getdata(scn, 0);

  if (!iter->syms) {

    pr_warn("elf: failed to get symbols for symtab section in '%s': %s\n",

      binary_path, elf_errmsg(-1));

    return -EINVAL;

  }

  iter->nr_syms = iter->syms->d_size / sh.sh_entsize;

  iter->elf = elf;

  iter->st_type = st_type;

  /* Version symbol table is meaningful to dynsym only */

  if (sh_type != SHT_DYNSYM)

    return 0;

  scn = elf_find_next_scn_by_type(elf, SHT_GNU_versym, NULL);

  if (!scn)

    return 0;

  iter->versyms = elf_getdata(scn, 0);

  scn = elf_find_next_scn_by_type(elf, SHT_GNU_verdef, NULL);

  if (!scn)

    return 0;

  iter->verdefs = elf_getdata(scn, 0);

  if (!iter->verdefs || !gelf_getshdr(scn, &sh)) {

    pr_warn("elf: failed to get verdef ELF section in '%s'\n", binary_path);

    return -EINVAL;

  }

  iter->verdef_strtabidx = sh.sh_link;

  return 0;

}

static struct elf_sym *elf_sym_iter_next(struct elf_sym_iter *iter)

{

  struct elf_sym *ret = &iter->sym;

  GElf_Sym *sym = &ret->sym;

  const char *name = NULL;

  GElf_Versym versym;

  Elf_Scn *sym_scn;

  size_t idx;

  for (idx = iter->next_sym_idx; idx < iter->nr_syms; idx++) {

    if (!gelf_getsym(iter->syms, idx, sym))

      continue;

    if (GELF_ST_TYPE(sym->st_info) != iter->st_type)

      continue;

    name = elf_strptr(iter->elf, iter->strtabidx, sym->st_name);

    if (!name)

      continue;

    sym_scn = elf_getscn(iter->elf, sym->st_shndx);

    if (!sym_scn)

      continue;

    if (!gelf_getshdr(sym_scn, &ret->sh))

      continue;

    iter->next_sym_idx = idx + 1;

    ret->name = name;

    ret->ver = 0;

    ret->hidden = false;

    if (iter->versyms) {

      if (!gelf_getversym(iter->versyms, idx, &versym))

        continue;

      ret->ver = versym & VERSYM_VERSION;

      ret->hidden = versym & VERSYM_HIDDEN;

    }

    return ret;

  }

  return NULL;

}

static const char *elf_get_vername(struct elf_sym_iter *iter, int ver)

{

  GElf_Verdaux verdaux;

  GElf_Verdef verdef;

  int offset;

  if (!iter->verdefs)

    return NULL;

  offset = 0;

  while (gelf_getverdef(iter->verdefs, offset, &verdef)) {

    if (verdef.vd_ndx != ver) {

      if (!verdef.vd_next)

        break;

      offset += verdef.vd_next;

      continue;

    }

    if (!gelf_getverdaux(iter->verdefs, offset + verdef.vd_aux, &verdaux))

      break;

    return elf_strptr(iter->elf, iter->verdef_strtabidx, verdaux.vda_name);

  }

  return NULL;

}

static bool symbol_match(struct elf_sym_iter *iter, int sh_type, struct elf_sym *sym,

       const char *name, size_t name_len, const char *lib_ver)

{

  const char *ver_name;

  /* Symbols are in forms of func, func@LIB_VER or func@@LIB_VER

   * make sure the func part matches the user specified name

   */

  if (strncmp(sym->name, name, name_len) != 0)

    return false;

  /* ...but we don't want a search for "foo" to match 'foo2" also, so any

   * additional characters in sname should be of the form "@@LIB".

   */

  if (sym->name[name_len] != '\0' && sym->name[name_len] != '@')

    return false;

  /* If user does not specify symbol version, then we got a match */

  if (!lib_ver)

    return true;

  /* If user specifies symbol version, for dynamic symbols,

   * get version name from ELF verdef section for comparison.

   */

  if (sh_type == SHT_DYNSYM) {

    ver_name = elf_get_vername(iter, sym->ver);

    if (!ver_name)

      return false;

    return strcmp(ver_name, lib_ver) == 0;

  }

  /* For normal symbols, it is already in form of func@LIB_VER */

  return strcmp(sym->name, name) == 0;

}

/* Transform symbol's virtual address (absolute for binaries and relative

 * for shared libs) into file offset, which is what kernel is expecting

 * for uprobe/uretprobe attachment.

 * See Documentation/trace/uprobetracer.rst for more details. This is done

 * by looking up symbol's containing section's header and using iter's virtual

 * address (sh_addr) and corresponding file offset (sh_offset) to transform

 * sym.st_value (virtual address) into desired final file offset.

 */

static unsigned long elf_sym_offset(struct elf_sym *sym)

{

  return sym->sym.st_value - sym->sh.sh_addr + sym->sh.sh_offset;

}

/* Find offset of function name in the provided ELF object. "binary_path" is

 * the path to the ELF binary represented by "elf", and only used for error

 * reporting matters. "name" matches symbol name or name@@LIB for library

 * functions.

 */

long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name)

{

  int i, sh_types[2] = { SHT_DYNSYM, SHT_SYMTAB };

  const char *at_symbol, *lib_ver;

  bool is_shared_lib;

  long ret = -ENOENT;

  size_t name_len;

  GElf_Ehdr ehdr;

  if (!gelf_getehdr(elf, &ehdr)) {

    pr_warn("elf: failed to get ehdr from %s: %s\n", binary_path, elf_errmsg(-1));

    ret = -LIBBPF_ERRNO__FORMAT;

    goto out;

  }

  /* for shared lib case, we do not need to calculate relative offset */

  is_shared_lib = ehdr.e_type == ET_DYN;

  /* Does name specify "@@LIB_VER" or "@LIB_VER" ? */

  at_symbol = strchr(name, '@');

  if (at_symbol) {

    name_len = at_symbol - name;

    /* skip second @ if it's @@LIB_VER case */

    if (at_symbol[1] == '@')

      at_symbol++;

    lib_ver = at_symbol + 1;

  } else {

    name_len = strlen(name);

    lib_ver = NULL;

  }

  /* Search SHT_DYNSYM, SHT_SYMTAB for symbol. This search order is used because if

   * a binary is stripped, it may only have SHT_DYNSYM, and a fully-statically

   * linked binary may not have SHT_DYMSYM, so absence of a section should not be

   * reported as a warning/error.

   */

  for (i = 0; i < ARRAY_SIZE(sh_types); i++) {

    struct elf_sym_iter iter;

    struct elf_sym *sym;

    int last_bind = -1;

    int cur_bind;

    ret = elf_sym_iter_new(&iter, elf, binary_path, sh_types[i], STT_FUNC);

    if (ret == -ENOENT)

      continue;

    if (ret)

      goto out;

    while ((sym = elf_sym_iter_next(&iter))) {

      if (!symbol_match(&iter, sh_types[i], sym, name, name_len, lib_ver))

        continue;

      cur_bind = GELF_ST_BIND(sym->sym.st_info);

      if (ret > 0) {

        /* handle multiple matches */

        if (elf_sym_offset(sym) == ret) {

          /* same offset, no problem */

          continue;

        } else if (last_bind != STB_WEAK && cur_bind != STB_WEAK) {

          /* Only accept one non-weak bind. */

          pr_warn("elf: ambiguous match for '%s', '%s' in '%s'\n",

            sym->name, name, binary_path);

          ret = -LIBBPF_ERRNO__FORMAT;

          goto out;

        } else if (cur_bind == STB_WEAK) {

          /* already have a non-weak bind, and

           * this is a weak bind, so ignore.

           */

          continue;

        }

      }

      ret = elf_sym_offset(sym);

      last_bind = cur_bind;

    }

    if (ret > 0)

      break;

  }

  if (ret > 0) {

    pr_debug("elf: symbol address match for '%s' in '%s': 0x%lx\n", name, binary_path,

       ret);

  } else {

    if (ret == 0) {

      pr_warn("elf: '%s' is 0 in symtab for '%s': %s\n", name, binary_path,

        is_shared_lib ? "should not be 0 in a shared library" :

            "try using shared library path instead");

      ret = -ENOENT;

    } else {

      pr_warn("elf: failed to find symbol '%s' in '%s'\n", name, binary_path);

    }

  }

out:

  return ret;

}

/* Find offset of function name in ELF object specified by path. "name" matches

 * symbol name or name@@LIB for library functions.

 */

long elf_find_func_offset_from_file(const char *binary_path, const char *name)

{

  struct elf_fd elf_fd;

  long ret = -ENOENT;

  ret = elf_open(binary_path, &elf_fd);

  if (ret)

    return ret;

  ret = elf_find_func_offset(elf_fd.elf, binary_path, name);

  elf_close(&elf_fd);

  return ret;

}

struct symbol {

  const char *name;

  int bind;

  int idx;

};

static int symbol_cmp(const void *a, const void *b)

{

  const struct symbol *sym_a = a;

  const struct symbol *sym_b = b;

  return strcmp(sym_a->name, sym_b->name);

}

/*

 * Return offsets in @poffsets for symbols specified in @syms array argument.

 * On success returns 0 and offsets are returned in allocated array with @cnt

 * size, that needs to be released by the caller.

 */

int elf_resolve_syms_offsets(const char *binary_path, int cnt,

           const char **syms, unsigned long **poffsets,

           int st_type)

{

  int sh_types[2] = { SHT_DYNSYM, SHT_SYMTAB };

  int err = 0, i, cnt_done = 0;

  unsigned long *offsets;

  struct symbol *symbols;

  struct elf_fd elf_fd;

  err = elf_open(binary_path, &elf_fd);

  if (err)

    return err;

  offsets = calloc(cnt, sizeof(*offsets));

  symbols = calloc(cnt, sizeof(*symbols));

  if (!offsets || !symbols) {

    err = -ENOMEM;

    goto out;

  }

  for (i = 0; i < cnt; i++) {

    symbols[i].name = syms[i];

    symbols[i].idx = i;

  }

  qsort(symbols, cnt, sizeof(*symbols), symbol_cmp);

  for (i = 0; i < ARRAY_SIZE(sh_types); i++) {

    struct elf_sym_iter iter;

    struct elf_sym *sym;

    err = elf_sym_iter_new(&iter, elf_fd.elf, binary_path, sh_types[i], st_type);

    if (err == -ENOENT)

      continue;

    if (err)

      goto out;

    while ((sym = elf_sym_iter_next(&iter))) {

      unsigned long sym_offset = elf_sym_offset(sym);

      int bind = GELF_ST_BIND(sym->sym.st_info);

      struct symbol *found, tmp = {

        .name = sym->name,

      };

      unsigned long *offset;

      found = bsearch(&tmp, symbols, cnt, sizeof(*symbols), symbol_cmp);

      if (!found)

        continue;

      offset = &offsets[found->idx];

      if (*offset > 0) {

        /* same offset, no problem */

        if (*offset == sym_offset)

          continue;

        /* handle multiple matches */

        if (found->bind != STB_WEAK && bind != STB_WEAK) {

          /* Only accept one non-weak bind. */

          pr_warn("elf: ambiguous match found '%s@%lu' in '%s' previous offset %lu\n",

            sym->name, sym_offset, binary_path, *offset);

          err = -ESRCH;

          goto out;

        } else if (bind == STB_WEAK) {

          /* already have a non-weak bind, and

           * this is a weak bind, so ignore.

           */

          continue;

        }

      } else {

        cnt_done++;

      }

      *offset = sym_offset;

      found->bind = bind;

    }

  }

  if (cnt != cnt_done) {

    err = -ENOENT;

    goto out;

  }

  *poffsets = offsets;

out:

  free(symbols);

  if (err)

    free(offsets);

  elf_close(&elf_fd);

  return err;

}

/*

 * Return offsets in @poffsets for symbols specified by @pattern argument.

 * On success returns 0 and offsets are returned in allocated @poffsets

 * array with the @pctn size, that needs to be released by the caller.

 */

int elf_resolve_pattern_offsets(const char *binary_path, const char *pattern,

        unsigned long **poffsets, size_t *pcnt)

{

  int sh_types[2] = { SHT_SYMTAB, SHT_DYNSYM };

  unsigned long *offsets = NULL;

  size_t cap = 0, cnt = 0;

  struct elf_fd elf_fd;

  int err = 0, i;

  err = elf_open(binary_path, &elf_fd);

  if (err)

    return err;

  for (i = 0; i < ARRAY_SIZE(sh_types); i++) {

    struct elf_sym_iter iter;

    struct elf_sym *sym;

    err = elf_sym_iter_new(&iter, elf_fd.elf, binary_path, sh_types[i], STT_FUNC);

    if (err == -ENOENT)

      continue;

    if (err)

      goto out;

    while ((sym = elf_sym_iter_next(&iter))) {

      if (!glob_match(sym->name, pattern))

        continue;

      err = libbpf_ensure_mem((void **) &offsets, &cap, sizeof(*offsets),

            cnt + 1);

      if (err)

        goto out;

      offsets[cnt++] = elf_sym_offset(sym);

    }

    /* If we found anything in the first symbol section,

     * do not search others to avoid duplicates.

     */

    if (cnt)

      break;

  }

  if (cnt) {

    *poffsets = offsets;

    *pcnt = cnt;

  } else {

    err = -ENOENT;

  }

out:

  if (err)

    free(offsets);

  elf_close(&elf_fd);

  return err;

}