/src/elfutils/lib/system.h

Source
/* Declarations for common convenience functions.
   Copyright (C) 2006-2011 Red Hat, Inc.
   Copyright (C) 2022, 2026 Mark J. Wielaard <mark@klomp.org>
   Copyright (C) 2023 Khem Raj.
   This file is part of elfutils.

   This file is free software; you can redistribute it and/or modify
   it under the terms of either

     * the GNU Lesser General Public License as published by the Free
       Software Foundation; either version 3 of the License, or (at
       your option) any later version

   or

     * the GNU General Public License as published by the Free
       Software Foundation; either version 2 of the License, or (at
       your option) any later version

   or both in parallel, as here.

   elfutils is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   You should have received copies of the GNU General Public License and
   the GNU Lesser General Public License along with this program.  If
   not, see <http://www.gnu.org/licenses/>.  */

#ifndef LIB_SYSTEM_H
#define LIB_SYSTEM_H  1

/* Prevent double inclusion of config.h, config.h includes eu-config.h.  */
#ifdef HAVE_CONFIG_H
#ifndef EU_CONFIG_H
# include <config.h>
#endif
#endif

#include <errno.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <stdarg.h>
#include <stdlib.h>

/* System dependent headers */
#include <byteswap.h>
#include <endian.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <unistd.h>

#if defined(HAVE_SYS_RANDOM_H)
#include <sys/random.h>
#endif

#if defined(HAVE_ERROR_H)
#include <error.h>
#elif defined(HAVE_ERR_H)
extern int error_message_count;
void error(int status, int errnum, const char *format, ...);
#else
#error "err.h or error.h must be available"
#endif

/* error (EXIT_FAILURE, ...) should be noreturn but on some systems it
   isn't.  This may cause warnings about code that should not be reachable.
   So have an explicit error_exit wrapper that is noreturn (because it
   calls exit explicitly).  */
#define error_exit(errnum,...) do { \
    error (EXIT_FAILURE,errnum,__VA_ARGS__); \
    exit (EXIT_FAILURE); \
  } while (0)

#if BYTE_ORDER == LITTLE_ENDIAN
# define LE32(n)  (n)
# define LE64(n)  (n)
# define BE32(n)  bswap_32 (n)
# define BE64(n)  bswap_64 (n)
#elif BYTE_ORDER == BIG_ENDIAN
# define BE32(n)  (n)
# define BE64(n)  (n)
# define LE32(n)  bswap_32 (n)
# define LE64(n)  bswap_64 (n)
#else
# error "Unknown byte order"
#endif

#ifndef MAX
#define MAX(m, n) ((m) < (n) ? (n) : (m))
#endif

#ifndef MIN
#define MIN(m, n) ((m) < (n) ? (m) : (n))
#endif

#if !HAVE_DECL_POWEROF2
#define powerof2(x) (((x) & ((x) - 1)) == 0)
#endif

#if !HAVE_DECL_MEMPCPY
#define mempcpy(dest, src, n) \
    ((void *) ((char *) memcpy (dest, src, n) + (size_t) n))
#endif

#if !HAVE_DECL_REALLOCARRAY
static inline void *
reallocarray (void *ptr, size_t nmemb, size_t size)
{
  if (size > 0 && nmemb > SIZE_MAX / size)
    {
      errno = ENOMEM;
      return NULL;
    }
  return realloc (ptr, nmemb * size);
}
#endif

/* Return TRUE if the start of STR matches PREFIX, FALSE otherwise.  */

static inline int
startswith (const char *str, const char *prefix)
{
  return strncmp (str, prefix, strlen (prefix)) == 0;
}

/* Return TRUE if STR[FROM] is a valid string with a zero terminator
   at or before STR[TO - 1].  Note FROM is an index into the STR
   array, while TO is the maximum size of the STR array.  This
   function returns FALSE when TO is zero or FROM >= TO.  */
static inline bool
validate_str (const char *str, size_t from, size_t to)
{
#if HAVE_DECL_MEMRCHR
  // Check end first, which is likely a zero terminator,
  // to prevent function call
  return (to > 0
    && (str[to - 1] == '\0'
        || (to > from
      && memrchr (&str[from], '\0', to - from - 1) != NULL)));
#else
  do {
    if (to <= from)
      return false;

    to--;
  } while (str[to]);

  return true;
#endif
}

/* A special gettext function we use if the strings are too short.  */
#define sgettext(Str) \
  ({ const char *__res = strrchr (_(Str), '|');           \
     __res ? __res + 1 : Str; })

#define gettext_noop(Str) Str

#ifndef TEMP_FAILURE_RETRY
#define TEMP_FAILURE_RETRY(expression) \
  ({ ssize_t __res; \
     do \
       __res = expression; \
     while (__res == -1 && errno == EINTR); \
     __res; })
#endif

#ifndef ACCESSPERMS
#define ACCESSPERMS (S_IRWXU|S_IRWXG|S_IRWXO) /* 0777 */
#endif

#ifndef ALLPERMS
#define ALLPERMS (S_ISUID|S_ISGID|S_ISVTX|S_IRWXU|S_IRWXG|S_IRWXO) /* 07777 */
#endif

#ifndef DEFFILEMODE
#define DEFFILEMODE (S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH)/* 0666 */
#endif

static inline ssize_t __attribute__ ((unused))
pwrite_retry (int fd, const void *buf, size_t len, off_t off)
{
  ssize_t recvd = 0;

  do
    {
      ssize_t ret = TEMP_FAILURE_RETRY (pwrite (fd, ((char *)buf) + recvd, len - recvd,
            off + recvd));
      if (ret <= 0)
  return ret < 0 ? ret : recvd;

      recvd += ret;
    }
  while ((size_t) recvd < len);

  return recvd;
}

static inline ssize_t __attribute__ ((unused))
write_retry (int fd, const void *buf, size_t len)
{
  ssize_t recvd = 0;

  do
    {
      ssize_t ret = TEMP_FAILURE_RETRY (write (fd, ((char *)buf) + recvd, len - recvd));
      if (ret <= 0)
  return ret < 0 ? ret : recvd;

      recvd += ret;
    }
  while ((size_t) recvd < len);

  return recvd;
}

static inline ssize_t __attribute__ ((unused))
pread_retry (int fd, void *buf, size_t len, off_t off)
{
  ssize_t recvd = 0;

  do
    {
      ssize_t ret = TEMP_FAILURE_RETRY (pread (fd, ((char *)buf) + recvd, len - recvd,
                 off + recvd));
      if (ret <= 0)
  return ret < 0 ? ret : recvd;

      recvd += ret;
    }
  while ((size_t) recvd < len);

  return recvd;
}

static inline ssize_t __attribute__ ((unused))
read_retry (int fd, void *buf, size_t len)
{
  ssize_t recvd = 0;

  do
    {
      ssize_t ret = TEMP_FAILURE_RETRY (read (fd, ((char *)buf) + recvd,
                len - recvd));
      if (ret <= 0)
  return ret < 0 ? ret : recvd;

      recvd += ret;
    }
  while ((size_t) recvd < len);

  return recvd;
}

/* The demangler from libstdc++.  */
extern char *__cxa_demangle (const char *mangled_name, char *output_buffer,
           size_t *length, int *status);

/* A static assertion.  This will cause a compile-time error if EXPR,
   which must be a compile-time constant, is false.  */

#define eu_static_assert(expr)            \
  extern int never_defined_just_used_for_checking[(expr) ? 1 : -1]  \
    __attribute__ ((unused))

/* We really want a basename implementation that doesn't modify the
   input argument.  Normally you get that from string.h with _GNU_SOURCE
   define.  But some libc implementations don't define it and other
   define it, but provide an implementation that still modifies the
   argument.  So define our own and poison a bare basename symbol.  */
static inline const char *
xbasename(const char *s)
{
  const char *p = strrchr(s, '/');
  return p ? p+1 : s;
}
#pragma GCC poison basename

/* Get a random uint64_t.  Returns zero on success, minus one on failure.  */
static inline int
xrandom64 (uint64_t *r)
{
  /* Prefer getentropy if it is available, fallback to getrandom, if
     both are missing, or if they fail try reading from /dev/urandom.  */
#if HAVE_DECL_GETENTROPY
  if (getentropy (r, sizeof (*r)) == 0)
    return 0;
#elif HAVE_DECL_GETRANDOM
  if (TEMP_FAILURE_RETRY (getrandom (r, sizeof (*r), 0)) == sizeof (*r))
    return 0;
#endif
  int fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
  if (fd < 0)
    return -1;
  if (read_retry (fd, r, sizeof (uint64_t)) == sizeof (uint64_t))
    {
      close (fd);
      return 0;
    }
  int save_errno = errno;
  close (fd);
  errno = save_errno;
  /* We could try some pseudo-random thing with getpid and
     clock_gettime.  But if even getting something from /dev/urandom
     fails it seems we tried hard enough already.  */
  return -1;
}

/* There is no mkstempat needed for creating a temp file in a specific
   directory. Needed e.g. in combination with renameat to atomicly
   replace a file. So define one ourselves. Like mkstemp the template
   must end in "XXXXXX", which are replaced by an unique filename
   suffix. The file is created with user read/write permissions only
   in the given dirfd using openat.
   https://sourceware.org/bugzilla/show_bug.cgi?id=19866 */
static inline int
xmkstempat (int dirfd, char *templ)
{
  /* Only use these 64 chars.  */
  const char chars[] =
    "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-_";

  /* Must end in 6X.  */
  size_t l = strlen (templ);
  if (l < 6 || memcmp (templ + l - 6, "XXXXXX", 6) != 0)
    {
      errno = EINVAL;
      return -1;
    }

  int tries = 128; /* Just fail with EEXIST if 128 tries wasn't enough.  */
  do
    {
      uint64_t r; /* We need at least 64^6 == 2^36  */
      if (xrandom64 (&r) != 0)
  return -1;

      /* Random chars for the template.  */
      for (int i = 0; i < 6; i++)
  {
    templ[l - 6 + i] = chars[r % 64];
    r /= 64;
  }

      /* Must be able to open exclusively.  */
      int fd = openat (dirfd, templ,
           O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC,
           S_IRUSR | S_IWUSR);
      if (fd >= 0)
  return fd;

      tries--;
    }
  while (tries > 0 && errno == EEXIST);

  return -1;
}

#endif /* system.h */

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Created: 2026-07-24 06:20