binreloc.c

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/*
 * BinReloc - a library for creating relocatable executables
 * Written by: Hongli Lai <h.lai@chello.nl>
 * http://autopackage.org/
 *
 * This source code is public domain. You can relicense this code
 * under whatever license you want.
 *
 * See http://autopackage.org/docs/binreloc/ for
 * more information and how to use this.
 */

#ifndef __BINRELOC_C__
#define __BINRELOC_C__

#include "config.h"

#ifdef ENABLE_BINRELOC
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#endif /* ENABLE_BINRELOC */
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <string.h>
#include "binreloc.h"

#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */


#ifdef OS_WIN32
# define DIRSEP "\\"
# define DIRSEP_C '\\'
#else
# define DIRSEP "/"
# define DIRSEP_C '/'
#endif

static char *
_br_find_exe (BrInitError *error) {
#ifndef ENABLE_BINRELOC
  if (error)
    *error = BR_INIT_ERROR_DISABLED;
  return NULL;
#else
  char *path, *path2, *line, *result;
  size_t buf_size;
  ssize_t size;
  struct stat stat_buf;
  FILE *f;

  /* Read from /proc/self/exe (symlink) */
  if (sizeof (path) > SSIZE_MAX)
    buf_size = SSIZE_MAX - 1;
  else
    buf_size = PATH_MAX - 1;
  path = (char *) malloc (buf_size);
  if (path == NULL) {
    /* Cannot allocate memory. */
    if (error)
      *error = BR_INIT_ERROR_NOMEM;
    return NULL;
  }
  path2 = (char *) malloc (buf_size);
  if (path2 == NULL) {
    /* Cannot allocate memory. */
    if (error)
      *error = BR_INIT_ERROR_NOMEM;
    free (path);
    return NULL;
  }

  strncpy (path2, "/proc/self/exe", buf_size - 1);

  while (1) {
    int i;

    size = readlink (path2, path, buf_size - 1);
    if (size == -1) {
      /* Error. */
      free (path2);
      break;
    }

    /* readlink() success. */
    path[size] = '\0';

    /* Check whether the symlink's target is also a symlink.
     * We want to get the final target. */
    i = stat (path, &stat_buf);
    if (i == -1) {
      /* Error. */
      free (path2);
      break;
    }

    /* stat() success. */
    if (!S_ISLNK (stat_buf.st_mode)) {
      /* path is not a symlink. Done. */
      free (path2);
      return path;
    }

    /* path is a symlink. Continue loop and resolve this. */
    strncpy (path, path2, buf_size - 1);
  }


  /* readlink() or stat() failed; this can happen when the program is
   * running in Valgrind 2.2. Read from /proc/self/maps as fallback. */

  buf_size = PATH_MAX + 128;
  line = (char *) realloc (path, buf_size);
  if (line == NULL) {
    /* Cannot allocate memory. */
    free (path);
    if (error)
      *error = BR_INIT_ERROR_NOMEM;
    return NULL;
  }

  f = fopen ("/proc/self/maps", "r");
  if (f == NULL) {
    free (line);
    if (error)
      *error = BR_INIT_ERROR_OPEN_MAPS;
    return NULL;
  }

  /* The first entry should be the executable name. */
  result = fgets (line, (int) buf_size, f);
  if (result == NULL) {
    fclose (f);
    free (line);
    if (error)
      *error = BR_INIT_ERROR_READ_MAPS;
    return NULL;
  }

  /* Get rid of newline character. */
  buf_size = strlen (line);
  if (buf_size <= 0) {
    /* Huh? An empty string? */
    fclose (f);
    free (line);
    if (error)
      *error = BR_INIT_ERROR_INVALID_MAPS;
    return NULL;
  }
  if (line[buf_size - 1] == 10)
    line[buf_size - 1] = 0;

  /* Extract the filename; it is always an absolute path. */
  path = strchr (line, DIRSEP_C);

  /* Sanity check. */
  if (strstr (line, " r-xp ") == NULL || path == NULL) {
    fclose (f);
    free (line);
    if (error)
      *error = BR_INIT_ERROR_INVALID_MAPS;
    return NULL;
  }

  path = strdup (path);
  free (line);
  fclose (f);
  return path;
#endif /* ENABLE_BINRELOC */
}


static char *
_br_find_exe_for_symbol (const void *symbol, BrInitError *error) {
#ifndef ENABLE_BINRELOC
  if (error)
    *error = BR_INIT_ERROR_DISABLED;
  return (char *) NULL;
#else
#define SIZE PATH_MAX + 100
  FILE *f;
  size_t address_string_len;
  char *address_string, line[SIZE], *found;

  if (symbol == NULL)
    return (char *) NULL;

  f = fopen ("/proc/self/maps", "r");
  if (f == NULL)
    return (char *) NULL;

  address_string_len = 4;
  address_string = (char *) malloc (address_string_len);
  found = (char *) NULL;

  while (!feof (f)) {
    char *start_addr, *end_addr, *end_addr_end, *file;
    void *start_addr_p, *end_addr_p;
    size_t len;

    if (fgets (line, SIZE, f) == NULL)
      break;

    /* Sanity check. */
    if (strstr (line, " r-xp ") == NULL || strchr (line, '/') == NULL)
      continue;

    /* Parse line. */
    start_addr = line;
    end_addr = strchr (line, '-');
    file = strchr (line, '/');

    /* More sanity check. */
    if (!(file > end_addr && end_addr != NULL && end_addr[0] == '-'))
      continue;

    end_addr[0] = '\0';
    end_addr++;
    end_addr_end = strchr (end_addr, ' ');
    if (end_addr_end == NULL)
      continue;

    end_addr_end[0] = '\0';
    len = strlen (file);
    if (len == 0)
      continue;
    if (file[len - 1] == '\n')
      file[len - 1] = '\0';

    /* Get rid of "(deleted)" from the filename. */
    len = strlen (file);
    if (len > 10 && strcmp (file + len - 10, " (deleted)") == 0)
      file[len - 10] = '\0';

    /* I don't know whether this can happen but better safe than sorry. */
    len = strlen (start_addr);
    if (len != strlen (end_addr))
      continue;


    /* Transform the addresses into a string in the form of 0xdeadbeef,
     * then transform that into a pointer. */
    if (address_string_len < len + 3) {
      address_string_len = len + 3;
      address_string = (char *) realloc (address_string, address_string_len);
    }

    memcpy (address_string, "0x", 2);
    memcpy (address_string + 2, start_addr, len);
    address_string[2 + len] = '\0';
    sscanf (address_string, "%p", &start_addr_p);

    memcpy (address_string, "0x", 2);
    memcpy (address_string + 2, end_addr, len);
    address_string[2 + len] = '\0';
    sscanf (address_string, "%p", &end_addr_p);


    if (symbol >= start_addr_p && symbol < end_addr_p) {
      found = file;
      break;
    }
  }

  free (address_string);
  fclose (f);

  if (found == NULL)
    return (char *) NULL;
  else
    return strdup (found);
#endif /* ENABLE_BINRELOC */
}


#ifndef BINRELOC_RUNNING_DOXYGEN
#undef NULL
#define NULL ((void *) 0) /* typecasted as char* for C++ type safeness */
#endif

static char *exe = (char *) NULL;


int
br_init (BrInitError *error) {
  exe = _br_find_exe (error);
  return exe != NULL;
}


int
br_init_lib (BrInitError *error) {
  exe = _br_find_exe_for_symbol ((const void *) "", error);
  return exe != NULL;
}


char *
br_find_exe (const char *default_exe) {
  if (exe == (char *) NULL) {
    /* BinReloc is not initialized. */
    if (default_exe != (const char *) NULL)
      return strdup (default_exe);
    else
      return (char *) NULL;
  }
  return strdup (exe);
}


char *
br_find_exe_dir (const char *default_dir) {
  if (exe == NULL) {
    /* BinReloc not initialized. */
    if (default_dir != NULL)
      return strdup (default_dir);
    else
      return NULL;
  }

  return br_dirname (exe);
}


char *
br_find_prefix (const char *default_prefix) {
  char *dir1, *dir2;

  if (exe == (char *) NULL) {
    /* BinReloc not initialized. */
    if (default_prefix != (const char *) NULL)
      return strdup (default_prefix);
    else
      return (char *) NULL;
  }

  dir1 = br_dirname (exe);
  dir2 = br_dirname (dir1);
  free (dir1);
  return dir2;
}


char *
br_find_bin_dir (const char *default_bin_dir) {
  char *prefix, *dir;

  prefix = br_find_prefix ((const char *) NULL);
  if (prefix == (char *) NULL) {
    /* BinReloc not initialized. */
    if (default_bin_dir != (const char *) NULL)
      return strdup (default_bin_dir);
    else
      return (char *) NULL;
  }

  dir = br_build_path (prefix, "bin");
  free (prefix);
  return dir;
}


char *
br_find_sbin_dir (const char *default_sbin_dir) {
  char *prefix, *dir;

  prefix = br_find_prefix ((const char *) NULL);
  if (prefix == (char *) NULL) {
    /* BinReloc not initialized. */
    if (default_sbin_dir != (const char *) NULL)
      return strdup (default_sbin_dir);
    else
      return (char *) NULL;
  }

  dir = br_build_path (prefix, "sbin");
  free (prefix);
  return dir;
}


char *
br_find_data_dir (const char *default_data_dir) {
  char *prefix, *dir;

  prefix = br_find_prefix ((const char *) NULL);
  if (prefix == (char *) NULL) {
    /* BinReloc not initialized. */
    if (default_data_dir != (const char *) NULL)
      return strdup (default_data_dir);
    else
      return (char *) NULL;
  }

  dir = br_build_path (prefix, "share");
  free (prefix);
  return dir;
}


char *
br_find_locale_dir (const char *default_locale_dir) {
  char *data_dir, *dir;

  data_dir = br_find_data_dir ((const char *) NULL);
  if (data_dir == (char *) NULL) {
    /* BinReloc not initialized. */
    if (default_locale_dir != (const char *) NULL)
      return strdup (default_locale_dir);
    else
      return (char *) NULL;
  }

  dir = br_build_path (data_dir, "locale");
  free (data_dir);
  return dir;
}


char *
br_find_lib_dir (const char *default_lib_dir) {
  char *prefix, *dir;

  prefix = br_find_prefix ((const char *) NULL);
  if (prefix == (char *) NULL) {
    /* BinReloc not initialized. */
    if (default_lib_dir != (const char *) NULL)
      return strdup (default_lib_dir);
    else
      return (char *) NULL;
  }

  dir = br_build_path (prefix, "lib");
  free (prefix);
  return dir;
}


char *
br_find_libexec_dir (const char *default_libexec_dir) {
  char *prefix, *dir;

  prefix = br_find_prefix ((const char *) NULL);
  if (prefix == (char *) NULL) {
    /* BinReloc not initialized. */
    if (default_libexec_dir != (const char *) NULL)
      return strdup (default_libexec_dir);
    else
      return (char *) NULL;
  }

  dir = br_build_path (prefix, "libexec");
  free (prefix);
  return dir;
}


char *
br_find_etc_dir (const char *default_etc_dir) {
  char *prefix, *dir;

  prefix = br_find_prefix ((const char *) NULL);
  if (prefix == (char *) NULL) {
    /* BinReloc not initialized. */
    if (default_etc_dir != (const char *) NULL)
      return strdup (default_etc_dir);
    else
      return (char *) NULL;
  }

  dir = br_build_path (prefix, "etc");
  free (prefix);
  return dir;
}


/***********************
 * Utility functions
 ***********************/

char *
br_strcat (const char *str1, const char *str2) {
  char *result;
  size_t len1, len2;

  if (str1 == NULL)
    str1 = "";
  if (str2 == NULL)
    str2 = "";

  len1 = strlen (str1);
  len2 = strlen (str2);

  result = (char *) malloc (len1 + len2 + 1);
  memcpy (result, str1, len1);
  memcpy (result + len1, str2, len2);
  result[len1 + len2] = '\0';

  return result;
}


char *
br_build_path (const char *dir, const char *file) {
  char *dir2, *result;
  size_t len;
  int must_free = 0;

  len = strlen (dir);
  if (len > 0 && dir[len - 1] != DIRSEP_C) {
    dir2 = br_strcat (dir, DIRSEP );
    must_free = 1;
  }
  else
    dir2 = (char *) dir;

  result = br_strcat (dir2, file);
  if (must_free)
    free (dir2);
  return result;
}


/* Emulates glibc's strndup() */
static char *
br_strndup (const char *str, size_t size) {
  char *result = (char *) NULL;
  size_t len;

  if (str == (const char *) NULL)
    return (char *) NULL;

  len = strlen (str);
  if (len == 0)
    return strdup ("");
  if (size > len)
    size = len;

  result = (char *) malloc (len + 1);
  memcpy (result, str, size);
  result[size] = '\0';
  return result;
}


char *
br_dirname (const char *path) {
  char *end, *result;

  if (path == (const char *) NULL)
    return (char *) NULL;

  end = strrchr (path, DIRSEP_C);
  if (end == (const char *) NULL)
    return strdup (".");

  while (end > path && *end == DIRSEP_C)
    end--;
  result = br_strndup (path, end - path + 1);
  if (result[0] == 0) {
    free (result);
    return strdup (DIRSEP);
  }
  else
    return result;
}


#ifdef __cplusplus
}
#endif /* __cplusplus */

#endif /* __BINRELOC_C__ */