src/include/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__

#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 */



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, '/');

        /* 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] != '/') {
                dir2 = br_strcat (dir, "/");
                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, '/');
        if (end == (const char *) NULL)
                return strdup (".");

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


#ifdef __cplusplus
}
#endif /* __cplusplus */

#endif /* __BINRELOC_C__ */

---