binreloc.c

/*
 * 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"
#include <glib.h>

G_BEGIN_DECLS


static char *
_br_find_exe (GbrInitError *error)
{
#ifndef ENABLE_BINRELOC
        if (error)
                *error = GBR_INIT_ERROR_DISABLED;
        return NULL;
#else
#ifdef G_OS_WIN32
        /* I *thought* this program code already included the
           relocation code for windows. Unfortunately this is not
           the case and we have to add this manually. This is only
           one possibility; other ways of looking up the full path
           of gnucash-bin.exe probably exist.*/
        gchar *prefix;
        gchar *result;

        /* From the glib docs: This function looks in the Windows
           Registry for the value #InstallationDirectory in the key
           #HKLM\Software\${package}, and if that value exists and is
           a string, returns that. */
        prefix = g_win32_get_package_installation_directory ("GnuCash", NULL);
        result = g_build_filename (prefix,
                                   "bin", "gnucash-bin.exe",
                                   (char*)NULL);
        g_free (prefix);
        return result;
#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 *) g_try_malloc (buf_size);
        if (path == NULL) {
                /* Cannot allocate memory. */
                if (error)
                        *error = GBR_INIT_ERROR_NOMEM;
                return NULL;
        }
        path2 = (char *) g_try_malloc (buf_size);
        if (path2 == NULL) {
                /* Cannot allocate memory. */
                if (error)
                        *error = GBR_INIT_ERROR_NOMEM;
                g_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. */
                        g_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. */
                        g_free (path2);
                        break;
                }

                /* stat() success. */
                if (!S_ISLNK (stat_buf.st_mode)) {
                        /* path is not a symlink. Done. */
                        g_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 *) g_try_realloc (path, buf_size);
        if (line == NULL) {
                /* Cannot allocate memory. */
                g_free (path);
                if (error)
                        *error = GBR_INIT_ERROR_NOMEM;
                return NULL;
        }

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

        path = g_strdup (path);
        g_free (line);
        fclose (f);
        return path;
#endif /* G_OS_WINDOWS */
#endif /* ENABLE_BINRELOC */
}


static char *
_br_find_exe_for_symbol (const void *symbol, GbrInitError *error)
{
#ifndef ENABLE_BINRELOC
        if (error)
                *error = GBR_INIT_ERROR_DISABLED;
        return (char *) NULL;
#else
#ifdef G_OS_WIN32
        g_warning ("_br_find_exe_for_symbol not implemented on win32.");
        if (error)
                *error = GBR_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 *) g_try_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 *) g_try_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;
                }
        }

        g_free (address_string);
        fclose (f);

        if (found == NULL)
                return (char *) NULL;
        else
                return g_strdup (found);
#endif /* G_OS_WIN32 */
#endif /* ENABLE_BINRELOC */
}


static gchar *exe = NULL;

static void set_gerror (GError **error, GbrInitError errcode);


gboolean
gbr_init (GError **error)
{
        GbrInitError errcode = 0;

        /* Locate the application's filename. */
        exe = _br_find_exe (&errcode);
        if (exe != NULL)
                /* Success! */
                return TRUE;
        else {
                /* Failed :-( */
                set_gerror (error, errcode);
                return FALSE;
        }
}


gboolean
gbr_init_lib (GError **error)
{
        GbrInitError errcode = 0;

        exe = _br_find_exe_for_symbol ((const void *) "", &errcode);
        if (exe != NULL)
                /* Success! */
                return TRUE;
        else {
                /* Failed :-( */
                set_gerror (error, errcode);
                return exe != NULL;
        }
}


static void
set_gerror (GError **error, GbrInitError errcode)
{
        gchar *error_message;

        if (error == NULL)
                return;

        switch (errcode) {
        case GBR_INIT_ERROR_NOMEM:
                error_message = "Cannot allocate memory.";
                break;
        case GBR_INIT_ERROR_OPEN_MAPS:
                error_message = "Unable to open /proc/self/maps for reading.";
                break;
        case GBR_INIT_ERROR_READ_MAPS:
                error_message = "Unable to read from /proc/self/maps.";
                break;
        case GBR_INIT_ERROR_INVALID_MAPS:
                error_message = "The file format of /proc/self/maps is invalid.";
                break;
        case GBR_INIT_ERROR_DISABLED:
                error_message = "Binary relocation support is disabled.";
                break;
        default:
                error_message = "Unknown error.";
                break;
        };
        g_set_error (error, g_quark_from_static_string ("GBinReloc"),
                     errcode, "%s", error_message);
}


gchar *
gbr_find_exe (const gchar *default_exe)
{
        if (exe == NULL) {
                /* BinReloc is not initialized. */
                if (default_exe != NULL)
                        return g_strdup (default_exe);
                else
                        return NULL;
        }
        return g_strdup (exe);
}


gchar *
gbr_find_exe_dir (const gchar *default_dir)
{
        if (exe == NULL) {
                /* BinReloc not initialized. */
                if (default_dir != NULL)
                        return g_strdup (default_dir);
                else
                        return NULL;
        }

        return g_path_get_dirname (exe);
}


gchar *
gbr_find_prefix (const gchar *default_prefix)
{
        gchar *dir1, *dir2;

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

        dir1 = g_path_get_dirname (exe);
        dir2 = g_path_get_dirname (dir1);
        g_free (dir1);
        return dir2;
}


gchar *
gbr_find_bin_dir (const gchar *default_bin_dir)
{
        gchar *prefix, *dir;

        prefix = gbr_find_prefix (NULL);
        if (prefix == NULL) {
                /* BinReloc not initialized. */
                if (default_bin_dir != NULL)
                        return g_strdup (default_bin_dir);
                else
                        return NULL;
        }

        dir = g_build_filename (prefix, "bin", NULL);
        g_free (prefix);
        return dir;
}


gchar *
gbr_find_sbin_dir (const gchar *default_sbin_dir)
{
        gchar *prefix, *dir;

        prefix = gbr_find_prefix (NULL);
        if (prefix == NULL) {
                /* BinReloc not initialized. */
                if (default_sbin_dir != NULL)
                        return g_strdup (default_sbin_dir);
                else
                        return NULL;
        }

        dir = g_build_filename (prefix, "sbin", NULL);
        g_free (prefix);
        return dir;
}


gchar *
gbr_find_data_dir (const gchar *default_data_dir)
{
        gchar *prefix, *dir;

        prefix = gbr_find_prefix (NULL);
        if (prefix == NULL) {
                /* BinReloc not initialized. */
                if (default_data_dir != NULL)
                        return g_strdup (default_data_dir);
                else
                        return NULL;
        }

        dir = g_build_filename (prefix, "share", NULL);
        g_free (prefix);
        return dir;
}


gchar *
gbr_find_lib_dir (const gchar *default_lib_dir)
{
        gchar *prefix, *dir;

        prefix = gbr_find_prefix (NULL);
        if (prefix == NULL) {
                /* BinReloc not initialized. */
                if (default_lib_dir != NULL)
                        return g_strdup (default_lib_dir);
                else
                        return NULL;
        }

        dir = g_build_filename (prefix, "lib", NULL);
        g_free (prefix);
        return dir;
}


gchar *
gbr_find_libexec_dir (const gchar *default_libexec_dir)
{
        gchar *prefix, *dir;

        prefix = gbr_find_prefix (NULL);
        if (prefix == NULL) {
                /* BinReloc not initialized. */
                if (default_libexec_dir != NULL)
                        return g_strdup (default_libexec_dir);
                else
                        return NULL;
        }

        dir = g_build_filename (prefix, "libexec", NULL);
        g_free (prefix);
        return dir;
}


gchar *
gbr_find_etc_dir (const gchar *default_etc_dir)
{
        gchar *prefix, *dir;

        prefix = gbr_find_prefix (NULL);
        if (prefix == NULL) {
                /* BinReloc not initialized. */
                if (default_etc_dir != NULL)
                        return g_strdup (default_etc_dir);
                else
                        return NULL;
        }

        dir = g_build_filename (prefix, "etc", NULL);
        g_free (prefix);
        return dir;
}


G_END_DECLS

#endif /* __BINRELOC_C__ */

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