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glibc/dlfcn/dlerror.c
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/* Return error detail for failing <dlfcn.h> functions. | |
Copyright (C) 1995-2016 Free Software Foundation, Inc. | |
This file is part of the GNU C Library. | |
The GNU C Library is free software; you can redistribute it and/or | |
modify it under the terms of the GNU Lesser General Public | |
License as published by the Free Software Foundation; either | |
version 2.1 of the License, or (at your option) any later version. | |
The GNU C Library 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 | |
Lesser General Public License for more details. | |
You should have received a copy of the GNU Lesser General Public | |
License along with the GNU C Library; if not, see | |
<http://www.gnu.org/licenses/>. */ | |
#include <dlfcn.h> | |
#include <libintl.h> | |
#include <stdbool.h> | |
#include <stdio.h> | |
#include <stdlib.h> | |
#include <string.h> | |
#include <libc-lock.h> | |
#include <ldsodefs.h> | |
#if !defined SHARED && IS_IN (libdl) | |
char * | |
dlerror (void) | |
{ | |
return __dlerror (); | |
} | |
#else | |
/* Type for storing results of dynamic loading actions. */ | |
struct dl_action_result | |
{ | |
int errcode; | |
int returned; | |
bool malloced; | |
const char *objname; | |
const char *errstring; | |
}; | |
static struct dl_action_result last_result; | |
static struct dl_action_result *static_buf; | |
/* This is the key for the thread specific memory. */ | |
static __libc_key_t key; | |
__libc_once_define (static, once); | |
/* Destructor for the thread-specific data. */ | |
static void init (void); | |
static void free_key_mem (void *mem); | |
char * | |
__dlerror (void) | |
{ | |
char *buf = NULL; | |
struct dl_action_result *result; | |
# ifdef SHARED | |
if (__glibc_unlikely (_dlfcn_hook != NULL)) | |
return _dlfcn_hook->dlerror (); | |
# endif | |
/* If we have not yet initialized the buffer do it now. */ | |
__libc_once (once, init); | |
/* Get error string. */ | |
result = (struct dl_action_result *) __libc_getspecific (key); | |
if (result == NULL) | |
result = &last_result; | |
/* Test whether we already returned the string. */ | |
if (result->returned != 0) | |
{ | |
/* We can now free the string. */ | |
if (result->errstring != NULL) | |
{ | |
if (strcmp (result->errstring, "out of memory") != 0) | |
free ((char *) result->errstring); | |
result->errstring = NULL; | |
} | |
} | |
else if (result->errstring != NULL) | |
{ | |
buf = (char *) result->errstring; | |
int n; | |
if (result->errcode == 0) | |
n = __asprintf (&buf, "%s%s%s", | |
result->objname, | |
result->objname[0] == '\0' ? "" : ": ", | |
_(result->errstring)); | |
else | |
n = __asprintf (&buf, "%s%s%s: %s", | |
result->objname, | |
result->objname[0] == '\0' ? "" : ": ", | |
_(result->errstring), | |
strerror (result->errcode)); | |
if (n != -1) | |
{ | |
/* We don't need the error string anymore. */ | |
if (strcmp (result->errstring, "out of memory") != 0) | |
free ((char *) result->errstring); | |
result->errstring = buf; | |
} | |
/* Mark the error as returned. */ | |
result->returned = 1; | |
} | |
return buf; | |
} | |
# ifdef SHARED | |
strong_alias (__dlerror, dlerror) | |
# endif | |
int | |
internal_function | |
_dlerror_run (void (*operate) (void *), void *args) | |
{ | |
struct dl_action_result *result; | |
/* If we have not yet initialized the buffer do it now. */ | |
__libc_once (once, init); | |
/* Get error string and number. */ | |
if (static_buf != NULL) | |
result = static_buf; | |
else | |
{ | |
/* We don't use the static buffer and so we have a key. Use it | |
to get the thread-specific buffer. */ | |
result = __libc_getspecific (key); | |
if (result == NULL) | |
{ | |
result = (struct dl_action_result *) calloc (1, sizeof (*result)); | |
if (result == NULL) | |
/* We are out of memory. Since this is no really critical | |
situation we carry on by using the global variable. | |
This might lead to conflicts between the threads but | |
they soon all will have memory problems. */ | |
result = &last_result; | |
else | |
/* Set the tsd. */ | |
__libc_setspecific (key, result); | |
} | |
} | |
if (result->errstring != NULL) | |
{ | |
/* Free the error string from the last failed command. This can | |
happen if `dlerror' was not run after an error was found. */ | |
if (result->malloced) | |
free ((char *) result->errstring); | |
result->errstring = NULL; | |
} | |
result->errcode = GLRO(dl_catch_error) (&result->objname, &result->errstring, | |
&result->malloced, operate, args); | |
/* If no error we mark that no error string is available. */ | |
result->returned = result->errstring == NULL; | |
return result->errstring != NULL; | |
} | |
/* Initialize buffers for results. */ | |
static void | |
init (void) | |
{ | |
if (__libc_key_create (&key, free_key_mem)) | |
/* Creating the key failed. This means something really went | |
wrong. In any case use a static buffer which is better than | |
nothing. */ | |
static_buf = &last_result; | |
} | |
static void | |
check_free (struct dl_action_result *rec) | |
{ | |
if (rec->errstring != NULL | |
&& strcmp (rec->errstring, "out of memory") != 0) | |
{ | |
/* We can free the string only if the allocation happened in the | |
C library used by the dynamic linker. This means, it is | |
always the C library in the base namespace. When we're statically | |
linked, the dynamic linker is part of the program and so always | |
uses the same C library we use here. */ | |
#ifdef SHARED | |
struct link_map *map = NULL; | |
Dl_info info; | |
if (_dl_addr (check_free, &info, &map, NULL) != 0 && map->l_ns == 0) | |
#endif | |
free ((char *) rec->errstring); | |
} | |
} | |
static void | |
__attribute__ ((destructor)) | |
fini (void) | |
{ | |
check_free (&last_result); | |
} | |
/* Free the thread specific data, this is done if a thread terminates. */ | |
static void | |
free_key_mem (void *mem) | |
{ | |
check_free ((struct dl_action_result *) mem); | |
free (mem); | |
__libc_setspecific (key, NULL); | |
} | |
# ifdef SHARED | |
struct dlfcn_hook *_dlfcn_hook __attribute__((nocommon)); | |
libdl_hidden_data_def (_dlfcn_hook) | |
# else | |
static struct dlfcn_hook _dlfcn_hooks = | |
{ | |
.dlopen = __dlopen, | |
.dlclose = __dlclose, | |
.dlsym = __dlsym, | |
.dlvsym = __dlvsym, | |
.dlerror = __dlerror, | |
.dladdr = __dladdr, | |
.dladdr1 = __dladdr1, | |
.dlinfo = __dlinfo, | |
.dlmopen = __dlmopen | |
}; | |
void | |
__libc_register_dlfcn_hook (struct link_map *map) | |
{ | |
struct dlfcn_hook **hook; | |
hook = (struct dlfcn_hook **) __libc_dlsym_private (map, "_dlfcn_hook"); | |
if (hook != NULL) | |
*hook = &_dlfcn_hooks; | |
} | |
# endif | |
#endif |