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/* Error handling for runtime dynamic linker.
Copyright (C) 1995-2014 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
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
<>. */
#include <libintl.h>
#include <setjmp.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <ldsodefs.h>
/* This structure communicates state between _dl_catch_error and
_dl_signal_error. */
struct catch
const char **objname; /* Object/File name. */
const char **errstring; /* Error detail filled in here. */
bool *malloced; /* Nonzero if the string is malloced
by the libc malloc. */
volatile int *errcode; /* Return value of _dl_signal_error. */
jmp_buf env; /* longjmp here on error. */
/* Multiple threads at once can use the `_dl_catch_error' function. The
calls can come from `_dl_map_object_deps', `_dlerror_run', or from
any of the libc functionality which loads dynamic objects (NSS, iconv).
Therefore we have to be prepared to save the state in thread-local
memory. The _dl_error_catch_tsd function pointer is reset by the thread
library so that it returns the address of a thread-local variable. */
/* This message we return as a last resort. We define the string in a
variable since we have to avoid freeing it and so have to enable
a pointer comparison. See below and in dlfcn/dlerror.c. */
static const char _dl_out_of_memory[] = "out of memory";
/* This points to a function which is called when an continuable error is
received. Unlike the handling of `catch' this function may return.
The arguments will be the `errstring' and `objname'.
Since this functionality is not used in normal programs (only in
we do not care about multi-threaded programs here. We keep this as a
global variable. */
static receiver_fct receiver;
# define CATCH_HOOK (*(struct catch **) (*GL(dl_error_catch_tsd)) ())
static struct catch *catch_hook;
# define CATCH_HOOK catch_hook
_dl_signal_error (int errcode, const char *objname, const char *occation,
const char *errstring)
struct catch *lcatch;
if (! errstring)
errstring = N_("DYNAMIC LINKER BUG!!!");
lcatch = CATCH_HOOK;
if (objname == NULL)
objname = "";
if (lcatch != NULL)
/* We are inside _dl_catch_error. Return to it. We have to
duplicate the error string since it might be allocated on the
stack. The object name is always a string constant. */
size_t len_objname = strlen (objname) + 1;
size_t len_errstring = strlen (errstring) + 1;
char *errstring_copy = malloc (len_objname + len_errstring);
if (errstring_copy != NULL)
/* Make a copy of the object file name and the error string. */
*lcatch->objname = memcpy (__mempcpy (errstring_copy,
errstring, len_errstring),
objname, len_objname);
*lcatch->errstring = errstring_copy;
/* If the main executable is relocated it means the libc's malloc
is used. */
bool malloced = true;
#ifdef SHARED
malloced = (GL(dl_ns)[LM_ID_BASE]._ns_loaded != NULL
&& (GL(dl_ns)[LM_ID_BASE]._ns_loaded->l_relocated != 0));
*lcatch->malloced = malloced;
/* This is better than nothing. */
*lcatch->objname = "";
*lcatch->errstring = _dl_out_of_memory;
*lcatch->malloced = false;
*lcatch->errcode = errcode;
/* We do not restore the signal mask because none was saved. */
__longjmp (lcatch->env[0].__jmpbuf, 1);
/* Lossage while resolving the program's own symbols is always fatal. */
char buffer[1024];
_dl_fatal_printf ("%s: %s: %s%s%s%s%s\n",
occation ?: N_("error while loading shared libraries"),
objname, *objname ? ": " : "",
errstring, errcode ? ": " : "",
? __strerror_r (errcode, buffer, sizeof buffer)
: ""));
_dl_signal_cerror (int errcode, const char *objname, const char *occation,
const char *errstring)
if (__builtin_expect (GLRO(dl_debug_mask)
_dl_debug_printf ("%s: error: %s: %s (%s)\n", objname, occation,
errstring, receiver ? "continued" : "fatal");
if (receiver)
/* We are inside _dl_receive_error. Call the user supplied
handler and resume the work. The receiver will still be
installed. */
(*receiver) (errcode, objname, errstring);
_dl_signal_error (errcode, objname, occation, errstring);
_dl_catch_error (const char **objname, const char **errstring,
bool *mallocedp, void (*operate) (void *), void *args)
/* We need not handle `receiver' since setting a `catch' is handled
before it. */
/* Only this needs to be marked volatile, because it is the only local
variable that gets changed between the setjmp invocation and the
longjmp call. All others are just set here (before setjmp) and read
in _dl_signal_error (before longjmp). */
volatile int errcode;
struct catch c;
/* Don't use an initializer since we don't need to clear C.env. */
c.objname = objname;
c.errstring = errstring;
c.malloced = mallocedp;
c.errcode = &errcode;
struct catch **const catchp = &CATCH_HOOK;
struct catch *const old = *catchp;
*catchp = &c;
/* Do not save the signal mask. */
if (__builtin_expect (__sigsetjmp (c.env, 0), 0) == 0)
(*operate) (args);
*catchp = old;
*objname = NULL;
*errstring = NULL;
*mallocedp = false;
return 0;
/* We get here only if we longjmp'd out of OPERATE. _dl_signal_error has
already stored values into *OBJNAME, *ERRSTRING, and *MALLOCEDP. */
*catchp = old;
return errcode;
_dl_receive_error (receiver_fct fct, void (*operate) (void *), void *args)
struct catch **const catchp = &CATCH_HOOK;
struct catch *old_catch;
receiver_fct old_receiver;
old_catch = *catchp;
old_receiver = receiver;
/* Set the new values. */
*catchp = NULL;
receiver = fct;
(*operate) (args);
*catchp = old_catch;
receiver = old_receiver;