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Implement _dl_catch_error, _dl_signal_error in libc.so [BZ #16628]
This change moves the main implementation of _dl_catch_error, _dl_signal_error to libc.so, where TLS variables can be used directly. This removes a writable function pointer from the rtld_global variable. For use during initial relocation, minimal implementations of these functions are provided in ld.so. These are eventually interposed by the libc.so implementations. This is implemented by compiling elf/dl-error-skeleton.c twice, via elf/dl-error.c and elf/dl-error-minimal.c. As a side effect of this change, the static version of dl-error.c no longer includes support for the _dl_signal_cerror/_dl_receive_error mechanism because it is only used in ld.so.
This commit is contained in:
Florian Weimer
230
elf/dl-error-skeleton.c
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230
elf/dl-error-skeleton.c
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/* Template for error handling for runtime dynamic linker.
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Copyright (C) 1995-2016 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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/* The following macro needs to be defined before including this
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skeleton file:
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DL_ERROR_BOOTSTRAP
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If 1, do not use TLS and implement _dl_signal_cerror and
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_dl_receive_error. If 0, TLS is used, and the variants with
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error callbacks are not provided. */
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#include <libintl.h>
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#include <setjmp.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <ldsodefs.h>
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#include <stdio.h>
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/* This structure communicates state between _dl_catch_error and
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_dl_signal_error. */
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struct catch
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{
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const char **objname; /* Object/File name. */
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const char **errstring; /* Error detail filled in here. */
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bool *malloced; /* Nonzero if the string is malloced
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by the libc malloc. */
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volatile int *errcode; /* Return value of _dl_signal_error. */
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jmp_buf env; /* longjmp here on error. */
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};
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/* Multiple threads at once can use the `_dl_catch_error' function. The
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calls can come from `_dl_map_object_deps', `_dlerror_run', or from
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any of the libc functionality which loads dynamic objects (NSS, iconv).
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Therefore we have to be prepared to save the state in thread-local
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memory. */
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#if !DL_ERROR_BOOTSTRAP
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static __thread struct catch *catch_hook attribute_tls_model_ie;
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#else
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/* The version of this code in ld.so cannot use thread-local variables
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and is used during bootstrap only. */
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static struct catch *catch_hook;
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#endif
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/* This message we return as a last resort. We define the string in a
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variable since we have to avoid freeing it and so have to enable
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a pointer comparison. See below and in dlfcn/dlerror.c. */
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static const char _dl_out_of_memory[] = "out of memory";
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#if DL_ERROR_BOOTSTRAP
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/* This points to a function which is called when an continuable error is
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received. Unlike the handling of `catch' this function may return.
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The arguments will be the `errstring' and `objname'.
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Since this functionality is not used in normal programs (only in ld.so)
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we do not care about multi-threaded programs here. We keep this as a
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global variable. */
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static receiver_fct receiver;
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#endif /* DL_ERROR_BOOTSTRAP */
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void
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internal_function
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_dl_signal_error (int errcode, const char *objname, const char *occation,
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const char *errstring)
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{
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struct catch *lcatch = catch_hook;
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if (! errstring)
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errstring = N_("DYNAMIC LINKER BUG!!!");
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if (objname == NULL)
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objname = "";
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if (lcatch != NULL)
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{
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/* We are inside _dl_catch_error. Return to it. We have to
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duplicate the error string since it might be allocated on the
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stack. The object name is always a string constant. */
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size_t len_objname = strlen (objname) + 1;
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size_t len_errstring = strlen (errstring) + 1;
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char *errstring_copy = malloc (len_objname + len_errstring);
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if (errstring_copy != NULL)
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{
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/* Make a copy of the object file name and the error string. */
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*lcatch->objname = memcpy (__mempcpy (errstring_copy,
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errstring, len_errstring),
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objname, len_objname);
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*lcatch->errstring = errstring_copy;
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/* If the main executable is relocated it means the libc's malloc
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is used. */
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bool malloced = true;
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#ifdef SHARED
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malloced = (GL(dl_ns)[LM_ID_BASE]._ns_loaded != NULL
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&& (GL(dl_ns)[LM_ID_BASE]._ns_loaded->l_relocated != 0));
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#endif
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*lcatch->malloced = malloced;
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}
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else
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{
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/* This is better than nothing. */
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*lcatch->objname = "";
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*lcatch->errstring = _dl_out_of_memory;
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*lcatch->malloced = false;
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}
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*lcatch->errcode = errcode;
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/* We do not restore the signal mask because none was saved. */
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__longjmp (lcatch->env[0].__jmpbuf, 1);
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}
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else
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{
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/* Lossage while resolving the program's own symbols is always fatal. */
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char buffer[1024];
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_dl_fatal_printf ("%s: %s: %s%s%s%s%s\n",
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RTLD_PROGNAME,
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occation ?: N_("error while loading shared libraries"),
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objname, *objname ? ": " : "",
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errstring, errcode ? ": " : "",
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(errcode
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? __strerror_r (errcode, buffer, sizeof buffer)
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: ""));
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}
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}
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libc_hidden_def (_dl_signal_error)
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#if DL_ERROR_BOOTSTRAP
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void
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internal_function
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_dl_signal_cerror (int errcode, const char *objname, const char *occation,
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const char *errstring)
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{
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if (__builtin_expect (GLRO(dl_debug_mask)
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& ~(DL_DEBUG_STATISTICS|DL_DEBUG_PRELINK), 0))
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_dl_debug_printf ("%s: error: %s: %s (%s)\n", objname, occation,
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errstring, receiver ? "continued" : "fatal");
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if (receiver)
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{
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/* We are inside _dl_receive_error. Call the user supplied
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handler and resume the work. The receiver will still be
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installed. */
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(*receiver) (errcode, objname, errstring);
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}
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else
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_dl_signal_error (errcode, objname, occation, errstring);
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}
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#endif /* DL_ERROR_BOOTSTRAP */
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int
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internal_function
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_dl_catch_error (const char **objname, const char **errstring,
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bool *mallocedp, void (*operate) (void *), void *args)
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{
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/* We need not handle `receiver' since setting a `catch' is handled
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before it. */
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/* Only this needs to be marked volatile, because it is the only local
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variable that gets changed between the setjmp invocation and the
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longjmp call. All others are just set here (before setjmp) and read
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in _dl_signal_error (before longjmp). */
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volatile int errcode;
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struct catch c;
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/* Don't use an initializer since we don't need to clear C.env. */
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c.objname = objname;
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c.errstring = errstring;
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c.malloced = mallocedp;
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c.errcode = &errcode;
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struct catch *const old = catch_hook;
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catch_hook = &c;
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/* Do not save the signal mask. */
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if (__builtin_expect (__sigsetjmp (c.env, 0), 0) == 0)
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{
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(*operate) (args);
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catch_hook = old;
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*objname = NULL;
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*errstring = NULL;
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*mallocedp = false;
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return 0;
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}
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/* We get here only if we longjmp'd out of OPERATE. _dl_signal_error has
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already stored values into *OBJNAME, *ERRSTRING, and *MALLOCEDP. */
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catch_hook = old;
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return errcode;
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}
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libc_hidden_def (_dl_catch_error)
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#if DL_ERROR_BOOTSTRAP
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void
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internal_function
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_dl_receive_error (receiver_fct fct, void (*operate) (void *), void *args)
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{
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struct catch *old_catch = catch_hook;
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receiver_fct old_receiver = receiver;
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/* Set the new values. */
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catch_hook = NULL;
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receiver = fct;
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(*operate) (args);
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catch_hook = old_catch;
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receiver = old_receiver;
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}
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#endif /* DL_ERROR_BOOTSTRAP */
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