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elf: Add _dl_find_object function
It can be used to speed up the libgcc unwinder, and the internal _dl_find_dso_for_object function (which is used for caller identification in dlopen and related functions, and in dladdr). _dl_find_object is in the internal namespace due to bug 28503. If libgcc switches to _dl_find_object, this namespace issue will be fixed. It is located in libc for two reasons: it is necessary to forward the call to the static libc after static dlopen, and there is a link ordering issue with -static-libgcc and libgcc_eh.a because libc.so is not a linker script that includes ld.so in the glibc build tree (so that GCC's internal -lc after libgcc_eh.a does not pick up ld.so). It is necessary to do the i386 customization in the sysdeps/x86/bits/dl_find_object.h header shared with x86-64 because otherwise, multilib installations are broken. The implementation uses software transactional memory, as suggested by Torvald Riegel. Two copies of the supporting data structures are used, also achieving full async-signal-safety. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This commit is contained in:
Florian Weimer
275
elf/tst-dl_find_object-threads.c
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275
elf/tst-dl_find_object-threads.c
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/* _dl_find_object test with parallelism.
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Copyright (C) 2021 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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<https://www.gnu.org/licenses/>. */
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#include <array_length.h>
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#include <dlfcn.h>
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#include <elf/dl-find_object.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <support/check.h>
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#include <support/support.h>
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#include <support/xdlfcn.h>
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#include <support/xthread.h>
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#include <support/xunistd.h>
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/* Computes the expected _dl_find_object result directly from the
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map. */
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static void
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from_map (struct link_map *l, struct dl_find_object *expected)
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{
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struct dl_find_object_internal internal;
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_dl_find_object_from_map (l, &internal);
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_dl_find_object_to_external (&internal, expected);
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}
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/* Returns the soname for the test object NUMBER. */
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static char *
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soname (int number)
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{
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return xasprintf ("tst-dl_find_object-mod%d.so", number);
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}
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/* Returns the data symbol name for the test object NUMBER. */
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static char *
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symbol (int number)
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{
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return xasprintf ("mod%d_data", number);
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}
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struct verify_data
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{
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char *soname;
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void *address; /* Address in the shared object. */
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struct dl_find_object dlfo;
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pthread_t thr;
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};
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/* Compare _dl_find_object result at ADDRESS with *EXPECTED. */
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static void
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check (void *address, struct dl_find_object *expected, int line)
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{
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struct dl_find_object actual;
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int ret = _dl_find_object (address, &actual);
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if (expected == NULL)
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{
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if (ret != -1)
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{
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support_record_failure ();
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printf ("%s:%d: unexpected success for %p\n",
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__FILE__, line, address);
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}
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return;
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}
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if (ret != 0)
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{
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support_record_failure ();
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printf ("%s:%d: unexpected failure for %p\n",
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__FILE__, line, address);
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return;
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}
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if (actual.dlfo_flags != expected->dlfo_flags)
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{
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support_record_failure ();
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printf ("%s:%d: error: %p: flags is %llu, expected %llu\n",
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__FILE__, line, address,
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actual.dlfo_flags, expected->dlfo_flags);
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}
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if (actual.dlfo_flags != expected->dlfo_flags)
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{
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support_record_failure ();
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printf ("%s:%d: error: %p: map start is %p, expected %p\n",
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__FILE__, line,
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address, actual.dlfo_map_start, expected->dlfo_map_start);
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}
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if (actual.dlfo_map_end != expected->dlfo_map_end)
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{
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support_record_failure ();
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printf ("%s:%d: error: %p: map end is %p, expected %p\n",
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__FILE__, line,
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address, actual.dlfo_map_end, expected->dlfo_map_end);
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}
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if (actual.dlfo_link_map != expected->dlfo_link_map)
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{
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support_record_failure ();
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printf ("%s:%d: error: %p: link map is %p, expected %p\n",
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__FILE__, line,
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address, actual.dlfo_link_map, expected->dlfo_link_map);
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}
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if (actual.dlfo_eh_frame != expected->dlfo_eh_frame)
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{
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support_record_failure ();
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printf ("%s:%d: error: %p: EH frame is %p, expected %p\n",
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__FILE__, line,
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address, actual.dlfo_eh_frame, expected->dlfo_eh_frame);
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}
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#if DLFO_STRUCT_HAS_EH_DBASE
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if (actual.dlfo_eh_dbase != expected->dlfo_eh_dbase)
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{
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support_record_failure ();
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printf ("%s:%d: error: %p: data base is %p, expected %p\n",
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__FILE__, line,
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address, actual.dlfo_eh_dbase, expected->dlfo_eh_dbase);
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}
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#endif
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#if DLFO_STRUCT_HAS_EH_COUNT
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if (actual.dlfo_eh_count != expected->dlfo_eh_count)
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{
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support_record_failure ();
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printf ("%s:%d: error: %p: count is %d, expected %d\n",
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__FILE__, line,
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address, actual.dlfo_eh_count, expected->dlfo_eh_count);
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}
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#endif
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}
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/* Request process termination after 3 seconds. */
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static bool exit_requested;
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static void *
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exit_thread (void *ignored)
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{
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usleep (3 * 100 * 1000);
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__atomic_store_n (&exit_requested, true, __ATOMIC_RELAXED);
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return NULL;
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}
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static void *
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verify_thread (void *closure)
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{
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struct verify_data *data = closure;
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while (!__atomic_load_n (&exit_requested, __ATOMIC_RELAXED))
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{
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check (data->address, &data->dlfo, __LINE__);
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check (data->dlfo.dlfo_map_start, &data->dlfo, __LINE__);
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check (data->dlfo.dlfo_map_end - 1, &data->dlfo, __LINE__);
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}
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return NULL;
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}
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/* Sets up the verification data, dlopen'ing shared object NUMBER, and
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launches a verification thread. */
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static void
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start_verify (int number, struct verify_data *data)
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{
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data->soname = soname (number);
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struct link_map *l = xdlopen (data->soname, RTLD_NOW);
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from_map (l, &data->dlfo);
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TEST_VERIFY_EXIT (data->dlfo.dlfo_link_map == l);
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char *sym = symbol (number);
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data->address = xdlsym (data->dlfo.dlfo_link_map, sym);
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free (sym);
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data->thr = xpthread_create (NULL, verify_thread, data);
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}
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static int
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do_test (void)
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{
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struct verify_data data_mod2;
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struct verify_data data_mod4;
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struct verify_data data_mod7;
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/* Load the modules with gaps. */
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{
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void *mod1 = xdlopen ("tst-dl_find_object-mod1.so", RTLD_NOW);
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start_verify (2, &data_mod2);
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void *mod3 = xdlopen ("tst-dl_find_object-mod3.so", RTLD_NOW);
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start_verify (4, &data_mod4);
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void *mod5 = xdlopen ("tst-dl_find_object-mod5.so", RTLD_NOW);
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void *mod6 = xdlopen ("tst-dl_find_object-mod6.so", RTLD_NOW);
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start_verify (7, &data_mod7);
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xdlclose (mod6);
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xdlclose (mod5);
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xdlclose (mod3);
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xdlclose (mod1);
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}
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/* Objects that continuously opened and closed. */
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struct temp_object
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{
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char *soname;
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char *symbol;
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struct link_map *link_map;
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void *address;
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} temp_objects[] =
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{
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{ soname (1), symbol (1), },
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{ soname (3), symbol (3), },
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{ soname (5), symbol (5), },
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{ soname (6), symbol (6), },
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{ soname (8), symbol (8), },
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{ soname (9), symbol (9), },
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};
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pthread_t exit_thr = xpthread_create (NULL, exit_thread, NULL);
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struct drand48_data state;
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srand48_r (1, &state);
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while (!__atomic_load_n (&exit_requested, __ATOMIC_RELAXED))
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{
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long int idx;
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lrand48_r (&state, &idx);
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idx %= array_length (temp_objects);
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if (temp_objects[idx].link_map == NULL)
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{
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temp_objects[idx].link_map = xdlopen (temp_objects[idx].soname,
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RTLD_NOW);
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temp_objects[idx].address = xdlsym (temp_objects[idx].link_map,
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temp_objects[idx].symbol);
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}
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else
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{
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xdlclose (temp_objects[idx].link_map);
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temp_objects[idx].link_map = NULL;
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struct dl_find_object dlfo;
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int ret = _dl_find_object (temp_objects[idx].address, &dlfo);
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if (ret != -1)
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{
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TEST_VERIFY_EXIT (ret == 0);
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support_record_failure ();
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printf ("%s: error: %s EH found after dlclose, link map %p\n",
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__FILE__, temp_objects[idx].soname, dlfo.dlfo_link_map);
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}
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}
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}
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xpthread_join (data_mod2.thr);
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xpthread_join (data_mod4.thr);
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xpthread_join (data_mod7.thr);
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xpthread_join (exit_thr);
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for (size_t i = 0; i < array_length (temp_objects); ++i)
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{
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free (temp_objects[i].soname);
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free (temp_objects[i].symbol);
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if (temp_objects[i].link_map != NULL)
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xdlclose (temp_objects[i].link_map);
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}
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free (data_mod2.soname);
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free (data_mod4.soname);
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xdlclose (data_mod4.dlfo.dlfo_link_map);
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free (data_mod7.soname);
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xdlclose (data_mod7.dlfo.dlfo_link_map);
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return 0;
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}
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#include <support/test-driver.c>
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