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elf: Relocate libc.so early during startup and dlmopen (bug 31083)
This makes it more likely that objects without dependencies can use IFUNC resolvers in libc.so. Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
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a74c2e1cbc
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21
elf/Makefile
21
elf/Makefile
@ -433,6 +433,8 @@ tests += \
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tst-nodelete-dlclose \
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tst-nodelete-opened \
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tst-nodelete2 \
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tst-nodeps1 \
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tst-nodeps2 \
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tst-noload \
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tst-non-directory-path \
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tst-null-argv \
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@ -863,6 +865,8 @@ modules-names += \
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tst-nodelete-dlclose-plugin \
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tst-nodelete-opened-lib \
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tst-nodelete2mod \
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tst-nodeps1-mod \
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tst-nodeps2-mod \
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tst-non-directory-mod \
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tst-null-argv-lib \
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tst-p_alignmod-base \
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@ -1030,6 +1034,8 @@ modules-names-nobuild += \
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tst-audit24bmod1 \
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tst-audit24bmod2 \
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tst-big-note-lib \
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tst-nodeps1-mod \
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tst-nodeps2-mod \
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tst-ro-dynamic-mod \
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# modules-names-nobuild
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@ -3009,3 +3015,18 @@ tst-env-setuid-ARGS = -- $(host-test-program-cmd)
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# Reuse a module with a SONAME, to specific as the LD_PROFILE.
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$(objpfx)tst-env-setuid: $(objpfx)tst-sonamemove-runmod2.so
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# The object tst-nodeps1-mod.so has no explicit dependencies on libc.so.
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$(objpfx)tst-nodeps1-mod.so: $(objpfx)tst-nodeps1-mod.os
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$(LINK.o) -nostartfiles -nostdlib -shared -o $@ $^
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tst-nodeps1.so-no-z-defs = yes
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# Link libc.so before the test module with the IFUNC resolver reference.
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LDFLAGS-tst-nodeps1 = $(common-objpfx)libc.so $(objpfx)tst-nodeps1-mod.so
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$(objpfx)tst-nodeps1: $(objpfx)tst-nodeps1-mod.so
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# Reuse the tst-nodeps1 module. Link libc.so before the test module
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# with the IFUNC resolver reference.
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$(objpfx)tst-nodeps2-mod.so: $(common-objpfx)libc.so \
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$(objpfx)tst-nodeps1-mod.so $(objpfx)tst-nodeps2-mod.os
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$(LINK.o) -Wl,--no-as-needed -nostartfiles -nostdlib -shared -o $@ $^
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$(objpfx)tst-nodeps2.out: \
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$(objpfx)tst-nodeps1-mod.so $(objpfx)tst-nodeps2-mod.so
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@ -708,6 +708,17 @@ dl_open_worker_begin (void *a)
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them. However, such relocation dependencies in IFUNC resolvers
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are undefined anyway, so this is not a problem. */
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/* Ensure that libc is relocated first. This helps with the
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execution of IFUNC resolvers in libc, and matters only to newly
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created dlmopen namespaces. Do not do this for static dlopen
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because libc has relocations against ld.so, which may not have
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been relocated at this point. */
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#ifdef SHARED
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if (GL(dl_ns)[args->nsid].libc_map != NULL)
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_dl_open_relocate_one_object (args, r, GL(dl_ns)[args->nsid].libc_map,
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reloc_mode, &relocation_in_progress);
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#endif
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for (unsigned int i = last; i-- > first; )
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_dl_open_relocate_one_object (args, r, new->l_initfini[i], reloc_mode,
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&relocation_in_progress);
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10
elf/rtld.c
10
elf/rtld.c
@ -2272,11 +2272,17 @@ dl_main (const ElfW(Phdr) *phdr,
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objects. We do not re-relocate the dynamic linker itself in this
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loop because that could result in the GOT entries for functions we
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call being changed, and that would break us. It is safe to relocate
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the dynamic linker out of order because it has no copy relocs (we
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know that because it is self-contained). */
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the dynamic linker out of order because it has no copy relocations.
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Likewise for libc, which is relocated early to ensure that IFUNC
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resolvers in libc work. */
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int consider_profiling = GLRO(dl_profile) != NULL;
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if (GL(dl_ns)[LM_ID_BASE].libc_map != NULL)
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_dl_relocate_object (GL(dl_ns)[LM_ID_BASE].libc_map,
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GL(dl_ns)[LM_ID_BASE].libc_map->l_scope,
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GLRO(dl_lazy) ? RTLD_LAZY : 0, consider_profiling);
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/* If we are profiling we also must do lazy reloaction. */
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GLRO(dl_lazy) |= consider_profiling;
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25
elf/tst-nodeps1-mod.c
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25
elf/tst-nodeps1-mod.c
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@ -0,0 +1,25 @@
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/* Test module with no libc.so dependency and string function references.
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Copyright (C) 2023 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 <string.h>
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/* Some references to libc symbols which are likely to have IFUNC
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resolvers. If they do not, this module does not exercise bug 31083. */
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void *memcpy_pointer = memcpy;
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void *memmove_pointer = memmove;
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void *memset_pointer = memset;
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23
elf/tst-nodeps1.c
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23
elf/tst-nodeps1.c
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@ -0,0 +1,23 @@
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/* Test initially loaded module with implicit libc.so dependency (bug 31083).
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Copyright (C) 2023 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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/* Testing happens before main. */
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int
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main (void)
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{
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}
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1
elf/tst-nodeps2-mod.c
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1
elf/tst-nodeps2-mod.c
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@ -0,0 +1 @@
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/* Empty test module which depends on tst-nodeps1-mod.so. */
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29
elf/tst-nodeps2.c
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29
elf/tst-nodeps2.c
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@ -0,0 +1,29 @@
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/* Test dlmopen with implicit libc.so dependency (bug 31083).
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Copyright (C) 2023 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 <support/xdlfcn.h>
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static int
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do_test (void)
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{
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void *handle = xdlmopen (LM_ID_NEWLM, "tst-nodeps2-mod.so", RTLD_NOW);
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xdlclose (handle);
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return 0;
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}
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#include <support/test-driver.c>
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