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225 lines
8.4 KiB
225 lines
8.4 KiB
8 months ago
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commit 78ca44da0160a0b442f0ca1f253e3360f044b2ec
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Mon Nov 27 11:28:13 2023 +0100
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elf: Relocate libc.so early during startup and dlmopen (bug 31083)
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This makes it more likely that objects without dependencies can
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use IFUNC resolvers in libc.so.
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Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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Conflicts:
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elf/Makefile
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(test backport differences)
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elf/rtld.c
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(prelink support was removed upstream)
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diff --git a/elf/Makefile b/elf/Makefile
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index 8e1f91bcd917fd4e..7b7c6c171ce23247 100644
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--- a/elf/Makefile
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+++ b/elf/Makefile
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@@ -419,6 +419,8 @@ tests += \
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tst-nodelete2 \
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tst-nodelete-dlclose \
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tst-nodelete-opened \
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+ tst-nodeps1 \
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+ tst-nodeps2 \
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tst-noload \
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tst-null-argv \
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tst-relsort1 \
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@@ -777,6 +779,8 @@ modules-names = \
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tst-nodelete-dlclose-dso \
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tst-nodelete-dlclose-plugin \
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tst-nodelete-opened-lib \
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+ tst-nodeps1-mod \
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+ tst-nodeps2-mod \
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tst-null-argv-lib \
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tst-relsort1mod1 \
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tst-relsort1mod2 \
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@@ -931,8 +935,15 @@ extra-test-objs += $(addsuffix .os,$(strip $(modules-names)))
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# filtmod1.so, tst-big-note-lib.so, tst-ro-dynamic-mod.so have special
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# rules.
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-modules-names-nobuild := filtmod1 tst-big-note-lib tst-ro-dynamic-mod \
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- tst-audit24bmod1 tst-audit24bmod2
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+modules-names-nobuild += \
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+ filtmod1 \
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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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tests += $(tests-static)
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@@ -2684,3 +2695,18 @@ LDFLAGS-tst-dlclose-lazy-mod1.so = -Wl,-z,lazy,--no-as-needed
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$(objpfx)tst-dlclose-lazy-mod1.so: $(objpfx)tst-dlclose-lazy-mod2.so
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$(objpfx)tst-dlclose-lazy.out: \
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$(objpfx)tst-dlclose-lazy-mod1.so $(objpfx)tst-dlclose-lazy-mod2.so
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+
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+# The object tst-nodeps1-mod.so has no explicit dependencies on libc.so.
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+$(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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diff --git a/elf/dl-open.c b/elf/dl-open.c
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index cf3baccccb461878..4b58bdd668634130 100644
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--- a/elf/dl-open.c
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+++ b/elf/dl-open.c
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@@ -705,6 +705,17 @@ 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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+
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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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diff --git a/elf/rtld.c b/elf/rtld.c
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index 9de53ccaed420a57..a638d14e77745baa 100644
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--- a/elf/rtld.c
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+++ b/elf/rtld.c
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@@ -2421,11 +2421,17 @@ 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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+
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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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diff --git a/elf/tst-nodeps1-mod.c b/elf/tst-nodeps1-mod.c
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new file mode 100644
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index 0000000000000000..45c8e3c631251a89
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--- /dev/null
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+++ b/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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+
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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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+
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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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+
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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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+
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+#include <string.h>
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+
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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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diff --git a/elf/tst-nodeps1.c b/elf/tst-nodeps1.c
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new file mode 100644
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index 0000000000000000..1a8bde36cdb71446
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--- /dev/null
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+++ b/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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+
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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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+
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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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+
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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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+
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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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diff --git a/elf/tst-nodeps2-mod.c b/elf/tst-nodeps2-mod.c
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new file mode 100644
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index 0000000000000000..4913feee9b56e0e1
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--- /dev/null
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+++ b/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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diff --git a/elf/tst-nodeps2.c b/elf/tst-nodeps2.c
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new file mode 100644
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index 0000000000000000..0bdc8eeb8cba3a99
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--- /dev/null
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+++ b/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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+
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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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+
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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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+
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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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+
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+#include <support/xdlfcn.h>
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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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+ 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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+
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+#include <support/test-driver.c>
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