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1bdda52fe9
This patch moves the vDSO setup from libc to loader code, just after the vDSO link_map setup. For static case the initialization is moved to _dl_non_dynamic_init instead. Instead of using the mangled pointer, the vDSO data is set as attribute_relro (on _rtld_global_ro for shared or _dl_vdso_* for static). It is read-only even with partial relro. It fixes BZ#24967 now that the vDSO pointer is setup earlier than malloc interposition is called. Also, vDSO calls should not be a problem for static dlopen as indicated by BZ#20802. The vDSO pointer would be zero-initialized and the syscall will be issued instead. Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu, arm-linux-gnueabihf, powerpc64le-linux-gnu, powerpc64-linux-gnu, powerpc-linux-gnu, s390x-linux-gnu, sparc64-linux-gnu, and sparcv9-linux-gnu. I also run some tests on mips. Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
59 lines
1.9 KiB
C
59 lines
1.9 KiB
C
/* ELF symbol resolve functions for VDSO objects.
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Copyright (C) 2005-2020 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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#ifndef _DL_VDSO_H
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#define _DL_VDSO_H 1
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#include <ldsodefs.h>
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#include <dl-hash.h>
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/* If the architecture support vDSO it should define which is the expected
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kernel version and hash value through both VDSO_NAME and VDSO_HASH
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(usually defined at architecture sysdep.h). */
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#ifndef VDSO_NAME
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# define VDSO_NAME "LINUX_0.0"
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#endif
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#ifndef VDSO_HASH
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# define VDSO_HASH 0
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#endif
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/* Functions for resolving symbols in the VDSO link map. */
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static inline void *
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dl_vdso_vsym (const char *name)
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{
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struct link_map *map = GLRO (dl_sysinfo_map);
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if (map == NULL)
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return NULL;
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/* Use a WEAK REF so we don't error out if the symbol is not found. */
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ElfW (Sym) wsym = { 0 };
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wsym.st_info = (unsigned char) ELFW (ST_INFO (STB_WEAK, STT_NOTYPE));
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struct r_found_version rfv = { VDSO_NAME, VDSO_HASH, 1, NULL };
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/* Search the scope of the vdso map. */
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const ElfW (Sym) *ref = &wsym;
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lookup_t result = GLRO (dl_lookup_symbol_x) (name, map, &ref,
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map->l_local_scope,
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&rfv, 0, 0, NULL);
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return ref != NULL ? DL_SYMBOL_ADDRESS (result, ref) : NULL;
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}
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#endif /* dl-vdso.h */
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