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30afd8c44d
Compilers may decide to put the rfv variable in .data rather than on the stack. It's slightly better to put it in .data.rel.ro.local instead. Regardles of that, making it const may enable further optimisations. Found when examining relative relocations (GOT ones in particular) as part of enabling static-pie for PowerPC64.
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) 2005-2022 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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const 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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