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On some targets static TLS surplus area can be used opportunistically for dynamically loaded modules such that the TLS access then becomes faster (TLSDESC and powerpc TLS optimization). However we don't want all surplus TLS to be used for this optimization because dynamically loaded modules with initial-exec model TLS can only use surplus TLS. The new contract for surplus static TLS use is: - libc.so can have up to 192 bytes of IE TLS, - other system libraries together can have up to 144 bytes of IE TLS. - Some "optional" static TLS is available for opportunistic use. The optional TLS is now tunable: rtld.optional_static_tls, so users can directly affect the allocated static TLS size. (Note that module unloading with dlclose does not reclaim static TLS. After the optional TLS runs out, TLS access is no longer optimized to use static TLS.) The default setting of rtld.optional_static_tls is 512 so the surplus TLS is 3*192 + 4*144 + 512 = 1664 by default, the same as before. Fixes BZ #25051. Tested on aarch64-linux-gnu and x86_64-linux-gnu. Reviewed-by: Carlos O'Donell <carlos@redhat.com>
204 lines
8.1 KiB
C
204 lines
8.1 KiB
C
/* Inline functions for dynamic linking.
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Copyright (C) 1995-2020 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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/* This macro is used as a callback from elf_machine_rel{a,} when a
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static TLS reloc is about to be performed. Since (in dl-load.c) we
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permit dynamic loading of objects that might use such relocs, we
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have to check whether each use is actually doable. If the object
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whose TLS segment the reference resolves to was allocated space in
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the static TLS block at startup, then it's ok. Otherwise, we make
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an attempt to allocate it in surplus space on the fly. If that
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can't be done, we fall back to the error that DF_STATIC_TLS is
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intended to produce. */
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#define HAVE_STATIC_TLS(map, sym_map) \
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(__builtin_expect ((sym_map)->l_tls_offset != NO_TLS_OFFSET \
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&& ((sym_map)->l_tls_offset \
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!= FORCED_DYNAMIC_TLS_OFFSET), 1))
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#define CHECK_STATIC_TLS(map, sym_map) \
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do { \
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if (!HAVE_STATIC_TLS (map, sym_map)) \
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_dl_allocate_static_tls (sym_map); \
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} while (0)
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#define TRY_STATIC_TLS(map, sym_map) \
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(__builtin_expect ((sym_map)->l_tls_offset \
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!= FORCED_DYNAMIC_TLS_OFFSET, 1) \
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&& (__builtin_expect ((sym_map)->l_tls_offset != NO_TLS_OFFSET, 1) \
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|| _dl_try_allocate_static_tls (sym_map, true) == 0))
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int _dl_try_allocate_static_tls (struct link_map *map, bool optional)
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attribute_hidden;
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#include <elf.h>
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#ifdef RESOLVE_MAP
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/* We pass reloc_addr as a pointer to void, as opposed to a pointer to
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ElfW(Addr), because not all architectures can assume that the
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relocated address is properly aligned, whereas the compiler is
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entitled to assume that a pointer to a type is properly aligned for
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the type. Even if we cast the pointer back to some other type with
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less strict alignment requirements, the compiler might still
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remember that the pointer was originally more aligned, thereby
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optimizing away alignment tests or using word instructions for
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copying memory, breaking the very code written to handle the
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unaligned cases. */
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# if ! ELF_MACHINE_NO_REL
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auto inline void __attribute__((always_inline))
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elf_machine_rel (struct link_map *map, const ElfW(Rel) *reloc,
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const ElfW(Sym) *sym, const struct r_found_version *version,
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void *const reloc_addr, int skip_ifunc);
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auto inline void __attribute__((always_inline))
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elf_machine_rel_relative (ElfW(Addr) l_addr, const ElfW(Rel) *reloc,
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void *const reloc_addr);
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# endif
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# if ! ELF_MACHINE_NO_RELA
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auto inline void __attribute__((always_inline))
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elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
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const ElfW(Sym) *sym, const struct r_found_version *version,
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void *const reloc_addr, int skip_ifunc);
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auto inline void __attribute__((always_inline))
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elf_machine_rela_relative (ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
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void *const reloc_addr);
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# endif
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# if ELF_MACHINE_NO_RELA || defined ELF_MACHINE_PLT_REL
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auto inline void __attribute__((always_inline))
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elf_machine_lazy_rel (struct link_map *map,
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ElfW(Addr) l_addr, const ElfW(Rel) *reloc,
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int skip_ifunc);
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# else
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auto inline void __attribute__((always_inline))
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elf_machine_lazy_rel (struct link_map *map,
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ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
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int skip_ifunc);
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# endif
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#endif
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#include <dl-machine.h>
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#include "get-dynamic-info.h"
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#ifdef RESOLVE_MAP
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# if defined RTLD_BOOTSTRAP || defined STATIC_PIE_BOOTSTRAP
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# define ELF_DURING_STARTUP (1)
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# else
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# define ELF_DURING_STARTUP (0)
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# endif
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/* Get the definitions of `elf_dynamic_do_rel' and `elf_dynamic_do_rela'.
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These functions are almost identical, so we use cpp magic to avoid
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duplicating their code. It cannot be done in a more general function
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because we must be able to completely inline. */
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/* On some machines, notably SPARC, DT_REL* includes DT_JMPREL in its
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range. Note that according to the ELF spec, this is completely legal!
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We are guarenteed that we have one of three situations. Either DT_JMPREL
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comes immediately after DT_REL*, or there is overlap and DT_JMPREL
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consumes precisely the very end of the DT_REL*, or DT_JMPREL and DT_REL*
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are completely separate and there is a gap between them. */
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# define _ELF_DYNAMIC_DO_RELOC(RELOC, reloc, map, do_lazy, skip_ifunc, test_rel) \
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do { \
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struct { ElfW(Addr) start, size; \
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__typeof (((ElfW(Dyn) *) 0)->d_un.d_val) nrelative; int lazy; } \
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ranges[2] = { { 0, 0, 0, 0 }, { 0, 0, 0, 0 } }; \
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\
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if ((map)->l_info[DT_##RELOC]) \
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{ \
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ranges[0].start = D_PTR ((map), l_info[DT_##RELOC]); \
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ranges[0].size = (map)->l_info[DT_##RELOC##SZ]->d_un.d_val; \
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if (map->l_info[VERSYMIDX (DT_##RELOC##COUNT)] != NULL) \
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ranges[0].nrelative \
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= map->l_info[VERSYMIDX (DT_##RELOC##COUNT)]->d_un.d_val; \
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} \
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if ((map)->l_info[DT_PLTREL] \
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&& (!test_rel || (map)->l_info[DT_PLTREL]->d_un.d_val == DT_##RELOC)) \
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{ \
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ElfW(Addr) start = D_PTR ((map), l_info[DT_JMPREL]); \
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ElfW(Addr) size = (map)->l_info[DT_PLTRELSZ]->d_un.d_val; \
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\
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if (ranges[0].start + ranges[0].size == (start + size)) \
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ranges[0].size -= size; \
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if (ELF_DURING_STARTUP \
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|| (!(do_lazy) \
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&& (ranges[0].start + ranges[0].size) == start)) \
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{ \
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/* Combine processing the sections. */ \
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ranges[0].size += size; \
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} \
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else \
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{ \
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ranges[1].start = start; \
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ranges[1].size = size; \
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ranges[1].lazy = (do_lazy); \
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} \
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} \
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\
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if (ELF_DURING_STARTUP) \
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elf_dynamic_do_##reloc ((map), ranges[0].start, ranges[0].size, \
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ranges[0].nrelative, 0, skip_ifunc); \
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else \
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{ \
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int ranges_index; \
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for (ranges_index = 0; ranges_index < 2; ++ranges_index) \
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elf_dynamic_do_##reloc ((map), \
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ranges[ranges_index].start, \
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ranges[ranges_index].size, \
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ranges[ranges_index].nrelative, \
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ranges[ranges_index].lazy, \
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skip_ifunc); \
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} \
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} while (0)
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# if ELF_MACHINE_NO_REL || ELF_MACHINE_NO_RELA
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# define _ELF_CHECK_REL 0
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# else
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# define _ELF_CHECK_REL 1
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# endif
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# if ! ELF_MACHINE_NO_REL
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# include "do-rel.h"
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# define ELF_DYNAMIC_DO_REL(map, lazy, skip_ifunc) \
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_ELF_DYNAMIC_DO_RELOC (REL, Rel, map, lazy, skip_ifunc, _ELF_CHECK_REL)
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# else
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# define ELF_DYNAMIC_DO_REL(map, lazy, skip_ifunc) /* Nothing to do. */
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# endif
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# if ! ELF_MACHINE_NO_RELA
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# define DO_RELA
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# include "do-rel.h"
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# define ELF_DYNAMIC_DO_RELA(map, lazy, skip_ifunc) \
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_ELF_DYNAMIC_DO_RELOC (RELA, Rela, map, lazy, skip_ifunc, _ELF_CHECK_REL)
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# else
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# define ELF_DYNAMIC_DO_RELA(map, lazy, skip_ifunc) /* Nothing to do. */
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# endif
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/* This can't just be an inline function because GCC is too dumb
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to inline functions containing inlines themselves. */
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# define ELF_DYNAMIC_RELOCATE(map, lazy, consider_profile, skip_ifunc) \
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do { \
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int edr_lazy = elf_machine_runtime_setup ((map), (lazy), \
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(consider_profile)); \
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ELF_DYNAMIC_DO_REL ((map), edr_lazy, skip_ifunc); \
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ELF_DYNAMIC_DO_RELA ((map), edr_lazy, skip_ifunc); \
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} while (0)
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#endif
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