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f64f4ce069
The patch removes the the ELF_DURING_STARTUP optimization and assume
both .rel.dyn and .rel.plt might not be subsequent. This allows some
code simplification since relocation will be handled independently
where it is done on bootstrap.
At least on x86_64_64, I can not measure any performance implications.
Running 10000 time the command
LD_DEBUG=statistics ./elf/ld.so ./libc.so
And filtering the "total startup time in dynamic loader" result,
the geometric mean is:
patched master
Ryzen 7 5900x 24140 24952
i7-4510U 45957 45982
(The results do show some variation, I did not make any statistical
analysis).
It also allows build arm with lld, since it inserts ".ARM.exidx"
between ".rel.dyn" and ".rel.plt" for the loader.
Checked on x86_64-linux-gnu and arm-linux-gnueabihf.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
160 lines
6.6 KiB
C
160 lines
6.6 KiB
C
/* Inline functions for dynamic linking.
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Copyright (C) 1995-2021 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 <dl-machine.h>
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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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static inline void __attribute__((always_inline))
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elf_machine_rel (struct link_map *map, struct r_scope_elem *scope[],
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const ElfW(Rel) *reloc, const ElfW(Sym) *sym,
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const struct r_found_version *version,
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void *const reloc_addr, int skip_ifunc);
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static 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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static inline void __attribute__((always_inline))
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elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
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const ElfW(Rela) *reloc, const ElfW(Sym) *sym,
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const struct r_found_version *version, void *const reloc_addr,
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int skip_ifunc);
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static 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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static inline void __attribute__((always_inline))
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elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
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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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static inline void __attribute__((always_inline))
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elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
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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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#ifdef RESOLVE_MAP
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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, scope, 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 (!(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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for (int ranges_index = 0; ranges_index < 2; ++ranges_index) \
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elf_dynamic_do_##reloc ((map), scope, \
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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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} 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, scope, lazy, skip_ifunc) \
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_ELF_DYNAMIC_DO_RELOC (REL, Rel, map, scope, lazy, skip_ifunc, _ELF_CHECK_REL)
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# else
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# define ELF_DYNAMIC_DO_REL(map, scope, 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, scope, lazy, skip_ifunc) \
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_ELF_DYNAMIC_DO_RELOC (RELA, Rela, map, scope, lazy, skip_ifunc, _ELF_CHECK_REL)
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# else
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# define ELF_DYNAMIC_DO_RELA(map, scope, 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, scope, lazy, consider_profile, skip_ifunc) \
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do { \
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int edr_lazy = elf_machine_runtime_setup ((map), (scope), (lazy), \
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(consider_profile)); \
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ELF_DYNAMIC_DO_REL ((map), (scope), edr_lazy, skip_ifunc); \
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ELF_DYNAMIC_DO_RELA ((map), (scope), edr_lazy, skip_ifunc); \
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} while (0)
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#endif
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