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117 lines
4.5 KiB
117 lines
4.5 KiB
9 months ago
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commit ddcacd91cc10ff92d6201eda87047d029c14158d
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Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
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Date: Thu Feb 11 11:40:11 2021 +0000
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i386: Avoid lazy relocation of tlsdesc [BZ #27137]
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Lazy tlsdesc relocation is racy because the static tls optimization and
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tlsdesc management operations are done without holding the dlopen lock.
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This similar to the commit b7cf203b5c17dd6d9878537d41e0c7cc3d270a67
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for aarch64, but it fixes a different race: bug 27137.
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On i386 the code is a bit more complicated than on x86_64 because both
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rel and rela relocs are supported.
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diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h
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index e5776ef7bc8ad749..3a30671591284d79 100644
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--- a/sysdeps/i386/dl-machine.h
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+++ b/sysdeps/i386/dl-machine.h
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@@ -679,50 +679,32 @@ elf_machine_lazy_rel (struct link_map *map,
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}
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else if (__glibc_likely (r_type == R_386_TLS_DESC))
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{
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- struct tlsdesc volatile * __attribute__((__unused__)) td =
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- (struct tlsdesc volatile *)reloc_addr;
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-
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- /* Handle relocations that reference the local *ABS* in a simple
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- way, so as to preserve a potential addend. */
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- if (ELF32_R_SYM (reloc->r_info) == 0)
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- td->entry = _dl_tlsdesc_resolve_abs_plus_addend;
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- /* Given a known-zero addend, we can store a pointer to the
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- reloc in the arg position. */
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- else if (td->arg == 0)
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- {
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- td->arg = (void*)reloc;
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- td->entry = _dl_tlsdesc_resolve_rel;
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- }
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- else
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- {
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- /* We could handle non-*ABS* relocations with non-zero addends
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- by allocating dynamically an arg to hold a pointer to the
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- reloc, but that sounds pointless. */
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- const Elf32_Rel *const r = reloc;
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- /* The code below was borrowed from elf_dynamic_do_rel(). */
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- const ElfW(Sym) *const symtab =
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- (const void *) D_PTR (map, l_info[DT_SYMTAB]);
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+ const Elf32_Rel *const r = reloc;
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+ /* The code below was borrowed from elf_dynamic_do_rel(). */
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+ const ElfW(Sym) *const symtab =
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+ (const void *) D_PTR (map, l_info[DT_SYMTAB]);
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+ /* Always initialize TLS descriptors completely at load time, in
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+ case static TLS is allocated for it that requires locking. */
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# ifdef RTLD_BOOTSTRAP
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- /* The dynamic linker always uses versioning. */
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- assert (map->l_info[VERSYMIDX (DT_VERSYM)] != NULL);
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+ /* The dynamic linker always uses versioning. */
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+ assert (map->l_info[VERSYMIDX (DT_VERSYM)] != NULL);
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# else
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- if (map->l_info[VERSYMIDX (DT_VERSYM)])
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+ if (map->l_info[VERSYMIDX (DT_VERSYM)])
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# endif
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- {
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- const ElfW(Half) *const version =
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- (const void *) D_PTR (map, l_info[VERSYMIDX (DT_VERSYM)]);
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- ElfW(Half) ndx = version[ELFW(R_SYM) (r->r_info)] & 0x7fff;
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- elf_machine_rel (map, r, &symtab[ELFW(R_SYM) (r->r_info)],
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- &map->l_versions[ndx],
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- (void *) (l_addr + r->r_offset), skip_ifunc);
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- }
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+ {
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+ const ElfW(Half) *const version =
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+ (const void *) D_PTR (map, l_info[VERSYMIDX (DT_VERSYM)]);
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+ ElfW(Half) ndx = version[ELFW(R_SYM) (r->r_info)] & 0x7fff;
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+ elf_machine_rel (map, r, &symtab[ELFW(R_SYM) (r->r_info)],
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+ &map->l_versions[ndx],
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+ (void *) (l_addr + r->r_offset), skip_ifunc);
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+ }
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# ifndef RTLD_BOOTSTRAP
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- else
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- elf_machine_rel (map, r, &symtab[ELFW(R_SYM) (r->r_info)], NULL,
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- (void *) (l_addr + r->r_offset), skip_ifunc);
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+ else
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+ elf_machine_rel (map, r, &symtab[ELFW(R_SYM) (r->r_info)], NULL,
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+ (void *) (l_addr + r->r_offset), skip_ifunc);
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# endif
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- }
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}
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else if (__glibc_unlikely (r_type == R_386_IRELATIVE))
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{
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@@ -749,11 +731,21 @@ elf_machine_lazy_rela (struct link_map *map,
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;
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else if (__glibc_likely (r_type == R_386_TLS_DESC))
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{
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- struct tlsdesc volatile * __attribute__((__unused__)) td =
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- (struct tlsdesc volatile *)reloc_addr;
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+ const Elf_Symndx symndx = ELFW (R_SYM) (reloc->r_info);
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+ const ElfW (Sym) *symtab = (const void *)D_PTR (map, l_info[DT_SYMTAB]);
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+ const ElfW (Sym) *sym = &symtab[symndx];
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+ const struct r_found_version *version = NULL;
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+
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+ if (map->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
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+ {
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+ const ElfW (Half) *vernum =
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+ (const void *)D_PTR (map, l_info[VERSYMIDX (DT_VERSYM)]);
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+ version = &map->l_versions[vernum[symndx] & 0x7fff];
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+ }
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- td->arg = (void*)reloc;
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- td->entry = _dl_tlsdesc_resolve_rela;
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+ /* Always initialize TLS descriptors completely at load time, in
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+ case static TLS is allocated for it that requires locking. */
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+ elf_machine_rela (map, reloc, sym, version, reloc_addr, skip_ifunc);
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}
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else if (__glibc_unlikely (r_type == R_386_IRELATIVE))
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{
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