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From: Fangrui Song <maskray@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc] x86-64: Handle fewer relocation types for RTLD_BOOTSTRAP Date: Thu, 16 Jun 2022 18:48:16 +0000 (GMT) [thread overview] Message-ID: <20220616184816.E45063850429@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4ef05df5ef70ed8e71c3b9236645b8c601a0b4b4 commit 4ef05df5ef70ed8e71c3b9236645b8c601a0b4b4 Author: Fangrui Song <maskray@google.com> Date: Thu Jun 16 11:48:15 2022 -0700 x86-64: Handle fewer relocation types for RTLD_BOOTSTRAP The RTLD_BOOTSTRAP branch is used to relocate ld.so itself. It only needs to handle RELATIVE, GLOB_DAT, and JUMP_SLOT. RELATIVE has been handled (by _ELF_DYNAMIC_DO_RELOC due to DT_RELACOUNT, or RELR), so the switch statement only needs to handle GLOB_DAT and JUMP_SLOT. We can drop these `#if[n]def RTLD_BOOTSTRAP` and add a large `# ifndef RTLD_BOOTSTRAP` instead. Diff: --- sysdeps/x86_64/dl-machine.h | 32 ++++++-------------------------- 1 file changed, 6 insertions(+), 26 deletions(-) diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h index 06c9a932b0..34766325ae 100644 --- a/sysdeps/x86_64/dl-machine.h +++ b/sysdeps/x86_64/dl-machine.h @@ -298,6 +298,11 @@ and creates an unsatisfiable circular dependency.\n", switch (r_type) { + case R_X86_64_GLOB_DAT: + case R_X86_64_JUMP_SLOT: + *reloc_addr = value; + break; + # ifndef RTLD_BOOTSTRAP # ifdef __ILP32__ case R_X86_64_SIZE64: @@ -314,29 +319,14 @@ and creates an unsatisfiable circular dependency.\n", value = sym->st_size; *reloc_addr = value + reloc->r_addend; break; -# endif - - case R_X86_64_GLOB_DAT: - case R_X86_64_JUMP_SLOT: - *reloc_addr = value; - break; case R_X86_64_DTPMOD64: -# ifdef RTLD_BOOTSTRAP - /* During startup the dynamic linker is always the module - with index 1. - XXX If this relocation is necessary move before RESOLVE - call. */ - *reloc_addr = 1; -# else /* Get the information from the link map returned by the resolve function. */ if (sym_map != NULL) *reloc_addr = sym_map->l_tls_modid; -# endif break; case R_X86_64_DTPOFF64: -# ifndef RTLD_BOOTSTRAP /* During relocation all TLS symbols are defined and used. Therefore the offset is already correct. */ if (sym != NULL) @@ -353,23 +343,19 @@ and creates an unsatisfiable circular dependency.\n", *reloc_addr = value; # endif } -# endif break; case R_X86_64_TLSDESC: { struct tlsdesc volatile *td = (struct tlsdesc volatile *)reloc_addr; -# ifndef RTLD_BOOTSTRAP if (! sym) { td->arg = (void*)reloc->r_addend; td->entry = _dl_tlsdesc_undefweak; } else -# endif { -# ifndef RTLD_BOOTSTRAP # ifndef SHARED CHECK_STATIC_TLS (map, sym_map); # else @@ -381,7 +367,6 @@ and creates an unsatisfiable circular dependency.\n", } else # endif -# endif { td->arg = (void*)(sym->st_value - sym_map->l_tls_offset + reloc->r_addend); @@ -392,13 +377,9 @@ and creates an unsatisfiable circular dependency.\n", } case R_X86_64_TPOFF64: /* The offset is negative, forward from the thread pointer. */ -# ifndef RTLD_BOOTSTRAP if (sym != NULL) -# endif { -# ifndef RTLD_BOOTSTRAP CHECK_STATIC_TLS (map, sym_map); -# endif /* We know the offset of the object the symbol is contained in. It is a negative value which will be added to the thread pointer. */ @@ -416,7 +397,6 @@ and creates an unsatisfiable circular dependency.\n", } break; -# ifndef RTLD_BOOTSTRAP case R_X86_64_64: /* value + r_addend may be > 0xffffffff and R_X86_64_64 relocation updates the whole 64-bit entry. */ @@ -481,7 +461,7 @@ and creates an unsatisfiable circular dependency.\n", default: _dl_reloc_bad_type (map, r_type, 0); break; -# endif +# endif /* !RTLD_BOOTSTRAP */ } } }
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