From e390f9a9689a42f477a6073e2e7df530a4c1b740 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Wed, 1 Mar 2017 12:04:44 -0600 Subject: [PATCH] objtool, modules: Discard objtool annotation sections for modules The '__unreachable' and '__func_stack_frame_non_standard' sections are only used at compile time. They're discarded for vmlinux but they should also be discarded for modules. Since this is a recurring pattern, prefix the section names with ".discard.". It's a nice convention and vmlinux.lds.h already discards such sections. Also remove the 'a' (allocatable) flag from the __unreachable section since it doesn't make sense for a discarded section. Suggested-by: Linus Torvalds Signed-off-by: Josh Poimboeuf Cc: Jessica Yu Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends") Link: http://lkml.kernel.org/r/20170301180444.lhd53c5tibc4ns77@treble Signed-off-by: Ingo Molnar --- arch/x86/kernel/vmlinux.lds.S | 2 -- include/linux/compiler-gcc.h | 2 +- include/linux/frame.h | 2 +- scripts/mod/modpost.c | 1 + scripts/module-common.lds | 5 ++++- tools/objtool/builtin-check.c | 6 +++--- 6 files changed, 10 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index ad0118fbce90..c74ae9ce8dc4 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -345,8 +345,6 @@ SECTIONS DISCARDS /DISCARD/ : { *(.eh_frame) - *(__func_stack_frame_non_standard) - *(__unreachable) } } diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index b6bb9019d87f..0efef9cf014f 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -200,7 +200,7 @@ #ifdef CONFIG_STACK_VALIDATION #define annotate_unreachable() ({ \ asm("%c0:\t\n" \ - ".pushsection __unreachable, \"a\"\t\n" \ + ".pushsection .discard.unreachable\t\n" \ ".long %c0b - .\t\n" \ ".popsection\t\n" : : "i" (__LINE__)); \ }) diff --git a/include/linux/frame.h b/include/linux/frame.h index e6baaba3f1ae..d772c61c31da 100644 --- a/include/linux/frame.h +++ b/include/linux/frame.h @@ -11,7 +11,7 @@ * For more information, see tools/objtool/Documentation/stack-validation.txt. */ #define STACK_FRAME_NON_STANDARD(func) \ - static void __used __section(__func_stack_frame_non_standard) \ + static void __used __section(.discard.func_stack_frame_non_standard) \ *__func_stack_frame_non_standard_##func = func #else /* !CONFIG_STACK_VALIDATION */ diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 4dedd0d3d3a7..30d752a4a6a6 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -854,6 +854,7 @@ static const char *const section_white_list[] = ".cmem*", /* EZchip */ ".fmt_slot*", /* EZchip */ ".gnu.lto*", + ".discard.*", NULL }; diff --git a/scripts/module-common.lds b/scripts/module-common.lds index 73a2c7da0e55..cf7e52e4781b 100644 --- a/scripts/module-common.lds +++ b/scripts/module-common.lds @@ -4,7 +4,10 @@ * combine them automatically. */ SECTIONS { - /DISCARD/ : { *(.discard) } + /DISCARD/ : { + *(.discard) + *(.discard.*) + } __ksymtab 0 : { *(SORT(___ksymtab+*)) } __ksymtab_gpl 0 : { *(SORT(___ksymtab_gpl+*)) } diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c index 5fc52ee3264c..4cfdbb5b6967 100644 --- a/tools/objtool/builtin-check.c +++ b/tools/objtool/builtin-check.c @@ -339,13 +339,13 @@ static int add_dead_ends(struct objtool_file *file) struct instruction *insn; bool found; - sec = find_section_by_name(file->elf, ".rela__unreachable"); + sec = find_section_by_name(file->elf, ".rela.discard.unreachable"); if (!sec) return 0; list_for_each_entry(rela, &sec->rela_list, list) { if (rela->sym->type != STT_SECTION) { - WARN("unexpected relocation symbol type in .rela__unreachable"); + WARN("unexpected relocation symbol type in %s", sec->name); return -1; } insn = find_insn(file, rela->sym->sec, rela->addend); @@ -1272,7 +1272,7 @@ int cmd_check(int argc, const char **argv) INIT_LIST_HEAD(&file.insn_list); hash_init(file.insn_hash); - file.whitelist = find_section_by_name(file.elf, "__func_stack_frame_non_standard"); + file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard"); file.rodata = find_section_by_name(file.elf, ".rodata"); file.ignore_unreachables = false; file.c_file = find_section_by_name(file.elf, ".comment"); -- 2.20.1