From dc02368164bd0ec603e3f5b3dd8252744a667b8a Mon Sep 17 00:00:00 2001 From: Joe Lawrence Date: Sun, 22 Aug 2021 18:50:36 -0400 Subject: objtool: Make .altinstructions section entry size consistent Commit e31694e0a7a7 ("objtool: Don't make .altinstructions writable") aligned objtool-created and kernel-created .altinstructions section flags, but there remains a minor discrepency in their use of a section entry size: objtool sets one while the kernel build does not. While sh_entsize of sizeof(struct alt_instr) seems intuitive, this small deviation can cause failures with external tooling (kpatch-build). Fix this by creating new .altinstructions sections with sh_entsize of 0 and then later updating sec->sh_size as alternatives are added to the section. An added benefit is avoiding the data descriptor and buffer created by elf_create_section(), but previously unused by elf_add_alternative(). Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls") Signed-off-by: Joe Lawrence Reviewed-by: Miroslav Benes Signed-off-by: Josh Poimboeuf Link: https://lore.kernel.org/r/20210822225037.54620-2-joe.lawrence@redhat.com Cc: Andy Lavr Cc: Peter Zijlstra Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- tools/objtool/arch/x86/decode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'tools') diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index bc821056aba9..0893436cc09f 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -684,7 +684,7 @@ static int elf_add_alternative(struct elf *elf, sec = find_section_by_name(elf, ".altinstructions"); if (!sec) { sec = elf_create_section(elf, ".altinstructions", - SHF_ALLOC, size, 0); + SHF_ALLOC, 0, 0); if (!sec) { WARN_ELF("elf_create_section"); -- cgit v1.2.3