From 2d49b721dc18c113d5221f4cf5a6104eb66cb7f2 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 10 Jun 2021 09:04:29 +0200 Subject: objtool: Only rewrite unconditional retpoline thunk calls It turns out that the compilers generate conditional branches to the retpoline thunks like: 5d5: 0f 85 00 00 00 00 jne 5db 5d7: R_X86_64_PLT32 __x86_indirect_thunk_r11-0x4 while the rewrite can only handle JMP/CALL to the thunks. The result is the alternative wrecking the code. Make sure to skip writing the alternatives for conditional branches. Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls") Reported-by: Lukasz Majczak Reported-by: Nathan Chancellor Signed-off-by: Peter Zijlstra (Intel) Tested-by: Nathan Chancellor --- tools/objtool/arch/x86/decode.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'tools/objtool') diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index 24295d39713b..523aa4157f80 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -747,6 +747,10 @@ int arch_rewrite_retpolines(struct objtool_file *file) list_for_each_entry(insn, &file->retpoline_call_list, call_node) { + if (insn->type != INSN_JUMP_DYNAMIC && + insn->type != INSN_CALL_DYNAMIC) + continue; + if (!strcmp(insn->sec->name, ".text.__x86.indirect_thunk")) continue; -- cgit v1.2.3