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Message-ID: <YCOb2byLJhLOjhrL@hirez.programming.kicks-ass.net> Date: Wed, 10 Feb 2021 09:39:53 +0100 From: Peter Zijlstra <peterz@...radead.org> To: Josh Poimboeuf <jpoimboe@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Dave Hansen <dave.hansen@...el.com>, x86@...nel.org, linux-kernel@...r.kernel.org Cc: Steven Rostedt <rostedt@...dmis.org>, yu-cheng.yu@...el.com Subject: [RFC][PATCH] objtool: WARN about ENDBR instructions Given all the ENDBR fun we recently had, do we want the below? Until someone comes and fixes up kprobes/ftrace/livepatch etc.. having them is a giant pain and we'd better warn about it. --- diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index 931cef78b857..e708731b10cd 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -91,7 +91,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec, { struct insn insn; int x86_64, sign; - unsigned char op1, op2, rex = 0, rex_b = 0, rex_r = 0, rex_w = 0, + unsigned char op1, op2, pfx = 0, rex = 0, rex_b = 0, rex_r = 0, rex_w = 0, rex_x = 0, modrm = 0, modrm_mod = 0, modrm_rm = 0, modrm_reg = 0, sib = 0; struct stack_op *op = NULL; @@ -118,6 +118,9 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec, op1 = insn.opcode.bytes[0]; op2 = insn.opcode.bytes[1]; + if (insn.prefixes.nbytes) + pfx = insn.prefixes.bytes[0]; + if (insn.rex_prefix.nbytes) { rex = insn.rex_prefix.bytes[0]; rex_w = X86_REX_W(rex) >> 3; @@ -444,6 +447,11 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec, /* nopl/nopw */ *type = INSN_NOP; + } else if (op2 == 0x1e && pfx == 0xf3 && (modrm == 0xfa || modrm == 0xfb)) { + + /* endbr32/endbr64 */ + WARN("endbr32/64 instruction at %s:0x%lx", sec->name, offset); + } else if (op2 == 0xa0 || op2 == 0xa8) { /* push fs/gs */
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