Messages in this thread Patch in this message | | | Date | Mon, 22 Nov 2021 19:09:47 +0100 | From | Peter Zijlstra <> | Subject | Re: [RFC][PATCH 3/6] x86: Add ENDBR to IRET-to-Self |
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On Mon, Nov 22, 2021 at 06:03:04PM +0100, Peter Zijlstra wrote: > The IRET-to-Self chunks trigger forward code references without ENDBR, > fix that.
Andy corrected me, IRET doesn't take ENBR, the alternative is the below.
--- --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1316,7 +1316,6 @@ SYM_CODE_START(asm_exc_nmi) iretq /* continues at repeat_nmi below */ UNWIND_HINT_IRET_REGS entry=0 1: - ENDBR #endif repeat_nmi: --- a/arch/x86/include/asm/sync_core.h +++ b/arch/x86/include/asm/sync_core.h @@ -6,7 +6,6 @@ #include <asm/processor.h> #include <asm/cpufeature.h> #include <asm/special_insns.h> -#include <asm/ibt.h> #ifdef CONFIG_X86_32 static inline void iret_to_self(void) @@ -35,7 +34,6 @@ static inline void iret_to_self(void) "pushq $1f\n\t" "iretq\n\t" "1:" - ASM_ENDBR : "=&r" (tmp), ASM_CALL_CONSTRAINT : : "cc", "memory"); } #endif /* CONFIG_X86_32 */ --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -598,6 +598,7 @@ int arch_decode_instruction(struct objto op->dest.type = OP_DEST_REG; op->dest.reg = CFI_SP; } + *type = INSN_IRET; break; } --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -3587,7 +3587,7 @@ static int validate_ibt_reloc(struct obj static void validate_ibt_insn(struct objtool_file *file, struct instruction *insn) { struct reloc *reloc = insn_reloc(file, insn); - struct instruction *target; + struct instruction *target, *n; unsigned long offset; if (!reloc) @@ -3599,8 +3599,16 @@ static void validate_ibt_insn(struct obj offset = reloc->sym->offset + reloc->addend; target = find_insn(file, reloc->sym->sec, offset); - if (target && insn->func == target->func && target->this_ip) - return; + if (target && insn->func == target->func) { + if (target->this_ip) + return; + + for (n = insn; n->offset <= target->offset; + n = next_insn_same_func(file, n)) { + if (n->type == INSN_IRET) + return; + } + } WARN_FUNC("relocation to !ENDBR: %s+0x%lx", insn->sec, insn->offset, --- a/tools/objtool/include/objtool/arch.h +++ b/tools/objtool/include/objtool/arch.h @@ -27,6 +27,7 @@ enum insn_type { INSN_STD, INSN_CLD, INSN_ENDBR, + INSN_IRET, INSN_OTHER, };
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