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Date: Thu, 2 Apr 2020 10:22:19 +0200 From: Alexandre Chartre <alexandre.chartre@...cle.com> To: x86@...nel.org Cc: linux-kernel@...r.kernel.org, jpoimboe@...hat.com, peterz@...radead.org, jthierry@...hat.com, tglx@...utronix.de, alexandre.chartre@...cle.com Subject: [PATCH 6/7] x86/speculation: Annotate retpoline return instructions With retpoline, the return instruction (ret) is used to branch to an address stored on the stack. Provide a macro to annotate such trampoline returns so they can be properly handled by objtool, and use this macro to annotate retpoline return instructions. Signed-off-by: Alexandre Chartre <alexandre.chartre@...cle.com> --- arch/x86/include/asm/nospec-branch.h | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index a2885f801e13..9ae6dde2f10b 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -91,6 +91,20 @@ call \dst .endm +/* + * Retpoline return instruction. This should be used as a substitute + * for the ret instruction when doing a trampoline return. It is + * similar to the ret instruction but it tells objtool this is a + * trampoline return. + */ +.macro RETPOLINE_RET + .Lannotate_\@: + .pushsection .discard.retpoline_ret + _ASM_PTR .Lannotate_\@ + .popsection + ret +.endm + /* * These are the bare retpoline primitives for indirect jmp and call. * Do not use these directly; they only exist to make the ALTERNATIVE @@ -104,7 +118,7 @@ jmp .Lspec_trap_\@ .Ldo_rop_\@: mov \reg, (%_ASM_SP) - ret + RETPOLINE_RET .endm /* -- 2.18.2
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