linux-kernel - [PATCH v2 01/11] x86/cpu: Fixup __x86_return

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Date:   Mon, 14 Aug 2023 13:44:27 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        David.Kaplan@....com, Andrew.Cooper3@...rix.com,
        jpoimboe@...nel.org, gregkh@...uxfoundation.org,
        nik.borisov@...e.com
Subject: [PATCH v2 01/11] x86/cpu: Fixup __x86_return_thunk

Patch fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow
mitigation") reimplemented __x86_return_thunk with a mix of
SYM_FUNC_START and SYM_CODE_END, this is not a sane combination.

Since nothing should ever actually 'CALL' this, make it consistently
CODE.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/lib/retpoline.S |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -264,7 +264,9 @@ SYM_CODE_END(srso_safe_ret)
 SYM_FUNC_END(srso_untrain_ret)
 __EXPORT_THUNK(srso_untrain_ret)
 
-SYM_FUNC_START(__x86_return_thunk)
+SYM_CODE_START(__x86_return_thunk)
+	UNWIND_HINT_FUNC
+	ANNOTATE_NOENDBR
 	ALTERNATIVE_2 "jmp __ret", "call srso_safe_ret", X86_FEATURE_SRSO, \
 			"call srso_safe_ret_alias", X86_FEATURE_SRSO_ALIAS
 	int3