linux-kernel - [PATCH 1/2] x86: Simplify Retpoline thunk

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Message-ID: <20220419205241.280037046@infradead.org>
Date:   Tue, 19 Apr 2022 22:41:10 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org, jpoimboe@...hat.com, brgerst@...il.com,
        jiangshanlai@...il.com, Andrew.Cooper3@...rix.com
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org
Subject: [PATCH 1/2] x86: Simplify Retpoline thunk

Now that we rewrite all the indirect call sites, per commit:

  750850090081 ("x86/alternative: Implement .retpoline_sites support")

it doesn't make sense to have the retpoline thunks be an ALTERNATIVE_2
that still includes a 'naked' indirect jump.

(this accidentally 'defunnels' i386 by going back to full retpolines)

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/lib/retpoline.S |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -32,9 +32,9 @@
 SYM_INNER_LABEL(__x86_indirect_thunk_\reg, SYM_L_GLOBAL)
 	UNWIND_HINT_EMPTY
 
-	ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \
-		      __stringify(RETPOLINE \reg), X86_FEATURE_RETPOLINE, \
-		      __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg; int3), X86_FEATURE_RETPOLINE_LFENCE
+	ALTERNATIVE __stringify(RETPOLINE \reg), \
+		    __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg; int3), \
+		    X86_FEATURE_RETPOLINE_LFENCE
 
 .endm