linux-kernel - [PATCH 7/7] x86/speculation: Remove most ANNOTATE_NOSPEC

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Date:   Thu,  2 Apr 2020 10:22:20 +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 7/7] x86/speculation: Remove most ANNOTATE_NOSPEC_ALTERNATIVE

Now that intra-function calls and retpoline return instructions have
been annotated and that they are supported by objtool, almost all
ANNOTATE_NOSPEC_ALTERNATIVE can be removed.

ANNOTATE_NOSPEC_ALTERNATIVE is still needed when using the
__FILL_RETURN_BUFFER macro because it loops on intra-function calls
and objtool doesn't handle loops modifying the stack pointer.

Signed-off-by: Alexandre Chartre <alexandre.chartre@...cle.com>
---
 arch/x86/include/asm/nospec-branch.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 9ae6dde2f10b..70d4444120b1 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -140,7 +140,6 @@
  */
 .macro JMP_NOSPEC reg:req
 #ifdef CONFIG_RETPOLINE
-	ANNOTATE_NOSPEC_ALTERNATIVE
 	ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *\reg),	\
 		__stringify(RETPOLINE_JMP \reg), X86_FEATURE_RETPOLINE,	\
 		__stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *\reg), X86_FEATURE_RETPOLINE_AMD
@@ -151,7 +150,6 @@
 
 .macro CALL_NOSPEC reg:req
 #ifdef CONFIG_RETPOLINE
-	ANNOTATE_NOSPEC_ALTERNATIVE
 	ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; call *\reg),	\
 		__stringify(RETPOLINE_CALL \reg), X86_FEATURE_RETPOLINE,\
 		__stringify(lfence; ANNOTATE_RETPOLINE_SAFE; call *\reg), X86_FEATURE_RETPOLINE_AMD
@@ -190,7 +188,6 @@
  * which is ensured when CONFIG_RETPOLINE is defined.
  */
 # define CALL_NOSPEC						\
-	ANNOTATE_NOSPEC_ALTERNATIVE				\
 	ALTERNATIVE_2(						\
 	ANNOTATE_RETPOLINE_SAFE					\
 	"call *%[thunk_target]\n",				\
@@ -209,7 +206,6 @@
  * here, anyway.
  */
 # define CALL_NOSPEC						\
-	ANNOTATE_NOSPEC_ALTERNATIVE				\
 	ALTERNATIVE_2(						\
 	ANNOTATE_RETPOLINE_SAFE					\
 	"call *%[thunk_target]\n",				\
-- 
2.18.2