linux-kernel - [RFC][PATCH 7/7] x86/nospec: Remove ANNOTATE_NOSPEC

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Message-Id: <20200416151025.123683762@infradead.org>
Date:   Thu, 16 Apr 2020 17:07:59 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     jpoimboe@...hat.com, alexandre.chartre@...cle.com
Cc:     linux-kernel@...r.kernel.org, jthierry@...hat.com,
        tglx@...utronix.de, x86@...nel.org, peterz@...radead.org
Subject: [RFC][PATCH 7/7] x86/nospec: Remove ANNOTATE_NOSPEC_ALTERNATIVE

Now that objtool is smart enough; remove ANNOTATE_NOSPEC_ALTERNATIVE
so that we might generate correct ORC unwind information.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/include/asm/nospec-branch.h |   26 +++++++-------------------
 1 file changed, 7 insertions(+), 19 deletions(-)

--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -10,15 +10,7 @@
 #include <asm/alternative-asm.h>
 #include <asm/cpufeatures.h>
 #include <asm/msr-index.h>
-
-/*
- * This should be used immediately before a retpoline alternative. It tells
- * objtool where the retpolines are so that it can make sense of the control
- * flow by just reading the original instruction(s) and ignoring the
- * alternatives.
- */
-#define ANNOTATE_NOSPEC_ALTERNATIVE \
-	ANNOTATE_IGNORE_ALTERNATIVE
+#include <asm/unwind_hints.h>
 
 /*
  * Fill the CPU return stack buffer.
@@ -50,6 +42,7 @@
 	ANNOTATE_INTRA_FUNCTION_CALL		\
 	call	772f;				\
 773:	/* speculation trap */			\
+	UNWIND_HINT_EMPTY;			\
 	pause;					\
 	lfence;					\
 	jmp	773b;				\
@@ -57,6 +50,7 @@
 	ANNOTATE_INTRA_FUNCTION_CALL		\
 	call	774f;				\
 775:	/* speculation trap */			\
+	UNWIND_HINT_EMPTY;			\
 	pause;					\
 	lfence;					\
 	jmp	775b;				\
@@ -117,10 +111,8 @@
   */
 .macro FILL_RETURN_BUFFER reg:req nr:req ftr:req
 #ifdef CONFIG_RETPOLINE
-	ANNOTATE_NOSPEC_ALTERNATIVE
-	ALTERNATIVE "jmp .Lskip_rsb_\@",				\
-		__stringify(__FILL_RETURN_BUFFER(\reg,\nr,%_ASM_SP))	\
-		\ftr
+	ALTERNATIVE "jmp .Lskip_rsb_\@", "", \ftr
+	__FILL_RETURN_BUFFER(\reg,\nr,%_ASM_SP)
 .Lskip_rsb_\@:
 #endif
 .endm
@@ -141,7 +133,6 @@
  * which is ensured when CONFIG_RETPOLINE is defined.
  */
 # define CALL_NOSPEC						\
-	ANNOTATE_NOSPEC_ALTERNATIVE				\
 	ALTERNATIVE("", "lfence", X86_FEATURE_RETPOLINE_AMD)	\
 	ALTERNATIVE(ANNOTATE_RETPOLINE_SAFE			\
 		    "call *%[thunk_target]\n",			\
@@ -157,7 +148,6 @@
  * here, anyway.
  */
 # define CALL_NOSPEC						\
-	ANNOTATE_NOSPEC_ALTERNATIVE				\
 	ALTERNATIVE_2(						\
 	ANNOTATE_RETPOLINE_SAFE					\
 	"call *%[thunk_target]\n",				\
@@ -225,10 +215,8 @@ static inline void vmexit_fill_RSB(void)
 #ifdef CONFIG_RETPOLINE
 	unsigned long loops;
 
-	asm volatile (ANNOTATE_NOSPEC_ALTERNATIVE
-		      ALTERNATIVE("jmp 910f",
-				  __stringify(__FILL_RETURN_BUFFER(%0, RSB_CLEAR_LOOPS, %1)),
-				  X86_FEATURE_RETPOLINE)
+	asm volatile (ALTERNATIVE("jmp 910f", "", X86_FEATURE_RETPOLINE)
+		      __stringify(__FILL_RETURN_BUFFER(%0, RSB_CLEAR_LOOPS, %1))
 		      "910:"
 		      : "=r" (loops), ASM_CALL_CONSTRAINT
 		      : : "memory" );