linux-kernel - [PATCH V3 9/9] x86/speculation: Annotate intra-function calls

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Message-Id: <20200414103618.12657-10-alexandre.chartre@oracle.com>
Date:   Tue, 14 Apr 2020 12:36:18 +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 V3 9/9] x86/speculation: Annotate intra-function calls

Some speculative execution mitigations (like retpoline) use intra-
function calls. Provide a macro to annotate such intra-function calls
so they can be properly handled by objtool, and use this macro to
annotate intra-function calls.

Signed-off-by: Alexandre Chartre <alexandre.chartre@...cle.com>
---
 arch/x86/include/asm/nospec-branch.h | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 20594ea99c21..89ae2f9cc873 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -3,6 +3,7 @@
 #ifndef _ASM_X86_NOSPEC_BRANCH_H_
 #define _ASM_X86_NOSPEC_BRANCH_H_
 
+#include <linux/frame.h>
 #include <linux/static_key.h>
 
 #include <asm/alternative.h>
@@ -20,6 +21,15 @@
 #define ANNOTATE_NOSPEC_ALTERNATIVE \
 	ANNOTATE_IGNORE_ALTERNATIVE
 
+/*
+ * Intra-function call instruction. This should be used as a substitute
+ * for the call instruction when doing an intra-function call. It is
+ * similar to the call instruction but it tells objtool that this is
+ * an intra-function call.
+ */
+#define INTRA_FUNCTION_CALL \
+	ANNOTATE_INTRA_FUNCTION_CALL call
+
 /*
  * Fill the CPU return stack buffer.
  *
@@ -47,13 +57,13 @@
 #define __FILL_RETURN_BUFFER_BEGIN(reg, nr, sp)	\
 	mov	$(nr/2), reg;			\
 771:						\
-	call	772f;				\
+	INTRA_FUNCTION_CALL 772f;		\
 773:	/* speculation trap */			\
 	pause;					\
 	lfence;					\
 	jmp	773b;				\
 772:						\
-	call	774f;				\
+	INTRA_FUNCTION_CALL 774f;		\
 775:	/* speculation trap */			\
 	pause;					\
 	lfence;					\
@@ -90,7 +100,7 @@
  * invocation below less ugly.
  */
 .macro RETPOLINE_JMP reg:req
-	call	.Ldo_rop_\@
+	INTRA_FUNCTION_CALL .Ldo_rop_\@
 .Lspec_trap_\@:
 	pause
 	lfence
@@ -110,7 +120,7 @@
 .Ldo_retpoline_jmp_\@:
 	RETPOLINE_JMP \reg
 .Ldo_call_\@:
-	call	.Ldo_retpoline_jmp_\@
+	INTRA_FUNCTION_CALL .Ldo_retpoline_jmp_\@
 .endm
 
 /*
-- 
2.18.2