linux-kernel - [RFC][PATCH 1/6] x86: Annotate _THIS_IP

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Date:   Mon, 22 Nov 2021 18:03:02 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org, joao@...rdrivepizza.com, hjl.tools@...il.com,
        jpoimboe@...hat.com, andrew.cooper3@...rix.com
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        ndesaulniers@...gle.com, keescook@...omium.org,
        samitolvanen@...gle.com
Subject: [RFC][PATCH 1/6] x86: Annotate _THIS_IP_

In order to find _THIS_IP_ code references in objtool, annotate them.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/include/asm/linkage.h      |   11 +++++++++++
 include/linux/instruction_pointer.h |    5 +++++
 2 files changed, 16 insertions(+)

--- a/arch/x86/include/asm/linkage.h
+++ b/arch/x86/include/asm/linkage.h
@@ -3,10 +3,21 @@
 #define _ASM_X86_LINKAGE_H
 
 #include <linux/stringify.h>
+#include <asm/asm.h>
 
 #undef notrace
 #define notrace __attribute__((no_instrument_function))
 
+#define _THIS_IP_						\
+	({	__label__ __here;				\
+		__here:						\
+		asm_volatile_goto (				\
+		    ".pushsection .discard.this_ip\n\t"		\
+		    _ASM_PTR " %l[__here]\n\t"			\
+		    ".popsection\n\t"				\
+		    : : : : __here);				\
+		(unsigned long)&&__here; })
+
 #ifdef CONFIG_X86_32
 #define asmlinkage CPP_ASMLINKAGE __attribute__((regparm(0)))
 #endif /* CONFIG_X86_32 */
--- a/include/linux/instruction_pointer.h
+++ b/include/linux/instruction_pointer.h
@@ -2,7 +2,12 @@
 #ifndef _LINUX_INSTRUCTION_POINTER_H
 #define _LINUX_INSTRUCTION_POINTER_H
 
+#include <asm/linkage.h>
+
 #define _RET_IP_		(unsigned long)__builtin_return_address(0)
+
+#ifndef _THIS_IP_
 #define _THIS_IP_  ({ __label__ __here; __here: (unsigned long)&&__here; })
+#endif
 
 #endif /* _LINUX_INSTRUCTION_POINTER_H */