linux-kernel - [RFC PATCH 07/10] x86/asm: add CFI hint annotations to sync

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Message-Id: <af236b09a2afde19de3ef59bbb6fd16e09cba459.1496293620.git.jpoimboe@redhat.com>
Date:   Thu,  1 Jun 2017 00:44:13 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>, Jiri Slaby <jslaby@...e.cz>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [RFC PATCH 07/10] x86/asm: add CFI hint annotations to sync_core()

This enables the unwinder to grok the iret in the middle of a C
function.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 arch/x86/include/asm/processor.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 3cada99..9b90129 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -22,6 +22,7 @@ struct vm86;
 #include <asm/nops.h>
 #include <asm/special_insns.h>
 #include <asm/fpu/types.h>
+#include <asm/undwarf.h>
 
 #include <linux/personality.h>
 #include <linux/cache.h>
@@ -676,6 +677,7 @@ static inline void sync_core(void)
 	unsigned int tmp;
 
 	asm volatile (
+		CFI_SAVE
 		"mov %%ss, %0\n\t"
 		"pushq %q0\n\t"
 		"pushq %%rsp\n\t"
@@ -685,6 +687,7 @@ static inline void sync_core(void)
 		"pushq %q0\n\t"
 		"pushq $1f\n\t"
 		"iretq\n\t"
+		CFI_RESTORE
 		"1:"
 		: "=&r" (tmp), "+r" (__sp) : : "cc", "memory");
 #endif
-- 
2.7.4