linux-kernel - [RFC PATCH 17/21] x86/asm/entry: Fix frame pointer usage in thunk functions

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Message-Id: <9868088e73dee9dd77810845e14b2f8867a929ef.1437150175.git.jpoimboe@redhat.com>
Date:	Fri, 17 Jul 2015 11:47:33 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Cc:	Michal Marek <mmarek@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Pedro Alves <palves@...hat.com>, x86@...nel.org,
	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 17/21] x86/asm/entry: Fix frame pointer usage in thunk functions

Thunk functions are callable non-leaf functions that don't honor
CONFIG_FRAME_POINTER, which can result in bad stack traces.  Also they
aren't annotated as ELF callable functions which can confuse tooling.

Create stack frames for them when CONFIG_FRAME_POINTER is enabled and
add the ELF function type.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 arch/x86/entry/thunk_64.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/entry/thunk_64.S b/arch/x86/entry/thunk_64.S
index efb2b93..03ee0cd 100644
--- a/arch/x86/entry/thunk_64.S
+++ b/arch/x86/entry/thunk_64.S
@@ -8,11 +8,14 @@
 #include <linux/linkage.h>
 #include "calling.h"
 #include <asm/asm.h>
+#include <asm/frame.h>
 
 	/* rdi:	arg1 ... normal C conventions. rax is saved/restored. */
 	.macro THUNK name, func, put_ret_addr_in_rdi=0
 	.globl \name
+	.type \name, @function
 \name:
+	FRAME
 
 	/* this one pushes 9 elems, the next one would be %rIP */
 	pushq %rdi
@@ -62,6 +65,7 @@ restore:
 	popq %rdx
 	popq %rsi
 	popq %rdi
+	ENDFRAME
 	ret
 	_ASM_NOKPROBE(restore)
 #endif
-- 
2.1.0

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