linux-kernel - [tip:x86/urgent] x86/boot/64: Push correct start

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Date:   Wed, 14 Dec 2016 00:37:31 -0800
From:   tip-bot for Josh Poimboeuf <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     jpoimboe@...hat.com, dvlasenk@...hat.com,
        linux-kernel@...r.kernel.org, hpa@...or.com, brgerst@...il.com,
        peterz@...radead.org, tglx@...utronix.de, mingo@...nel.org,
        luto@...nel.org, bp@...en8.de, torvalds@...ux-foundation.org
Subject: [tip:x86/urgent] x86/boot/64: Push correct start_cpu() return
 address

Commit-ID:  31dcfec11f827e9a5d8720fe4728f1305894884f
Gitweb:     http://git.kernel.org/tip/31dcfec11f827e9a5d8720fe4728f1305894884f
Author:     Josh Poimboeuf <jpoimboe@...hat.com>
AuthorDate: Tue, 13 Dec 2016 21:25:36 -0600
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 14 Dec 2016 08:48:05 +0100

x86/boot/64: Push correct start_cpu() return address

start_cpu() pushes a text address on the stack so that stack traces from
idle tasks will show start_cpu() at the end.  But it currently shows the
wrong function offset.  It's more correct to show the address
immediately after the 'lretq' instruction.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/2cadd9f16c77da7ee7957bfc5e1c67928c23ca48.1481685203.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/head_64.S | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 1facaf4..b467b14 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -298,12 +298,13 @@ ENTRY(start_cpu)
 	 *	REX.W + FF /5 JMP m16:64 Jump far, absolute indirect,
 	 *		address given in m16:64.
 	 */
-	pushq	$1f		# put return address on stack for unwinder
-1:	xorq	%rbp, %rbp	# clear frame pointer
+	pushq	$.Lafter_lret	# put return address on stack for unwinder
+	xorq	%rbp, %rbp	# clear frame pointer
 	movq	initial_code(%rip), %rax
 	pushq	$__KERNEL_CS	# set correct cs
 	pushq	%rax		# target address in negative space
 	lretq
+.Lafter_lret:
 ENDPROC(start_cpu)
 
 #include "verify_cpu.S"