[tip:x86/urgent] x86/boot/64: Push correct start_cpu() return address

From: tip-bot for Josh Poimboeuf
Date: Wed Dec 14 2016 - 03:38:55 EST


Commit-ID: 31dcfec11f827e9a5d8720fe4728f1305894884f
Gitweb: http://git.kernel.org/tip/31dcfec11f827e9a5d8720fe4728f1305894884f
Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate: Tue, 13 Dec 2016 21:25:36 -0600
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/2cadd9f16c77da7ee7957bfc5e1c67928c23ca48.1481685203.git.jpoimboe@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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"