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@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/2cadd9f16c77da7ee7957bfc5e1c67928c23ca48.1481685203.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 1facaf4..b467b14 100644 (file)
--- 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"