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x86/asm/suspend: Get rid of bogus_64_magic

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bogus_64_magic is only a dead-end loop. There is no need for an
out-of-order function (and unannotated local label), so just handle it
in-place and also store 0xbad-m-a-g-i-c to %rcx beforehand, in case
someone is inspecting registers.

Here a qemu+gdb example:

  Remote debugging using localhost:1235
  wakeup_long64 () at arch/x86/kernel/acpi/wakeup_64.S:26
  26              jmp 1b
  (gdb) info registers
  rax            0x123456789abcdef0       1311768467463790320
  rbx            0x0      0
  rcx            0xbad6d61676963  3286910041024867
  		 ^^^^^^^^^^^^^^^

 [ bp: Add the gdb example. ]

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Len Brown <lenb@kernel.org>
Cc: linux-pm@vger.kernel.org
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190906075550.23435-1-jslaby@suse.cz
This commit is contained in:
Jiri Slaby 2019-09-06 09:55:49 +02:00 committed by Borislav Petkov
parent db4e919d9a
commit 559ceeed62
1 changed files with 6 additions and 4 deletions
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10
arch/x86/kernel/acpi/wakeup_64.S
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@ -18,8 +18,13 @@ ENTRY(wakeup_long64)
movq saved_magic, %rax
movq $0x123456789abcdef0, %rdx
cmpq %rdx, %rax
jne bogus_64_magic
je 2f
/* stop here on a saved_magic mismatch */
movq $0xbad6d61676963, %rcx
1:
jmp 1b
2:
movw $__KERNEL_DS, %ax
movw %ax, %ss
movw %ax, %ds
@ -37,9 +42,6 @@ ENTRY(wakeup_long64)
jmp *%rax
ENDPROC(wakeup_long64)
bogus_64_magic:
jmp bogus_64_magic
ENTRY(do_suspend_lowlevel)
FRAME_BEGIN
subq $8, %rsp