Re: [PATCH 05/18] x86/asm/64: Shrink paranoid_exit_restore and make labels local

Borislav Petkov
2017-10-27T20:07:16Z

On Thu, Oct 26, 2017 at 01:26:37AM -0700, Andy Lutomirski wrote:
> paranoid_exit_restore was a copy of
> restore_regs_and_return_to_kernel. Merge them and make the
> paranoid_exit internal labels local.
>
> Keeping .Lparanoid_exit makes the code a bit shorter because it
> allows a 2-byte jnz instead of a 5-byte jnz.
>
> Saves 96 bytes of text.
>
> (This is still a bit suboptimal in a non-CONFIG_TRACE_IRQFLAGS
> kernel, but fixing that would make the code rather messy.)
>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
> arch/x86/entry/entry_64.S | 13 +++++--------
> 1 file changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
> index 4ad40067162a..d6404a613df4 100644
> --- a/arch/x86/entry/entry_64.S
> +++ b/arch/x86/entry/entry_64.S
> @@ -1119,17 +1119,14 @@ ENTRY(paranoid_exit)
> DISABLE_INTERRUPTS(CLBR_ANY)
> TRACE_IRQS_OFF_DEBUG
> testl %ebx, %ebx /* swapgs needed? */
> - jnz paranoid_exit_no_swapgs
> + jnz .Lparanoid_exit_no_swapgs
> TRACE_IRQS_IRETQ
> SWAPGS_UNSAFE_STACK
> - jmp paranoid_exit_restore
> -paranoid_exit_no_swapgs:
> + jmp .Lparanoid_exit_restore

Kill that paranoid_exit_restore too and save everybody a jump:

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 1b9e8079ca3a..b88e17e120fa 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1122,10 +1122,9 @@ ENTRY(paranoid_exit)
jnz .Lparanoid_exit_no_swapgs
TRACE_IRQS_IRETQ
SWAPGS_UNSAFE_STACK
- jmp .Lparanoid_exit_restore
+ jmp restore_regs_and_return_to_kernel
.Lparanoid_exit_no_swapgs:
TRACE_IRQS_IRETQ_DEBUG
-.Lparanoid_exit_restore:
jmp restore_regs_and_return_to_kernel
END(paranoid_exit)

--
Regards/Gruss,
Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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