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SubjectRe: [PATCH 02/11] x86: code shrink in paranoid_exit
On Wed, Jan 14, 2015 at 1:48 PM, Denys Vlasenko <dvlasenk@redhat.com> wrote:
> RESTORE_EXTRA_REGS + RESTORE_C_REGS looks small, but it's
> a lot of instructions (fourteen). Let's reuse them.
>
> Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
> CC: Linus Torvalds <torvalds@linux-foundation.org>
> CC: Oleg Nesterov <oleg@redhat.com>
> CC: Borislav Petkov <bp@alien8.de>
> CC: "H. Peter Anvin" <hpa@zytor.com>
> CC: Andy Lutomirski <luto@amacapital.net>
> CC: Frederic Weisbecker <fweisbec@gmail.com>
> CC: X86 ML <x86@kernel.org>
> CC: Alexei Starovoitov <ast@plumgrid.com>
> CC: Will Drewry <wad@chromium.org>
> CC: Kees Cook <keescook@chromium.org>
> CC: linux-kernel@vger.kernel.org
> ---
> arch/x86/kernel/entry_64.S | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
> index a21b5b3..f5e815e 100644
> --- a/arch/x86/kernel/entry_64.S
> +++ b/arch/x86/kernel/entry_64.S
> @@ -1270,12 +1270,10 @@ ENTRY(paranoid_exit)
> jnz paranoid_restore
> TRACE_IRQS_IRETQ 0
> SWAPGS_UNSAFE_STACK
> - RESTORE_EXTRA_REGS
> - RESTORE_C_REGS
> - REMOVE_PT_GPREGS_FROM_STACK 8
> - INTERRUPT_RETURN
> + jmp paranoid_restore1
> paranoid_restore:
> TRACE_IRQS_IRETQ_DEBUG 0
> +paranoid_restore1:
> RESTORE_EXTRA_REGS
> RESTORE_C_REGS
> REMOVE_PT_GPREGS_FROM_STACK 8

This is sort of a reply to the wrong thread, but wouldn't it be nicer
if we could pop a bunch of regs instead of using mov followed by add?
(Yes, this could be a followup, but it could be easier to spot now by
changing macros like RESTORE_XYZ.)

--Andy


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