Re: [PATCH 3/3] x86: do not save callee-preserved registers around lockdep_sys_exit_thunk

[Andy Lutomirski]

On Fri, Feb 27, 2015 at 4:29 PM, Denys Vlasenko <dvlasenk@xxxxxxxxxx> wrote:
> Internally, lockdep_sys_exit_thunk saves callee-clobbered registers,
> and calls a C function, lockdep_sys_exix. Thus, callee-preserved
> won't be mangled, there is no need to save them.
>
> Patch was run-tested.

Peterz, I think this was your code.

--Andy

>
> Signed-off-by: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
> CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
> CC: Ingo Molnar <mingo@xxxxxxxxxx>
> CC: Borislav Petkov <bp@xxxxxxxxx>
> CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
> CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> CC: Oleg Nesterov <oleg@xxxxxxxxxx>
> CC: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> CC: Alexei Starovoitov <ast@xxxxxxxxxxxx>
> CC: Will Drewry <wad@xxxxxxxxxxxx>
> CC: Kees Cook <keescook@xxxxxxxxxxxx>
> CC: x86@xxxxxxxxxx
> CC: linux-kernel@xxxxxxxxxxxxxxx
> ---
>  arch/x86/include/asm/irqflags.h | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
> index 19355f3..9a63eae 100644
> --- a/arch/x86/include/asm/irqflags.h
> +++ b/arch/x86/include/asm/irqflags.h
> @@ -179,9 +179,7 @@ static inline int arch_irqs_disabled(void)
>  #    define LOCKDEP_SYS_EXIT_IRQ \
>         TRACE_IRQS_ON; \
>         sti; \
> -       SAVE_EXTRA_REGS; \
>         call lockdep_sys_exit_thunk; \
> -       RESTORE_EXTRA_REGS; \
>         cli; \
>         TRACE_IRQS_OFF;
>  #  else
> --
> 1.8.1.4
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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