lkml.org 
[lkml]   [2017]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH 3/4] x86/asm: Make alternative macro interfaces more clear and consistent
On Thu, Sep 14, 2017 at 11:28:30AM -0700, Linus Torvalds wrote:
> On Thu, Sep 14, 2017 at 10:33 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >>
> >> a) uglifying the 15 or so relevant inline asm locations with ifdefs; or
> >
> > Actually I guess we could put the "sp" in a macro... I'll try it.
>
> Exactly. Do something like
>
> #ifdef CONFIG_FRAME_POINTER
> # define EXTRA_ASM_CLOBBERS "rsp"
> #else
> # define EXTRA_ASM_CLOBBERS
> #endif
>
> and then replace the nasty
>
> register void *__sp asm(_ASM_SP);
> ..
> "+r" (__sp)
>
> games with just that EXTRA_ASM_CLOBBERS thing at the end of the clobbers.
>
> Yes, you'd probably have to document that the alternative_call_2()
> thing doesn't take a "input" argument, but a input_and_clobbers, but
> all users do that anyway.
>
> I dunno.

There's also alternative_call(), which doesn't yet have the '__rsp'
annotation, but it probably should. It has some callers which pass
clobbers and some which don't, so its conversion would be trickier.

So my plan is to keep patch 3 of this series, which clarifies those
alternative macro interfaces, and also separates the inputs from the
clobbers. That'll make it really easy to add something like
EXTRA_ASM_CLOBBERS above.

In fact I'll probably keep patches 1-3, because they're all
improvements. Then I'll replace the original patch 4 (ASM_CALL) with
the "sp" clobbers thing.

--
Josh

\
 
 \ /
  Last update: 2017-09-14 20:46    [W:0.053 / U:1.112 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site