Re: [PATCH] MIPS: use 32-bit wrapper for compat_sys_futex

[David Daney]

On 08/17/2011 07:32 PM, Yong Zhang wrote:
> On Wed, Aug 17, 2011 at 10:17:52AM -0700, David Daney wrote:
> > > diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
> > > index 46c4763..f48b18e 100644
> > > --- a/arch/mips/kernel/scall64-o32.S
> > > +++ b/arch/mips/kernel/scall64-o32.S
> > > @@ -441,7 +441,7 @@ sys_call_table:
> > >   	PTR	sys_fremovexattr		/* 4235 */
> > >   	PTR	sys_tkill
> > >   	PTR	sys_sendfile64
> > > -	PTR	compat_sys_futex
> > > +	PTR	sys_32_futex
> >
> > This change is redundant, scall64-o32.S already does the right thing
>
> My first virsion(not sent out) doesn't include scall64-o32.S either.
>
> > so additional zero extending is not needed and is just extra
> > instructions to execute for no reason.
>
> Why I'm adding it here is for:
> 1)code consistent, otherwise we must move SYSCALL_DEFINE6(32_futex,...)
>    under CONFIG_MIPS32_N32;

No, you don't have to move it.  Just don't call it.


> 2)I'm afraid there may be some other way to touch the high 32-bit of a
>    register, so touching scall64-o32.S is also for safety(due to unknown
>    reason, fix me if I'm wrong).

OK: You are mistaken.  You claim you don't understand what the code 
does.  That is really a poor justification for modifying it.

David Daney
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