Re: [patch 1/1] x86-64: forgot asmlinkage on sys_mmap

[Blaisorblade]

On Wednesday 09 March 2005 20:34, Andi Kleen wrote:
> On Wed, Mar 09, 2005 at 07:24:00PM +0100, Blaisorblade wrote:
> > On Wednesday 09 March 2005 18:24, Andi Kleen wrote:
> > > blaisorblade@xxxxxxxx writes:
> > > > CC: Andi Kleen <ak@xxxxxxx>
> > > >
> > > > I think it should be there, please check better.
> > >
> > > It doesn't matter. asmlinkage is a nop on x86-64.
> >
> > Yes, otherwise nothing would work on x86-64 with mmap broken, but for
> > cleanness and for the case this change it should be there (otherwise why
> > asmlinkage is used in the rest of the file).
>
> Only because it was cut'n'pasted from i386 originally.
>
> > And for i386 asmlinkage acquired significance only recently.
>
> Actually it doesn't neither on i386. That's because entry.S happens to put
> the arguments both into registers and the stack in the right order, so both
> register and stack argument calling conventions work.
>
> But it is slightly safer to have it. When you use the stack arguments
> the C code is allowed to modify it, and when the system call is restarted
> later you could see garbage. In practice that's not a big issue because
> only very few system calls are restartable.
>
> ptrace also could see corrupted state, but that's in general a non issue.
Ok, thanks for the info, I hope it's applied anyway.
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade

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