Re: [PATCH v2 5/5] aarch64: Define __ASSUME_SYSCALL_NAMED_WORKS for Linux

[Xi Ruoyao <xry111@xry111.site>]

On Mon, 2023-03-27 at 10:06 -0300, Adhemerval Zanella Netto wrote:
> 
> 
> On 25/03/23 11:08, Xi Ruoyao wrote:
> > AAPCS treats the variable arguments same as named ones, and when
> > each
> > argument is an integer not wider than 8 bytes, the ith argument is
> > in
> > register xi (0 <= i < 8), or the stack slot at (sp + 8 * (i - 8))
> > (i >= 8) no matter how many arguments are passed.  So we can define
> > __ASSUME_SYSCALL_NAMED_WORKS to avoid unnecessary stack stores in
> > the
> > syscall wrappers caused by va_start.
> 
> This triggered a build failure on i686 patchwork buildbot [1].

Ouch, misused #if as #ifdef.

Will fix and submit v3.

> 
> [1] https://www.delorie.com/trybots/32bit/18431/
> 
> > ---
> >  sysdeps/unix/sysv/linux/aarch64/kernel-features.h | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/sysdeps/unix/sysv/linux/aarch64/kernel-features.h
> > b/sysdeps/unix/sysv/linux/aarch64/kernel-features.h
> > index 3546f6de96..c39ff39da2 100644
> > --- a/sysdeps/unix/sysv/linux/aarch64/kernel-features.h
> > +++ b/sysdeps/unix/sysv/linux/aarch64/kernel-features.h
> > @@ -21,3 +21,12 @@
> >  
> >  #undef __ASSUME_CLONE_DEFAULT
> >  #define __ASSUME_CLONE_BACKWARDS 1
> > +
> > +/* Define this if the calling convention for passing x named
> > arguments and y
> > +   variable arguments is same as passing (x + y) named arguments,
> > while each
> > +   argument is either an integer of which the width is less than or
> > equal to
> > +   "long", or a pointer; and an argument can be fetched from the
> > same register
> > +   or the same offset from the stack pointer no matter how many
> > (maybe zero)
> > +   arguments are passed after it.  It avoids useless stack stores
> > caused by
> > +   usage of va_start.  */
> > +#define __ASSUME_SYSCALL_NAMED_WORKS   1

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University