Re: [PATCH v5 2/3] aarch64: Set the syscall register right before doing the syscall.

[Joe Simmons-Talbott <josimmon@redhat.com>]

On Wed, Apr 19, 2023 at 03:56:05PM +0100, Szabolcs Nagy wrote:
> The 04/19/2023 09:58, Joe Simmons-Talbott via Libc-alpha wrote:
> > --- a/sysdeps/unix/sysv/linux/aarch64/sysdep.h
> > +++ b/sysdeps/unix/sysv/linux/aarch64/sysdep.h
> > @@ -168,15 +168,26 @@
> >  # define HAVE_CLONE3_WRAPPER		1
> >  
> >  # undef INTERNAL_SYSCALL_RAW
> > -# define INTERNAL_SYSCALL_RAW(name, nr, args...)		\
> > -  ({ long _sys_result;						\
> > -     {								\
> > -       LOAD_ARGS_##nr (args)					\
> > -       register long _x8 asm ("x8") = (name);			\
> > -       asm volatile ("svc	0	// syscall " # name     \
> > -		     : "=r" (_x0) : "r"(_x8) ASM_ARGS_##nr : "memory");	\
> > -       _sys_result = _x0;					\
> > -     }								\
> > +# define INTERNAL_SYSCALL_RAW(name, nr, args...)			\
> > +  ({ long _sys_result;							\
> > +     {									\
> > +       LOAD_ARGS_##nr (args)						\
> > +       if (__builtin_constant_p(name))					\
> > +         asm volatile ("mov	x8, %1	// syscall " # name "\n"	\
> > +		       "svc	0"					\
> > +                       : "=r" (_x0)					\
> > +		       : "i" (name) ASM_ARGS_##nr			\
> > +		       : "x8", "memory");				\
> > +       else								\
> > +         {								\
> > +           register long _x8 asm ("x8") = (name);			\
> > +           asm volatile ("svc	0\n\t"					\
> 
> why \n\t ?
> 
> i don't think that's needed.

I'll remove it in v6.

Thanks,
Joe