[PATCH 3/3] mips: remove register spill

[Adhemerval Zanella]

On 28/11/2020 05:18, Huang Pei wrote:
> Before Linux/MIPS 2.6.36, kernel expected setting syscall number(aka
> "li v0, #sys_number") right precedes "syscall", so the kernel syscall
> restart sequence can use CP0 EPC - 4 to restart the syscall, because
> kernel DID NOT save v0 during syscall handling. Linux 2.6.36 canceled
> this restriction.
> 
> See sysdeps/unix/sysv/linux/mips/{mips32/sysdep.h,mips64/sysdep.h,sysdep.h}
> 
> Since glibc-2.24 the minimum kernel version is 3.2(much higer than
> 2.6.36), I think it is OK to remove the ugly register spill in
> syscall.S just because of the old convention
> 
> Signed-off-by: Huang Pei <huangpei@loongson.cn>

We do not use SCO, but rather Copyright assignment.	

The rest of the patch looks ok.

> ---
>  sysdeps/unix/sysv/linux/mips/mips64/syscall.S | 14 ++------------
>  1 file changed, 2 insertions(+), 12 deletions(-)
> 
> diff --git a/sysdeps/unix/sysv/linux/mips/mips64/syscall.S b/sysdeps/unix/sysv/linux/mips/mips64/syscall.S
> index aab1f389aa..089524a40b 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips64/syscall.S
> +++ b/sysdeps/unix/sysv/linux/mips/mips64/syscall.S
> @@ -27,14 +27,9 @@
>  
>  	.text
>  NESTED (syscall, SZREG, ra)
> -	.mask 0x00010000, -2 * SZREG
> +	.mask 0x00000000, 0
>  	.fmask 0x00000000, 0
> -	PTR_ADDIU sp, -2 * SZREG
> -	cfi_adjust_cfa_offset (2 * SZREG)
> -	REG_S s0, (sp)
> -	cfi_rel_offset (s0, 0)
> -
> -	move s0, a0
> +	move v0, a0
>  	move a0, a1		/* shift arg1 - arg7.  */
>  	move a1, a2
>  	move a2, a3
> @@ -43,13 +38,8 @@ NESTED (syscall, SZREG, ra)
>  	move a5, a6
>  	move a6, a7
>  
> -	move v0, s0		/* Syscall number -> v0 */
>  	syscall			/* Do the system call.  */
>  
> -	REG_L s0, (sp)
> -	cfi_restore (s0)
> -	PTR_ADDIU sp, 2 * SZREG
> -	cfi_adjust_cfa_offset (-2 * 2 * SZREG)
>  	bne a3, zero, L(error)
>  
>  	ret
>