diff mbox series

[3/3] mips: remove register spill

Message ID 20201127092233.29416-4-huangpei@loongson.cn
State New
Headers show
Series [1/3] mips: add hp-timing support for MIPS R2 | expand

Commit Message

Huang Pei Nov. 27, 2020, 9:22 a.m. UTC
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 the old convention

Signed-off-by: Huang Pei <huangpei@loongson.cn>
---
 sysdeps/unix/sysv/linux/mips/mips64/syscall.S | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)
diff mbox series

Patch

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