[RFC PATCH 0/2] LoongArch: Modify handle_syscall

[RFC PATCH 0/2] LoongArch: Modify handle_syscall

[Tiezhu Yang]

Tiezhu Yang (2):
  LoongArch: Only clone and clone3 need to call SAVE_STATIC
  LoongArch: No need to call RESTORE_ALL_AND_RET for all syscalls

 arch/loongarch/include/asm/stackframe.h | 10 ++++++++++
 arch/loongarch/kernel/entry.S           | 25 ++++++++++++++++++++++++-
 2 files changed, 34 insertions(+), 1 deletion(-)

-- 
2.1.0

[RFC PATCH 1/2] LoongArch: Only clone and clone3 need to call SAVE_STATIC

[Tiezhu Yang]

In handle_syscall, it is unnecessary to call SAVE_STATIC for all syscalls,
only clone and clone3 need to do this operation, so it is better to check
the syscall number before call SAVE_STATIC.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/loongarch/kernel/entry.S | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/loongarch/kernel/entry.S b/arch/loongarch/kernel/entry.S
index d5b3dbc..551b6ec 100644
--- a/arch/loongarch/kernel/entry.S
+++ b/arch/loongarch/kernel/entry.S
@@ -14,6 +14,7 @@
 #include <asm/regdef.h>
 #include <asm/stackframe.h>
 #include <asm/thread_info.h>
+#include <asm/unistd.h>
 
 	.text
 	.cfi_sections	.debug_frame
@@ -56,8 +57,20 @@ SYM_FUNC_START(handle_syscall)
 	cfi_st	u0, PT_R21
 	cfi_st	fp, PT_R22
 
+	/*
+	 * Syscall number held in a7.
+	 * If syscall number is __NR_clone and __NR_clone3, call SAVE_STATIC.
+	 */
+	li.w	t3, __NR_clone
+	beq	a7, t3, 1f
+	li.w	t3, __NR_clone3
+	beq	a7, t3, 1f
+	b	2f
+
+1:
 	SAVE_STATIC
 
+2:
 	move	u0, t0
 	li.d	tp, ~_THREAD_MASK
 	and	tp, tp, sp
-- 
2.1.0

[RFC PATCH 2/2] LoongArch: No need to call RESTORE_ALL_AND_RET for all syscalls

[Tiezhu Yang]

In handle_syscall, it is unnecessary to call RESTORE_ALL_AND_RET for all
syscalls, clone and clone3 should call RESTORE_STATIC_SOME_AND_RET, and
the other syscalls should call RESTORE_SOME_AND_RET.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/loongarch/include/asm/stackframe.h | 10 ++++++++++
 arch/loongarch/kernel/entry.S           | 12 +++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/arch/loongarch/include/asm/stackframe.h b/arch/loongarch/include/asm/stackframe.h
index 4ca9530..9869b39 100644
--- a/arch/loongarch/include/asm/stackframe.h
+++ b/arch/loongarch/include/asm/stackframe.h
@@ -216,4 +216,14 @@
 	RESTORE_SP_AND_RET \docfi
 	.endm
 
+	.macro	RESTORE_STATIC_SOME_AND_RET docfi=0
+	RESTORE_STATIC \docfi
+	RESTORE_SOME \docfi
+	RESTORE_SP_AND_RET \docfi
+	.endm
+
+	.macro	RESTORE_SOME_AND_RET docfi=0
+	RESTORE_SOME \docfi
+	RESTORE_SP_AND_RET \docfi
+	.endm
 #endif /* _ASM_STACKFRAME_H */
diff --git a/arch/loongarch/kernel/entry.S b/arch/loongarch/kernel/entry.S
index 551b6ec..8176094 100644
--- a/arch/loongarch/kernel/entry.S
+++ b/arch/loongarch/kernel/entry.S
@@ -78,7 +78,17 @@ SYM_FUNC_START(handle_syscall)
 	move	a0, sp
 	bl	do_syscall
 
-	RESTORE_ALL_AND_RET
+	/*
+	 * Syscall number held in a7.
+	 * If syscall number is __NR_clone and __NR_clone3, call RESTORE_STATIC_SOME_AND_RET.
+	 */
+	li.w	t3, __NR_clone
+	beq	a7, t3, 3f
+	li.w	t3, __NR_clone3
+	beq	a7, t3, 3f
+	RESTORE_SOME_AND_RET
+3:
+	RESTORE_STATIC_SOME_AND_RET
 SYM_FUNC_END(handle_syscall)
 
 SYM_CODE_START(ret_from_fork)
-- 
2.1.0