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Subject[PATCH 2/9] arm64: entry: add a new macro to restore the registers for syscall
Date
This patch adds restore_syscall_regs to restore the x0~x7 arguments from
the stack.
And this patch also uses this macro to simplify the code.

Signed-off-by: Huang Shijie <shijie.huang@arm.com>
---
arch/arm64/kernel/entry.S | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 7dcfd49..21b6068 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -32,6 +32,17 @@
#include <asm/unistd.h>

/*
+ * Use this macro to restore the syscall arguments from the
+ * values already saved on the stack during kernel_entry.
+ */
+ .macro restore_syscall_regs
+ ldp x0, x1, [sp]
+ ldp x2, x3, [sp, #S_X2]
+ ldp x4, x5, [sp, #S_X4]
+ ldp x6, x7, [sp, #S_X6]
+ .endm
+
+/*
* Context tracking subsystem. Used to instrument transitions
* between user and kernel mode.
*/
@@ -39,14 +50,7 @@
#ifdef CONFIG_CONTEXT_TRACKING
bl context_tracking_user_exit
.if \syscall == 1
- /*
- * Save/restore needed during syscalls. Restore syscall arguments from
- * the values already saved on stack during kernel_entry.
- */
- ldp x0, x1, [sp]
- ldp x2, x3, [sp, #S_X2]
- ldp x4, x5, [sp, #S_X4]
- ldp x6, x7, [sp, #S_X6]
+ restore_syscall_regs
.endif
#endif
.endm
@@ -761,10 +765,7 @@ __sys_trace:
mov x1, sp // pointer to regs
cmp scno, sc_nr // check upper syscall limit
b.hs __ni_sys_trace
- ldp x0, x1, [sp] // restore the syscall args
- ldp x2, x3, [sp, #S_X2]
- ldp x4, x5, [sp, #S_X4]
- ldp x6, x7, [sp, #S_X6]
+ restore_syscall_regs
ldr x16, [stbl, scno, lsl #3] // address in the syscall table
blr x16 // call sys_* routine

--
2.5.5
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