[patch 13/13] syslets: x86: optimized sys_umem_add()

[Ingo Molnar]

From: Ingo Molnar <mingo@xxxxxxx>

provide an optimized assembly version of sys_umem_add().
It is about 2 times faster than the C version.

Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
---
 arch/i386/lib/getuser.S |   27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

Index: linux/arch/i386/lib/getuser.S
===================================================================
--- linux.orig/arch/i386/lib/getuser.S
+++ linux/arch/i386/lib/getuser.S
@@ -11,6 +11,33 @@
 #include <asm/thread_info.h>
 
 /*
+ * Optimized user-memory arithmetics system-call:
+ */
+
+.text
+.align 4
+.globl sys_umem_add
+sys_umem_add:
+	movl 0x4(%esp), %ecx			# uptr
+	movl 0x8(%esp), %edx			# inc
+
+	cmpl $__PAGE_OFFSET, %ecx		# access_ok(uptr)
+	jae bad_sys_umem_add
+
+1:	addl %edx, (%ecx)			# *uptr += inc
+2:	movl (%ecx), %eax			# return *uptr
+	ret
+
+bad_sys_umem_add:
+	movl $-14, %eax
+	ret
+
+.section __ex_table,"a"
+	.long 1b, bad_sys_umem_add
+	.long 2b, bad_sys_umem_add
+.previous
+
+/*
  * copy_uatom() - copy a syslet_atom from user-space into kernel-space:
  */
 
-
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