ARM: Use a definition for the userspace cmpxchg emulation syscall

Use a definition for the cmpxchg SWI instead of hard-coding the number.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Nicolas Pitre <nico@fluxnic.net>

3 files changed, 14 insertions, 4 deletions

diff --git a/arch/arm/include/asm/unistd.h b/arch/arm/include/asm/unistd.h
index 7020217fc49f..4e506d09e5f9 100644
--- a/arch/arm/include/asm/unistd.h
+++ b/arch/arm/include/asm/unistd.h
@@ -403,6 +403,15 @@
 #define __ARM_NR_set_tls                (__ARM_NR_BASE+5)
 
 /*
+ * *NOTE*: This is a ghost syscall private to the kernel.  Only the
+ * __kuser_cmpxchg code in entry-armv.S should be aware of its
+ * existence.  Don't ever use this from user code.
+ */
+#ifdef __KERNEL__
+#define __ARM_NR_cmpxchg                (__ARM_NR_BASE+0x00fff0)
+#endif
+
+/*
  * The following syscalls are obsolete and no longer available for EABI.
  */
 #if defined(__ARM_EABI__) && !defined(__KERNEL__)
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 0022b4d57f8b..d2903e3bc861 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -21,6 +21,7 @@
 #include <mach/entry-macro.S>
 #include <asm/thread_notify.h>
 #include <asm/unwind.h>
+#include <asm/unistd.h>
 
 #include "entry-header.S"
 
@@ -908,10 +909,10 @@ __kuser_cmpxchg:				@ 0xffff0fc0
          * A special ghost syscall is used for that (see traps.c).
          */
         stmfd   sp!, {r7, lr}
-        mov     r7, #0xff00             @ 0xfff0 into r7 for EABI
-        orr     r7, r7, #0xf0
-        swi     #0x9ffff0
+        ldr     r7, =1f                 @ it's 20 bits
+        swi     __ARM_NR_cmpxchg
         ldmfd   sp!, {r7, pc}
+1:      .word   __ARM_NR_cmpxchg
 
 #elif __LINUX_ARM_ARCH__ < 6
 
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 1bbda04a5380..3f361a783f43 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -528,7 +528,7 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
          * __kuser_cmpxchg code in entry-armv.S should be aware of its
          * existence.  Don't ever use this from user code.
          */
-        case 0xfff0:
+        case NR(cmpxchg):
         for (;;) {
                 extern void do_DataAbort(unsigned long addr, unsigned int fsr,
                                          struct pt_regs *regs);