[PATCH] fix ppc32 sys_swapcontext

This fixes a bug in the swapcontext system call on ppc32.

On ppc32, the system call entry only saves the volatile registers,
except in the case of a few system calls (e.g.  fork) which need all the
registers saved.  Swapcontext needs all the registers but we weren't
saving them all. So fixes that.

arch/ppc/kernel/entry.S

@@ -414,6 +414,14 @@ ppc_clone:
 	stw	r0,TRAP(r1)		/* register set saved */
 	b	sys_clone
 
+	.globl	ppc_swapcontext
+ppc_swapcontext:
+	SAVE_NVGPRS(r1)
+	lwz	r0,TRAP(r1)
+	rlwinm	r0,r0,0,0,30		/* clear LSB to indicate full */
+	stw	r0,TRAP(r1)		/* register set saved */
+	b	sys_swapcontext
+
 /*
  * This routine switches between two different tasks.  The process
  * state of one is saved on its kernel stack.  Then the state

arch/ppc/kernel/misc.S

@@ -1363,7 +1363,7 @@ _GLOBAL(sys_call_table)
 	.long sys_clock_gettime
 	.long sys_clock_getres
 	.long sys_clock_nanosleep
-	.long sys_swapcontext
+	.long ppc_swapcontext
 	.long sys_tgkill	/* 250 */
 	.long sys_utimes
 	.long sys_statfs64