powerpc/signal: Use code patching instead of hardcoding

Instead of hardcoding code modifications, use code patching functions.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/ppc-opcode.h

@@ -257,6 +257,7 @@
 #define PPC_INST_MTSPR_DSCR_USER_MASK	0xfc1ffffe
 #define PPC_INST_MFVSRD			0x7c000066
 #define PPC_INST_MTVSRD			0x7c000166
+#define PPC_INST_SC			0x44000002
 #define PPC_INST_SLBFEE			0x7c0007a7
 #define PPC_INST_SLBIA			0x7c0003e4
 

arch/powerpc/kernel/signal_32.c

@@ -470,9 +470,9 @@ static int save_user_regs(struct pt_regs *regs, struct mcontext __user *frame,
 		return 1;
 
 	if (sigret) {
-		/* Set up the sigreturn trampoline: li r0,sigret; sc */
-		if (__put_user(0x38000000UL + sigret, &frame->tramp[0])
-		    || __put_user(0x44000002UL, &frame->tramp[1]))
+		/* Set up the sigreturn trampoline: li 0,sigret; sc */
+		if (__put_user(PPC_INST_ADDI + sigret, &frame->tramp[0])
+		    || __put_user(PPC_INST_SC, &frame->tramp[1]))
 			return 1;
 		flush_icache_range((unsigned long) &frame->tramp[0],
 				   (unsigned long) &frame->tramp[2]);
@@ -619,9 +619,9 @@ static int save_tm_user_regs(struct pt_regs *regs,
 	if (__put_user(msr, &frame->mc_gregs[PT_MSR]))
 		return 1;
 	if (sigret) {
-		/* Set up the sigreturn trampoline: li r0,sigret; sc */
-		if (__put_user(0x38000000UL + sigret, &frame->tramp[0])
-		    || __put_user(0x44000002UL, &frame->tramp[1]))
+		/* Set up the sigreturn trampoline: li 0,sigret; sc */
+		if (__put_user(PPC_INST_ADDI + sigret, &frame->tramp[0])
+		    || __put_user(PPC_INST_SC, &frame->tramp[1]))
 			return 1;
 		flush_icache_range((unsigned long) &frame->tramp[0],
 				   (unsigned long) &frame->tramp[2]);

arch/powerpc/kernel/signal_64.c

@@ -598,11 +598,12 @@ static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
 	long err = 0;
 
 	/* addi r1, r1, __SIGNAL_FRAMESIZE  # Pop the dummy stackframe */
-	err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
+	err |= __put_user(PPC_INST_ADDI | __PPC_RT(R1) | __PPC_RA(R1) |
+			  (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
 	/* li r0, __NR_[rt_]sigreturn| */
-	err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
+	err |= __put_user(PPC_INST_ADDI | (syscall & 0xffff), &tramp[1]);
 	/* sc */
-	err |= __put_user(0x44000002UL, &tramp[2]);
+	err |= __put_user(PPC_INST_SC, &tramp[2]);
 
 	/* Minimal traceback info */
 	for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)