parisc: Add error checks when building up signal trampoline handler

Add checks if the userspace trampoline code was correctly generated by the
signal trampoline generation code. In addition only flush caches as needed and
fix the old flushing code which didn't flushed all generated instructions.
Signed-off-by: Helge Deller <deller@gmx.de>

arch/parisc/kernel/signal.c

@@ -476,6 +476,9 @@ insert_restart_trampoline(struct pt_regs *regs)
 	case -ERESTART_RESTARTBLOCK: {
 		/* Restart the system call - no handlers present */
 		unsigned int *usp = (unsigned int *)regs->gr[30];
+		unsigned long start = (unsigned long) &usp[2];
+		unsigned long end  = (unsigned long) &usp[5];
+		long err = 0;
 
 		/* Setup a trampoline to restart the syscall
 		 * with __NR_restart_syscall
@@ -487,23 +490,21 @@ insert_restart_trampoline(struct pt_regs *regs)
 		 * 16: ldi __NR_restart_syscall, %r20
 		 */
 #ifdef CONFIG_64BIT
-		put_user(regs->gr[31] >> 32, &usp[0]);
-		put_user(regs->gr[31] & 0xffffffff, &usp[1]);
-		put_user(0x0fc010df, &usp[2]);
+		err |= put_user(regs->gr[31] >> 32, &usp[0]);
+		err |= put_user(regs->gr[31] & 0xffffffff, &usp[1]);
+		err |= put_user(0x0fc010df, &usp[2]);
 #else
-		put_user(regs->gr[31], &usp[0]);
-		put_user(0x0fc0109f, &usp[2]);
+		err |= put_user(regs->gr[31], &usp[0]);
+		err |= put_user(0x0fc0109f, &usp[2]);
 #endif
-		put_user(0xe0008200, &usp[3]);
-		put_user(0x34140000, &usp[4]);
+		err |= put_user(0xe0008200, &usp[3]);
+		err |= put_user(0x34140000, &usp[4]);
 
-		/* Stack is 64-byte aligned, and we only need
-		 * to flush 1 cache line.
-		 * Flushing one cacheline is cheap.
-		 * "sync" on bigger (> 4 way) boxes is not.
-		 */
-		flush_user_dcache_range(regs->gr[30], regs->gr[30] + 4);
-		flush_user_icache_range(regs->gr[30], regs->gr[30] + 4);
+		WARN_ON(err);
+
+		/* flush data/instruction cache for new insns */
+		flush_user_dcache_range(start, end);
+		flush_user_icache_range(start, end);
 
 		regs->gr[31] = regs->gr[30] + 8;
 		return;