[PARISC] Add ability for prctl to change unaligned trap behaviour

Add support for changing unaligned trap behaviour on a
per-thread basis.
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>

arch/parisc/kernel/unaligned.c

@@ -513,15 +513,18 @@ void handle_unaligned(struct pt_regs *regs)
 	register int flop=0;	/* true if this is a flop */
 
 	/* log a message with pacing */
-	if (user_mode(regs))
-	{
-		if (unaligned_count > 5 && jiffies - last_time > 5*HZ)
-		{
+	if (user_mode(regs)) {
+		if (current->thread.flags & PARISC_UAC_SIGBUS) {
+			goto force_sigbus;
+		}
+
+		if (unaligned_count > 5 && jiffies - last_time > 5*HZ) {
 			unaligned_count = 0;
 			last_time = jiffies;
 		}
-		if (++unaligned_count < 5)
-		{
+
+		if (!(current->thread.flags & PARISC_UAC_NOPRINT) 
+		    && ++unaligned_count < 5) {
 			char buf[256];
 			sprintf(buf, "%s(%d): unaligned access to 0x" RFMT " at ip=0x" RFMT "\n",
 				current->comm, current->pid, regs->ior, regs->iaoq[0]);
@@ -530,6 +533,7 @@ void handle_unaligned(struct pt_regs *regs)
 			show_regs(regs);
 #endif		
 		}
+
 		if (!unaligned_enabled)
 			goto force_sigbus;
 	}

include/asm-parisc/processor.h

@@ -122,8 +122,27 @@ struct thread_struct {
 }; 
 
 /* Thread struct flags. */
+#define PARISC_UAC_NOPRINT	(1UL << 0)	/* see prctl and unaligned.c */
+#define PARISC_UAC_SIGBUS	(1UL << 1)
 #define PARISC_KERNEL_DEATH	(1UL << 31)	/* see die_if_kernel()... */
 
+#define PARISC_UAC_SHIFT	0
+#define PARISC_UAC_MASK		(PARISC_UAC_NOPRINT|PARISC_UAC_SIGBUS)
+
+#define SET_UNALIGN_CTL(task,value)                                       \
+        ({                                                                \
+        (task)->thread.flags = (((task)->thread.flags & ~PARISC_UAC_MASK) \
+                                | (((value) << PARISC_UAC_SHIFT) &        \
+                                   PARISC_UAC_MASK));                     \
+        0;                                                                \
+        })
+
+#define GET_UNALIGN_CTL(task,addr)                                        \
+        ({                                                                \
+        put_user(((task)->thread.flags & PARISC_UAC_MASK)                 \
+                 >> PARISC_UAC_SHIFT, (int __user *) (addr));             \
+        })
+
 #define INIT_THREAD { \
 	regs:	{	gr: { 0, }, \
 			fr: { 0, }, \