[ARM] 3168/1: Update ARM signal delivery and masking

Patch from Daniel Jacobowitz

After delivering a signal (creating its stack frame) we must check for
additional pending unblocked signals before returning to userspace.
Otherwise signals may be delayed past the next syscall or reschedule.

Once that was fixed it became obvious that the ARM signal mask manipulation
was broken.  It was a little bit broken before the recent SA_NODEFER
changes, and then very broken after them.  We must block the requested
signals before starting the handler or the same signal can be delivered
again before the handler even gets a chance to run.

Signed-off-by: Daniel Jacobowitz <dan@codesourcery.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/entry-common.S

@@ -48,8 +48,7 @@ work_pending:
 	mov	r0, sp				@ 'regs'
 	mov	r2, why				@ 'syscall'
 	bl	do_notify_resume
-	disable_irq				@ disable interrupts
-	b	no_work_pending
+	b	ret_slow_syscall		@ Check work again
 
 work_resched:
 	bl	schedule

arch/arm/kernel/signal.c

@@ -595,23 +595,22 @@ handle_signal(unsigned long sig, struct k_sigaction *ka,
 	 */
 	ret |= !valid_user_regs(regs);
 
-	/*
-	 * Block the signal if we were unsuccessful.
-	 */
 	if (ret != 0) {
-		spin_lock_irq(&tsk->sighand->siglock);
-		sigorsets(&tsk->blocked, &tsk->blocked,
-			  &ka->sa.sa_mask);
-		if (!(ka->sa.sa_flags & SA_NODEFER))
-			sigaddset(&tsk->blocked, sig);
-		recalc_sigpending();
-		spin_unlock_irq(&tsk->sighand->siglock);
+		force_sigsegv(sig, tsk);
+		return;
 	}
 
-	if (ret == 0)
-		return;
+	/*
+	 * Block the signal if we were successful.
+	 */
+	spin_lock_irq(&tsk->sighand->siglock);
+	sigorsets(&tsk->blocked, &tsk->blocked,
+		  &ka->sa.sa_mask);
+	if (!(ka->sa.sa_flags & SA_NODEFER))
+		sigaddset(&tsk->blocked, sig);
+	recalc_sigpending();
+	spin_unlock_irq(&tsk->sighand->siglock);
 
-	force_sigsegv(sig, tsk);
 }
 
 /*

arch/arm/mm/Makefile

@@ -51,4 +51,4 @@ obj-$(CONFIG_CPU_ARM1026)	+= proc-arm1026.o
 obj-$(CONFIG_CPU_SA110)		+= proc-sa110.o
 obj-$(CONFIG_CPU_SA1100)	+= proc-sa1100.o
 obj-$(CONFIG_CPU_XSCALE)	+= proc-xscale.o
-obj-$(CONFIG_CPU_V6)		+= proc-v6.o blockops.o
+obj-$(CONFIG_CPU_V6)		+= proc-v6.o