ARM: 7322/1: Print BUG instead of undefined instruction on BUG_ON()

The ARM kernel uses undefined instructions to implement
BUG/BUG_ON(). This leads to problems where people don't read one
line above the Oops message and see the "kernel BUG at ..."
message and so they wrongly assume the kernel has hit an
undefined instruction.

Instead of printing:

 Internal error: Oops - undefined instruction: 0 [#1] PREEMPT SMP

print

 Internal error: Oops - BUG: 0 [#1] PREEMPT SMP

This should prevent people from thinking the BUG_ON was an
undefined instruction when it was actually intentional.
Signed-off-by: NStephen Boyd <sboyd@codeaurora.org>
Acked-by: NSimon Glass <sjg@chromium.org>
Tested-by: NSimon Glass <sjg@chromium.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/traps.c

@@ -266,6 +266,7 @@ void die(const char *str, struct pt_regs *regs, int err)
 {
 	struct thread_info *thread = current_thread_info();
 	int ret;
+	enum bug_trap_type bug_type = BUG_TRAP_TYPE_NONE;
 
 	oops_enter();
 
@@ -273,7 +274,9 @@ void die(const char *str, struct pt_regs *regs, int err)
 	console_verbose();
 	bust_spinlocks(1);
 	if (!user_mode(regs))
-		report_bug(regs->ARM_pc, regs);
+		bug_type = report_bug(regs->ARM_pc, regs);
+	if (bug_type != BUG_TRAP_TYPE_NONE)
+		str = "Oops - BUG";
 	ret = __die(str, err, thread, regs);
 
 	if (regs && kexec_should_crash(thread->task))