panic: print out stacktrace if DEBUG_BUGVERBOSE

if CONFIG_DEBUG_BUGVERBOSE is set then the user most definitely wanted
to see as much information about kernel crashes as possible - so give
them at least a stack dump.

this is particularly useful for stackprotector related panics, where
the stacktrace can give us the exact location of the (attempted)
attack.

Pointed out by pageexec@freemail.hu in the stackprotector breakage
threads.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

kernel/panic.c

@@ -80,6 +80,9 @@ NORET_TYPE void panic(const char * fmt, ...)
 	vsnprintf(buf, sizeof(buf), fmt, args);
 	va_end(args);
 	printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
+#ifdef CONFIG_DEBUG_BUGVERBOSE
+	dump_stack();
+#endif
 	bust_spinlocks(0);
 
 	/*