lib: taint kernel in common report_bug() WARN path.

Commit 95b570c9ce ("Taint kernel after
WARN_ON(condition)") introduced a TAINT_WARN that was implemented for
all architectures using the generic warn_on_slowpath(), which excluded
any architecture that set HAVE_ARCH_WARN_ON.

As all of the architectures that implement their own WARN_ON() all go
through the report_bug() path (specifically handling BUG_TRAP_TYPE_WARN),
taint the kernel there as well for consistency.

Tested on avr32 and sh. Also relevant for s390, parisc, and powerpc.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Acked-by: Kyle McMartin <kyle@mcmartin.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/bug.c

@@ -37,6 +37,7 @@
  */
 #include <linux/list.h>
 #include <linux/module.h>
+#include <linux/kernel.h>
 #include <linux/bug.h>
 #include <linux/sched.h>
 
@@ -149,6 +150,7 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
 			       (void *)bugaddr);
 
 		show_regs(regs);
+		add_taint(TAINT_WARN);
 		return BUG_TRAP_TYPE_WARN;
 	}