lib/nmi_backtrace.c: fix kernel text address leak

Don't leak idle function address in NMI backtrace.

Link: http://lkml.kernel.org/r/20171106165648.GA95243@sofiaSigned-off-by: Liu Changcheng <changcheng.liu@intel.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/nmi_backtrace.c

@@ -93,8 +93,8 @@ bool nmi_cpu_backtrace(struct pt_regs *regs)
 	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
 		arch_spin_lock(&lock);
 		if (regs && cpu_in_idle(instruction_pointer(regs))) {
-			pr_warn("NMI backtrace for cpu %d skipped: idling at pc %#lx\n",
-				cpu, instruction_pointer(regs));
+			pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",
+				cpu, (void *)instruction_pointer(regs));
 		} else {
 			pr_warn("NMI backtrace for cpu %d\n", cpu);
 			if (regs)