lib/bug.c: use common WARN helper

The traceoff_on_warning option doesn't have any effect on s390, powerpc,
arm64, parisc, and sh because there are two different types of WARN
implementations:

1) The above mentioned architectures treat WARN() as a special case of a
   BUG() exception.  They handle warnings in report_bug() in lib/bug.c.

2) All other architectures just call warn_slowpath_*() directly.  Their
   warnings are handled in warn_slowpath_common() in kernel/panic.c.

Support traceoff_on_warning on all architectures and prevent any future
divergence by using a single common function to emit the warning.

Also remove the '()' from '%pS()', because the parentheses look funky:

  [   45.607629] WARNING: at /root/warn_mod/warn_mod.c:17 .init_dummy+0x20/0x40 [warn_mod]()

Reported-by: Chunyu Hu <chuhu@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: Prarit Bhargava <prarit@redhat.com>
Acked-by: Prarit Bhargava <prarit@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 26 insertions, 15 deletions

diff --git a/kernel/panic.c b/kernel/panic.c
index d96469d..fa40085 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -24,6 +24,7 @@
 #include <linux/init.h>
 #include <linux/nmi.h>
 #include <linux/console.h>
+#include <linux/bug.h>
 
 #define PANIC_TIMER_STEP 100
 #define PANIC_BLINK_SPD 18
@@ -449,20 +450,25 @@ void oops_exit(void)
 	kmsg_dump(KMSG_DUMP_OOPS);
 }
 
-#ifdef WANT_WARN_ON_SLOWPATH
-struct slowpath_args {
+struct warn_args {
 	const char *fmt;
 	va_list args;
 };
 
-static void warn_slowpath_common(const char *file, int line, void *caller,
-				 unsigned taint, struct slowpath_args *args)
+void __warn(const char *file, int line, void *caller, unsigned taint,
+	    struct pt_regs *regs, struct warn_args *args)
 {
 	disable_trace_on_warning();
 
 	pr_warn("------------[ cut here ]------------\n");
-	pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS()\n",
-		raw_smp_processor_id(), current->pid, file, line, caller);
+
+	if (file)
+		pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n",
+			raw_smp_processor_id(), current->pid, file, line,
+			caller);
+	else
+		pr_warn("WARNING: CPU: %d PID: %d at %pS\n",
+			raw_smp_processor_id(), current->pid, caller);
 
 	if (args)
 		vprintk(args->fmt, args->args);
@@ -479,20 +485,27 @@ static void warn_slowpath_common(const char *file, int line, void *caller,
 	}
 
 	print_modules();
-	dump_stack();
+
+	if (regs)
+		show_regs(regs);
+	else
+		dump_stack();
+
 	print_oops_end_marker();
+
 	/* Just a warning, don't kill lockdep. */
 	add_taint(taint, LOCKDEP_STILL_OK);
 }
 
+#ifdef WANT_WARN_ON_SLOWPATH
 void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
 {
-	struct slowpath_args args;
+	struct warn_args args;
 
 	args.fmt = fmt;
 	va_start(args.args, fmt);
-	warn_slowpath_common(file, line, __builtin_return_address(0),
-			     TAINT_WARN, &args);
+	__warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL,
+	       &args);
 	va_end(args.args);
 }
 EXPORT_SYMBOL(warn_slowpath_fmt);
@@ -500,20 +513,18 @@ EXPORT_SYMBOL(warn_slowpath_fmt);
 void warn_slowpath_fmt_taint(const char *file, int line,
 			     unsigned taint, const char *fmt, ...)
 {
-	struct slowpath_args args;
+	struct warn_args args;
 
 	args.fmt = fmt;
 	va_start(args.args, fmt);
-	warn_slowpath_common(file, line, __builtin_return_address(0),
-			     taint, &args);
+	__warn(file, line, __builtin_return_address(0), taint, NULL, &args);
 	va_end(args.args);
 }
 EXPORT_SYMBOL(warn_slowpath_fmt_taint);
 
 void warn_slowpath_null(const char *file, int line)
 {
-	warn_slowpath_common(file, line, __builtin_return_address(0),
-			     TAINT_WARN, NULL);
+	__warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL, NULL);
 }
 EXPORT_SYMBOL(warn_slowpath_null);
 #endif