There have been several times where I have had to rebuild a kernel to
cause a panic when hitting a WARN() in the code in order to get a crash
dump from a system. Sometimes this is easy to do, other times (such as
in the case of a remote admin) it is not trivial to send new images to the
user.
A much easier method would be a switch to change the WARN() over to a
BUG(). This makes debugging easier in that I can now test the actual
image the WARN() was seen on and I do not have to engage in remote
debugging.
This patch adds a bug_on_warn kernel parameter, which calls BUG() in the
warn_slowpath_common() path. The function will still print out the
location of the warning.
Successfully tested by me.
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Fabian Frederick <fabf@xxxxxxxxx>
Cc: linux-doc@xxxxxxxxxxxxxxx
Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
---
Documentation/kernel-parameters.txt | 2 ++
kernel/panic.c | 16 +++++++++++++++-
2 files changed, 17 insertions(+), 1 deletion(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7dbe5ec..2967542 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -553,6 +553,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
bttv.pll= See Documentation/video4linux/bttv/Insmod-options
bttv.tuner=
+ bug_on_warn BUG() instead of WARN()
+
bulk_remove=off [PPC] This parameter disables the use of the pSeries
firmware feature for flushing multiple hpte entries
at a time.
diff --git a/kernel/panic.c b/kernel/panic.c
index d09dc5c..258a7be 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -33,6 +33,7 @@ static int pause_on_oops;
static int pause_on_oops_flag;
static DEFINE_SPINLOCK(pause_on_oops_lock);
static bool crash_kexec_post_notifiers;
+static bool bug_on_warn;
int panic_timeout = CONFIG_PANIC_TIMEOUT;
EXPORT_SYMBOL_GPL(panic_timeout);
@@ -420,13 +421,19 @@ static void warn_slowpath_common(const char *file, int line, void *caller,
{
disable_trace_on_warning();
- pr_warn("------------[ cut here ]------------\n");
+ if (!bug_on_warn)
+ 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 (args)
vprintk(args->fmt, args->args);
+ if (bug_on_warn) {
+ pr_warn("bug_on_warn set, calling BUG()...\n");
+ BUG();
+ }
+
print_modules();
dump_stack();
print_oops_end_marker();
@@ -501,3 +508,10 @@ static int __init oops_setup(char *s)
return 0;
}
early_param("oops", oops_setup);
+
+static int __init bug_on_warn_setup(char *s)
+{
+ bug_on_warn = true;
+ return 0;
+}
+early_param("bug_on_warn", bug_on_warn_setup);
--
1.7.9.3
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