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-rw-r--r--include/linux/ftrace.h2
-rw-r--r--kernel/sysctl.c10
-rw-r--r--kernel/trace/trace.c29
3 files changed, 38 insertions, 3 deletions
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index a3d46151be1..9623b7b9e5a 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -165,6 +165,8 @@ static inline void __ftrace_enabled_restore(int enabled)
#endif
#ifdef CONFIG_TRACING
+extern int ftrace_dump_on_oops;
+
extern void
ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index a13bd4dfaeb..84754f5801e 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -484,6 +484,16 @@ static struct ctl_table kern_table[] = {
.proc_handler = &ftrace_enable_sysctl,
},
#endif
+#ifdef CONFIG_TRACING
+ {
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "ftrace_dump_on_opps",
+ .data = &ftrace_dump_on_oops,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
+#endif
#ifdef CONFIG_MODULES
{
.ctl_name = KERN_MODPROBE,
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d345d649d07..47f46cbdd86 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -63,6 +63,28 @@ static cpumask_t __read_mostly tracing_buffer_mask;
static int tracing_disabled = 1;
+/*
+ * ftrace_dump_on_oops - variable to dump ftrace buffer on oops
+ *
+ * If there is an oops (or kernel panic) and the ftrace_dump_on_oops
+ * is set, then ftrace_dump is called. This will output the contents
+ * of the ftrace buffers to the console. This is very useful for
+ * capturing traces that lead to crashes and outputing it to a
+ * serial console.
+ *
+ * It is default off, but you can enable it with either specifying
+ * "ftrace_dump_on_oops" in the kernel command line, or setting
+ * /proc/sys/kernel/ftrace_dump_on_oops to true.
+ */
+int ftrace_dump_on_oops;
+
+static int __init set_ftrace_dump_on_oops(char *str)
+{
+ ftrace_dump_on_oops = 1;
+ return 1;
+}
+__setup("ftrace_dump_on_oops", set_ftrace_dump_on_oops);
+
long
ns2usecs(cycle_t nsec)
{
@@ -3021,7 +3043,8 @@ EXPORT_SYMBOL_GPL(__ftrace_printk);
static int trace_panic_handler(struct notifier_block *this,
unsigned long event, void *unused)
{
- ftrace_dump();
+ if (ftrace_dump_on_oops)
+ ftrace_dump();
return NOTIFY_OK;
}
@@ -3037,7 +3060,8 @@ static int trace_die_handler(struct notifier_block *self,
{
switch (val) {
case DIE_OOPS:
- ftrace_dump();
+ if (ftrace_dump_on_oops)
+ ftrace_dump();
break;
default:
break;
@@ -3078,7 +3102,6 @@ trace_printk_seq(struct trace_seq *s)
trace_seq_reset(s);
}
-
void ftrace_dump(void)
{
static DEFINE_SPINLOCK(ftrace_dump_lock);