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Subject[PATCH v6 4/5]: core: Add kernel message dumper to call on oopses and panics
The core functionality is implemented as per Linus suggestion from

http://lists.infradead.org/pipermail/linux-mtd/2009-October/027620.html

(with the dump_kmsg implementation by Linus). A struct kmsg_dumper has
been added which contains a callback to dump the kernel log buffers on
crashes. The dump_kmsg function gets called from oops_exit() and panic()
and invokes this callbacks with the crash reason.

Signed-off-by: Simon Kagstrom <simon.kagstrom@netinsight.net>
Reviewed-by: Anders Grafstrom <anders.grafstrom@netinsight.net>
---
ChangeLog:
Review comments from Linus Torvalds and Anders Grafström:
* Rename structures and file names
* Remove setup callback and unify panic/oops callbacks and
instead add a reason parameter
* Use a regular spinlock and try it when dumping (fail
if held)
* Check if the dumper is already registered
* Various style fixes/cleanup
include/linux/kmsg_dump.h | 37 ++++++++++++++++
kernel/panic.c | 3 +
kernel/printk.c | 105 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 145 insertions(+), 0 deletions(-)
create mode 100644 include/linux/kmsg_dump.h
diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h
new file mode 100644
index 0000000..a0d6b55
--- /dev/null
+++ b/include/linux/kmsg_dump.h
@@ -0,0 +1,37 @@
+/*
+ * linux/include/kmsg_dump.h
+ *
+ * Copyright (C) 2009 Net Insight AB
+ *
+ * Author: Simon Kagstrom <simon.kagstrom@netinsight.net>
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of this archive
+ * for more details.
+ */
+#ifndef _LINUX_KMSG_DUMP_H
+#define _LINUX_KMSG_DUMP_H
+
+#include <linux/list.h>
+
+enum kmsg_dump_reason {
+ kmsg_dump_oops,
+ kmsg_dump_panic,
+};
+
+struct kmsg_dumper {
+ void (*dump)(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason,
+ const char *s1, unsigned long l1,
+ const char *s2, unsigned long l2);
+ void *priv;
+ struct list_head list;
+ int registered;
+};
+
+void dump_kmsg(enum kmsg_dump_reason reason);
+
+int register_kmsg_dumper(struct kmsg_dumper *dumper, void *priv);
+
+void unregister_kmsg_dumper(struct kmsg_dumper *dumper);
+
+#endif /* _LINUX_DUMP_DEVICE_H */
diff --git a/kernel/panic.c b/kernel/panic.c
index c0b33b8..3a5a93f 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -10,6 +10,7 @@
*/
#include <linux/debug_locks.h>
#include <linux/interrupt.h>
+#include <linux/kmsg_dump.h>
#include <linux/kallsyms.h>
#include <linux/notifier.h>
#include <linux/module.h>
@@ -76,6 +77,7 @@ NORET_TYPE void panic(const char * fmt, ...)
dump_stack();
#endif

+ dump_kmsg(kmsg_dump_panic);
/*
* If we have crashed and we have a crash kernel loaded let it handle
* everything else.
@@ -341,6 +343,7 @@ void oops_exit(void)
{
do_oops_enter_exit();
print_oops_end_marker();
+ dump_kmsg(kmsg_dump_oops);
}

#ifdef WANT_WARN_ON_SLOWPATH
diff --git a/kernel/printk.c b/kernel/printk.c
index f38b07f..a97abb0 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -33,6 +33,8 @@
#include <linux/bootmem.h>
#include <linux/syscalls.h>
#include <linux/kexec.h>
+#include <linux/kmsg_dump.h>
+#include <linux/spinlock.h>

#include <asm/uaccess.h>

@@ -1405,3 +1407,106 @@ bool printk_timed_ratelimit(unsigned long *caller_jiffies,
}
EXPORT_SYMBOL(printk_timed_ratelimit);
#endif
+
+static LIST_HEAD(dump_list);
+static DEFINE_SPINLOCK(dump_list_lock);
+
+/**
+ * register_dump_device - register a kernel log dumper.
+ * @dump: pointer to the dump structure
+ * @priv: private data for the structure
+ *
+ * Adds a kernel log dumper to the system. The dump callback in the
+ * structure will be called when the kernel oopses or panics and must be
+ * set. Returns zero on success and -EINVAL or -EBUSY otherwise.
+ */
+int register_kmsg_dumper(struct kmsg_dumper *dumper, void *priv)
+{
+ unsigned long flags;
+
+ /* The dump callback needs to be set */
+ if (!dumper->dump)
+ return -EINVAL;
+
+ /* Don't allow registering multiple times */
+ if (dumper->registered)
+ return -EBUSY;
+
+ dumper->priv = priv;
+ dumper->registered = 1;
+
+ spin_lock_irqsave(&dump_list_lock, flags);
+ list_add(&dumper->list, &dump_list);
+ spin_unlock_irqrestore(&dump_list_lock, flags);
+ return 0;
+}
+EXPORT_SYMBOL(register_kmsg_dumper);
+
+/**
+ * unregister_dump_device - unregister a dumpdevice.
+ * @dump: pointer to the dump structure
+ *
+ * Removes a dump device from the system.
+ */
+void unregister_kmsg_dumper(struct kmsg_dumper *dumper)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&dump_list_lock, flags);
+ list_del(&dumper->list);
+ spin_unlock_irqrestore(&dump_list_lock, flags);
+}
+EXPORT_SYMBOL(unregister_kmsg_dumper);
+
+static const char *kmsg_reasons[] = {
+ [kmsg_dump_oops] = "oops",
+ [kmsg_dump_panic] = "panic",
+};
+
+static const char *kmsg_to_str(enum kmsg_dump_reason reason)
+{
+ if (reason > ARRAY_SIZE(kmsg_reasons) || reason < 0)
+ return "unknown";
+
+ return kmsg_reasons[reason];
+}
+
+/**
+ * dump_kmsg - dump kernel log to kernel message dumpers.
+ * @reason: the reason (oops, panic etc) for dumping
+ *
+ * Iterate through each of the dump devices and call the oops/panic
+ * callbacks with the log buffer.
+ */
+void dump_kmsg(enum kmsg_dump_reason reason)
+{
+ unsigned long len = ACCESS_ONCE(log_end);
+ struct kmsg_dumper *dumper;
+ const char *s1, *s2;
+ unsigned long l1, l2;
+
+ s1 = "";
+ l1 = 0;
+ s2 = log_buf;
+ l2 = len;
+
+ /* Have we rotated around the circular buffer? */
+ if (len > log_buf_len) {
+ unsigned long pos = len & LOG_BUF_MASK;
+
+ s1 = log_buf + pos;
+ l1 = log_buf_len - pos;
+
+ s2 = log_buf;
+ l2 = pos;
+ }
+
+ if (!spin_trylock(&dump_list_lock)) {
+ printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n",
+ kmsg_to_str(reason));
+ return;
+ }
+ list_for_each_entry(dumper, &dump_list, list)
+ dumper->dump(dumper, reason, s1, l1, s2, l2);
+ spin_unlock(&dump_list_lock);
+}
--
1.6.0.4
--
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