From 456b565cc52fbcdaa2e19ffdf40d9dd3b726d603 Mon Sep 17 00:00:00 2001 From: Simon Kagstrom Date: Fri, 16 Oct 2009 14:09:18 +0200 Subject: 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 kmsg_dump implementation by Linus). A struct kmsg_dumper has been added which contains a callback to dump the kernel log buffers on crashes. The kmsg_dump function gets called from oops_exit() and panic() and invokes this callbacks with the crash reason. [dwmw2: Fix log_end handling] Signed-off-by: Simon Kagstrom Reviewed-by: Anders Grafstrom Reviewed-by: Linus Torvalds Acked-by: Ingo Molnar Signed-off-by: Artem Bityutskiy Signed-off-by: David Woodhouse --- kernel/printk.c | 119 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 119 insertions(+) (limited to 'kernel/printk.c') diff --git a/kernel/printk.c b/kernel/printk.c index f38b07f78a4e..051d1f50648f 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -33,6 +33,7 @@ #include #include #include +#include #include @@ -1405,3 +1406,121 @@ bool printk_timed_ratelimit(unsigned long *caller_jiffies, } EXPORT_SYMBOL(printk_timed_ratelimit); #endif + +static DEFINE_SPINLOCK(dump_list_lock); +static LIST_HEAD(dump_list); + +/** + * kmsg_dump_register - register a kernel log dumper. + * @dump: pointer to the kmsg_dumper 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 kmsg_dump_register(struct kmsg_dumper *dumper) +{ + unsigned long flags; + int err = -EBUSY; + + /* The dump callback needs to be set */ + if (!dumper->dump) + return -EINVAL; + + spin_lock_irqsave(&dump_list_lock, flags); + /* Don't allow registering multiple times */ + if (!dumper->registered) { + dumper->registered = 1; + list_add_tail(&dumper->list, &dump_list); + err = 0; + } + spin_unlock_irqrestore(&dump_list_lock, flags); + + return err; +} +EXPORT_SYMBOL_GPL(kmsg_dump_register); + +/** + * kmsg_dump_unregister - unregister a kmsg dumper. + * @dump: pointer to the kmsg_dumper structure + * + * Removes a dump device from the system. Returns zero on success and + * %-EINVAL otherwise. + */ +int kmsg_dump_unregister(struct kmsg_dumper *dumper) +{ + unsigned long flags; + int err = -EINVAL; + + spin_lock_irqsave(&dump_list_lock, flags); + if (dumper->registered) { + dumper->registered = 0; + list_del(&dumper->list); + err = 0; + } + spin_unlock_irqrestore(&dump_list_lock, flags); + + return err; +} +EXPORT_SYMBOL_GPL(kmsg_dump_unregister); + +static const char const *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]; +} + +/** + * kmsg_dump - 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 kmsg_dump(enum kmsg_dump_reason reason) +{ + unsigned long end; + unsigned chars; + struct kmsg_dumper *dumper; + const char *s1, *s2; + unsigned long l1, l2; + unsigned long flags; + + /* Theoretically, the log could move on after we do this, but + there's not a lot we can do about that. The new messages + will overwrite the start of what we dump. */ + spin_lock_irqsave(&logbuf_lock, flags); + end = log_end & LOG_BUF_MASK; + chars = logged_chars; + spin_unlock_irqrestore(&logbuf_lock, flags); + + if (logged_chars > end) { + s1 = log_buf + log_buf_len - logged_chars + end; + l1 = logged_chars - end; + + s2 = log_buf; + l2 = end; + } else { + s1 = ""; + l1 = 0; + + s2 = log_buf + end - logged_chars; + l2 = logged_chars; + } + + if (!spin_trylock_irqsave(&dump_list_lock, flags)) { + 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_irqrestore(&dump_list_lock, flags); +} -- cgit v1.2.3 From 595dd3d8bf953254d8d2f30f99c54fe09c470040 Mon Sep 17 00:00:00 2001 From: Randy Dunlap Date: Tue, 1 Dec 2009 10:52:02 -0800 Subject: kmsg_dump: fix build for CONFIG_PRINTK=n kmsg_dump() fails to build when CONFIG_PRINTK=n; provide stubs for the kmsg_dump*() functions when CONFIG_PRINTK=n. kernel/printk.c: In function 'kmsg_dump': kernel/printk.c:1501: error: 'log_buf_len' undeclared (first use in this function) kernel/printk.c:1502: error: 'logged_chars' undeclared (first use in this function) kernel/printk.c:1506: error: 'log_buf' undeclared (first use in this function) Signed-off-by: Randy Dunlap Acked-by: Simon Kagstrom Signed-off-by: David Woodhouse --- include/linux/kmsg_dump.h | 16 ++++++++++++++++ kernel/printk.c | 2 +- 2 files changed, 17 insertions(+), 1 deletion(-) (limited to 'kernel/printk.c') diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h index 7f089ec5ef32..e32aa268efac 100644 --- a/include/linux/kmsg_dump.h +++ b/include/linux/kmsg_dump.h @@ -35,10 +35,26 @@ struct kmsg_dumper { int registered; }; +#ifdef CONFIG_PRINTK void kmsg_dump(enum kmsg_dump_reason reason); int kmsg_dump_register(struct kmsg_dumper *dumper); int kmsg_dump_unregister(struct kmsg_dumper *dumper); +#else +static inline void kmsg_dump(enum kmsg_dump_reason reason) +{ +} + +static inline int kmsg_dump_register(struct kmsg_dumper *dumper) +{ + return -EINVAL; +} + +static inline int kmsg_dump_unregister(struct kmsg_dumper *dumper) +{ + return -EINVAL; +} +#endif #endif /* _LINUX_KMSG_DUMP_H */ diff --git a/kernel/printk.c b/kernel/printk.c index 051d1f50648f..2a564570f822 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -1405,7 +1405,6 @@ bool printk_timed_ratelimit(unsigned long *caller_jiffies, return false; } EXPORT_SYMBOL(printk_timed_ratelimit); -#endif static DEFINE_SPINLOCK(dump_list_lock); static LIST_HEAD(dump_list); @@ -1524,3 +1523,4 @@ void kmsg_dump(enum kmsg_dump_reason reason) dumper->dump(dumper, reason, s1, l1, s2, l2); spin_unlock_irqrestore(&dump_list_lock, flags); } +#endif -- cgit v1.2.3