kernel: add the new 'crashlog' feature, which tries to store kernel oops/panic logs in a fixed location in RAM to recover them after the reboot and make them available to user space using debugfs

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@22305 3c298f89-4303-0410-b956-a3cf2f4a3e73

9 files changed, 1173 insertions, 0 deletions

diff --git a/target/linux/generic/config-2.6.32 b/target/linux/generic/config-2.6.32
index 3cd83c2b1c..7740db18f0 100644
--- a/target/linux/generic/config-2.6.32
+++ b/target/linux/generic/config-2.6.32
@@ -352,6 +352,7 @@ CONFIG_CONSTRUCTORS=y
 # CONFIG_CPU_IDLE is not set
 # CONFIG_CRAMFS is not set
 # CONFIG_CRASH_DUMP is not set
+CONFIG_CRASHLOG=y
 # CONFIG_CRC16 is not set
 CONFIG_CRC32=y
 # CONFIG_CRC7 is not set
diff --git a/target/linux/generic/config-2.6.33 b/target/linux/generic/config-2.6.33
index fb8ac7a5a1..d39dd6feab 100644
--- a/target/linux/generic/config-2.6.33
+++ b/target/linux/generic/config-2.6.33
@@ -357,6 +357,7 @@ CONFIG_CONSTRUCTORS=y
 # CONFIG_CPU_IDLE is not set
 # CONFIG_CRAMFS is not set
 # CONFIG_CRASH_DUMP is not set
+CONFIG_CRASHLOG=y
 # CONFIG_CRC16 is not set
 CONFIG_CRC32=y
 # CONFIG_CRC7 is not set
diff --git a/target/linux/generic/config-2.6.34 b/target/linux/generic/config-2.6.34
index a8ad0fe3ba..661d1429f2 100644
--- a/target/linux/generic/config-2.6.34
+++ b/target/linux/generic/config-2.6.34
@@ -360,6 +360,7 @@ CONFIG_CONSTRUCTORS=y
 # CONFIG_CPU_IDLE is not set
 # CONFIG_CRAMFS is not set
 # CONFIG_CRASH_DUMP is not set
+CONFIG_CRASHLOG=y
 # CONFIG_CRC16 is not set
 CONFIG_CRC32=y
 # CONFIG_CRC7 is not set
diff --git a/target/linux/generic/config-2.6.35 b/target/linux/generic/config-2.6.35
index f3bd97b1d6..e834c1313d 100644
--- a/target/linux/generic/config-2.6.35
+++ b/target/linux/generic/config-2.6.35
@@ -367,6 +367,7 @@ CONFIG_CONSTRUCTORS=y
 # CONFIG_CPU_IDLE is not set
 # CONFIG_CRAMFS is not set
 # CONFIG_CRASH_DUMP is not set
+CONFIG_CRASHLOG=y
 # CONFIG_CRC16 is not set
 CONFIG_CRC32=y
 # CONFIG_CRC7 is not set
diff --git a/target/linux/generic/patches-2.6.32/930-kmsg_dump_backport.patch b/target/linux/generic/patches-2.6.32/930-kmsg_dump_backport.patch
new file mode 100644
index 0000000000..4b0369059e
--- /dev/null
+++ b/target/linux/generic/patches-2.6.32/930-kmsg_dump_backport.patch
@@ -0,0 +1,205 @@
+--- /dev/null
++++ b/include/linux/kmsg_dump.h
+@@ -0,0 +1,44 @@
++/*
++ * 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 - kernel crash message dumper structure
++ * @dump:	The callback which gets called on crashes. The buffer is passed
++ * 		as two sections, where s1 (length l1) contains the older
++ * 		messages and s2 (length l2) contains the newer.
++ * @list:	Entry in the dumper list (private)
++ * @registered:	Flag that specifies if this is already registered
++ */
++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);
++	struct list_head list;
++	int registered;
++};
++
++void kmsg_dump(enum kmsg_dump_reason reason);
++
++int kmsg_dump_register(struct kmsg_dumper *dumper);
++
++int kmsg_dump_unregister(struct kmsg_dumper *dumper);
++
++#endif /* _LINUX_KMSG_DUMP_H */
+--- 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>
+@@ -74,6 +75,7 @@ NORET_TYPE void panic(const char * fmt, 
+ 	dump_stack();
+ #endif
+ 
++	kmsg_dump(KMSG_DUMP_PANIC);
+ 	/*
+ 	 * If we have crashed and we have a crash kernel loaded let it handle
+ 	 * everything else.
+@@ -339,6 +341,7 @@ void oops_exit(void)
+ {
+ 	do_oops_enter_exit();
+ 	print_oops_end_marker();
++	kmsg_dump(KMSG_DUMP_OOPS);
+ }
+ 
+ #ifdef WANT_WARN_ON_SLOWPATH
+--- a/kernel/printk.c
++++ b/kernel/printk.c
+@@ -33,6 +33,7 @@
+ #include <linux/bootmem.h>
+ #include <linux/syscalls.h>
+ #include <linux/kexec.h>
++#include <linux/kmsg_dump.h>
+ 
+ #include <asm/uaccess.h>
+ 
+@@ -1405,3 +1406,121 @@ bool printk_timed_ratelimit(unsigned lon
+ }
+ 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);
++}
diff --git a/target/linux/generic/patches-2.6.32/931-crashlog.patch b/target/linux/generic/patches-2.6.32/931-crashlog.patch
new file mode 100644
index 0000000000..0c06700aef
--- /dev/null
+++ b/target/linux/generic/patches-2.6.32/931-crashlog.patch
@@ -0,0 +1,241 @@
+--- /dev/null
++++ b/include/linux/crashlog.h
+@@ -0,0 +1,12 @@
++#ifndef __CRASHLOG_H
++#define __CRASHLOG_H
++
++#ifdef CONFIG_CRASHLOG
++void __init crashlog_init_mem(struct bootmem_data *bdata);
++#else
++static inline void crashlog_init_mem(struct bootmem_data *bdata)
++{
++}
++#endif
++
++#endif
+--- a/init/Kconfig
++++ b/init/Kconfig
+@@ -710,6 +710,9 @@ config NET_NS
+ 	  Allow user space to create what appear to be multiple instances
+ 	  of the network stack.
+ 
++config CRASHLOG
++	bool "Crash logging"
++
+ config BLK_DEV_INITRD
+ 	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
+ 	depends on BROKEN || !FRV
+--- a/kernel/Makefile
++++ b/kernel/Makefile
+@@ -96,6 +96,7 @@ obj-$(CONFIG_SMP) += sched_cpupri.o
+ obj-$(CONFIG_SLOW_WORK) += slow-work.o
+ obj-$(CONFIG_SLOW_WORK_DEBUG) += slow-work-debugfs.o
+ obj-$(CONFIG_PERF_EVENTS) += perf_event.o
++obj-$(CONFIG_CRASHLOG) += crashlog.o
+ 
+ ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
+ # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
+--- /dev/null
++++ b/kernel/crashlog.c
+@@ -0,0 +1,171 @@
++/*
++ * Crash information logger
++ * Copyright (C) 2010 Felix Fietkau <nbd@openwrt.org>
++ *
++ * Based on ramoops.c
++ *   Copyright (C) 2010 Marco Stornelli <marco.stornelli@gmail.com>
++ *
++ * This program is free software; you can redistribute it and/or
++ * modify it under the terms of the GNU General Public License
++ * version 2 as published by the Free Software Foundation.
++ *
++ * This program is distributed in the hope that it will be useful, but
++ * WITHOUT ANY WARRANTY; without even the implied warranty of
++ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
++ * General Public License for more details.
++ *
++ * You should have received a copy of the GNU General Public License
++ * along with this program; if not, write to the Free Software
++ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
++ * 02110-1301 USA
++ *
++ */
++
++#include <linux/module.h>
++#include <linux/bootmem.h>
++#include <linux/debugfs.h>
++#include <linux/crashlog.h>
++#include <linux/kmsg_dump.h>
++#include <linux/module.h>
++#include <linux/pfn.h>
++#include <asm/io.h>
++
++#define CRASHLOG_PAGES	4
++#define CRASHLOG_SIZE	(CRASHLOG_PAGES * PAGE_SIZE)
++#define CRASHLOG_MAGIC	0xa1eedead
++
++/*
++ * Start the log at 1M before the end of RAM, as some boot loaders like
++ * to use the end of the RAM for stack usage and other things
++ * If this fails, fall back to using the last part.
++ */
++#define CRASHLOG_OFFSET	(1024 * 1024)
++
++struct crashlog_data {
++	u32 magic;
++	u32 len;
++	u8 data[];
++};
++
++static struct debugfs_blob_wrapper crashlog_blob;
++static unsigned long crashlog_addr = 0;
++static struct crashlog_data *crashlog_buf;
++static struct kmsg_dumper dump;
++static bool first = true;
++
++extern struct list_head *crashlog_modules;
++
++void __init crashlog_init_mem(bootmem_data_t *bdata)
++{
++	unsigned long addr;
++
++	if (crashlog_addr)
++		return;
++
++	addr = PFN_PHYS(bdata->node_low_pfn) - CRASHLOG_OFFSET;
++	if (reserve_bootmem(addr, CRASHLOG_SIZE, BOOTMEM_EXCLUSIVE) < 0) {
++		printk("Crashlog failed to allocate RAM at address 0x%lx\n", addr);
++		bdata->node_low_pfn -= CRASHLOG_PAGES;
++		addr = PFN_PHYS(bdata->node_low_pfn);
++	}
++	crashlog_addr = addr;
++}
++
++static void __init crashlog_copy(void)
++{
++	if (crashlog_buf->magic != CRASHLOG_MAGIC)
++		return;
++
++	if (!crashlog_buf->len || crashlog_buf->len >
++	    CRASHLOG_SIZE - sizeof(*crashlog_buf))
++		return;
++
++	crashlog_blob.size = crashlog_buf->len;
++	crashlog_blob.data = kmemdup(crashlog_buf->data,
++		crashlog_buf->len, GFP_KERNEL);
++
++	debugfs_create_blob("crashlog", 0700, NULL, &crashlog_blob);
++}
++
++static int get_maxlen(void)
++{
++	return CRASHLOG_SIZE - sizeof(*crashlog_buf) - crashlog_buf->len;
++}
++
++static void crashlog_printf(const char *fmt, ...)
++{
++	va_list args;
++	int len = get_maxlen();
++
++	if (!len)
++		return;
++
++	va_start(args, fmt);
++	crashlog_buf->len += vsnprintf(
++		&crashlog_buf->data[crashlog_buf->len],
++		len, fmt, args);
++	va_end(args);
++}
++
++static void crashlog_do_dump(struct kmsg_dumper *dumper,
++		enum kmsg_dump_reason reason, const char *s1, unsigned long l1,
++		const char *s2, unsigned long l2)
++{
++	unsigned long s1_start, s2_start;
++	unsigned long l1_cpy, l2_cpy;
++	struct timeval tv;
++	struct module *m;
++	char *buf;
++	int len;
++
++	if (!first)
++		crashlog_printf("\n===================================\n");
++
++	do_gettimeofday(&tv);
++	crashlog_printf("Time: %lu.%lu\n",
++		(long)tv.tv_sec, (long)tv.tv_usec);
++
++	if (first) {
++		crashlog_printf("Modules:");
++		list_for_each_entry(m, crashlog_modules, list) {
++			crashlog_printf("\t%s@%p+%x", m->name,
++			m->module_core, m->core_size,
++			m->module_init, m->init_size);
++		}
++		crashlog_printf("\n");
++		first = false;
++	}
++
++	buf = (char *)&crashlog_buf->data[crashlog_buf->len];
++	len = get_maxlen();
++
++	l2_cpy = min(l2, (unsigned long)len);
++	l1_cpy = min(l1, (unsigned long)len - l2_cpy);
++
++	s2_start = l2 - l2_cpy;
++	s1_start = l1 - l1_cpy;
++
++	memcpy(buf, s1 + s1_start, l1_cpy);
++	memcpy(buf + l1_cpy, s2 + s2_start, l2_cpy);
++	crashlog_buf->len += l1_cpy + l2_cpy;
++}
++
++
++int __init crashlog_init_fs(void)
++{
++	if (!crashlog_addr)
++		return -ENOMEM;
++
++	crashlog_buf = ioremap(crashlog_addr, CRASHLOG_SIZE);
++
++	crashlog_copy();
++
++	crashlog_buf->magic = CRASHLOG_MAGIC;
++	crashlog_buf->len = 0;
++
++	dump.dump = crashlog_do_dump;
++	kmsg_dump_register(&dump);
++
++	return 0;
++}
++module_init(crashlog_init_fs);
+--- a/mm/bootmem.c
++++ b/mm/bootmem.c
+@@ -13,6 +13,7 @@
+ #include <linux/bootmem.h>
+ #include <linux/module.h>
+ #include <linux/kmemleak.h>
++#include <linux/crashlog.h>
+ 
+ #include <asm/bug.h>
+ #include <asm/io.h>
+@@ -152,6 +153,7 @@ static unsigned long __init free_all_boo
+ 	if (!bdata->node_bootmem_map)
+ 		return 0;
+ 
++	crashlog_init_mem(bdata);
+ 	start = bdata->node_min_pfn;
+ 	end = bdata->node_low_pfn;
+ 
+--- a/kernel/module.c
++++ b/kernel/module.c
+@@ -79,6 +79,9 @@ EXPORT_TRACEPOINT_SYMBOL(module_get);
+ DEFINE_MUTEX(module_mutex);
+ EXPORT_SYMBOL_GPL(module_mutex);
+ static LIST_HEAD(modules);
++#ifdef CONFIG_CRASHLOG
++struct list_head *crashlog_modules = &modules;
++#endif
+ 
+ /* Block module loading/unloading? */
+ int modules_disabled = 0;
diff --git a/target/linux/generic/patches-2.6.33/930-crashlog.patch b/target/linux/generic/patches-2.6.33/930-crashlog.patch
new file mode 100644
index 0000000000..62bcc5a6df
--- /dev/null
+++ b/target/linux/generic/patches-2.6.33/930-crashlog.patch
@@ -0,0 +1,241 @@
+--- /dev/null
++++ b/include/linux/crashlog.h
+@@ -0,0 +1,12 @@
++#ifndef __CRASHLOG_H
++#define __CRASHLOG_H
++
++#ifdef CONFIG_CRASHLOG
++void __init crashlog_init_mem(struct bootmem_data *bdata);
++#else
++static inline void crashlog_init_mem(struct bootmem_data *bdata)
++{
++}
++#endif
++
++#endif
+--- a/init/Kconfig
++++ b/init/Kconfig
+@@ -719,6 +719,9 @@ config NET_NS
+ 	  Allow user space to create what appear to be multiple instances
+ 	  of the network stack.
+ 
++config CRASHLOG
++	bool "Crash logging"
++
+ config BLK_DEV_INITRD
+ 	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
+ 	depends on BROKEN || !FRV
+--- a/kernel/Makefile
++++ b/kernel/Makefile
+@@ -100,6 +100,7 @@ obj-$(CONFIG_SLOW_WORK_DEBUG) += slow-wo
+ obj-$(CONFIG_PERF_EVENTS) += perf_event.o
+ obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
+ obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
++obj-$(CONFIG_CRASHLOG) += crashlog.o
+ 
+ ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
+ # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
+--- /dev/null
++++ b/kernel/crashlog.c
+@@ -0,0 +1,171 @@
++/*
++ * Crash information logger
++ * Copyright (C) 2010 Felix Fietkau <nbd@openwrt.org>
++ *
++ * Based on ramoops.c
++ *   Copyright (C) 2010 Marco Stornelli <marco.stornelli@gmail.com>
++ *
++ * This program is free software; you can redistribute it and/or
++ * modify it under the terms of the GNU General Public License
++ * version 2 as published by the Free Software Foundation.
++ *
++ * This program is distributed in the hope that it will be useful, but
++ * WITHOUT ANY WARRANTY; without even the implied warranty of
++ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
++ * General Public License for more details.
++ *
++ * You should have received a copy of the GNU General Public License
++ * along with this program; if not, write to the Free Software
++ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
++ * 02110-1301 USA
++ *
++ */
++
++#include <linux/module.h>
++#include <linux/bootmem.h>
++#include <linux/debugfs.h>
++#include <linux/crashlog.h>
++#include <linux/kmsg_dump.h>
++#include <linux/module.h>
++#include <linux/pfn.h>
++#include <asm/io.h>
++
++#define CRASHLOG_PAGES	4
++#define CRASHLOG_SIZE	(CRASHLOG_PAGES * PAGE_SIZE)
++#define CRASHLOG_MAGIC	0xa1eedead
++
++/*
++ * Start the log at 1M before the end of RAM, as some boot loaders like
++ * to use the end of the RAM for stack usage and other things
++ * If this fails, fall back to using the last part.
++ */
++#define CRASHLOG_OFFSET	(1024 * 1024)
++
++struct crashlog_data {
++	u32 magic;
++	u32 len;
++	u8 data[];
++};
++
++static struct debugfs_blob_wrapper crashlog_blob;
++static unsigned long crashlog_addr = 0;
++static struct crashlog_data *crashlog_buf;
++static struct kmsg_dumper dump;
++static bool first = true;
++
++extern struct list_head *crashlog_modules;
++
++void __init crashlog_init_mem(bootmem_data_t *bdata)
++{
++	unsigned long addr;
++
++	if (crashlog_addr)
++		return;
++
++	addr = PFN_PHYS(bdata->node_low_pfn) - CRASHLOG_OFFSET;
++	if (reserve_bootmem(addr, CRASHLOG_SIZE, BOOTMEM_EXCLUSIVE) < 0) {
++		printk("Crashlog failed to allocate RAM at address 0x%lx\n", addr);
++		bdata->node_low_pfn -= CRASHLOG_PAGES;
++		addr = PFN_PHYS(bdata->node_low_pfn);
++	}
++	crashlog_addr = addr;
++}
++
++static void __init crashlog_copy(void)
++{
++	if (crashlog_buf->magic != CRASHLOG_MAGIC)
++		return;
++
++	if (!crashlog_buf->len || crashlog_buf->len >
++	    CRASHLOG_SIZE - sizeof(*crashlog_buf))
++		return;
++
++	crashlog_blob.size = crashlog_buf->len;
++	crashlog_blob.data = kmemdup(crashlog_buf->data,
++		crashlog_buf->len, GFP_KERNEL);
++
++	debugfs_create_blob("crashlog", 0700, NULL, &crashlog_blob);
++}
++
++static int get_maxlen(void)
++{
++	return CRASHLOG_SIZE - sizeof(*crashlog_buf) - crashlog_buf->len;
++}
++
++static void crashlog_printf(const char *fmt, ...)
++{
++	va_list args;
++	int len = get_maxlen();
++
++	if (!len)
++		return;
++
++	va_start(args, fmt);
++	crashlog_buf->len += vsnprintf(
++		&crashlog_buf->data[crashlog_buf->len],
++		len, fmt, args);
++	va_end(args);
++}
++
++static void crashlog_do_dump(struct kmsg_dumper *dumper,
++		enum kmsg_dump_reason reason, const char *s1, unsigned long l1,
++		const char *s2, unsigned long l2)
++{
++	unsigned long s1_start, s2_start;
++	unsigned long l1_cpy, l2_cpy;
++	struct timeval tv;
++	struct module *m;
++	char *buf;
++	int len;
++
++	if (!first)
++		crashlog_printf("\n===================================\n");
++
++	do_gettimeofday(&tv);
++	crashlog_printf("Time: %lu.%lu\n",
++		(long)tv.tv_sec, (long)tv.tv_usec);
++
++	if (first) {
++		crashlog_printf("Modules:");
++		list_for_each_entry(m, crashlog_modules, list) {
++			crashlog_printf("\t%s@%p+%x", m->name,
++			m->module_core, m->core_size,
++			m->module_init, m->init_size);
++		}
++		crashlog_printf("\n");
++		first = false;
++	}
++
++	buf = (char *)&crashlog_buf->data[crashlog_buf->len];
++	len = get_maxlen();
++
++	l2_cpy = min(l2, (unsigned long)len);
++	l1_cpy = min(l1, (unsigned long)len - l2_cpy);
++
++	s2_start = l2 - l2_cpy;
++	s1_start = l1 - l1_cpy;
++
++	memcpy(buf, s1 + s1_start, l1_cpy);
++	memcpy(buf + l1_cpy, s2 + s2_start, l2_cpy);
++	crashlog_buf->len += l1_cpy + l2_cpy;
++}
++
++
++int __init crashlog_init_fs(void)
++{
++	if (!crashlog_addr)
++		return -ENOMEM;
++
++	crashlog_buf = ioremap(crashlog_addr, CRASHLOG_SIZE);
++
++	crashlog_copy();
++
++	crashlog_buf->magic = CRASHLOG_MAGIC;
++	crashlog_buf->len = 0;
++
++	dump.dump = crashlog_do_dump;
++	kmsg_dump_register(&dump);
++
++	return 0;
++}
++module_init(crashlog_init_fs);
+--- a/mm/bootmem.c
++++ b/mm/bootmem.c
+@@ -13,6 +13,7 @@
+ #include <linux/bootmem.h>
+ #include <linux/module.h>
+ #include <linux/kmemleak.h>
++#include <linux/crashlog.h>
+ 
+ #include <asm/bug.h>
+ #include <asm/io.h>
+@@ -176,6 +177,7 @@ static unsigned long __init free_all_boo
+ 	if (!bdata->node_bootmem_map)
+ 		return 0;
+ 
++	crashlog_init_mem(bdata);
+ 	start = bdata->node_min_pfn;
+ 	end = bdata->node_low_pfn;
+ 
+--- a/kernel/module.c
++++ b/kernel/module.c
+@@ -79,6 +79,9 @@ EXPORT_TRACEPOINT_SYMBOL(module_get);
+ DEFINE_MUTEX(module_mutex);
+ EXPORT_SYMBOL_GPL(module_mutex);
+ static LIST_HEAD(modules);
++#ifdef CONFIG_CRASHLOG
++struct list_head *crashlog_modules = &modules;
++#endif
+ 
+ /* Block module loading/unloading? */
+ int modules_disabled = 0;
diff --git a/target/linux/generic/patches-2.6.34/930-crashlog.patch b/target/linux/generic/patches-2.6.34/930-crashlog.patch
new file mode 100644
index 0000000000..ab6f542714
--- /dev/null
+++ b/target/linux/generic/patches-2.6.34/930-crashlog.patch
@@ -0,0 +1,241 @@
+--- /dev/null
++++ b/include/linux/crashlog.h
+@@ -0,0 +1,12 @@
++#ifndef __CRASHLOG_H
++#define __CRASHLOG_H
++
++#ifdef CONFIG_CRASHLOG
++void __init crashlog_init_mem(struct bootmem_data *bdata);
++#else
++static inline void crashlog_init_mem(struct bootmem_data *bdata)
++{
++}
++#endif
++
++#endif
+--- a/init/Kconfig
++++ b/init/Kconfig
+@@ -715,6 +715,9 @@ config NET_NS
+ 	  Allow user space to create what appear to be multiple instances
+ 	  of the network stack.
+ 
++config CRASHLOG
++	bool "Crash logging"
++
+ config BLK_DEV_INITRD
+ 	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
+ 	depends on BROKEN || !FRV
+--- a/kernel/Makefile
++++ b/kernel/Makefile
+@@ -105,6 +105,7 @@ obj-$(CONFIG_PERF_EVENTS) += perf_event.
+ obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
+ obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
+ obj-$(CONFIG_PADATA) += padata.o
++obj-$(CONFIG_CRASHLOG) += crashlog.o
+ 
+ ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
+ # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
+--- /dev/null
++++ b/kernel/crashlog.c
+@@ -0,0 +1,171 @@
++/*
++ * Crash information logger
++ * Copyright (C) 2010 Felix Fietkau <nbd@openwrt.org>
++ *
++ * Based on ramoops.c
++ *   Copyright (C) 2010 Marco Stornelli <marco.stornelli@gmail.com>
++ *
++ * This program is free software; you can redistribute it and/or
++ * modify it under the terms of the GNU General Public License
++ * version 2 as published by the Free Software Foundation.
++ *
++ * This program is distributed in the hope that it will be useful, but
++ * WITHOUT ANY WARRANTY; without even the implied warranty of
++ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
++ * General Public License for more details.
++ *
++ * You should have received a copy of the GNU General Public License
++ * along with this program; if not, write to the Free Software
++ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
++ * 02110-1301 USA
++ *
++ */
++
++#include <linux/module.h>
++#include <linux/bootmem.h>
++#include <linux/debugfs.h>
++#include <linux/crashlog.h>
++#include <linux/kmsg_dump.h>
++#include <linux/module.h>
++#include <linux/pfn.h>
++#include <asm/io.h>
++
++#define CRASHLOG_PAGES	4
++#define CRASHLOG_SIZE	(CRASHLOG_PAGES * PAGE_SIZE)
++#define CRASHLOG_MAGIC	0xa1eedead
++
++/*
++ * Start the log at 1M before the end of RAM, as some boot loaders like
++ * to use the end of the RAM for stack usage and other things
++ * If this fails, fall back to using the last part.
++ */
++#define CRASHLOG_OFFSET	(1024 * 1024)
++
++struct crashlog_data {
++	u32 magic;
++	u32 len;
++	u8 data[];
++};
++
++static struct debugfs_blob_wrapper crashlog_blob;
++static unsigned long crashlog_addr = 0;
++static struct crashlog_data *crashlog_buf;
++static struct kmsg_dumper dump;
++static bool first = true;
++
++extern struct list_head *crashlog_modules;
++
++void __init crashlog_init_mem(bootmem_data_t *bdata)
++{
++	unsigned long addr;
++
++	if (crashlog_addr)
++		return;
++
++	addr = PFN_PHYS(bdata->node_low_pfn) - CRASHLOG_OFFSET;
++	if (reserve_bootmem(addr, CRASHLOG_SIZE, BOOTMEM_EXCLUSIVE) < 0) {
++		printk("Crashlog failed to allocate RAM at address 0x%lx\n", addr);
++		bdata->node_low_pfn -= CRASHLOG_PAGES;
++		addr = PFN_PHYS(bdata->node_low_pfn);
++	}
++	crashlog_addr = addr;
++}
++
++static void __init crashlog_copy(void)
++{
++	if (crashlog_buf->magic != CRASHLOG_MAGIC)
++		return;
++
++	if (!crashlog_buf->len || crashlog_buf->len >
++	    CRASHLOG_SIZE - sizeof(*crashlog_buf))
++		return;
++
++	crashlog_blob.size = crashlog_buf->len;
++	crashlog_blob.data = kmemdup(crashlog_buf->data,
++		crashlog_buf->len, GFP_KERNEL);
++
++	debugfs_create_blob("crashlog", 0700, NULL, &crashlog_blob);
++}
++
++static int get_maxlen(void)
++{
++	return CRASHLOG_SIZE - sizeof(*crashlog_buf) - crashlog_buf->len;
++}
++
++static void crashlog_printf(const char *fmt, ...)
++{
++	va_list args;
++	int len = get_maxlen();
++
++	if (!len)
++		return;
++
++	va_start(args, fmt);
++	crashlog_buf->len += vsnprintf(
++		&crashlog_buf->data[crashlog_buf->len],
++		len, fmt, args);
++	va_end(args);
++}
++
++static void crashlog_do_dump(struct kmsg_dumper *dumper,
++		enum kmsg_dump_reason reason, const char *s1, unsigned long l1,
++		const char *s2, unsigned long l2)
++{
++	unsigned long s1_start, s2_start;
++	unsigned long l1_cpy, l2_cpy;
++	struct timeval tv;
++	struct module *m;
++	char *buf;
++	int len;
++
++	if (!first)
++		crashlog_printf("\n===================================\n");
++
++	do_gettimeofday(&tv);
++	crashlog_printf("Time: %lu.%lu\n",
++		(long)tv.tv_sec, (long)tv.tv_usec);
++
++	if (first) {
++		crashlog_printf("Modules:");
++		list_for_each_entry(m, crashlog_modules, list) {
++			crashlog_printf("\t%s@%p+%x", m->name,
++			m->module_core, m->core_size,
++			m->module_init, m->init_size);
++		}
++		crashlog_printf("\n");
++		first = false;
++	}
++
++	buf = (char *)&crashlog_buf->data[crashlog_buf->len];
++	len = get_maxlen();
++
++	l2_cpy = min(l2, (unsigned long)len);
++	l1_cpy = min(l1, (unsigned long)len - l2_cpy);
++
++	s2_start = l2 - l2_cpy;
++	s1_start = l1 - l1_cpy;
++
++	memcpy(buf, s1 + s1_start, l1_cpy);
++	memcpy(buf + l1_cpy, s2 + s2_start, l2_cpy);
++	crashlog_buf->len += l1_cpy + l2_cpy;
++}
++
++
++int __init crashlog_init_fs(void)
++{
++	if (!crashlog_addr)
++		return -ENOMEM;
++
++	crashlog_buf = ioremap(crashlog_addr, CRASHLOG_SIZE);
++
++	crashlog_copy();
++
++	crashlog_buf->magic = CRASHLOG_MAGIC;
++	crashlog_buf->len = 0;
++
++	dump.dump = crashlog_do_dump;
++	kmsg_dump_register(&dump);
++
++	return 0;
++}
++module_init(crashlog_init_fs);
+--- a/mm/bootmem.c
++++ b/mm/bootmem.c
+@@ -15,6 +15,7 @@
+ #include <linux/module.h>
+ #include <linux/kmemleak.h>
+ #include <linux/range.h>
++#include <linux/crashlog.h>
+ 
+ #include <asm/bug.h>
+ #include <asm/io.h>
+@@ -226,6 +227,7 @@ static unsigned long __init free_all_boo
+ 	if (!bdata->node_bootmem_map)
+ 		return 0;
+ 
++	crashlog_init_mem(bdata);
+ 	start = bdata->node_min_pfn;
+ 	end = bdata->node_low_pfn;
+ 
+--- a/kernel/module.c
++++ b/kernel/module.c
+@@ -79,6 +79,9 @@ EXPORT_TRACEPOINT_SYMBOL(module_get);
+ DEFINE_MUTEX(module_mutex);
+ EXPORT_SYMBOL_GPL(module_mutex);
+ static LIST_HEAD(modules);
++#ifdef CONFIG_CRASHLOG
++struct list_head *crashlog_modules = &modules;
++#endif
+ 
+ /* Block module loading/unloading? */
+ int modules_disabled = 0;
diff --git a/target/linux/generic/patches-2.6.35/930-crashlog.patch b/target/linux/generic/patches-2.6.35/930-crashlog.patch
new file mode 100644
index 0000000000..4a6a89bc11
--- /dev/null
+++ b/target/linux/generic/patches-2.6.35/930-crashlog.patch
@@ -0,0 +1,241 @@
+--- /dev/null
++++ b/include/linux/crashlog.h
+@@ -0,0 +1,12 @@
++#ifndef __CRASHLOG_H
++#define __CRASHLOG_H
++
++#ifdef CONFIG_CRASHLOG
++void __init crashlog_init_mem(struct bootmem_data *bdata);
++#else
++static inline void crashlog_init_mem(struct bootmem_data *bdata)
++{
++}
++#endif
++
++#endif
+--- a/init/Kconfig
++++ b/init/Kconfig
+@@ -749,6 +749,9 @@ config NET_NS
+ 	  Allow user space to create what appear to be multiple instances
+ 	  of the network stack.
+ 
++config CRASHLOG
++	bool "Crash logging"
++
+ config BLK_DEV_INITRD
+ 	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
+ 	depends on BROKEN || !FRV
+--- a/kernel/Makefile
++++ b/kernel/Makefile
+@@ -105,6 +105,7 @@ obj-$(CONFIG_PERF_EVENTS) += perf_event.
+ obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
+ obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
+ obj-$(CONFIG_PADATA) += padata.o
++obj-$(CONFIG_CRASHLOG) += crashlog.o
+ 
+ ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
+ # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
+--- /dev/null
++++ b/kernel/crashlog.c
+@@ -0,0 +1,171 @@
++/*
++ * Crash information logger
++ * Copyright (C) 2010 Felix Fietkau <nbd@openwrt.org>
++ *
++ * Based on ramoops.c
++ *   Copyright (C) 2010 Marco Stornelli <marco.stornelli@gmail.com>
++ *
++ * This program is free software; you can redistribute it and/or
++ * modify it under the terms of the GNU General Public License
++ * version 2 as published by the Free Software Foundation.
++ *
++ * This program is distributed in the hope that it will be useful, but
++ * WITHOUT ANY WARRANTY; without even the implied warranty of
++ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
++ * General Public License for more details.
++ *
++ * You should have received a copy of the GNU General Public License
++ * along with this program; if not, write to the Free Software
++ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
++ * 02110-1301 USA
++ *
++ */
++
++#include <linux/module.h>
++#include <linux/bootmem.h>
++#include <linux/debugfs.h>
++#include <linux/crashlog.h>
++#include <linux/kmsg_dump.h>
++#include <linux/module.h>
++#include <linux/pfn.h>
++#include <asm/io.h>
++
++#define CRASHLOG_PAGES	4
++#define CRASHLOG_SIZE	(CRASHLOG_PAGES * PAGE_SIZE)
++#define CRASHLOG_MAGIC	0xa1eedead
++
++/*
++ * Start the log at 1M before the end of RAM, as some boot loaders like
++ * to use the end of the RAM for stack usage and other things
++ * If this fails, fall back to using the last part.
++ */
++#define CRASHLOG_OFFSET	(1024 * 1024)
++
++struct crashlog_data {
++	u32 magic;
++	u32 len;
++	u8 data[];
++};
++
++static struct debugfs_blob_wrapper crashlog_blob;
++static unsigned long crashlog_addr = 0;
++static struct crashlog_data *crashlog_buf;
++static struct kmsg_dumper dump;
++static bool first = true;
++
++extern struct list_head *crashlog_modules;
++
++void __init crashlog_init_mem(bootmem_data_t *bdata)
++{
++	unsigned long addr;
++
++	if (crashlog_addr)
++		return;
++
++	addr = PFN_PHYS(bdata->node_low_pfn) - CRASHLOG_OFFSET;
++	if (reserve_bootmem(addr, CRASHLOG_SIZE, BOOTMEM_EXCLUSIVE) < 0) {
++		printk("Crashlog failed to allocate RAM at address 0x%lx\n", addr);
++		bdata->node_low_pfn -= CRASHLOG_PAGES;
++		addr = PFN_PHYS(bdata->node_low_pfn);
++	}
++	crashlog_addr = addr;
++}
++
++static void __init crashlog_copy(void)
++{
++	if (crashlog_buf->magic != CRASHLOG_MAGIC)
++		return;
++
++	if (!crashlog_buf->len || crashlog_buf->len >
++	    CRASHLOG_SIZE - sizeof(*crashlog_buf))
++		return;
++
++	crashlog_blob.size = crashlog_buf->len;
++	crashlog_blob.data = kmemdup(crashlog_buf->data,
++		crashlog_buf->len, GFP_KERNEL);
++
++	debugfs_create_blob("crashlog", 0700, NULL, &crashlog_blob);
++}
++
++static int get_maxlen(void)
++{
++	return CRASHLOG_SIZE - sizeof(*crashlog_buf) - crashlog_buf->len;
++}
++
++static void crashlog_printf(const char *fmt, ...)
++{
++	va_list args;
++	int len = get_maxlen();
++
++	if (!len)
++		return;
++
++	va_start(args, fmt);
++	crashlog_buf->len += vsnprintf(
++		&crashlog_buf->data[crashlog_buf->len],
++		len, fmt, args);
++	va_end(args);
++}
++
++static void crashlog_do_dump(struct kmsg_dumper *dumper,
++		enum kmsg_dump_reason reason, const char *s1, unsigned long l1,
++		const char *s2, unsigned long l2)
++{
++	unsigned long s1_start, s2_start;
++	unsigned long l1_cpy, l2_cpy;
++	struct timeval tv;
++	struct module *m;
++	char *buf;
++	int len;
++
++	if (!first)
++		crashlog_printf("\n===================================\n");
++
++	do_gettimeofday(&tv);
++	crashlog_printf("Time: %lu.%lu\n",
++		(long)tv.tv_sec, (long)tv.tv_usec);
++
++	if (first) {
++		crashlog_printf("Modules:");
++		list_for_each_entry(m, crashlog_modules, list) {
++			crashlog_printf("\t%s@%p+%x", m->name,
++			m->module_core, m->core_size,
++			m->module_init, m->init_size);
++		}
++		crashlog_printf("\n");
++		first = false;
++	}
++
++	buf = (char *)&crashlog_buf->data[crashlog_buf->len];
++	len = get_maxlen();
++
++	l2_cpy = min(l2, (unsigned long)len);
++	l1_cpy = min(l1, (unsigned long)len - l2_cpy);
++
++	s2_start = l2 - l2_cpy;
++	s1_start = l1 - l1_cpy;
++
++	memcpy(buf, s1 + s1_start, l1_cpy);
++	memcpy(buf + l1_cpy, s2 + s2_start, l2_cpy);
++	crashlog_buf->len += l1_cpy + l2_cpy;
++}
++
++
++int __init crashlog_init_fs(void)
++{
++	if (!crashlog_addr)
++		return -ENOMEM;
++
++	crashlog_buf = ioremap(crashlog_addr, CRASHLOG_SIZE);
++
++	crashlog_copy();
++
++	crashlog_buf->magic = CRASHLOG_MAGIC;
++	crashlog_buf->len = 0;
++
++	dump.dump = crashlog_do_dump;
++	kmsg_dump_register(&dump);
++
++	return 0;
++}
++module_init(crashlog_init_fs);
+--- a/mm/bootmem.c
++++ b/mm/bootmem.c
+@@ -15,6 +15,7 @@
+ #include <linux/module.h>
+ #include <linux/kmemleak.h>
+ #include <linux/range.h>
++#include <linux/crashlog.h>
+ 
+ #include <asm/bug.h>
+ #include <asm/io.h>
+@@ -226,6 +227,7 @@ static unsigned long __init free_all_boo
+ 	if (!bdata->node_bootmem_map)
+ 		return 0;
+ 
++	crashlog_init_mem(bdata);
+ 	start = bdata->node_min_pfn;
+ 	end = bdata->node_low_pfn;
+ 
+--- a/kernel/module.c
++++ b/kernel/module.c
+@@ -84,6 +84,9 @@ static LIST_HEAD(modules);
+ #ifdef CONFIG_KGDB_KDB
+ struct list_head *kdb_modules = &modules; /* kdb needs the list of modules */
+ #endif /* CONFIG_KGDB_KDB */
++#ifdef CONFIG_CRASHLOG
++struct list_head *crashlog_modules = &modules;
++#endif
+ 
+ 
+ /* Block module loading/unloading? */