[PATCH/RFC] oops and panic message logging to MTD

Richard Purdie
2007-06-18T16:32:02Z

Kernel oops and panic messages are invaluable when debugging crashes.
These messages often don't make it to flash based logging methods (say a
syslog on jffs2) due to the overheads involved in writing to flash.

This patch allows you to turn an MTD partition into a circular log
buffer where kernel oops and panic messages are written to. The messages
are obtained by registering a console driver and checking
oops_in_progress. Erases are performed in advance to maximise the
chances of a saving messages.

To activate it, add console=ttyMTDx to the kernel commandline (where x
is the mtd device number to use).

http://folks.o-hand.com/richard/oopslog.c is an example of extracting
this information in userspace. It will work with an mtdblock device or a
dump of an mtd partition.

Signed-off-by: Richard Purdie <rpurdie@openedhand.com>

---
drivers/mtd/Kconfig | 8 +
drivers/mtd/Makefile | 1
drivers/mtd/mtdoops.c | 365 ++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 374 insertions(+)

Index: linux/drivers/mtd/Kconfig
===================================================================
--- linux.orig/drivers/mtd/Kconfig 2007-05-13 12:30:39.000000000 +0100
+++ linux/drivers/mtd/Kconfig 2007-05-29 11:16:29.000000000 +0100
@@ -278,6 +278,15 @@ config SSFDC
This enables read only access to SmartMedia formatted NAND
flash. You can mount it with FAT file system.

+config MTD_OOPS
+ tristate "Log panic/oops to an MTD buffer"
+ depends on MTD
+ help
+ This enables panic and oops messages to be logged to a circular
+ buffer in a flash partition where it can be read back at some
+ later point. Add console=ttyMTDx to the commandline to activate
+ (where x is the MTD partition number to use).
+
source "drivers/mtd/chips/Kconfig"

source "drivers/mtd/maps/Kconfig"
Index: linux/drivers/mtd/Makefile
===================================================================
--- linux.orig/drivers/mtd/Makefile 2007-05-10 10:21:28.000000000 +0100
+++ linux/drivers/mtd/Makefile 2007-05-29 11:16:51.000000000 +0100
@@ -23,6 +23,7 @@ obj-$(CONFIG_NFTL) += nftl.o
obj-$(CONFIG_INFTL) += inftl.o
obj-$(CONFIG_RFD_FTL) += rfd_ftl.o
obj-$(CONFIG_SSFDC) += ssfdc.o
+obj-$(CONFIG_MTD_OOPS) += mtdoops.o

nftl-objs := nftlcore.o nftlmount.o
inftl-objs := inftlcore.o inftlmount.o
Index: linux/drivers/mtd/mtdoops.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux/drivers/mtd/mtdoops.c 2007-05-29 11:16:29.000000000 +0100
@@ -0,0 +1,365 @@
+/*
+ * MTD Oops/Panic logger
+ *
+ * Copyright (C) 2007 Nokia Corporation. All rights reserved.
+ *
+ * Author: Richard Purdie <rpurdie@openedhand.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/kernel.h>
+#include <linux/module.h>
+#include <linux/console.h>
+#include <linux/vmalloc.h>
+#include <linux/workqueue.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/mtd/mtd.h>
+
+#define OOPS_PAGE_SIZE 4096
+
+static struct mtdoops_context {
+ int mtd_index;
+ struct work_struct work;
+ struct mtd_info *mtd;
+ int oops_pages;
+ int nextpage;
+ int nextcount;
+
+ void *oops_buf;
+ int ready;
+ int writecount;
+} oops_cxt;
+
+static void mtdoops_erase_callback(struct erase_info *done)
+{
+ wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv;
+ wake_up(wait_q);
+}
+
+static int mtdoops_erase_block(struct mtd_info *mtd, int offset)
+{
+ struct erase_info erase;
+ DECLARE_WAITQUEUE(wait, current);
+ wait_queue_head_t wait_q;
+ int ret;
+
+ init_waitqueue_head(&wait_q);
+ erase.mtd = mtd;
+ erase.callback = mtdoops_erase_callback;
+ erase.addr = offset;
+ if (mtd->erasesize < OOPS_PAGE_SIZE)
+ erase.len = OOPS_PAGE_SIZE;
+ else
+ erase.len = mtd->erasesize;
+ erase.priv = (u_long)&wait_q;
+
+ set_current_state(TASK_INTERRUPTIBLE);
+ add_wait_queue(&wait_q, &wait);
+
+ ret = mtd->erase(mtd, &erase);
+ if (ret) {
+ set_current_state(TASK_RUNNING);
+ remove_wait_queue(&wait_q, &wait);
+ printk(KERN_WARNING "mtdoops: erase of region [0x%x, 0x%x] "
+ "on \"%s\" failed\n",
+ erase.addr, erase.len, mtd->name);
+ return ret;
+ }
+
+ schedule(); /* Wait for erase to finish. */
+ remove_wait_queue(&wait_q, &wait);
+
+ return 0;
+}
+
+static int mtdoops_inc_counter(struct mtdoops_context *cxt)
+{
+ struct mtd_info *mtd = cxt->mtd;
+ size_t retlen;
+ u32 count;
+ int ret;
+
+ cxt->nextpage++;
+ if (cxt->nextpage > cxt->oops_pages)
+ cxt->nextpage = 0;
+ cxt->nextcount++;
+ if (cxt->nextcount == 0xffffffff)
+ cxt->nextcount = 0;
+
+ ret = mtd->read(mtd, cxt->nextpage * OOPS_PAGE_SIZE, 4,
+ &retlen, (u_char *) &count);
+ if ((retlen != 4) || (ret < 0)) {
+ printk(KERN_ERR "mtdoops: Read failure at %d (%d of 4 read)"
+ ", err %d.\n", cxt->nextpage * OOPS_PAGE_SIZE,
+ retlen, ret);
+ return 1;
+ }
+
+ /* See if we need to erase the next block */
+ if (count != 0xffffffff)
+ return 1;
+
+ printk(KERN_DEBUG "mtdoops: Ready %d, %d (no erase)\n",
+ cxt->nextpage, cxt->nextcount);
+ cxt->ready = 1;
+ return 0;
+}
+
+static void mtdoops_prepare(struct mtdoops_context *cxt)
+{
+ struct mtd_info *mtd = cxt->mtd;
+ int i = 0, j, ret, mod;
+
+ /* We were unregistered */
+ if (!mtd)
+ return;
+
+ mod = (cxt->nextpage * OOPS_PAGE_SIZE) % mtd->erasesize;
+ if (mod != 0) {
+ cxt->nextpage = cxt->nextpage + ((mtd->erasesize - mod) / OOPS_PAGE_SIZE);
+ if (cxt->nextpage > cxt->oops_pages)
+ cxt->nextpage = 0;
+ }
+
+ while (mtd->block_isbad &&
+ mtd->block_isbad(mtd, cxt->nextpage * OOPS_PAGE_SIZE)) {
+badblock:
+ printk(KERN_WARNING "mtdoops: Bad block at %08x\n",
+ cxt->nextpage * OOPS_PAGE_SIZE);
+ i++;
+ cxt->nextpage = cxt->nextpage + (mtd->erasesize / OOPS_PAGE_SIZE);
+ if (cxt->nextpage > cxt->oops_pages)
+ cxt->nextpage = 0;
+ if (i == (cxt->oops_pages / (mtd->erasesize / OOPS_PAGE_SIZE))) {
+ printk(KERN_ERR "mtdoops: All blocks bad!\n");
+ return;
+ }
+ }
+
+ for (j = 0, ret = -1; (j < 3) && (ret < 0); j++)
+ ret = mtdoops_erase_block(mtd, cxt->nextpage * OOPS_PAGE_SIZE);
+
+ if (ret < 0) {
+ if (mtd->block_markbad)
+ mtd->block_markbad(mtd, cxt->nextpage * OOPS_PAGE_SIZE);
+ goto badblock;
+ }
+
+ printk(KERN_DEBUG "mtdoops: Ready %d, %d \n", cxt->nextpage, cxt->nextcount);
+
+ cxt->ready = 1;
+}
+
+static void mtdoops_workfunc(struct work_struct *work)
+{
+ struct mtdoops_context *cxt =
+ container_of(work, struct mtdoops_context, work);
+
+ mtdoops_prepare(cxt);
+}
+
+static int find_next_position(struct mtdoops_context *cxt)
+{
+ struct mtd_info *mtd = cxt->mtd;
+ int page, maxpos = 0;
+ u32 count, maxcount = 0xffffffff;
+ size_t retlen;
+
+ for (page = 0; page < cxt->oops_pages; page++) {
+ mtd->read(mtd, page * OOPS_PAGE_SIZE, 4, &retlen, (u_char *) &count);
+ if (count == 0xffffffff)
+ continue;
+ if (maxcount == 0xffffffff) {
+ maxcount = count;
+ maxpos = page;
+ } else if ((count < 0x40000000) && (maxcount > 0xc0000000)) {
+ maxcount = count;
+ maxpos = page;
+ } else if ((count > maxcount) && (count < 0xc0000000)) {
+ maxcount = count;
+ maxpos = page;
+ } else if ((count > maxcount) && (count > 0xc0000000)
+ && (maxcount > 0x80000000)) {
+ maxcount = count;
+ maxpos = page;
+ }
+ }
+ if (maxcount == 0xffffffff) {
+ cxt->nextpage = 0;
+ cxt->nextcount = 1;
+ cxt->ready = 1;
+ printk(KERN_DEBUG "mtdoops: Ready %d, %d (first init)\n",
+ cxt->nextpage, cxt->nextcount);
+ return 0;
+ }
+
+ cxt->nextpage = maxpos;
+ cxt->nextcount = maxcount;
+
+ return mtdoops_inc_counter(cxt);
+}
+
+
+static void mtdoops_notify_add(struct mtd_info *mtd)
+{
+ struct mtdoops_context *cxt = &oops_cxt;
+ int ret;
+
+ if ((mtd->index != cxt->mtd_index) || cxt->mtd_index < 0)
+ return;
+
+ if (mtd->size < (mtd->erasesize * 2)) {
+ printk(KERN_ERR "MTD partition %d not big enough for mtdoops\n",
+ mtd->index);
+ return;
+ }
+
+ cxt->mtd = mtd;
+ cxt->oops_pages = mtd->size / OOPS_PAGE_SIZE;
+
+ ret = find_next_position(cxt);
+ if (ret == 1)
+ mtdoops_prepare(cxt);
+
+ printk(KERN_DEBUG "mtdoops: Attached to MTD device %d\n", mtd->index);
+}
+
+static void mtdoops_notify_remove(struct mtd_info *mtd)
+{
+ struct mtdoops_context *cxt = &oops_cxt;
+
+ if ((mtd->index != cxt->mtd_index) || cxt->mtd_index < 0)
+ return;
+
+ cxt->mtd = NULL;
+ flush_scheduled_work();
+}
+
+
+static void
+mtdoops_console_write(struct console *co, const char *s, unsigned int count)
+{
+ struct mtdoops_context *cxt = co->data;
+ struct mtd_info *mtd = cxt->mtd;
+ int i, ret;
+
+ if (!cxt->ready || !mtd)
+ return;
+
+ if (!oops_in_progress && cxt->writecount != 0) {
+ size_t retlen;
+ if (cxt->writecount < OOPS_PAGE_SIZE)
+ memset(cxt->oops_buf + cxt->writecount, 0xff,
+ OOPS_PAGE_SIZE - cxt->writecount);
+
+ ret = mtd->write(mtd, cxt->nextpage * OOPS_PAGE_SIZE,
+ OOPS_PAGE_SIZE, &retlen, cxt->oops_buf);
+ cxt->ready = 0;
+ cxt->writecount = 0;
+
+ if ((retlen != OOPS_PAGE_SIZE) || (ret < 0))
+ printk(KERN_ERR "mtdoops: Write failure at %d (%d of %d"
+ " written), err %d.\n",
+ cxt->nextpage * OOPS_PAGE_SIZE, retlen,
+ OOPS_PAGE_SIZE, ret);
+
+ ret = mtdoops_inc_counter(cxt);
+ if (ret == 1)
+ schedule_work(&cxt->work);
+ }
+
+ if (!oops_in_progress)
+ return;
+
+ if (cxt->writecount == 0) {
+ u32 *stamp = cxt->oops_buf;
+ *stamp = cxt->nextcount;
+ cxt->writecount = 4;
+ }
+
+ if ((count + cxt->writecount) > OOPS_PAGE_SIZE)
+ count = OOPS_PAGE_SIZE - cxt->writecount;
+
+ for (i = 0; i < count; i++, s++)
+ *((char *)(cxt->oops_buf) + cxt->writecount + i) = *s;
+
+ cxt->writecount = cxt->writecount + count;
+}
+
+static int __init mtdoops_console_setup(struct console *co, char *options)
+{
+ struct mtdoops_context *cxt = co->data;
+
+ if (cxt->mtd_index != -1)
+ return -EBUSY;
+ if (co->index == -1)
+ return -EINVAL;
+
+ cxt->mtd_index = co->index;
+ return 0;
+}
+
+static struct mtd_notifier mtdoops_notifier = {
+ .add = mtdoops_notify_add,
+ .remove = mtdoops_notify_remove,
+};
+
+static struct console mtdoops_console = {
+ .name = "ttyMTD",
+ .write = mtdoops_console_write,
+ .setup = mtdoops_console_setup,
+ .flags = CON_PRINTBUFFER,
+ .index = -1,
+ .data = &oops_cxt,
+};
+
+static int __init mtdoops_console_init(void)
+{
+ struct mtdoops_context *cxt = &oops_cxt;
+
+ cxt->mtd_index = -1;
+ cxt->oops_buf = vmalloc(OOPS_PAGE_SIZE);
+
+ if (!cxt->oops_buf) {
+ printk(KERN_ERR "Failed to allocate oops buffer workspace\n");
+ return -ENOMEM;
+ }
+
+ INIT_WORK(&cxt->work, mtdoops_workfunc);
+
+ register_console(&mtdoops_console);
+ register_mtd_user(&mtdoops_notifier);
+ return 0;
+}
+
+static void __exit mtdoops_console_exit(void)
+{
+ struct mtdoops_context *cxt = &oops_cxt;
+
+ unregister_mtd_user(&mtdoops_notifier);
+ unregister_console(&mtdoops_console);
+ vfree(cxt->oops_buf);
+}
+
+
+subsys_initcall(mtdoops_console_init);
+module_exit(mtdoops_console_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Richard Purdie <rpurdie@openedhand.com>");
+MODULE_DESCRIPTION("MTD Oops/Panic console logger/driver");