[PATCH v2 3/3]: mtdoops: store all kernel messages in a circular buffer

Simon Kagstrom
2009-10-06T14:51:11Z

The last messages which happens before a crash might contain interesting
information about the crash. This patch reworks mtdoops to keep a
circular buffer of _all_ kernel messages, not just those that are
printed when an oops is initiated.

A handler that is called on panic is also added instead of
mtdoops_console_sync so that panic_on_oops and true panics are stored.

Signed-off-by: Simon Kagstrom <simon.kagstrom@netinsight.net>
---
ChangeLog:

v2:
* Fix output bug when writing out on large pages (ff's were at the
start of the printout).
* Fix garbled text issues on wrapping
* Add a BUG_ON assertion for writecount

drivers/mtd/mtdoops.c | 117 +++++++++++++++++++++++++++++-------------------
1 files changed, 71 insertions(+), 46 deletions(-)

diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c
index cc2c187..c24e11f 100644
--- a/drivers/mtd/mtdoops.c
+++ b/drivers/mtd/mtdoops.c
@@ -52,6 +52,7 @@ static struct mtdoops_context {
char *name;

void *oops_buf;
+ void *oops_buf_write;

/* writecount and disabling ready are spin lock protected */
spinlock_t writecount_lock;
@@ -196,20 +197,36 @@ static void mtdoops_write(struct mtdoops_context *cxt, int panic)
{
struct mtd_info *mtd = cxt->mtd;
size_t retlen;
+ u32 * stamp;
+ int p;
int ret;

- if (cxt->writecount < cxt->page_size)
- memset(cxt->oops_buf + cxt->writecount, 0xff,
- cxt->page_size - cxt->writecount);
+ cxt->ready = 0;
+
+ BUG_ON(cxt->writecount < 8);
+ BUG_ON(cxt->writecount > cxt->page_size - 8);
+
+ /* oops_write_buf = [:8] + [writecount:] + [:writecount] */
+ stamp = cxt->oops_buf_write;
+ *stamp++ = cxt->nextcount;
+ *stamp = MTDOOPS_KERNMSG_MAGIC;
+
+ /* Find out the first non-0xff character */
+ for (p = cxt->writecount; p < cxt->page_size; p++) {
+ if ( ((u8*)cxt->oops_buf)[p] != 0xff)
+ break;
+ }
+ memcpy(cxt->oops_buf_write + 8, cxt->oops_buf + p,
+ cxt->page_size - p);
+ memcpy(cxt->oops_buf_write + 8 + cxt->page_size - p,
+ cxt->oops_buf + 8, p - 8);

if (panic)
ret = mtd->panic_write(mtd, cxt->nextpage * cxt->page_size,
- cxt->page_size, &retlen, cxt->oops_buf);
+ cxt->page_size, &retlen, cxt->oops_buf_write);
else
ret = mtd->write(mtd, cxt->nextpage * cxt->page_size,
- cxt->page_size, &retlen, cxt->oops_buf);
-
- cxt->writecount = 0;
+ cxt->page_size, &retlen, cxt->oops_buf_write);

if ((retlen != cxt->page_size) || (ret < 0))
printk(KERN_ERR "mtdoops: Write failure at %d (%td of %d written), err %d.\n",
@@ -222,6 +239,26 @@ static void mtdoops_write(struct mtdoops_context *cxt, int panic)
mtdoops_inc_counter(cxt);
}

+static int mtdoops_panic(struct notifier_block *this, unsigned long event,
+ void *ptr)
+{
+ struct mtdoops_context *cxt = &oops_cxt;
+
+ cancel_work_sync(&cxt->work_write);
+ cxt->ready = 0;
+ if (cxt->mtd->panic_write)
+ mtdoops_write(cxt, 1);
+ else
+ printk(KERN_WARNING "mtdoops: panic_write is not defined, "
+ "cannot store dump from panic\n");
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block panic_block = {
+ .notifier_call = mtdoops_panic,
+};
+

static void mtdoops_workfunc_write(struct work_struct *work)
{
@@ -309,6 +346,7 @@ static void mtdoops_notify_add(struct mtd_info *mtd)

find_next_position(cxt);

+ atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
printk(KERN_INFO "mtdoops: Attached to MTD device %d\n", mtd->index);
}

@@ -326,28 +364,9 @@ static void mtdoops_notify_remove(struct mtd_info *mtd)
static void mtdoops_console_sync(void)
{
struct mtdoops_context *cxt = &oops_cxt;
- struct mtd_info *mtd = cxt->mtd;
- unsigned long flags;
-
- if (!cxt->ready || !mtd || cxt->writecount == 0)
- return;

- /*
- * Once ready is 0 and we've held the lock no further writes to the
- * buffer will happen
- */
- spin_lock_irqsave(&cxt->writecount_lock, flags);
- if (!cxt->ready) {
- spin_unlock_irqrestore(&cxt->writecount_lock, flags);
- return;
- }
- cxt->ready = 0;
- spin_unlock_irqrestore(&cxt->writecount_lock, flags);
-
- if (mtd->panic_write && (in_interrupt() || panic_on_oops))
- /* Interrupt context, we're going to panic so try and log */
- mtdoops_write(cxt, 1);
- else
+ /* Write out the buffer if we are called during an oops */
+ if (oops_in_progress)
schedule_work(&cxt->work_write);
}

@@ -356,13 +375,11 @@ 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 copy_from;
+ int copy_wrap = 0;
+ int copy_wrap_diff = 0;
unsigned long flags;

- if (!oops_in_progress) {
- mtdoops_console_sync();
- return;
- }
-
if (!cxt->ready || !mtd)
return;

@@ -375,23 +392,21 @@ mtdoops_console_write(struct console *co, const char *s, unsigned int count)
return;
}

- if (cxt->writecount == 0) {
- u32 *stamp = cxt->oops_buf;
- *stamp++ = cxt->nextcount;
- *stamp = MTDOOPS_KERNMSG_MAGIC;
+ /* Handle wraps */
+ if ((count + cxt->writecount) >= cxt->page_size) {
+ copy_wrap_diff = cxt->page_size - cxt->writecount;
+ copy_wrap = cxt->writecount;
+
cxt->writecount = 8;
+ count -= copy_wrap_diff;
}
-
- if ((count + cxt->writecount) > cxt->page_size)
- count = cxt->page_size - cxt->writecount;
-
- memcpy(cxt->oops_buf + cxt->writecount, s, count);
+ copy_from = cxt->writecount;
cxt->writecount += count;
-
spin_unlock_irqrestore(&cxt->writecount_lock, flags);

- if (cxt->writecount == cxt->page_size)
- mtdoops_console_sync();
+ if (copy_wrap)
+ memcpy(cxt->oops_buf + copy_wrap, s, copy_wrap_diff);
+ memcpy(cxt->oops_buf + copy_from, s + copy_wrap_diff, count);
}

static int __init mtdoops_console_setup(struct console *co, char *options)
@@ -429,15 +444,24 @@ static int __init mtdoops_console_init(void)
{
struct mtdoops_context *cxt = &oops_cxt;

+ cxt->writecount = 8; /* Start after the header */
cxt->mtd_index = -1;
cxt->page_size = mtdoops_page_size;
- cxt->oops_buf = vmalloc(cxt->page_size);
spin_lock_init(&cxt->writecount_lock);

+ cxt->oops_buf = vmalloc(cxt->page_size);
if (!cxt->oops_buf) {
printk(KERN_ERR "Failed to allocate mtdoops buffer workspace\n");
return -ENOMEM;
}
+ cxt->oops_buf_write = vmalloc(cxt->page_size);
+ if (!cxt->oops_buf_write) {
+ printk(KERN_ERR "Failed to allocate mtdoops write buffer workspace\n");
+ vfree(cxt->oops_buf);
+ return -ENOMEM;
+ }
+ memset(cxt->oops_buf_write, 0xff, cxt->page_size);
+ memset(cxt->oops_buf, 0xff, cxt->page_size);

INIT_WORK(&cxt->work_erase, mtdoops_workfunc_erase);
INIT_WORK(&cxt->work_write, mtdoops_workfunc_write);
@@ -455,6 +479,7 @@ static void __exit mtdoops_console_exit(void)
unregister_console(&mtdoops_console);
kfree(cxt->name);
vfree(cxt->oops_buf);
+ vfree(cxt->oops_buf_write);
}

--
1.6.0.4