Commit 78c08247 authored by WeiXiong Liao's avatar WeiXiong Liao Committed by Kees Cook
Browse files

mtd: Support kmsg dumper based on pstore/blk 



This introduces mtdpstore, which is similar to mtdoops but more
powerful. It uses pstore/blk, and aims to store panic and oops logs to
a flash partition, where pstore can later read back and present as files
in the mounted pstore filesystem.

To make mtdpstore work, the "blkdev" of pstore/blk should be set
as MTD device name or MTD device number. For more details, see
Documentation/admin-guide/pstore-blk.rst

This solves a number of issues:
- Work duplication: both of pstore and mtdoops do the same job storing
  panic/oops log. They have very similar logic, registering to kmsg
  dumper and storing logs to several chunks one by one.
- Layer violations: drivers should provides methods instead of polices.
  MTD should provide read/write/erase operations, and allow a higher
  level drivers to provide the chunk management, kmsg dump
  configuration, etc.
- Missing features: pstore provides many additional features, including
  presenting the logs as files, logging dump time and count, and
  supporting other frontends like pmsg, console, etc.

Signed-off-by: default avatarWeiXiong Liao <liaoweixiong@allwinnertech.com>
Link: https://lore.kernel.org/lkml/20200511233229.27745-11-keescook@chromium.org/
Link: https://lore.kernel.org/r/1589266715-4168-1-git-send-email-liaoweixiong@allwinnertech.com


Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent f8feafea

Documentation/admin-guide/pstore-blk.rst

+7 −2
Original line number Diff line number Diff line
@@ -43,9 +43,9 @@ blkdev 
~~~~~~



The block device to use. Most of the time, it is a partition of block device.

It's required for pstore/blk.

It's required for pstore/blk. It is also used for MTD device.



It accepts the following variants:

It accepts the following variants for block device:



1. <hex_major><hex_minor> device number in hexadecimal represents itself; no

   leading 0x, for example b302.
@@ -64,6 +64,11 @@ It accepts the following variants: 
   partition with a known unique id.

#. <major>:<minor> major and minor number of the device separated by a colon.



It accepts the following variants for MTD device:



1. <device name> MTD device name. "pstore" is recommended.

#. <device number> MTD device number.



kmsg_size

~~~~~~~~~

drivers/mtd/Kconfig

+10 −0
Original line number Diff line number Diff line
@@ -170,6 +170,16 @@ config MTD_OOPS 
	  buffer in a flash partition where it can be read back at some

	  later point.



config MTD_PSTORE

	tristate "Log panic/oops to an MTD buffer based on pstore"

	depends on PSTORE_BLK

	help

	  This enables panic and oops messages to be logged to a circular

	  buffer in a flash partition where it can be read back as files after

	  mounting pstore filesystem.



	  If unsure, say N.



config MTD_SWAP

	tristate "Swap on MTD device support"

	depends on MTD && SWAP

drivers/mtd/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ obj-$(CONFIG_RFD_FTL) += rfd_ftl.o 
obj-$(CONFIG_SSFDC)		+= ssfdc.o

obj-$(CONFIG_SM_FTL)		+= sm_ftl.o

obj-$(CONFIG_MTD_OOPS)		+= mtdoops.o

obj-$(CONFIG_MTD_PSTORE)	+= mtdpstore.o

obj-$(CONFIG_MTD_SWAP)		+= mtdswap.o



nftl-objs		:= nftlcore.o nftlmount.o

drivers/mtd/mtdpstore.c

0 → 100644
+578 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



#define dev_fmt(fmt) "mtdoops-pstore: " fmt



#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/pstore_blk.h>

#include <linux/mtd/mtd.h>

#include <linux/bitops.h>



static struct mtdpstore_context {

	int index;

	struct pstore_blk_config info;

	struct pstore_device_info dev;

	struct mtd_info *mtd;

	unsigned long *rmmap;		/* removed bit map */

	unsigned long *usedmap;		/* used bit map */

	/*

	 * used for panic write

	 * As there are no block_isbad for panic case, we should keep this

	 * status before panic to ensure panic_write not failed.

	 */

	unsigned long *badmap;		/* bad block bit map */

} oops_cxt;



static int mtdpstore_block_isbad(struct mtdpstore_context *cxt, loff_t off)

{

	int ret;

	struct mtd_info *mtd = cxt->mtd;

	u64 blknum;



	off = ALIGN_DOWN(off, mtd->erasesize);

	blknum = div_u64(off, mtd->erasesize);



	if (test_bit(blknum, cxt->badmap))

		return true;

	ret = mtd_block_isbad(mtd, off);

	if (ret < 0) {

		dev_err(&mtd->dev, "mtd_block_isbad failed, aborting\n");

		return ret;

	} else if (ret > 0) {

		set_bit(blknum, cxt->badmap);

		return true;

	}

	return false;

}



static inline int mtdpstore_panic_block_isbad(struct mtdpstore_context *cxt,

		loff_t off)

{

	struct mtd_info *mtd = cxt->mtd;

	u64 blknum;



	off = ALIGN_DOWN(off, mtd->erasesize);

	blknum = div_u64(off, mtd->erasesize);

	return test_bit(blknum, cxt->badmap);

}



static inline void mtdpstore_mark_used(struct mtdpstore_context *cxt,

		loff_t off)

{

	struct mtd_info *mtd = cxt->mtd;

	u64 zonenum = div_u64(off, cxt->info.kmsg_size);



	dev_dbg(&mtd->dev, "mark zone %llu used\n", zonenum);

	set_bit(zonenum, cxt->usedmap);

}



static inline void mtdpstore_mark_unused(struct mtdpstore_context *cxt,

		loff_t off)

{

	struct mtd_info *mtd = cxt->mtd;

	u64 zonenum = div_u64(off, cxt->info.kmsg_size);



	dev_dbg(&mtd->dev, "mark zone %llu unused\n", zonenum);

	clear_bit(zonenum, cxt->usedmap);

}



static inline void mtdpstore_block_mark_unused(struct mtdpstore_context *cxt,

		loff_t off)

{

	struct mtd_info *mtd = cxt->mtd;

	u32 zonecnt = mtd->erasesize / cxt->info.kmsg_size;

	u64 zonenum;



	off = ALIGN_DOWN(off, mtd->erasesize);

	zonenum = div_u64(off, cxt->info.kmsg_size);

	while (zonecnt > 0) {

		dev_dbg(&mtd->dev, "mark zone %llu unused\n", zonenum);

		clear_bit(zonenum, cxt->usedmap);

		zonenum++;

		zonecnt--;

	}

}



static inline int mtdpstore_is_used(struct mtdpstore_context *cxt, loff_t off)

{

	u64 zonenum = div_u64(off, cxt->info.kmsg_size);

	u64 blknum = div_u64(off, cxt->mtd->erasesize);



	if (test_bit(blknum, cxt->badmap))

		return true;

	return test_bit(zonenum, cxt->usedmap);

}



static int mtdpstore_block_is_used(struct mtdpstore_context *cxt,

		loff_t off)

{

	struct mtd_info *mtd = cxt->mtd;

	u32 zonecnt = mtd->erasesize / cxt->info.kmsg_size;

	u64 zonenum;



	off = ALIGN_DOWN(off, mtd->erasesize);

	zonenum = div_u64(off, cxt->info.kmsg_size);

	while (zonecnt > 0) {

		if (test_bit(zonenum, cxt->usedmap))

			return true;

		zonenum++;

		zonecnt--;

	}

	return false;

}



static int mtdpstore_is_empty(struct mtdpstore_context *cxt, char *buf,

		size_t size)

{

	struct mtd_info *mtd = cxt->mtd;

	size_t sz;

	int i;



	sz = min_t(uint32_t, size, mtd->writesize / 4);

	for (i = 0; i < sz; i++) {

		if (buf[i] != (char)0xFF)

			return false;

	}

	return true;

}



static void mtdpstore_mark_removed(struct mtdpstore_context *cxt, loff_t off)

{

	struct mtd_info *mtd = cxt->mtd;

	u64 zonenum = div_u64(off, cxt->info.kmsg_size);



	dev_dbg(&mtd->dev, "mark zone %llu removed\n", zonenum);

	set_bit(zonenum, cxt->rmmap);

}



static void mtdpstore_block_clear_removed(struct mtdpstore_context *cxt,

		loff_t off)

{

	struct mtd_info *mtd = cxt->mtd;

	u32 zonecnt = mtd->erasesize / cxt->info.kmsg_size;

	u64 zonenum;



	off = ALIGN_DOWN(off, mtd->erasesize);

	zonenum = div_u64(off, cxt->info.kmsg_size);

	while (zonecnt > 0) {

		clear_bit(zonenum, cxt->rmmap);

		zonenum++;

		zonecnt--;

	}

}



static int mtdpstore_block_is_removed(struct mtdpstore_context *cxt,

		loff_t off)

{

	struct mtd_info *mtd = cxt->mtd;

	u32 zonecnt = mtd->erasesize / cxt->info.kmsg_size;

	u64 zonenum;



	off = ALIGN_DOWN(off, mtd->erasesize);

	zonenum = div_u64(off, cxt->info.kmsg_size);

	while (zonecnt > 0) {

		if (test_bit(zonenum, cxt->rmmap))

			return true;

		zonenum++;

		zonecnt--;

	}

	return false;

}



static int mtdpstore_erase_do(struct mtdpstore_context *cxt, loff_t off)

{

	struct mtd_info *mtd = cxt->mtd;

	struct erase_info erase;

	int ret;



	off = ALIGN_DOWN(off, cxt->mtd->erasesize);

	dev_dbg(&mtd->dev, "try to erase off 0x%llx\n", off);

	erase.len = cxt->mtd->erasesize;

	erase.addr = off;

	ret = mtd_erase(cxt->mtd, &erase);

	if (!ret)

		mtdpstore_block_clear_removed(cxt, off);

	else

		dev_err(&mtd->dev, "erase of region [0x%llx, 0x%llx] on \"%s\" failed\n",

		       (unsigned long long)erase.addr,

		       (unsigned long long)erase.len, cxt->info.device);

	return ret;

}



/*

 * called while removing file

 *

 * Avoiding over erasing, do erase block only when the whole block is unused.

 * If the block contains valid log, do erase lazily on flush_removed() when

 * unregister.

 */

static ssize_t mtdpstore_erase(size_t size, loff_t off)

{

	struct mtdpstore_context *cxt = &oops_cxt;



	if (mtdpstore_block_isbad(cxt, off))

		return -EIO;



	mtdpstore_mark_unused(cxt, off);



	/* If the block still has valid data, mtdpstore do erase lazily */

	if (likely(mtdpstore_block_is_used(cxt, off))) {

		mtdpstore_mark_removed(cxt, off);

		return 0;

	}



	/* all zones are unused, erase it */

	return mtdpstore_erase_do(cxt, off);

}



/*

 * What is security for mtdpstore?

 * As there is no erase for panic case, we should ensure at least one zone

 * is writable. Otherwise, panic write will fail.

 * If zone is used, write operation will return -ENOMSG, which means that

 * pstore/blk will try one by one until gets an empty zone. So, it is not

 * needed to ensure the next zone is empty, but at least one.

 */

static int mtdpstore_security(struct mtdpstore_context *cxt, loff_t off)

{

	int ret = 0, i;

	struct mtd_info *mtd = cxt->mtd;

	u32 zonenum = (u32)div_u64(off, cxt->info.kmsg_size);

	u32 zonecnt = (u32)div_u64(cxt->mtd->size, cxt->info.kmsg_size);

	u32 blkcnt = (u32)div_u64(cxt->mtd->size, cxt->mtd->erasesize);

	u32 erasesize = cxt->mtd->erasesize;



	for (i = 0; i < zonecnt; i++) {

		u32 num = (zonenum + i) % zonecnt;



		/* found empty zone */

		if (!test_bit(num, cxt->usedmap))

			return 0;

	}



	/* If there is no any empty zone, we have no way but to do erase */

	while (blkcnt--) {

		div64_u64_rem(off + erasesize, cxt->mtd->size, (u64 *)&off);



		if (mtdpstore_block_isbad(cxt, off))

			continue;



		ret = mtdpstore_erase_do(cxt, off);

		if (!ret) {

			mtdpstore_block_mark_unused(cxt, off);

			break;

		}

	}



	if (ret)

		dev_err(&mtd->dev, "all blocks bad!\n");

	dev_dbg(&mtd->dev, "end security\n");

	return ret;

}



static ssize_t mtdpstore_write(const char *buf, size_t size, loff_t off)

{

	struct mtdpstore_context *cxt = &oops_cxt;

	struct mtd_info *mtd = cxt->mtd;

	size_t retlen;

	int ret;



	if (mtdpstore_block_isbad(cxt, off))

		return -ENOMSG;



	/* zone is used, please try next one */

	if (mtdpstore_is_used(cxt, off))

		return -ENOMSG;



	dev_dbg(&mtd->dev, "try to write off 0x%llx size %zu\n", off, size);

	ret = mtd_write(cxt->mtd, off, size, &retlen, (u_char *)buf);

	if (ret < 0 || retlen != size) {

		dev_err(&mtd->dev, "write failure at %lld (%zu of %zu written), err %d\n",

				off, retlen, size, ret);

		return -EIO;

	}

	mtdpstore_mark_used(cxt, off);



	mtdpstore_security(cxt, off);

	return retlen;

}



static inline bool mtdpstore_is_io_error(int ret)

{

	return ret < 0 && !mtd_is_bitflip(ret) && !mtd_is_eccerr(ret);

}



/*

 * All zones will be read as pstore/blk will read zone one by one when do

 * recover.

 */

static ssize_t mtdpstore_read(char *buf, size_t size, loff_t off)

{

	struct mtdpstore_context *cxt = &oops_cxt;

	struct mtd_info *mtd = cxt->mtd;

	size_t retlen, done;

	int ret;



	if (mtdpstore_block_isbad(cxt, off))

		return -ENOMSG;



	dev_dbg(&mtd->dev, "try to read off 0x%llx size %zu\n", off, size);

	for (done = 0, retlen = 0; done < size; done += retlen) {

		retlen = 0;



		ret = mtd_read(cxt->mtd, off + done, size - done, &retlen,

				(u_char *)buf + done);

		if (mtdpstore_is_io_error(ret)) {

			dev_err(&mtd->dev, "read failure at %lld (%zu of %zu read), err %d\n",

					off + done, retlen, size - done, ret);

			/* the zone may be broken, try next one */

			return -ENOMSG;

		}



		/*

		 * ECC error. The impact on log data is so small. Maybe we can

		 * still read it and try to understand. So mtdpstore just hands

		 * over what it gets and user can judge whether the data is

		 * valid or not.

		 */

		if (mtd_is_eccerr(ret)) {

			dev_err(&mtd->dev, "ecc error at %lld (%zu of %zu read), err %d\n",

					off + done, retlen, size - done, ret);

			/* driver may not set retlen when ecc error */

			retlen = retlen == 0 ? size - done : retlen;

		}

	}



	if (mtdpstore_is_empty(cxt, buf, size))

		mtdpstore_mark_unused(cxt, off);

	else

		mtdpstore_mark_used(cxt, off);



	mtdpstore_security(cxt, off);

	return retlen;

}



static ssize_t mtdpstore_panic_write(const char *buf, size_t size, loff_t off)

{

	struct mtdpstore_context *cxt = &oops_cxt;

	struct mtd_info *mtd = cxt->mtd;

	size_t retlen;

	int ret;



	if (mtdpstore_panic_block_isbad(cxt, off))

		return -ENOMSG;



	/* zone is used, please try next one */

	if (mtdpstore_is_used(cxt, off))

		return -ENOMSG;



	ret = mtd_panic_write(cxt->mtd, off, size, &retlen, (u_char *)buf);

	if (ret < 0 || size != retlen) {

		dev_err(&mtd->dev, "panic write failure at %lld (%zu of %zu read), err %d\n",

				off, retlen, size, ret);

		return -EIO;

	}

	mtdpstore_mark_used(cxt, off);



	return retlen;

}



static void mtdpstore_notify_add(struct mtd_info *mtd)

{

	int ret;

	struct mtdpstore_context *cxt = &oops_cxt;

	struct pstore_blk_config *info = &cxt->info;

	unsigned long longcnt;



	if (!strcmp(mtd->name, info->device))

		cxt->index = mtd->index;



	if (mtd->index != cxt->index || cxt->index < 0)

		return;



	dev_dbg(&mtd->dev, "found matching MTD device %s\n", mtd->name);



	if (mtd->size < info->kmsg_size * 2) {

		dev_err(&mtd->dev, "MTD partition %d not big enough\n",

				mtd->index);

		return;

	}

	/*

	 * kmsg_size must be aligned to 4096 Bytes, which is limited by

	 * psblk. The default value of kmsg_size is 64KB. If kmsg_size

	 * is larger than erasesize, some errors will occur since mtdpsotre

	 * is designed on it.

	 */

	if (mtd->erasesize < info->kmsg_size) {

		dev_err(&mtd->dev, "eraseblock size of MTD partition %d too small\n",

				mtd->index);

		return;

	}

	if (unlikely(info->kmsg_size % mtd->writesize)) {

		dev_err(&mtd->dev, "record size %lu KB must align to write size %d KB\n",

				info->kmsg_size / 1024,

				mtd->writesize / 1024);

		return;

	}



	longcnt = BITS_TO_LONGS(div_u64(mtd->size, info->kmsg_size));

	cxt->rmmap = kcalloc(longcnt, sizeof(long), GFP_KERNEL);

	cxt->usedmap = kcalloc(longcnt, sizeof(long), GFP_KERNEL);



	longcnt = BITS_TO_LONGS(div_u64(mtd->size, mtd->erasesize));

	cxt->badmap = kcalloc(longcnt, sizeof(long), GFP_KERNEL);



	cxt->dev.total_size = mtd->size;

	/* just support dmesg right now */

	cxt->dev.flags = PSTORE_FLAGS_DMESG;

	cxt->dev.read = mtdpstore_read;

	cxt->dev.write = mtdpstore_write;

	cxt->dev.erase = mtdpstore_erase;

	cxt->dev.panic_write = mtdpstore_panic_write;



	ret = register_pstore_device(&cxt->dev);

	if (ret) {

		dev_err(&mtd->dev, "mtd%d register to psblk failed\n",

				mtd->index);

		return;

	}

	cxt->mtd = mtd;

	dev_info(&mtd->dev, "Attached to MTD device %d\n", mtd->index);

}



static int mtdpstore_flush_removed_do(struct mtdpstore_context *cxt,

		loff_t off, size_t size)

{

	struct mtd_info *mtd = cxt->mtd;

	u_char *buf;

	int ret;

	size_t retlen;

	struct erase_info erase;



	buf = kmalloc(mtd->erasesize, GFP_KERNEL);

	if (!buf)

		return -ENOMEM;



	/* 1st. read to cache */

	ret = mtd_read(mtd, off, mtd->erasesize, &retlen, buf);

	if (mtdpstore_is_io_error(ret))

		goto free;



	/* 2nd. erase block */

	erase.len = mtd->erasesize;

	erase.addr = off;

	ret = mtd_erase(mtd, &erase);

	if (ret)

		goto free;



	/* 3rd. write back */

	while (size) {

		unsigned int zonesize = cxt->info.kmsg_size;



		/* there is valid data on block, write back */

		if (mtdpstore_is_used(cxt, off)) {

			ret = mtd_write(mtd, off, zonesize, &retlen, buf);

			if (ret)

				dev_err(&mtd->dev, "write failure at %lld (%zu of %u written), err %d\n",

						off, retlen, zonesize, ret);

		}



		off += zonesize;

		size -= min_t(unsigned int, zonesize, size);

	}



free:

	kfree(buf);

	return ret;

}



/*

 * What does mtdpstore_flush_removed() do?

 * When user remove any log file on pstore filesystem, mtdpstore should do

 * something to ensure log file removed. If the whole block is no longer used,

 * it's nice to erase the block. However if the block still contains valid log,

 * what mtdpstore can do is to erase and write the valid log back.

 */

static int mtdpstore_flush_removed(struct mtdpstore_context *cxt)

{

	struct mtd_info *mtd = cxt->mtd;

	int ret;

	loff_t off;

	u32 blkcnt = (u32)div_u64(mtd->size, mtd->erasesize);



	for (off = 0; blkcnt > 0; blkcnt--, off += mtd->erasesize) {

		ret = mtdpstore_block_isbad(cxt, off);

		if (ret)

			continue;



		ret = mtdpstore_block_is_removed(cxt, off);

		if (!ret)

			continue;



		ret = mtdpstore_flush_removed_do(cxt, off, mtd->erasesize);

		if (ret)

			return ret;

	}

	return 0;

}



static void mtdpstore_notify_remove(struct mtd_info *mtd)

{

	struct mtdpstore_context *cxt = &oops_cxt;



	if (mtd->index != cxt->index || cxt->index < 0)

		return;



	mtdpstore_flush_removed(cxt);



	unregister_pstore_device(&cxt->dev);

	kfree(cxt->badmap);

	kfree(cxt->usedmap);

	kfree(cxt->rmmap);

	cxt->mtd = NULL;

	cxt->index = -1;

}



static struct mtd_notifier mtdpstore_notifier = {

	.add	= mtdpstore_notify_add,

	.remove	= mtdpstore_notify_remove,

};



static int __init mtdpstore_init(void)

{

	int ret;

	struct mtdpstore_context *cxt = &oops_cxt;

	struct pstore_blk_config *info = &cxt->info;



	ret = pstore_blk_get_config(info);

	if (unlikely(ret))

		return ret;



	if (strlen(info->device) == 0) {

		pr_err("mtd device must be supplied (device name is empty)\n");

		return -EINVAL;

	}

	if (!info->kmsg_size) {

		pr_err("no backend enabled (kmsg_size is 0)\n");

		return -EINVAL;

	}



	/* Setup the MTD device to use */

	ret = kstrtoint((char *)info->device, 0, &cxt->index);

	if (ret)

		cxt->index = -1;



	register_mtd_user(&mtdpstore_notifier);

	return 0;

}

module_init(mtdpstore_init);



static void __exit mtdpstore_exit(void)

{

	unregister_mtd_user(&mtdpstore_notifier);

}

module_exit(mtdpstore_exit);



MODULE_LICENSE("GPL");

MODULE_AUTHOR("WeiXiong Liao <liaoweixiong@allwinnertech.com>");

MODULE_DESCRIPTION("MTD backend for pstore/blk");

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