// SPDX-License-Identifier: GPL-2.0-only
/*
 * MTD Oops/Panic logger
 *
 * Copyright © 2007 Nokia Corporation. All rights reserved.
 *
 * Author: Richard Purdie <rpurdie@openedhand.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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/delay.h>
#include <linux/interrupt.h>
#include <linux/timekeeping.h>
#include <linux/mtd/mtd.h>
#include <linux/kmsg_dump.h>

/* Maximum MTD partition size */
#define MTDOOPS_MAX_MTD_SIZE (8 * 1024 * 1024)

static unsigned long record_size = 4096;
module_param(record_size, ulong, 0400);
MODULE_PARM_DESC(record_size,
		"record size for MTD OOPS pages in bytes (default 4096)");

static char mtddev[80];
module_param_string(mtddev, mtddev, 80, 0400);
MODULE_PARM_DESC(mtddev,
		"name or index number of the MTD device to use");

static int dump_oops = 1;
module_param(dump_oops, int, 0600);
MODULE_PARM_DESC(dump_oops,
		"set to 1 to dump oopses, 0 to only dump panics (default 1)");

#define MTDOOPS_KERNMSG_MAGIC_v1 0x5d005d00  /* Original */
#define MTDOOPS_KERNMSG_MAGIC_v2 0x5d005e00  /* Adds the timestamp */

struct mtdoops_hdr {
	u32 seq;
	u32 magic;
	ktime_t timestamp;
} __packed;

static struct mtdoops_context {
	struct kmsg_dumper dump;

	int mtd_index;
	struct work_struct work_erase;
	struct work_struct work_write;
	struct mtd_info *mtd;
	int oops_pages;
	int nextpage;
	int nextcount;
	unsigned long *oops_page_used;

	unsigned long oops_buf_busy;
	void *oops_buf;
} oops_cxt;

static void mark_page_used(struct mtdoops_context *cxt, int page)
{
	set_bit(page, cxt->oops_page_used);
}

static void mark_page_unused(struct mtdoops_context *cxt, int page)
{
	clear_bit(page, cxt->oops_page_used);
}

static int page_is_used(struct mtdoops_context *cxt, int page)
{
	return test_bit(page, cxt->oops_page_used);
}

static int mtdoops_erase_block(struct mtdoops_context *cxt, int offset)
{
	struct mtd_info *mtd = cxt->mtd;
	u32 start_page_offset = mtd_div_by_eb(offset, mtd) * mtd->erasesize;
	u32 start_page = start_page_offset / record_size;
	u32 erase_pages = mtd->erasesize / record_size;
	struct erase_info erase;
	int ret;
	int page;

	erase.addr = offset;
	erase.len = mtd->erasesize;

	ret = mtd_erase(mtd, &erase);
	if (ret) {
		pr_warn("erase of region [0x%llx, 0x%llx] on \"%s\" failed\n",
			(unsigned long long)erase.addr,
			(unsigned long long)erase.len, mtddev);
		return ret;
	}

	/* Mark pages as unused */
	for (page = start_page; page < start_page + erase_pages; page++)
		mark_page_unused(cxt, page);

	return 0;
}

static void mtdoops_erase(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 * record_size) % mtd->erasesize;
	if (mod != 0) {
		cxt->nextpage = cxt->nextpage + ((mtd->erasesize - mod) / record_size);
		if (cxt->nextpage >= cxt->oops_pages)
			cxt->nextpage = 0;
	}

	while ((ret = mtd_block_isbad(mtd, cxt->nextpage * record_size)) > 0) {
badblock:
		pr_warn("bad block at %08lx\n",
			cxt->nextpage * record_size);
		i++;
		cxt->nextpage = cxt->nextpage + (mtd->erasesize / record_size);
		if (cxt->nextpage >= cxt->oops_pages)
			cxt->nextpage = 0;
		if (i == cxt->oops_pages / (mtd->erasesize / record_size)) {
			pr_err("all blocks bad!\n");
			return;
		}
	}

	if (ret < 0) {
		pr_err("mtd_block_isbad failed, aborting\n");
		return;
	}

	for (j = 0, ret = -1; (j < 3) && (ret < 0); j++)
		ret = mtdoops_erase_block(cxt, cxt->nextpage * record_size);

	if (ret >= 0) {
		pr_debug("ready %d, %d\n",
			 cxt->nextpage, cxt->nextcount);
		return;
	}

	if (ret == -EIO) {
		ret = mtd_block_markbad(mtd, cxt->nextpage * record_size);
		if (ret < 0 && ret != -EOPNOTSUPP) {
			pr_err("block_markbad failed, aborting\n");
			return;
		}
	}
	goto badblock;
}

/* Scheduled work - when we can't proceed without erasing a block */
static void mtdoops_workfunc_erase(struct work_struct *work)
{
	struct mtdoops_context *cxt =
			container_of(work, struct mtdoops_context, work_erase);
	mtdoops_erase(cxt);
}

static void mtdoops_inc_counter(struct mtdoops_context *cxt, int panic)
{
	cxt->nextpage++;
	if (cxt->nextpage >= cxt->oops_pages)
		cxt->nextpage = 0;
	cxt->nextcount++;
	if (cxt->nextcount == 0xffffffff)
		cxt->nextcount = 0;

	if (page_is_used(cxt, cxt->nextpage)) {
		pr_debug("not ready %d, %d (erase %s)\n",
			 cxt->nextpage, cxt->nextcount,
			 panic ? "immediately" : "scheduled");
		if (panic) {
			/* In case of panic, erase immediately */
			mtdoops_erase(cxt);
		} else {
			/* Otherwise, schedule work to erase it "nicely" */
			schedule_work(&cxt->work_erase);
		}
	} else {
		pr_debug("ready %d, %d (no erase)\n",
			 cxt->nextpage, cxt->nextcount);
	}
}

static void mtdoops_write(struct mtdoops_context *cxt, int panic)
{
	struct mtd_info *mtd = cxt->mtd;
	size_t retlen;
	struct mtdoops_hdr *hdr;
	int ret;

	if (test_and_set_bit(0, &cxt->oops_buf_busy))
		return;

	/* Add mtdoops header to the buffer */
	hdr = (struct mtdoops_hdr *)cxt->oops_buf;
	hdr->seq = cxt->nextcount;
	hdr->magic = MTDOOPS_KERNMSG_MAGIC_v2;
	hdr->timestamp = ktime_get_real();

	if (panic) {
		ret = mtd_panic_write(mtd, cxt->nextpage * record_size,
				      record_size, &retlen, cxt->oops_buf);
		if (ret == -EOPNOTSUPP) {
			pr_err("Cannot write from panic without panic_write\n");
			goto out;
		}
	} else
		ret = mtd_write(mtd, cxt->nextpage * record_size,
				record_size, &retlen, cxt->oops_buf);

	if (retlen != record_size || ret < 0)
		pr_err("write failure at %ld (%td of %ld written), error %d\n",
		       cxt->nextpage * record_size, retlen, record_size, ret);
	mark_page_used(cxt, cxt->nextpage);
	memset(cxt->oops_buf, 0xff, record_size);

	mtdoops_inc_counter(cxt, panic);
out:
	clear_bit(0, &cxt->oops_buf_busy);
}

static void mtdoops_workfunc_write(struct work_struct *work)
{
	struct mtdoops_context *cxt =
			container_of(work, struct mtdoops_context, work_write);

	mtdoops_write(cxt, 0);
}

static void find_next_position(struct mtdoops_context *cxt)
{
	struct mtd_info *mtd = cxt->mtd;
	struct mtdoops_hdr hdr;
	int ret, page, maxpos = 0;
	u32 maxcount = 0xffffffff;
	size_t retlen;

	for (page = 0; page < cxt->oops_pages; page++) {
		if (mtd_block_isbad(mtd, page * record_size))
			continue;
		/* Assume the page is used */
		mark_page_used(cxt, page);
		ret = mtd_read(mtd, page * record_size, sizeof(hdr),
			       &retlen, (u_char *)&hdr);
		if (retlen != sizeof(hdr) ||
				(ret < 0 && !mtd_is_bitflip(ret))) {
			pr_err("read failure at %ld (%zu of %zu read), err %d\n",
			       page * record_size, retlen, sizeof(hdr), ret);
			continue;
		}

		if (hdr.seq == 0xffffffff && hdr.magic == 0xffffffff)
			mark_page_unused(cxt, page);
		if (hdr.seq == 0xffffffff ||
		    (hdr.magic != MTDOOPS_KERNMSG_MAGIC_v1 &&
		     hdr.magic != MTDOOPS_KERNMSG_MAGIC_v2))
			continue;
		if (maxcount == 0xffffffff) {
			maxcount = hdr.seq;
			maxpos = page;
		} else if (hdr.seq < 0x40000000 && maxcount > 0xc0000000) {
			maxcount = hdr.seq;
			maxpos = page;
		} else if (hdr.seq > maxcount && hdr.seq < 0xc0000000) {
			maxcount = hdr.seq;
			maxpos = page;
		} else if (hdr.seq > maxcount && hdr.seq > 0xc0000000
					&& maxcount > 0x80000000) {
			maxcount = hdr.seq;
			maxpos = page;
		}
	}
	if (maxcount == 0xffffffff) {
		cxt->nextpage = cxt->oops_pages - 1;
		cxt->nextcount = 0;
	}
	else {
		cxt->nextpage = maxpos;
		cxt->nextcount = maxcount;
	}

	mtdoops_inc_counter(cxt, 0);
}

static void mtdoops_do_dump(struct kmsg_dumper *dumper,
			    enum kmsg_dump_reason reason)
{
	struct mtdoops_context *cxt = container_of(dumper,
			struct mtdoops_context, dump);
	struct kmsg_dump_iter iter;

	/* Only dump oopses if dump_oops is set */
	if (reason == KMSG_DUMP_OOPS && !dump_oops)
		return;

	kmsg_dump_rewind(&iter);

	if (test_and_set_bit(0, &cxt->oops_buf_busy))
		return;
	kmsg_dump_get_buffer(&iter, true,
			     cxt->oops_buf + sizeof(struct mtdoops_hdr),
			     record_size - sizeof(struct mtdoops_hdr), NULL);
	clear_bit(0, &cxt->oops_buf_busy);

	if (reason != KMSG_DUMP_OOPS) {
		/* Panics must be written immediately */
		mtdoops_write(cxt, 1);
	} else {
		/* For other cases, schedule work to write it "nicely" */
		schedule_work(&cxt->work_write);
	}
}

static void mtdoops_notify_add(struct mtd_info *mtd)
{
	struct mtdoops_context *cxt = &oops_cxt;
	u64 mtdoops_pages = div_u64(mtd->size, record_size);
	int err;

	if (!strcmp(mtd->name, mtddev))
		cxt->mtd_index = mtd->index;

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

	if (mtd->size < mtd->erasesize * 2) {
		pr_err("MTD partition %d not big enough for mtdoops\n",
		       mtd->index);
		return;
	}
	if (mtd->erasesize < record_size) {
		pr_err("eraseblock size of MTD partition %d too small\n",
		       mtd->index);
		return;
	}
	if (mtd->size > MTDOOPS_MAX_MTD_SIZE) {
		pr_err("mtd%d is too large (limit is %d MiB)\n",
		       mtd->index, MTDOOPS_MAX_MTD_SIZE / 1024 / 1024);
		return;
	}

	/* oops_page_used is a bit field */
	cxt->oops_page_used =
		vmalloc(array_size(sizeof(unsigned long),
				   DIV_ROUND_UP(mtdoops_pages,
						BITS_PER_LONG)));
	if (!cxt->oops_page_used) {
		pr_err("could not allocate page array\n");
		return;
	}

	cxt->dump.max_reason = KMSG_DUMP_OOPS;
	cxt->dump.dump = mtdoops_do_dump;
	err = kmsg_dump_register(&cxt->dump);
	if (err) {
		pr_err("registering kmsg dumper failed, error %d\n", err);
		vfree(cxt->oops_page_used);
		cxt->oops_page_used = NULL;
		return;
	}

	cxt->mtd = mtd;
	cxt->oops_pages = (int)mtd->size / record_size;
	find_next_position(cxt);
	pr_info("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;

	if (kmsg_dump_unregister(&cxt->dump) < 0)
		pr_warn("could not unregister kmsg_dumper\n");

	cxt->mtd = NULL;
	flush_work(&cxt->work_erase);
	flush_work(&cxt->work_write);
}


static struct mtd_notifier mtdoops_notifier = {
	.add	= mtdoops_notify_add,
	.remove	= mtdoops_notify_remove,
};

static int __init mtdoops_init(void)
{
	struct mtdoops_context *cxt = &oops_cxt;
	int mtd_index;
	char *endp;

	if (strlen(mtddev) == 0) {
		pr_err("mtd device (mtddev=name/number) must be supplied\n");
		return -EINVAL;
	}
	if ((record_size & 4095) != 0) {
		pr_err("record_size must be a multiple of 4096\n");
		return -EINVAL;
	}
	if (record_size < 4096) {
		pr_err("record_size must be over 4096 bytes\n");
		return -EINVAL;
	}

	/* Setup the MTD device to use */
	cxt->mtd_index = -1;
	mtd_index = simple_strtoul(mtddev, &endp, 0);
	if (*endp == '\0')
		cxt->mtd_index = mtd_index;

	cxt->oops_buf = vmalloc(record_size);
	if (!cxt->oops_buf)
		return -ENOMEM;
	memset(cxt->oops_buf, 0xff, record_size);
	cxt->oops_buf_busy = 0;

	INIT_WORK(&cxt->work_erase, mtdoops_workfunc_erase);
	INIT_WORK(&cxt->work_write, mtdoops_workfunc_write);

	register_mtd_user(&mtdoops_notifier);
	return 0;
}

static void __exit mtdoops_exit(void)
{
	struct mtdoops_context *cxt = &oops_cxt;

	unregister_mtd_user(&mtdoops_notifier);
	vfree(cxt->oops_buf);
	vfree(cxt->oops_page_used);
}


module_init(mtdoops_init);
module_exit(mtdoops_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Richard Purdie <rpurdie@openedhand.com>");
MODULE_DESCRIPTION("MTD Oops/Panic console logger/driver"