// 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,
                            struct kmsg_dump_detail *detail)
{
        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 (detail->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 (detail->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(DIV_ROUND_UP(mtdoops_pages, BITS_PER_LONG),
                              sizeof(unsigned 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");