// SPDX-License-Identifier: GPL-2.0
/*
 * Provide a pstore intermediate backend, organized into kernel memory
 * allocated zones that are then mapped and flushed into a single
 * contiguous region on a storage backend of some kind (block, mtd, etc).
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/mount.h>
#include <linux/printk.h>
#include <linux/fs.h>
#include <linux/pstore_zone.h>
#include <linux/kdev_t.h>
#include <linux/device.h>
#include <linux/namei.h>
#include <linux/fcntl.h>
#include <linux/uio.h>
#include <linux/writeback.h>
#include "internal.h"

/**
 * struct psz_buffer - header of zone to flush to storage
 *
 * @sig: signature to indicate header (PSZ_SIG xor PSZONE-type value)
 * @datalen: length of data in @data
 * @start: offset into @data where the beginning of the stored bytes begin
 * @data: zone data.
 */
struct psz_buffer {
#define PSZ_SIG (0x43474244) /* DBGC */
        uint32_t sig;
        atomic_t datalen;
        atomic_t start;
        uint8_t data[];
};

/**
 * struct psz_kmsg_header - kmsg dump-specific header to flush to storage
 *
 * @magic: magic num for kmsg dump header
 * @time: kmsg dump trigger time
 * @compressed: whether compressed
 * @counter: kmsg dump counter
 * @reason: the kmsg dump reason (e.g. oops, panic, etc)
 * @data: pointer to log data
 *
 * This is a sub-header for a kmsg dump, trailing after &psz_buffer.
 */
struct psz_kmsg_header {
#define PSTORE_KMSG_HEADER_MAGIC 0x4dfc3ae5 /* Just a random number */
        uint32_t magic;
        struct timespec64 time;
        bool compressed;
        uint32_t counter;
        enum kmsg_dump_reason reason;
        uint8_t data[];
};

/**
 * struct pstore_zone - single stored buffer
 *
 * @off: zone offset of storage
 * @type: front-end type for this zone
 * @name: front-end name for this zone
 * @buffer: pointer to data buffer managed by this zone
 * @oldbuf: pointer to old data buffer
 * @buffer_size: bytes in @buffer->data
 * @should_recover: whether this zone should recover from storage
 * @dirty: whether the data in @buffer dirty
 *
 * zone structure in memory.
 */
struct pstore_zone {
        loff_t off;
        const char *name;
        enum pstore_type_id type;

        struct psz_buffer *buffer;
        struct psz_buffer *oldbuf;
        size_t buffer_size;
        bool should_recover;
        atomic_t dirty;
};

/**
 * struct psz_context - all about running state of pstore/zone
 *
 * @kpszs: kmsg dump storage zones
 * @ppsz: pmsg storage zone
 * @cpsz: console storage zone
 * @fpszs: ftrace storage zones
 * @kmsg_max_cnt: max count of @kpszs
 * @kmsg_read_cnt: counter of total read kmsg dumps
 * @kmsg_write_cnt: counter of total kmsg dump writes
 * @pmsg_read_cnt: counter of total read pmsg zone
 * @console_read_cnt: counter of total read console zone
 * @ftrace_max_cnt: max count of @fpszs
 * @ftrace_read_cnt: counter of max read ftrace zone
 * @oops_counter: counter of oops dumps
 * @panic_counter: counter of panic dumps
 * @recovered: whether finished recovering data from storage
 * @on_panic: whether panic is happening
 * @pstore_zone_info_lock: lock to @pstore_zone_info
 * @pstore_zone_info: information from backend
 * @pstore: structure for pstore
 */
struct psz_context {
        struct pstore_zone **kpszs;
        struct pstore_zone *ppsz;
        struct pstore_zone *cpsz;
        struct pstore_zone **fpszs;
        unsigned int kmsg_max_cnt;
        unsigned int kmsg_read_cnt;
        unsigned int kmsg_write_cnt;
        unsigned int pmsg_read_cnt;
        unsigned int console_read_cnt;
        unsigned int ftrace_max_cnt;
        unsigned int ftrace_read_cnt;
        /*
         * These counters should be calculated during recovery.
         * It records the oops/panic times after crashes rather than boots.
         */
        unsigned int oops_counter;
        unsigned int panic_counter;
        atomic_t recovered;
        atomic_t on_panic;

        /*
         * pstore_zone_info_lock protects this entire structure during calls
         * to register_pstore_zone()/unregister_pstore_zone().
         */
        struct mutex pstore_zone_info_lock;
        struct pstore_zone_info *pstore_zone_info;
        struct pstore_info pstore;
};
static struct psz_context pstore_zone_cxt;

static void psz_flush_all_dirty_zones(struct work_struct *);
static DECLARE_DELAYED_WORK(psz_cleaner, psz_flush_all_dirty_zones);

/**
 * enum psz_flush_mode - flush mode for psz_zone_write()
 *
 * @FLUSH_NONE: do not flush to storage but update data on memory
 * @FLUSH_PART: just flush part of data including meta data to storage
 * @FLUSH_META: just flush meta data of zone to storage
 * @FLUSH_ALL: flush all of zone
 */
enum psz_flush_mode {
        FLUSH_NONE = 0,
        FLUSH_PART,
        FLUSH_META,
        FLUSH_ALL,
};

static inline int buffer_datalen(struct pstore_zone *zone)
{
        return atomic_read(&zone->buffer->datalen);
}

static inline int buffer_start(struct pstore_zone *zone)
{
        return atomic_read(&zone->buffer->start);
}

static inline bool is_on_panic(void)
{
        return atomic_read(&pstore_zone_cxt.on_panic);
}

static ssize_t psz_zone_read_buffer(struct pstore_zone *zone, char *buf,
                size_t len, unsigned long off)
{
        if (!buf || !zone || !zone->buffer)
                return -EINVAL;
        if (off > zone->buffer_size)
                return -EINVAL;
        len = min_t(size_t, len, zone->buffer_size - off);
        memcpy(buf, zone->buffer->data + off, len);
        return len;
}

static int psz_zone_read_oldbuf(struct pstore_zone *zone, char *buf,
                size_t len, unsigned long off)
{
        if (!buf || !zone || !zone->oldbuf)
                return -EINVAL;
        if (off > zone->buffer_size)
                return -EINVAL;
        len = min_t(size_t, len, zone->buffer_size - off);
        memcpy(buf, zone->oldbuf->data + off, len);
        return 0;
}

static int psz_zone_write(struct pstore_zone *zone,
                enum psz_flush_mode flush_mode, const char *buf,
                size_t len, unsigned long off)
{
        struct pstore_zone_info *info = pstore_zone_cxt.pstore_zone_info;
        ssize_t wcnt = 0;
        ssize_t (*writeop)(const char *buf, size_t bytes, loff_t pos);
        size_t wlen;

        if (off > zone->buffer_size)
                return -EINVAL;

        wlen = min_t(size_t, len, zone->buffer_size - off);
        if (buf && wlen) {
                memcpy(zone->buffer->data + off, buf, wlen);
                atomic_set(&zone->buffer->datalen, wlen + off);
        }

        /* avoid damaging old records */
        if (!is_on_panic() && !atomic_read(&pstore_zone_cxt.recovered))
                goto dirty;

        writeop = is_on_panic() ? info->panic_write : info->write;
        if (!writeop)
                goto dirty;

        switch (flush_mode) {
        case FLUSH_NONE:
                if (unlikely(buf && wlen))
                        goto dirty;
                return 0;
        case FLUSH_PART:
                wcnt = writeop((const char *)zone->buffer->data + off, wlen,
                                zone->off + sizeof(*zone->buffer) + off);
                if (wcnt != wlen)
                        goto dirty;
                fallthrough;
        case FLUSH_META:
                wlen = sizeof(struct psz_buffer);
                wcnt = writeop((const char *)zone->buffer, wlen, zone->off);
                if (wcnt != wlen)
                        goto dirty;
                break;
        case FLUSH_ALL:
                wlen = zone->buffer_size + sizeof(*zone->buffer);
                wcnt = writeop((const char *)zone->buffer, wlen, zone->off);
                if (wcnt != wlen)
                        goto dirty;
                break;
        }

        return 0;
dirty:
        /* no need to mark it dirty if going to try next zone */
        if (wcnt == -ENOMSG)
                return -ENOMSG;
        atomic_set(&zone->dirty, true);
        /* flush dirty zones nicely */
        if (wcnt == -EBUSY && !is_on_panic())
                schedule_delayed_work(&psz_cleaner, msecs_to_jiffies(500));
        return -EBUSY;
}

static int psz_flush_dirty_zone(struct pstore_zone *zone)
{
        int ret;

        if (unlikely(!zone))
                return -EINVAL;

        if (unlikely(!atomic_read(&pstore_zone_cxt.recovered)))
                return -EBUSY;

        if (!atomic_xchg(&zone->dirty, false))
                return 0;

        ret = psz_zone_write(zone, FLUSH_ALL, NULL, 0, 0);
        if (ret)
                atomic_set(&zone->dirty, true);
        return ret;
}

static int psz_flush_dirty_zones(struct pstore_zone **zones, unsigned int cnt)
{
        int i, ret;
        struct pstore_zone *zone;

        if (!zones)
                return -EINVAL;

        for (i = 0; i < cnt; i++) {
                zone = zones[i];
                if (!zone)
                        return -EINVAL;
                ret = psz_flush_dirty_zone(zone);
                if (ret)
                        return ret;
        }
        return 0;
}

static int psz_move_zone(struct pstore_zone *old, struct pstore_zone *new)
{
        const char *data = (const char *)old->buffer->data;
        int ret;

        ret = psz_zone_write(new, FLUSH_ALL, data, buffer_datalen(old), 0);
        if (ret) {
                atomic_set(&new->buffer->datalen, 0);
                atomic_set(&new->dirty, false);
                return ret;
        }
        atomic_set(&old->buffer->datalen, 0);
        return 0;
}

static void psz_flush_all_dirty_zones(struct work_struct *work)
{
        struct psz_context *cxt = &pstore_zone_cxt;
        int ret = 0;

        if (cxt->ppsz)
                ret |= psz_flush_dirty_zone(cxt->ppsz);
        if (cxt->cpsz)
                ret |= psz_flush_dirty_zone(cxt->cpsz);
        if (cxt->kpszs)
                ret |= psz_flush_dirty_zones(cxt->kpszs, cxt->kmsg_max_cnt);
        if (cxt->fpszs)
                ret |= psz_flush_dirty_zones(cxt->fpszs, cxt->ftrace_max_cnt);
        if (ret && cxt->pstore_zone_info)
                schedule_delayed_work(&psz_cleaner, msecs_to_jiffies(1000));
}

static int psz_kmsg_recover_data(struct psz_context *cxt)
{
        struct pstore_zone_info *info = cxt->pstore_zone_info;
        struct pstore_zone *zone = NULL;
        struct psz_buffer *buf;
        unsigned long i;
        ssize_t rcnt;

        if (!info->read)
                return -EINVAL;

        for (i = 0; i < cxt->kmsg_max_cnt; i++) {
                zone = cxt->kpszs[i];
                if (unlikely(!zone))
                        return -EINVAL;
                if (atomic_read(&zone->dirty)) {
                        unsigned int wcnt = cxt->kmsg_write_cnt;
                        struct pstore_zone *new = cxt->kpszs[wcnt];
                        int ret;

                        ret = psz_move_zone(zone, new);
                        if (ret) {
                                pr_err("move zone from %lu to %d failed\n",
                                                i, wcnt);
                                return ret;
                        }
                        cxt->kmsg_write_cnt = (wcnt + 1) % cxt->kmsg_max_cnt;
                }
                if (!zone->should_recover)
                        continue;
                buf = zone->buffer;
                rcnt = info->read((char *)buf, zone->buffer_size + sizeof(*buf),
                                zone->off);
                if (rcnt != zone->buffer_size + sizeof(*buf))
                        return rcnt < 0 ? rcnt : -EIO;
        }
        return 0;
}

static int psz_kmsg_recover_meta(struct psz_context *cxt)
{
        struct pstore_zone_info *info = cxt->pstore_zone_info;
        struct pstore_zone *zone;
        ssize_t rcnt, len;
        struct psz_buffer *buf;
        struct psz_kmsg_header *hdr;
        struct timespec64 time = { };
        unsigned long i;
        /*
         * Recover may happen on panic, we can't allocate any memory by kmalloc.
         * So, we use local array instead.
         */
        char buffer_header[sizeof(*buf) + sizeof(*hdr)] = {0};

        if (!info->read)
                return -EINVAL;

        len = sizeof(*buf) + sizeof(*hdr);
        buf = (struct psz_buffer *)buffer_header;
        for (i = 0; i < cxt->kmsg_max_cnt; i++) {
                zone = cxt->kpszs[i];
                if (unlikely(!zone))
                        return -EINVAL;

                rcnt = info->read((char *)buf, len, zone->off);
                if (rcnt == -ENOMSG) {
                        pr_debug("%s with id %lu may be broken, skip\n",
                                        zone->name, i);
                        continue;
                } else if (rcnt != len) {
                        pr_err("read %s with id %lu failed\n", zone->name, i);
                        return rcnt < 0 ? rcnt : -EIO;
                }

                if (buf->sig != zone->buffer->sig) {
                        pr_debug("no valid data in kmsg dump zone %lu\n", i);
                        continue;
                }

                if (zone->buffer_size < atomic_read(&buf->datalen)) {
                        pr_info("found overtop zone: %s: id %lu, off %lld, size %zu\n",
                                        zone->name, i, zone->off,
                                        zone->buffer_size);
                        continue;
                }

                hdr = (struct psz_kmsg_header *)buf->data;
                if (hdr->magic != PSTORE_KMSG_HEADER_MAGIC) {
                        pr_info("found invalid zone: %s: id %lu, off %lld, size %zu\n",
                                        zone->name, i, zone->off,
                                        zone->buffer_size);
                        continue;
                }

                /*
                 * we get the newest zone, and the next one must be the oldest
                 * or unused zone, because we do write one by one like a circle.
                 */
                if (hdr->time.tv_sec >= time.tv_sec) {
                        time.tv_sec = hdr->time.tv_sec;
                        cxt->kmsg_write_cnt = (i + 1) % cxt->kmsg_max_cnt;
                }

                if (hdr->reason == KMSG_DUMP_OOPS)
                        cxt->oops_counter =
                                max(cxt->oops_counter, hdr->counter);
                else if (hdr->reason == KMSG_DUMP_PANIC)
                        cxt->panic_counter =
                                max(cxt->panic_counter, hdr->counter);

                if (!atomic_read(&buf->datalen)) {
                        pr_debug("found erased zone: %s: id %lu, off %lld, size %zu, datalen %d\n",
                                        zone->name, i, zone->off,
                                        zone->buffer_size,
                                        atomic_read(&buf->datalen));
                        continue;
                }

                if (!is_on_panic())
                        zone->should_recover = true;
                pr_debug("found nice zone: %s: id %lu, off %lld, size %zu, datalen %d\n",
                                zone->name, i, zone->off,
                                zone->buffer_size, atomic_read(&buf->datalen));
        }

        return 0;
}

static int psz_kmsg_recover(struct psz_context *cxt)
{
        int ret;

        if (!cxt->kpszs)
                return 0;

        ret = psz_kmsg_recover_meta(cxt);
        if (ret)
                goto recover_fail;

        ret = psz_kmsg_recover_data(cxt);
        if (ret)
                goto recover_fail;

        return 0;
recover_fail:
        pr_debug("psz_recover_kmsg failed\n");
        return ret;
}

static int psz_recover_zone(struct psz_context *cxt, struct pstore_zone *zone)
{
        struct pstore_zone_info *info = cxt->pstore_zone_info;
        struct psz_buffer *oldbuf, tmpbuf;
        int ret = 0;
        char *buf;
        ssize_t rcnt, len, start, off;

        if (!zone || zone->oldbuf)
                return 0;

        if (is_on_panic()) {
                /* save data as much as possible */
                psz_flush_dirty_zone(zone);
                return 0;
        }

        if (unlikely(!info->read))
                return -EINVAL;

        len = sizeof(struct psz_buffer);
        rcnt = info->read((char *)&tmpbuf, len, zone->off);
        if (rcnt != len) {
                pr_debug("read zone %s failed\n", zone->name);
                return rcnt < 0 ? rcnt : -EIO;
        }

        if (tmpbuf.sig != zone->buffer->sig) {
                pr_debug("no valid data in zone %s\n", zone->name);
                return 0;
        }

        if (zone->buffer_size < atomic_read(&tmpbuf.datalen) ||
                zone->buffer_size < atomic_read(&tmpbuf.start)) {
                pr_info("found overtop zone: %s: off %lld, size %zu\n",
                                zone->name, zone->off, zone->buffer_size);
                /* just keep going */
                return 0;
        }

        if (!atomic_read(&tmpbuf.datalen)) {
                pr_debug("found erased zone: %s: off %lld, size %zu, datalen %d\n",
                                zone->name, zone->off, zone->buffer_size,
                                atomic_read(&tmpbuf.datalen));
                return 0;
        }

        pr_debug("found nice zone: %s: off %lld, size %zu, datalen %d\n",
                        zone->name, zone->off, zone->buffer_size,
                        atomic_read(&tmpbuf.datalen));

        len = atomic_read(&tmpbuf.datalen) + sizeof(*oldbuf);
        oldbuf = kzalloc(len, GFP_KERNEL);
        if (!oldbuf)
                return -ENOMEM;

        memcpy(oldbuf, &tmpbuf, sizeof(*oldbuf));
        buf = (char *)oldbuf + sizeof(*oldbuf);
        len = atomic_read(&oldbuf->datalen);
        start = atomic_read(&oldbuf->start);
        off = zone->off + sizeof(*oldbuf);

        /* get part of data */
        rcnt = info->read(buf, len - start, off + start);
        if (rcnt != len - start) {
                pr_err("read zone %s failed\n", zone->name);
                ret = rcnt < 0 ? rcnt : -EIO;
                goto free_oldbuf;
        }

        /* get the rest of data */
        rcnt = info->read(buf + len - start, start, off);
        if (rcnt != start) {
                pr_err("read zone %s failed\n", zone->name);
                ret = rcnt < 0 ? rcnt : -EIO;
                goto free_oldbuf;
        }

        zone->oldbuf = oldbuf;
        psz_flush_dirty_zone(zone);
        return 0;

free_oldbuf:
        kfree(oldbuf);
        return ret;
}

static int psz_recover_zones(struct psz_context *cxt,
                struct pstore_zone **zones, unsigned int cnt)
{
        int ret;
        unsigned int i;
        struct pstore_zone *zone;

        if (!zones)
                return 0;

        for (i = 0; i < cnt; i++) {
                zone = zones[i];
                if (unlikely(!zone))
                        continue;
                ret = psz_recover_zone(cxt, zone);
                if (ret)
                        goto recover_fail;
        }

        return 0;
recover_fail:
        pr_debug("recover %s[%u] failed\n", zone->name, i);
        return ret;
}

/**
 * psz_recovery() - recover data from storage
 * @cxt: the context of pstore/zone
 *
 * recovery means reading data back from storage after rebooting
 *
 * Return: 0 on success, others on failure.
 */
static inline int psz_recovery(struct psz_context *cxt)
{
        int ret;

        if (atomic_read(&cxt->recovered))
                return 0;

        ret = psz_kmsg_recover(cxt);
        if (ret)
                goto out;

        ret = psz_recover_zone(cxt, cxt->ppsz);
        if (ret)
                goto out;

        ret = psz_recover_zone(cxt, cxt->cpsz);
        if (ret)
                goto out;

        ret = psz_recover_zones(cxt, cxt->fpszs, cxt->ftrace_max_cnt);

out:
        if (unlikely(ret))
                pr_err("recover failed\n");
        else {
                pr_debug("recover end!\n");
                atomic_set(&cxt->recovered, 1);
        }
        return ret;
}

static int psz_pstore_open(struct pstore_info *psi)
{
        struct psz_context *cxt = psi->data;

        cxt->kmsg_read_cnt = 0;
        cxt->pmsg_read_cnt = 0;
        cxt->console_read_cnt = 0;
        cxt->ftrace_read_cnt = 0;
        return 0;
}

static inline bool psz_old_ok(struct pstore_zone *zone)
{
        if (zone && zone->oldbuf && atomic_read(&zone->oldbuf->datalen))
                return true;
        return false;
}

static inline bool psz_ok(struct pstore_zone *zone)
{
        if (zone && zone->buffer && buffer_datalen(zone))
                return true;
        return false;
}

static inline int psz_kmsg_erase(struct psz_context *cxt,
                struct pstore_zone *zone, struct pstore_record *record)
{
        struct psz_buffer *buffer = zone->buffer;
        struct psz_kmsg_header *hdr =
                (struct psz_kmsg_header *)buffer->data;
        size_t size;

        if (unlikely(!psz_ok(zone)))
                return 0;

        /* this zone is already updated, no need to erase */
        if (record->count != hdr->counter)
                return 0;

        size = buffer_datalen(zone) + sizeof(*zone->buffer);
        atomic_set(&zone->buffer->datalen, 0);
        if (cxt->pstore_zone_info->erase)
                return cxt->pstore_zone_info->erase(size, zone->off);
        else
                return psz_zone_write(zone, FLUSH_META, NULL, 0, 0);
}

static inline int psz_record_erase(struct psz_context *cxt,
                struct pstore_zone *zone)
{
        if (unlikely(!psz_old_ok(zone)))
                return 0;

        kfree(zone->oldbuf);
        zone->oldbuf = NULL;
        /*
         * if there are new data in zone buffer, that means the old data
         * are already invalid. It is no need to flush 0 (erase) to
         * block device.
         */
        if (!buffer_datalen(zone))
                return psz_zone_write(zone, FLUSH_META, NULL, 0, 0);
        psz_flush_dirty_zone(zone);
        return 0;
}

static int psz_pstore_erase(struct pstore_record *record)
{
        struct psz_context *cxt = record->psi->data;

        switch (record->type) {
        case PSTORE_TYPE_DMESG:
                if (record->id >= cxt->kmsg_max_cnt)
                        return -EINVAL;
                return psz_kmsg_erase(cxt, cxt->kpszs[record->id], record);
        case PSTORE_TYPE_PMSG:
                return psz_record_erase(cxt, cxt->ppsz);
        case PSTORE_TYPE_CONSOLE:
                return psz_record_erase(cxt, cxt->cpsz);
        case PSTORE_TYPE_FTRACE:
                if (record->id >= cxt->ftrace_max_cnt)
                        return -EINVAL;
                return psz_record_erase(cxt, cxt->fpszs[record->id]);
        default: return -EINVAL;
        }
}

static void psz_write_kmsg_hdr(struct pstore_zone *zone,
                struct pstore_record *record)
{
        struct psz_context *cxt = record->psi->data;
        struct psz_buffer *buffer = zone->buffer;
        struct psz_kmsg_header *hdr =
                (struct psz_kmsg_header *)buffer->data;

        hdr->magic = PSTORE_KMSG_HEADER_MAGIC;
        hdr->compressed = record->compressed;
        hdr->time.tv_sec = record->time.tv_sec;
        hdr->time.tv_nsec = record->time.tv_nsec;
        hdr->reason = record->reason;
        if (hdr->reason == KMSG_DUMP_OOPS)
                hdr->counter = ++cxt->oops_counter;
        else if (hdr->reason == KMSG_DUMP_PANIC)
                hdr->counter = ++cxt->panic_counter;
        else
                hdr->counter = 0;
}

/*
 * In case zone is broken, which may occur to MTD device, we try each zones,
 * start at cxt->kmsg_write_cnt.
 */
static inline int notrace psz_kmsg_write_record(struct psz_context *cxt,
                struct pstore_record *record)
{
        size_t size, hlen;
        struct pstore_zone *zone;
        unsigned int i;

        for (i = 0; i < cxt->kmsg_max_cnt; i++) {
                unsigned int zonenum, len;
                int ret;

                zonenum = (cxt->kmsg_write_cnt + i) % cxt->kmsg_max_cnt;
                zone = cxt->kpszs[zonenum];
                if (unlikely(!zone))
                        return -ENOSPC;

                /* avoid destroying old data, allocate a new one */
                len = zone->buffer_size + sizeof(*zone->buffer);
                zone->oldbuf = zone->buffer;
                zone->buffer = kzalloc(len, GFP_ATOMIC);
                if (!zone->buffer) {
                        zone->buffer = zone->oldbuf;
                        return -ENOMEM;
                }
                zone->buffer->sig = zone->oldbuf->sig;

                pr_debug("write %s to zone id %d\n", zone->name, zonenum);
                psz_write_kmsg_hdr(zone, record);
                hlen = sizeof(struct psz_kmsg_header);
                size = min_t(size_t, record->size, zone->buffer_size - hlen);
                ret = psz_zone_write(zone, FLUSH_ALL, record->buf, size, hlen);
                if (likely(!ret || ret != -ENOMSG)) {
                        cxt->kmsg_write_cnt = zonenum + 1;
                        cxt->kmsg_write_cnt %= cxt->kmsg_max_cnt;
                        /* no need to try next zone, free last zone buffer */
                        kfree(zone->oldbuf);
                        zone->oldbuf = NULL;
                        return ret;
                }

                pr_debug("zone %u may be broken, try next dmesg zone\n",
                                zonenum);
                kfree(zone->buffer);
                zone->buffer = zone->oldbuf;
                zone->oldbuf = NULL;
        }

        return -EBUSY;
}

static int notrace psz_kmsg_write(struct psz_context *cxt,
                struct pstore_record *record)
{
        int ret;

        /*
         * Explicitly only take the first part of any new crash.
         * If our buffer is larger than kmsg_bytes, this can never happen,
         * and if our buffer is smaller than kmsg_bytes, we don't want the
         * report split across multiple records.
         */
        if (record->part != 1)
                return -ENOSPC;

        if (!cxt->kpszs)
                return -ENOSPC;

        ret = psz_kmsg_write_record(cxt, record);
        if (!ret && is_on_panic()) {
                /* ensure all data are flushed to storage when panic */
                pr_debug("try to flush other dirty zones\n");
                psz_flush_all_dirty_zones(NULL);
        }

        /* always return 0 as we had handled it on buffer */
        return 0;
}

static int notrace psz_record_write(struct pstore_zone *zone,
                struct pstore_record *record)
{
        size_t start, rem;
        bool is_full_data = false;
        char *buf;
        int cnt;

        if (!zone || !record)
                return -ENOSPC;

        if (atomic_read(&zone->buffer->datalen) >= zone->buffer_size)
                is_full_data = true;

        cnt = record->size;
        buf = record->buf;
        if (unlikely(cnt > zone->buffer_size)) {
                buf += cnt - zone->buffer_size;
                cnt = zone->buffer_size;
        }

        start = buffer_start(zone);
        rem = zone->buffer_size - start;
        if (unlikely(rem < cnt)) {
                psz_zone_write(zone, FLUSH_PART, buf, rem, start);
                buf += rem;
                cnt -= rem;
                start = 0;
                is_full_data = true;
        }

        atomic_set(&zone->buffer->start, cnt + start);
        psz_zone_write(zone, FLUSH_PART, buf, cnt, start);

        /**
         * psz_zone_write will set datalen as start + cnt.
         * It works if actual data length is lesser than buffer size.
         * If data length is greater than buffer size, pmsg will rewrite to
         * the beginning of the zone, which makes buffer->datalen wrong.
         * So we should reset datalen as buffer size once actual data length
         * is greater than buffer size.
         */
        if (is_full_data) {
                atomic_set(&zone->buffer->datalen, zone->buffer_size);
                psz_zone_write(zone, FLUSH_META, NULL, 0, 0);
        }
        return 0;
}

static int notrace psz_pstore_write(struct pstore_record *record)
{
        struct psz_context *cxt = record->psi->data;

        if (record->type == PSTORE_TYPE_DMESG &&
                        record->reason == KMSG_DUMP_PANIC)
                atomic_set(&cxt->on_panic, 1);

        /*
         * If on panic, do not write anything except panic records.
         * Fix the case when panic_write prints log that wakes up
         * console backend.
         */
        if (is_on_panic() && record->type != PSTORE_TYPE_DMESG)
                return -EBUSY;

        switch (record->type) {
        case PSTORE_TYPE_DMESG:
                return psz_kmsg_write(cxt, record);
        case PSTORE_TYPE_CONSOLE:
                return psz_record_write(cxt->cpsz, record);
        case PSTORE_TYPE_PMSG:
                return psz_record_write(cxt->ppsz, record);
        case PSTORE_TYPE_FTRACE: {
                int zonenum = smp_processor_id();

                if (!cxt->fpszs)
                        return -ENOSPC;
                return psz_record_write(cxt->fpszs[zonenum], record);
        }
        default:
                return -EINVAL;
        }
}

static struct pstore_zone *psz_read_next_zone(struct psz_context *cxt)
{
        struct pstore_zone *zone = NULL;

        while (cxt->kmsg_read_cnt < cxt->kmsg_max_cnt) {
                zone = cxt->kpszs[cxt->kmsg_read_cnt++];
                if (psz_ok(zone))
                        return zone;
        }

        if (cxt->ftrace_read_cnt < cxt->ftrace_max_cnt)
                /*
                 * No need psz_old_ok(). Let psz_ftrace_read() do so for
                 * combination. psz_ftrace_read() should traverse over
                 * all zones in case of some zone without data.
                 */
                return cxt->fpszs[cxt->ftrace_read_cnt++];

        if (cxt->pmsg_read_cnt == 0) {
                cxt->pmsg_read_cnt++;
                zone = cxt->ppsz;
                if (psz_old_ok(zone))
                        return zone;
        }

        if (cxt->console_read_cnt == 0) {
                cxt->console_read_cnt++;
                zone = cxt->cpsz;
                if (psz_old_ok(zone))
                        return zone;
        }

        return NULL;
}

static int psz_kmsg_read_hdr(struct pstore_zone *zone,
                struct pstore_record *record)
{
        struct psz_buffer *buffer = zone->buffer;
        struct psz_kmsg_header *hdr =
                (struct psz_kmsg_header *)buffer->data;

        if (hdr->magic != PSTORE_KMSG_HEADER_MAGIC)
                return -EINVAL;
        record->compressed = hdr->compressed;
        record->time.tv_sec = hdr->time.tv_sec;
        record->time.tv_nsec = hdr->time.tv_nsec;
        record->reason = hdr->reason;
        record->count = hdr->counter;
        return 0;
}

static ssize_t psz_kmsg_read(struct pstore_zone *zone,
                struct pstore_record *record)
{
        ssize_t size, hlen = 0;

        size = buffer_datalen(zone);
        /* Clear and skip this kmsg dump record if it has no valid header */
        if (psz_kmsg_read_hdr(zone, record)) {
                atomic_set(&zone->buffer->datalen, 0);
                atomic_set(&zone->dirty, 0);
                return -ENOMSG;
        }
        size -= sizeof(struct psz_kmsg_header);

        if (!record->compressed) {
                char *buf = kasprintf(GFP_KERNEL, "%s: Total %d times\n",
                                      kmsg_dump_reason_str(record->reason),
                                      record->count);
                if (!buf)
                        return -ENOMEM;
                hlen = strlen(buf);
                record->buf = krealloc(buf, hlen + size, GFP_KERNEL);
                if (!record->buf) {
                        kfree(buf);
                        return -ENOMEM;
                }
        } else {
                record->buf = kmalloc(size, GFP_KERNEL);
                if (!record->buf)
                        return -ENOMEM;
        }

        size = psz_zone_read_buffer(zone, record->buf + hlen, size,
                        sizeof(struct psz_kmsg_header));
        if (unlikely(size < 0)) {
                kfree(record->buf);
                return -ENOMSG;
        }

        return size + hlen;
}

/* try to combine all ftrace zones */
static ssize_t psz_ftrace_read(struct pstore_zone *zone,
                struct pstore_record *record)
{
        struct psz_context *cxt;
        struct psz_buffer *buf;
        int ret;

        if (!zone || !record)
                return -ENOSPC;

        if (!psz_old_ok(zone))
                goto out;

        buf = (struct psz_buffer *)zone->oldbuf;
        if (!buf)
                return -ENOMSG;

        ret = pstore_ftrace_combine_log(&record->buf, &record->size,
                        (char *)buf->data, atomic_read(&buf->datalen));
        if (unlikely(ret))
                return ret;

out:
        cxt = record->psi->data;
        if (cxt->ftrace_read_cnt < cxt->ftrace_max_cnt)
                /* then, read next ftrace zone */
                return -ENOMSG;
        record->id = 0;
        return record->size ? record->size : -ENOMSG;
}

static ssize_t psz_record_read(struct pstore_zone *zone,
                struct pstore_record *record)
{
        size_t len;
        struct psz_buffer *buf;

        if (!zone || !record)
                return -ENOSPC;

        buf = (struct psz_buffer *)zone->oldbuf;
        if (!buf)
                return -ENOMSG;

        len = atomic_read(&buf->datalen);
        record->buf = kmalloc(len, GFP_KERNEL);
        if (!record->buf)
                return -ENOMEM;

        if (unlikely(psz_zone_read_oldbuf(zone, record->buf, len, 0))) {
                kfree(record->buf);
                return -ENOMSG;
        }

        return len;
}

static ssize_t psz_pstore_read(struct pstore_record *record)
{
        struct psz_context *cxt = record->psi->data;
        ssize_t (*readop)(struct pstore_zone *zone,
                        struct pstore_record *record);
        struct pstore_zone *zone;
        ssize_t ret;

        /* before read, we must recover from storage */
        ret = psz_recovery(cxt);
        if (ret)
                return ret;

next_zone:
        zone = psz_read_next_zone(cxt);
        if (!zone)
                return 0;

        record->type = zone->type;
        switch (record->type) {
        case PSTORE_TYPE_DMESG:
                readop = psz_kmsg_read;
                record->id = cxt->kmsg_read_cnt - 1;
                break;
        case PSTORE_TYPE_FTRACE:
                readop = psz_ftrace_read;
                break;
        case PSTORE_TYPE_CONSOLE:
        case PSTORE_TYPE_PMSG:
                readop = psz_record_read;
                break;
        default:
                goto next_zone;
        }

        ret = readop(zone, record);
        if (ret == -ENOMSG)
                goto next_zone;
        return ret;
}

static struct psz_context pstore_zone_cxt = {
        .pstore_zone_info_lock =
                __MUTEX_INITIALIZER(pstore_zone_cxt.pstore_zone_info_lock),
        .recovered = ATOMIC_INIT(0),
        .on_panic = ATOMIC_INIT(0),
        .pstore = {
                .owner = THIS_MODULE,
                .open = psz_pstore_open,
                .read = psz_pstore_read,
                .write = psz_pstore_write,
                .erase = psz_pstore_erase,
        },
};

static void psz_free_zone(struct pstore_zone **pszone)
{
        struct pstore_zone *zone = *pszone;

        if (!zone)
                return;

        kfree(zone->buffer);
        kfree(zone);
        *pszone = NULL;
}

static void psz_free_zones(struct pstore_zone ***pszones, unsigned int *cnt)
{
        struct pstore_zone **zones = *pszones;

        if (!zones)
                return;

        while (*cnt > 0) {
                (*cnt)--;
                psz_free_zone(&(zones[*cnt]));
        }
        kfree(zones);
        *pszones = NULL;
}

static void psz_free_all_zones(struct psz_context *cxt)
{
        if (cxt->kpszs)
                psz_free_zones(&cxt->kpszs, &cxt->kmsg_max_cnt);
        if (cxt->ppsz)
                psz_free_zone(&cxt->ppsz);
        if (cxt->cpsz)
                psz_free_zone(&cxt->cpsz);
        if (cxt->fpszs)
                psz_free_zones(&cxt->fpszs, &cxt->ftrace_max_cnt);
}

static struct pstore_zone *psz_init_zone(enum pstore_type_id type,
                loff_t *off, size_t size)
{
        struct pstore_zone_info *info = pstore_zone_cxt.pstore_zone_info;
        struct pstore_zone *zone;
        const char *name = pstore_type_to_name(type);

        if (!size)
                return NULL;

        if (*off + size > info->total_size) {
                pr_err("no room for %s (0x%zx@0x%llx over 0x%lx)\n",
                        name, size, *off, info->total_size);
                return ERR_PTR(-ENOMEM);
        }

        zone = kzalloc_obj(struct pstore_zone);
        if (!zone)
                return ERR_PTR(-ENOMEM);

        zone->buffer = kmalloc(size, GFP_KERNEL);
        if (!zone->buffer) {
                kfree(zone);
                return ERR_PTR(-ENOMEM);
        }
        memset(zone->buffer, 0xFF, size);
        zone->off = *off;
        zone->name = name;
        zone->type = type;
        zone->buffer_size = size - sizeof(struct psz_buffer);
        zone->buffer->sig = type ^ PSZ_SIG;
        zone->oldbuf = NULL;
        atomic_set(&zone->dirty, 0);
        atomic_set(&zone->buffer->datalen, 0);
        atomic_set(&zone->buffer->start, 0);

        *off += size;

        pr_debug("pszone %s: off 0x%llx, %zu header, %zu data\n", zone->name,
                        zone->off, sizeof(*zone->buffer), zone->buffer_size);
        return zone;
}

static struct pstore_zone **psz_init_zones(enum pstore_type_id type,
        loff_t *off, size_t total_size, ssize_t record_size,
        unsigned int *cnt)
{
        struct pstore_zone_info *info = pstore_zone_cxt.pstore_zone_info;
        struct pstore_zone **zones, *zone;
        const char *name = pstore_type_to_name(type);
        int c, i;

        *cnt = 0;
        if (!total_size || !record_size)
                return NULL;

        if (*off + total_size > info->total_size) {
                pr_err("no room for zones %s (0x%zx@0x%llx over 0x%lx)\n",
                        name, total_size, *off, info->total_size);
                return ERR_PTR(-ENOMEM);
        }

        c = total_size / record_size;
        if (unlikely(!c)) {
                pr_err("zone %s total_size too small\n", name);
                return ERR_PTR(-EINVAL);
        }

        zones = kzalloc_objs(*zones, c);
        if (!zones) {
                pr_err("allocate for zones %s failed\n", name);
                return ERR_PTR(-ENOMEM);
        }

        for (i = 0; i < c; i++) {
                zone = psz_init_zone(type, off, record_size);
                if (!zone || IS_ERR(zone)) {
                        pr_err("initialize zones %s failed\n", name);
                        psz_free_zones(&zones, &i);
                        return (void *)zone;
                }
                zones[i] = zone;
        }

        *cnt = c;
        return zones;
}

static int psz_alloc_zones(struct psz_context *cxt)
{
        struct pstore_zone_info *info = cxt->pstore_zone_info;
        loff_t off = 0;
        int err;
        size_t off_size = 0;

        off_size += info->pmsg_size;
        cxt->ppsz = psz_init_zone(PSTORE_TYPE_PMSG, &off, info->pmsg_size);
        if (IS_ERR(cxt->ppsz)) {
                err = PTR_ERR(cxt->ppsz);
                cxt->ppsz = NULL;
                goto free_out;
        }

        off_size += info->console_size;
        cxt->cpsz = psz_init_zone(PSTORE_TYPE_CONSOLE, &off,
                        info->console_size);
        if (IS_ERR(cxt->cpsz)) {
                err = PTR_ERR(cxt->cpsz);
                cxt->cpsz = NULL;
                goto free_out;
        }

        off_size += info->ftrace_size;
        cxt->fpszs = psz_init_zones(PSTORE_TYPE_FTRACE, &off,
                        info->ftrace_size,
                        info->ftrace_size / nr_cpu_ids,
                        &cxt->ftrace_max_cnt);
        if (IS_ERR(cxt->fpszs)) {
                err = PTR_ERR(cxt->fpszs);
                cxt->fpszs = NULL;
                goto free_out;
        }

        cxt->kpszs = psz_init_zones(PSTORE_TYPE_DMESG, &off,
                        info->total_size - off_size,
                        info->kmsg_size, &cxt->kmsg_max_cnt);
        if (IS_ERR(cxt->kpszs)) {
                err = PTR_ERR(cxt->kpszs);
                cxt->kpszs = NULL;
                goto free_out;
        }

        return 0;
free_out:
        psz_free_all_zones(cxt);
        return err;
}

/**
 * register_pstore_zone() - register to pstore/zone
 *
 * @info: back-end driver information. See &struct pstore_zone_info.
 *
 * Only one back-end at one time.
 *
 * Return: 0 on success, others on failure.
 */
int register_pstore_zone(struct pstore_zone_info *info)
{
        int err = -EINVAL;
        struct psz_context *cxt = &pstore_zone_cxt;

        if (info->total_size < 4096) {
                pr_warn("total_size must be >= 4096\n");
                return -EINVAL;
        }
        if (info->total_size > SZ_128M) {
                pr_warn("capping size to 128MiB\n");
                info->total_size = SZ_128M;
        }

        if (!info->kmsg_size && !info->pmsg_size && !info->console_size &&
            !info->ftrace_size) {
                pr_warn("at least one record size must be non-zero\n");
                return -EINVAL;
        }

        if (!info->name || !info->name[0])
                return -EINVAL;

#define check_size(name, size) {                                        \
                if (info->name > 0 && info->name < (size)) {            \
                        pr_err(#name " must be over %d\n", (size));     \
                        return -EINVAL;                                 \
                }                                                       \
                if (info->name & (size - 1)) {                          \
                        pr_err(#name " must be a multiple of %d\n",     \
                                        (size));                        \
                        return -EINVAL;                                 \
                }                                                       \
        }

        check_size(total_size, 4096);
        check_size(kmsg_size, SECTOR_SIZE);
        check_size(pmsg_size, SECTOR_SIZE);
        check_size(console_size, SECTOR_SIZE);
        check_size(ftrace_size, SECTOR_SIZE);

#undef check_size

        /*
         * the @read and @write must be applied.
         * if no @read, pstore may mount failed.
         * if no @write, pstore do not support to remove record file.
         */
        if (!info->read || !info->write) {
                pr_err("no valid general read/write interface\n");
                return -EINVAL;
        }

        mutex_lock(&cxt->pstore_zone_info_lock);
        if (cxt->pstore_zone_info) {
                pr_warn("'%s' already loaded: ignoring '%s'\n",
                                cxt->pstore_zone_info->name, info->name);
                mutex_unlock(&cxt->pstore_zone_info_lock);
                return -EBUSY;
        }
        cxt->pstore_zone_info = info;

        pr_debug("register %s with properties:\n", info->name);
        pr_debug("\ttotal size : %ld Bytes\n", info->total_size);
        pr_debug("\tkmsg size : %ld Bytes\n", info->kmsg_size);
        pr_debug("\tpmsg size : %ld Bytes\n", info->pmsg_size);
        pr_debug("\tconsole size : %ld Bytes\n", info->console_size);
        pr_debug("\tftrace size : %ld Bytes\n", info->ftrace_size);

        err = psz_alloc_zones(cxt);
        if (err) {
                pr_err("alloc zones failed\n");
                goto fail_out;
        }

        if (info->kmsg_size) {
                cxt->pstore.bufsize = cxt->kpszs[0]->buffer_size -
                        sizeof(struct psz_kmsg_header);
                cxt->pstore.buf = kzalloc(cxt->pstore.bufsize, GFP_KERNEL);
                if (!cxt->pstore.buf) {
                        err = -ENOMEM;
                        goto fail_free;
                }
        }
        cxt->pstore.data = cxt;

        pr_info("registered %s as backend for", info->name);
        cxt->pstore.max_reason = info->max_reason;
        cxt->pstore.name = info->name;
        if (info->kmsg_size) {
                cxt->pstore.flags |= PSTORE_FLAGS_DMESG;
                pr_cont(" kmsg(%s",
                        kmsg_dump_reason_str(cxt->pstore.max_reason));
                if (cxt->pstore_zone_info->panic_write)
                        pr_cont(",panic_write");
                pr_cont(")");
        }
        if (info->pmsg_size) {
                cxt->pstore.flags |= PSTORE_FLAGS_PMSG;
                pr_cont(" pmsg");
        }
        if (info->console_size) {
                cxt->pstore.flags |= PSTORE_FLAGS_CONSOLE;
                pr_cont(" console");
        }
        if (info->ftrace_size) {
                cxt->pstore.flags |= PSTORE_FLAGS_FTRACE;
                pr_cont(" ftrace");
        }
        pr_cont("\n");

        err = pstore_register(&cxt->pstore);
        if (err) {
                pr_err("registering with pstore failed\n");
                goto fail_free;
        }
        mutex_unlock(&pstore_zone_cxt.pstore_zone_info_lock);

        return 0;

fail_free:
        kfree(cxt->pstore.buf);
        cxt->pstore.buf = NULL;
        cxt->pstore.bufsize = 0;
        psz_free_all_zones(cxt);
fail_out:
        pstore_zone_cxt.pstore_zone_info = NULL;
        mutex_unlock(&pstore_zone_cxt.pstore_zone_info_lock);
        return err;
}
EXPORT_SYMBOL_GPL(register_pstore_zone);

/**
 * unregister_pstore_zone() - unregister to pstore/zone
 *
 * @info: back-end driver information. See struct pstore_zone_info.
 */
void unregister_pstore_zone(struct pstore_zone_info *info)
{
        struct psz_context *cxt = &pstore_zone_cxt;

        mutex_lock(&cxt->pstore_zone_info_lock);
        if (!cxt->pstore_zone_info) {
                mutex_unlock(&cxt->pstore_zone_info_lock);
                return;
        }

        /* Stop incoming writes from pstore. */
        pstore_unregister(&cxt->pstore);

        /* Flush any pending writes. */
        psz_flush_all_dirty_zones(NULL);
        flush_delayed_work(&psz_cleaner);

        /* Clean up allocations. */
        kfree(cxt->pstore.buf);
        cxt->pstore.buf = NULL;
        cxt->pstore.bufsize = 0;
        cxt->pstore_zone_info = NULL;

        psz_free_all_zones(cxt);

        /* Clear counters and zone state. */
        cxt->oops_counter = 0;
        cxt->panic_counter = 0;
        atomic_set(&cxt->recovered, 0);
        atomic_set(&cxt->on_panic, 0);

        mutex_unlock(&cxt->pstore_zone_info_lock);
}
EXPORT_SYMBOL_GPL(unregister_pstore_zone);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("WeiXiong Liao <liaoweixiong@allwinnertech.com>");
MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
MODULE_DESCRIPTION("Storage Manager for pstore/blk");