/*
 * Persistent Storage - platform driver interface parts.
 *
 * Copyright (C) 2007-2008 Google, Inc.
 * Copyright (C) 2010 Intel Corporation <tony.luck@intel.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/atomic.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kmsg_dump.h>
#include <linux/console.h>
#include <linux/module.h>
#include <linux/pstore.h>
#include <linux/string.h>
#include <linux/timer.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/hardirq.h>
#include <linux/jiffies.h>
#include <linux/workqueue.h>

#include "internal.h"

/*
 * We defer making "oops" entries appear in pstore - see
 * whether the system is actually still running well enough
 * to let someone see the entry
 */
static int pstore_update_ms = -1;
module_param_named(update_ms, pstore_update_ms, int, 0600);
MODULE_PARM_DESC(update_ms, "milliseconds before pstore updates its content "
                 "(default is -1, which means runtime updates are disabled; "
                 "enabling this option is not safe, it may lead to further "
                 "corruption on Oopses)");

static int pstore_new_entry;

static void pstore_timefunc(unsigned long);
static DEFINE_TIMER(pstore_timer, pstore_timefunc, 0, 0);

static void pstore_dowork(struct work_struct *);
static DECLARE_WORK(pstore_work, pstore_dowork);

/*
 * pstore_lock just protects "psinfo" during
 * calls to pstore_register()
 */
static DEFINE_SPINLOCK(pstore_lock);
struct pstore_info *psinfo;

static char *backend;

/* How much of the console log to snapshot */
static unsigned long kmsg_bytes = 10240;

void pstore_set_kmsg_bytes(int bytes)
{
        kmsg_bytes = bytes;
}

/* Tag each group of saved records with a sequence number */
static int      oopscount;

static const char *get_reason_str(enum kmsg_dump_reason reason)
{
        switch (reason) {
        case KMSG_DUMP_PANIC:
                return "Panic";
        case KMSG_DUMP_OOPS:
                return "Oops";
        case KMSG_DUMP_EMERG:
                return "Emergency";
        case KMSG_DUMP_RESTART:
                return "Restart";
        case KMSG_DUMP_HALT:
                return "Halt";
        case KMSG_DUMP_POWEROFF:
                return "Poweroff";
        default:
                return "Unknown";
        }
}

bool pstore_cannot_block_path(enum kmsg_dump_reason reason)
{
        /*
         * In case of NMI path, pstore shouldn't be blocked
         * regardless of reason.
         */
        if (in_nmi())
                return true;

        switch (reason) {
        /* In panic case, other cpus are stopped by smp_send_stop(). */
        case KMSG_DUMP_PANIC:
        /* Emergency restart shouldn't be blocked by spin lock. */
        case KMSG_DUMP_EMERG:
                return true;
        default:
                return false;
        }
}
EXPORT_SYMBOL_GPL(pstore_cannot_block_path);

/*
 * callback from kmsg_dump. (s2,l2) has the most recently
 * written bytes, older bytes are in (s1,l1). Save as much
 * as we can from the end of the buffer.
 */
static void pstore_dump(struct kmsg_dumper *dumper,
                        enum kmsg_dump_reason reason)
{
        unsigned long   total = 0;
        const char      *why;
        u64             id;
        unsigned int    part = 1;
        unsigned long   flags = 0;
        int             is_locked = 0;
        int             ret;

        why = get_reason_str(reason);

        if (pstore_cannot_block_path(reason)) {
                is_locked = spin_trylock_irqsave(&psinfo->buf_lock, flags);
                if (!is_locked) {
                        pr_err("pstore dump routine blocked in %s path, may corrupt error record\n"
                                       , in_nmi() ? "NMI" : why);
                }
        } else
                spin_lock_irqsave(&psinfo->buf_lock, flags);
        oopscount++;
        while (total < kmsg_bytes) {
                char *dst;
                unsigned long size;
                int hsize;
                size_t len;

                dst = psinfo->buf;
                hsize = sprintf(dst, "%s#%d Part%d\n", why, oopscount, part);
                size = psinfo->bufsize - hsize;
                dst += hsize;

                if (!kmsg_dump_get_buffer(dumper, true, dst, size, &len))
                        break;

                ret = psinfo->write(PSTORE_TYPE_DMESG, reason, &id, part,
                                    oopscount, hsize, hsize + len, psinfo);
                if (ret == 0 && reason == KMSG_DUMP_OOPS && pstore_is_mounted())
                        pstore_new_entry = 1;

                total += hsize + len;
                part++;
        }
        if (pstore_cannot_block_path(reason)) {
                if (is_locked)
                        spin_unlock_irqrestore(&psinfo->buf_lock, flags);
        } else
                spin_unlock_irqrestore(&psinfo->buf_lock, flags);
}

static struct kmsg_dumper pstore_dumper = {
        .dump = pstore_dump,
};

#ifdef CONFIG_PSTORE_CONSOLE
static void pstore_console_write(struct console *con, const char *s, unsigned c)
{
        const char *e = s + c;

        while (s < e) {
                unsigned long flags;
                u64 id;

                if (c > psinfo->bufsize)
                        c = psinfo->bufsize;

                if (oops_in_progress) {
                        if (!spin_trylock_irqsave(&psinfo->buf_lock, flags))
                                break;
                } else {
                        spin_lock_irqsave(&psinfo->buf_lock, flags);
                }
                memcpy(psinfo->buf, s, c);
                psinfo->write(PSTORE_TYPE_CONSOLE, 0, &id, 0, 0, 0, c, psinfo);
                spin_unlock_irqrestore(&psinfo->buf_lock, flags);
                s += c;
                c = e - s;
        }
}

static struct console pstore_console = {
        .name   = "pstore",
        .write  = pstore_console_write,
        .flags  = CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME,
        .index  = -1,
};

static void pstore_register_console(void)
{
        register_console(&pstore_console);
}
#else
static void pstore_register_console(void) {}
#endif

static int pstore_write_compat(enum pstore_type_id type,
                               enum kmsg_dump_reason reason,
                               u64 *id, unsigned int part, int count,
                               size_t hsize, size_t size,
                               struct pstore_info *psi)
{
        return psi->write_buf(type, reason, id, part, psinfo->buf, hsize,
                             size, psi);
}

/*
 * platform specific persistent storage driver registers with
 * us here. If pstore is already mounted, call the platform
 * read function right away to populate the file system. If not
 * then the pstore mount code will call us later to fill out
 * the file system.
 *
 * Register with kmsg_dump to save last part of console log on panic.
 */
int pstore_register(struct pstore_info *psi)
{
        struct module *owner = psi->owner;

        if (backend && strcmp(backend, psi->name))
                return -EPERM;

        spin_lock(&pstore_lock);
        if (psinfo) {
                spin_unlock(&pstore_lock);
                return -EBUSY;
        }

        if (!psi->write)
                psi->write = pstore_write_compat;
        psinfo = psi;
        mutex_init(&psinfo->read_mutex);
        spin_unlock(&pstore_lock);

        if (owner && !try_module_get(owner)) {
                psinfo = NULL;
                return -EINVAL;
        }

        if (pstore_is_mounted())
                pstore_get_records(0);

        kmsg_dump_register(&pstore_dumper);
        pstore_register_console();
        pstore_register_ftrace();

        if (pstore_update_ms >= 0) {
                pstore_timer.expires = jiffies +
                        msecs_to_jiffies(pstore_update_ms);
                add_timer(&pstore_timer);
        }

        pr_info("pstore: Registered %s as persistent store backend\n",
                psi->name);

        return 0;
}
EXPORT_SYMBOL_GPL(pstore_register);

/*
 * Read all the records from the persistent store. Create
 * files in our filesystem.  Don't warn about -EEXIST errors
 * when we are re-scanning the backing store looking to add new
 * error records.
 */
void pstore_get_records(int quiet)
{
        struct pstore_info *psi = psinfo;
        char                    *buf = NULL;
        ssize_t                 size;
        u64                     id;
        int                     count;
        enum pstore_type_id     type;
        struct timespec         time;
        int                     failed = 0, rc;

        if (!psi)
                return;

        mutex_lock(&psi->read_mutex);
        if (psi->open && psi->open(psi))
                goto out;

        while ((size = psi->read(&id, &type, &count, &time, &buf, psi)) > 0) {
                rc = pstore_mkfile(type, psi->name, id, count, buf,
                                  (size_t)size, time, psi);
                kfree(buf);
                buf = NULL;
                if (rc && (rc != -EEXIST || !quiet))
                        failed++;
        }
        if (psi->close)
                psi->close(psi);
out:
        mutex_unlock(&psi->read_mutex);

        if (failed)
                printk(KERN_WARNING "pstore: failed to load %d record(s) from '%s'\n",
                       failed, psi->name);
}

static void pstore_dowork(struct work_struct *work)
{
        pstore_get_records(1);
}

static void pstore_timefunc(unsigned long dummy)
{
        if (pstore_new_entry) {
                pstore_new_entry = 0;
                schedule_work(&pstore_work);
        }

        mod_timer(&pstore_timer, jiffies + msecs_to_jiffies(pstore_update_ms));
}

module_param(backend, charp, 0444);
MODULE_PARM_DESC(backend, "Pstore backend to use");