// SPDX-License-Identifier: GPL-2.0-only
/*
 * Persistent Storage - platform driver interface parts.
 *
 * Copyright (C) 2007-2008 Google, Inc.
 * Copyright (C) 2010 Intel Corporation <tony.luck@intel.com>
 */

#define pr_fmt(fmt) "pstore: " fmt

#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>
#if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
#include <linux/lzo.h>
#endif
#if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS) || IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
#include <linux/lz4.h>
#endif
#if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
#include <linux/zstd.h>
#endif
#include <linux/crypto.h>
#include <linux/string.h>
#include <linux/timer.h>
#include <linux/slab.h>
#include <linux/uaccess.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 may not be safe; it may lead to further "
                 "corruption on Oopses)");

/* Names should be in the same order as the enum pstore_type_id */
static const char * const pstore_type_names[] = {
        "dmesg",
        "mce",
        "console",
        "ftrace",
        "rtas",
        "powerpc-ofw",
        "powerpc-common",
        "pmsg",
        "powerpc-opal",
};

static int pstore_new_entry;

static void pstore_timefunc(struct timer_list *);
static DEFINE_TIMER(pstore_timer, pstore_timefunc);

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

/*
 * psinfo_lock protects "psinfo" during calls to
 * pstore_register(), pstore_unregister(), and
 * the filesystem mount/unmount routines.
 */
static DEFINE_MUTEX(psinfo_lock);
struct pstore_info *psinfo;

static char *backend;
module_param(backend, charp, 0444);
MODULE_PARM_DESC(backend, "specific backend to use");

static char *compress =
#ifdef CONFIG_PSTORE_COMPRESS_DEFAULT
                CONFIG_PSTORE_COMPRESS_DEFAULT;
#else
                NULL;
#endif
module_param(compress, charp, 0444);
MODULE_PARM_DESC(compress, "compression to use");

/* Compression parameters */
static struct crypto_comp *tfm;

struct pstore_zbackend {
        int (*zbufsize)(size_t size);
        const char *name;
};

static char *big_oops_buf;
static size_t big_oops_buf_sz;

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

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

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

const char *pstore_type_to_name(enum pstore_type_id type)
{
        BUILD_BUG_ON(ARRAY_SIZE(pstore_type_names) != PSTORE_TYPE_MAX);

        if (WARN_ON_ONCE(type >= PSTORE_TYPE_MAX))
                return "unknown";

        return pstore_type_names[type];
}
EXPORT_SYMBOL_GPL(pstore_type_to_name);

enum pstore_type_id pstore_name_to_type(const char *name)
{
        int i;

        for (i = 0; i < PSTORE_TYPE_MAX; i++) {
                if (!strcmp(pstore_type_names[i], name))
                        return i;
        }

        return PSTORE_TYPE_MAX;
}
EXPORT_SYMBOL_GPL(pstore_name_to_type);

static void pstore_timer_kick(void)
{
        if (pstore_update_ms < 0)
                return;

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

/*
 * Should pstore_dump() wait for a concurrent pstore_dump()? If
 * not, the current pstore_dump() will report a failure to dump
 * and return.
 */
static bool pstore_cannot_wait(enum kmsg_dump_reason reason)
{
        /* In NMI path, pstore shouldn't block 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. */
        case KMSG_DUMP_EMERG:
                return true;
        default:
                return false;
        }
}

#if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)
static int zbufsize_deflate(size_t size)
{
        size_t cmpr;

        switch (size) {
        /* buffer range for efivars */
        case 1000 ... 2000:
                cmpr = 56;
                break;
        case 2001 ... 3000:
                cmpr = 54;
                break;
        case 3001 ... 3999:
                cmpr = 52;
                break;
        /* buffer range for nvram, erst */
        case 4000 ... 10000:
                cmpr = 45;
                break;
        default:
                cmpr = 60;
                break;
        }

        return (size * 100) / cmpr;
}
#endif

#if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
static int zbufsize_lzo(size_t size)
{
        return lzo1x_worst_compress(size);
}
#endif

#if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS) || IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
static int zbufsize_lz4(size_t size)
{
        return LZ4_compressBound(size);
}
#endif

#if IS_ENABLED(CONFIG_PSTORE_842_COMPRESS)
static int zbufsize_842(size_t size)
{
        return size;
}
#endif

#if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
static int zbufsize_zstd(size_t size)
{
        return zstd_compress_bound(size);
}
#endif

static const struct pstore_zbackend *zbackend __ro_after_init;

static const struct pstore_zbackend zbackends[] = {
#if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)
        {
                .zbufsize       = zbufsize_deflate,
                .name           = "deflate",
        },
#endif
#if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
        {
                .zbufsize       = zbufsize_lzo,
                .name           = "lzo",
        },
#endif
#if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS)
        {
                .zbufsize       = zbufsize_lz4,
                .name           = "lz4",
        },
#endif
#if IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
        {
                .zbufsize       = zbufsize_lz4,
                .name           = "lz4hc",
        },
#endif
#if IS_ENABLED(CONFIG_PSTORE_842_COMPRESS)
        {
                .zbufsize       = zbufsize_842,
                .name           = "842",
        },
#endif
#if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
        {
                .zbufsize       = zbufsize_zstd,
                .name           = "zstd",
        },
#endif
        { }
};

static int pstore_compress(const void *in, void *out,
                           unsigned int inlen, unsigned int outlen)
{
        int ret;

        if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS))
                return -EINVAL;

        ret = crypto_comp_compress(tfm, in, inlen, out, &outlen);
        if (ret) {
                pr_err("crypto_comp_compress failed, ret = %d!\n", ret);
                return ret;
        }

        return outlen;
}

static void allocate_buf_for_compression(void)
{
        struct crypto_comp *ctx;
        int size;
        char *buf;

        /* Skip if not built-in or compression backend not selected yet. */
        if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !zbackend)
                return;

        /* Skip if no pstore backend yet or compression init already done. */
        if (!psinfo || tfm)
                return;

        if (!crypto_has_comp(zbackend->name, 0, 0)) {
                pr_err("Unknown compression: %s\n", zbackend->name);
                return;
        }

        size = zbackend->zbufsize(psinfo->bufsize);
        if (size <= 0) {
                pr_err("Invalid compression size for %s: %d\n",
                       zbackend->name, size);
                return;
        }

        buf = kmalloc(size, GFP_KERNEL);
        if (!buf) {
                pr_err("Failed %d byte compression buffer allocation for: %s\n",
                       size, zbackend->name);
                return;
        }

        ctx = crypto_alloc_comp(zbackend->name, 0, 0);
        if (IS_ERR_OR_NULL(ctx)) {
                kfree(buf);
                pr_err("crypto_alloc_comp('%s') failed: %ld\n", zbackend->name,
                       PTR_ERR(ctx));
                return;
        }

        /* A non-NULL big_oops_buf indicates compression is available. */
        tfm = ctx;
        big_oops_buf_sz = size;
        big_oops_buf = buf;

        pr_info("Using crash dump compression: %s\n", zbackend->name);
}

static void free_buf_for_compression(void)
{
        if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && tfm) {
                crypto_free_comp(tfm);
                tfm = NULL;
        }
        kfree(big_oops_buf);
        big_oops_buf = NULL;
        big_oops_buf_sz = 0;
}

/*
 * Called when compression fails, since the printk buffer
 * would be fetched for compression calling it again when
 * compression fails would have moved the iterator of
 * printk buffer which results in fetching old contents.
 * Copy the recent messages from big_oops_buf to psinfo->buf
 */
static size_t copy_kmsg_to_buffer(int hsize, size_t len)
{
        size_t total_len;
        size_t diff;

        total_len = hsize + len;

        if (total_len > psinfo->bufsize) {
                diff = total_len - psinfo->bufsize + hsize;
                memcpy(psinfo->buf, big_oops_buf, hsize);
                memcpy(psinfo->buf + hsize, big_oops_buf + diff,
                                        psinfo->bufsize - hsize);
                total_len = psinfo->bufsize;
        } else
                memcpy(psinfo->buf, big_oops_buf, total_len);

        return total_len;
}

void pstore_record_init(struct pstore_record *record,
                        struct pstore_info *psinfo)
{
        memset(record, 0, sizeof(*record));

        record->psi = psinfo;

        /* Report zeroed timestamp if called before timekeeping has resumed. */
        record->time = ns_to_timespec64(ktime_get_real_fast_ns());
}

/*
 * callback from kmsg_dump. Save as much as we can (up to kmsg_bytes) from the
 * end of the buffer.
 */
static void pstore_dump(struct kmsg_dumper *dumper,
                        enum kmsg_dump_reason reason)
{
        struct kmsg_dump_iter iter;
        unsigned long   total = 0;
        const char      *why;
        unsigned int    part = 1;
        int             ret;

        why = kmsg_dump_reason_str(reason);

        if (down_trylock(&psinfo->buf_lock)) {
                /* Failed to acquire lock: give up if we cannot wait. */
                if (pstore_cannot_wait(reason)) {
                        pr_err("dump skipped in %s path: may corrupt error record\n",
                                in_nmi() ? "NMI" : why);
                        return;
                }
                if (down_interruptible(&psinfo->buf_lock)) {
                        pr_err("could not grab semaphore?!\n");
                        return;
                }
        }

        kmsg_dump_rewind(&iter);

        oopscount++;
        while (total < kmsg_bytes) {
                char *dst;
                size_t dst_size;
                int header_size;
                int zipped_len = -1;
                size_t dump_size;
                struct pstore_record record;

                pstore_record_init(&record, psinfo);
                record.type = PSTORE_TYPE_DMESG;
                record.count = oopscount;
                record.reason = reason;
                record.part = part;
                record.buf = psinfo->buf;

                if (big_oops_buf) {
                        dst = big_oops_buf;
                        dst_size = big_oops_buf_sz;
                } else {
                        dst = psinfo->buf;
                        dst_size = psinfo->bufsize;
                }

                /* Write dump header. */
                header_size = snprintf(dst, dst_size, "%s#%d Part%u\n", why,
                                 oopscount, part);
                dst_size -= header_size;

                /* Write dump contents. */
                if (!kmsg_dump_get_buffer(&iter, true, dst + header_size,
                                          dst_size, &dump_size))
                        break;

                if (big_oops_buf) {
                        zipped_len = pstore_compress(dst, psinfo->buf,
                                                header_size + dump_size,
                                                psinfo->bufsize);

                        if (zipped_len > 0) {
                                record.compressed = true;
                                record.size = zipped_len;
                        } else {
                                record.size = copy_kmsg_to_buffer(header_size,
                                                                  dump_size);
                        }
                } else {
                        record.size = header_size + dump_size;
                }

                ret = psinfo->write(&record);
                if (ret == 0 && reason == KMSG_DUMP_OOPS) {
                        pstore_new_entry = 1;
                        pstore_timer_kick();
                }

                total += record.size;
                part++;
        }

        up(&psinfo->buf_lock);
}

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

/*
 * Register with kmsg_dump to save last part of console log on panic.
 */
static void pstore_register_kmsg(void)
{
        kmsg_dump_register(&pstore_dumper);
}

static void pstore_unregister_kmsg(void)
{
        kmsg_dump_unregister(&pstore_dumper);
}

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

        if (!c)
                return;

        pstore_record_init(&record, psinfo);
        record.type = PSTORE_TYPE_CONSOLE;

        record.buf = (char *)s;
        record.size = c;
        psinfo->write(&record);
}

static struct console pstore_console = {
        .write  = pstore_console_write,
        .index  = -1,
};

static void pstore_register_console(void)
{
        /* Show which backend is going to get console writes. */
        strscpy(pstore_console.name, psinfo->name,
                sizeof(pstore_console.name));
        /*
         * Always initialize flags here since prior unregister_console()
         * calls may have changed settings (specifically CON_ENABLED).
         */
        pstore_console.flags = CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME;
        register_console(&pstore_console);
}

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

static int pstore_write_user_compat(struct pstore_record *record,
                                    const char __user *buf)
{
        int ret = 0;

        if (record->buf)
                return -EINVAL;

        record->buf = memdup_user(buf, record->size);
        if (IS_ERR(record->buf)) {
                ret = PTR_ERR(record->buf);
                goto out;
        }

        ret = record->psi->write(record);

        kfree(record->buf);
out:
        record->buf = NULL;

        return unlikely(ret < 0) ? ret : record->size;
}

/*
 * 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.
 */
int pstore_register(struct pstore_info *psi)
{
        if (backend && strcmp(backend, psi->name)) {
                pr_warn("ignoring unexpected backend '%s'\n", psi->name);
                return -EPERM;
        }

        /* Sanity check flags. */
        if (!psi->flags) {
                pr_warn("backend '%s' must support at least one frontend\n",
                        psi->name);
                return -EINVAL;
        }

        /* Check for required functions. */
        if (!psi->read || !psi->write) {
                pr_warn("backend '%s' must implement read() and write()\n",
                        psi->name);
                return -EINVAL;
        }

        mutex_lock(&psinfo_lock);
        if (psinfo) {
                pr_warn("backend '%s' already loaded: ignoring '%s'\n",
                        psinfo->name, psi->name);
                mutex_unlock(&psinfo_lock);
                return -EBUSY;
        }

        if (!psi->write_user)
                psi->write_user = pstore_write_user_compat;
        psinfo = psi;
        mutex_init(&psinfo->read_mutex);
        sema_init(&psinfo->buf_lock, 1);

        if (psi->flags & PSTORE_FLAGS_DMESG)
                allocate_buf_for_compression();

        pstore_get_records(0);

        if (psi->flags & PSTORE_FLAGS_DMESG) {
                pstore_dumper.max_reason = psinfo->max_reason;
                pstore_register_kmsg();
        }
        if (psi->flags & PSTORE_FLAGS_CONSOLE)
                pstore_register_console();
        if (psi->flags & PSTORE_FLAGS_FTRACE)
                pstore_register_ftrace();
        if (psi->flags & PSTORE_FLAGS_PMSG)
                pstore_register_pmsg();

        /* Start watching for new records, if desired. */
        pstore_timer_kick();

        /*
         * Update the module parameter backend, so it is visible
         * through /sys/module/pstore/parameters/backend
         */
        backend = kstrdup(psi->name, GFP_KERNEL);

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

        mutex_unlock(&psinfo_lock);
        return 0;
}
EXPORT_SYMBOL_GPL(pstore_register);

void pstore_unregister(struct pstore_info *psi)
{
        /* It's okay to unregister nothing. */
        if (!psi)
                return;

        mutex_lock(&psinfo_lock);

        /* Only one backend can be registered at a time. */
        if (WARN_ON(psi != psinfo)) {
                mutex_unlock(&psinfo_lock);
                return;
        }

        /* Unregister all callbacks. */
        if (psi->flags & PSTORE_FLAGS_PMSG)
                pstore_unregister_pmsg();
        if (psi->flags & PSTORE_FLAGS_FTRACE)
                pstore_unregister_ftrace();
        if (psi->flags & PSTORE_FLAGS_CONSOLE)
                pstore_unregister_console();
        if (psi->flags & PSTORE_FLAGS_DMESG)
                pstore_unregister_kmsg();

        /* Stop timer and make sure all work has finished. */
        del_timer_sync(&pstore_timer);
        flush_work(&pstore_work);

        /* Remove all backend records from filesystem tree. */
        pstore_put_backend_records(psi);

        free_buf_for_compression();

        psinfo = NULL;
        kfree(backend);
        backend = NULL;
        mutex_unlock(&psinfo_lock);
}
EXPORT_SYMBOL_GPL(pstore_unregister);

static void decompress_record(struct pstore_record *record)
{
        int ret;
        int unzipped_len;
        char *unzipped, *workspace;

        if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !record->compressed)
                return;

        /* Only PSTORE_TYPE_DMESG support compression. */
        if (record->type != PSTORE_TYPE_DMESG) {
                pr_warn("ignored compressed record type %d\n", record->type);
                return;
        }

        /* Missing compression buffer means compression was not initialized. */
        if (!big_oops_buf) {
                pr_warn("no decompression method initialized!\n");
                return;
        }

        /* Allocate enough space to hold max decompression and ECC. */
        unzipped_len = big_oops_buf_sz;
        workspace = kmalloc(unzipped_len + record->ecc_notice_size,
                            GFP_KERNEL);
        if (!workspace)
                return;

        /* After decompression "unzipped_len" is almost certainly smaller. */
        ret = crypto_comp_decompress(tfm, record->buf, record->size,
                                          workspace, &unzipped_len);
        if (ret) {
                pr_err("crypto_comp_decompress failed, ret = %d!\n", ret);
                kfree(workspace);
                return;
        }

        /* Append ECC notice to decompressed buffer. */
        memcpy(workspace + unzipped_len, record->buf + record->size,
               record->ecc_notice_size);

        /* Copy decompressed contents into an minimum-sized allocation. */
        unzipped = kmemdup(workspace, unzipped_len + record->ecc_notice_size,
                           GFP_KERNEL);
        kfree(workspace);
        if (!unzipped)
                return;

        /* Swap out compressed contents with decompressed contents. */
        kfree(record->buf);
        record->buf = unzipped;
        record->size = unzipped_len;
        record->compressed = false;
}

/*
 * Read all the records from one persistent store backend. 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_backend_records(struct pstore_info *psi,
                                struct dentry *root, int quiet)
{
        int failed = 0;
        unsigned int stop_loop = 65536;

        if (!psi || !root)
                return;

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

        /*
         * Backend callback read() allocates record.buf. decompress_record()
         * may reallocate record.buf. On success, pstore_mkfile() will keep
         * the record.buf, so free it only on failure.
         */
        for (; stop_loop; stop_loop--) {
                struct pstore_record *record;
                int rc;

                record = kzalloc(sizeof(*record), GFP_KERNEL);
                if (!record) {
                        pr_err("out of memory creating record\n");
                        break;
                }
                pstore_record_init(record, psi);

                record->size = psi->read(record);

                /* No more records left in backend? */
                if (record->size <= 0) {
                        kfree(record);
                        break;
                }

                decompress_record(record);
                rc = pstore_mkfile(root, record);
                if (rc) {
                        /* pstore_mkfile() did not take record, so free it. */
                        kfree(record->buf);
                        kfree(record);
                        if (rc != -EEXIST || !quiet)
                                failed++;
                }
        }
        if (psi->close)
                psi->close(psi);
out:
        mutex_unlock(&psi->read_mutex);

        if (failed)
                pr_warn("failed to create %d record(s) from '%s'\n",
                        failed, psi->name);
        if (!stop_loop)
                pr_err("looping? Too many records seen from '%s'\n",
                        psi->name);
}

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

static void pstore_timefunc(struct timer_list *unused)
{
        if (pstore_new_entry) {
                pstore_new_entry = 0;
                schedule_work(&pstore_work);
        }

        pstore_timer_kick();
}

static void __init pstore_choose_compression(void)
{
        const struct pstore_zbackend *step;

        if (!compress)
                return;

        for (step = zbackends; step->name; step++) {
                if (!strcmp(compress, step->name)) {
                        zbackend = step;
                        return;
                }
        }
}

static int __init pstore_init(void)
{
        int ret;

        pstore_choose_compression();

        /*
         * Check if any pstore backends registered earlier but did not
         * initialize compression because crypto was not ready. If so,
         * initialize compression now.
         */
        allocate_buf_for_compression();

        ret = pstore_init_fs();
        if (ret)
                free_buf_for_compression();

        return ret;
}
late_initcall(pstore_init);

static void __exit pstore_exit(void)
{
        pstore_exit_fs();
}
module_exit(pstore_exit)

MODULE_AUTHOR("Tony Luck <tony.luck@intel.com>");
MODULE_LICENSE("GPL");