// 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/mm.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/jiffies.h>
#include <linux/vmalloc.h>
#include <linux/workqueue.h>
#include <linux/zlib.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");

/*
 * pstore no longer implements compression via the crypto API, and only
 * supports zlib deflate compression implemented using the zlib library
 * interface. This removes additional complexity which is hard to justify for a
 * diagnostic facility that has to operate in conditions where the system may
 * have become unstable. Zlib deflate is comparatively small in terms of code
 * size, and compresses ASCII text comparatively well. In terms of compression
 * speed, deflate is not the best performer but for recording the log output on
 * a kernel panic, this is not considered critical.
 *
 * The only remaining arguments supported by the compress= module parameter are
 * 'deflate' and 'none'. To retain compatibility with existing installations,
 * all other values are logged and replaced with 'deflate'.
 */
static char *compress = "deflate";
module_param(compress, charp, 0444);
MODULE_PARM_DESC(compress, "compression to use");

/* How much of the kernel log to snapshot */
unsigned int kmsg_bytes = CONFIG_PSTORE_DEFAULT_KMSG_BYTES;
module_param(kmsg_bytes, uint, 0444);
MODULE_PARM_DESC(kmsg_bytes, "amount of kernel log to snapshot (in bytes)");

static void *compress_workspace;

/*
 * Compression is only used for dmesg output, which consists of low-entropy
 * ASCII text, and so we can assume worst-case 60%.
 */
#define DMESG_COMP_PERCENT      60

static char *big_oops_buf;
static size_t max_compressed_size;

void pstore_set_kmsg_bytes(unsigned int bytes)
{
        WRITE_ONCE(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));
}

static 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 spinning on
         * pstore_info::buf_lock.
         */
        case KMSG_DUMP_EMERG:
                return true;
        default:
                return false;
        }
}

static int pstore_compress(const void *in, void *out,
                           unsigned int inlen, unsigned int outlen)
{
        struct z_stream_s zstream = {
                .next_in        = in,
                .avail_in       = inlen,
                .next_out       = out,
                .avail_out      = outlen,
                .workspace      = compress_workspace,
        };
        int ret;

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

        ret = zlib_deflateInit2(&zstream, Z_DEFAULT_COMPRESSION, Z_DEFLATED,
                                -MAX_WBITS, DEF_MEM_LEVEL, Z_DEFAULT_STRATEGY);
        if (ret != Z_OK)
                return -EINVAL;

        ret = zlib_deflate(&zstream, Z_FINISH);
        if (ret != Z_STREAM_END)
                return -EINVAL;

        ret = zlib_deflateEnd(&zstream);
        if (ret != Z_OK)
                pr_warn_once("zlib_deflateEnd() failed: %d\n", ret);

        return zstream.total_out;
}

static void allocate_buf_for_compression(void)
{
        size_t compressed_size;
        char *buf;

        /* Skip if not built-in or compression disabled. */
        if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !compress ||
            !strcmp(compress, "none")) {
                compress = NULL;
                return;
        }

        if (strcmp(compress, "deflate")) {
                pr_err("Unsupported compression '%s', falling back to deflate\n",
                       compress);
                compress = "deflate";
        }

        /*
         * The compression buffer only needs to be as large as the maximum
         * uncompressed record size, since any record that would be expanded by
         * compression is just stored uncompressed.
         */
        compressed_size = (psinfo->bufsize * 100) / DMESG_COMP_PERCENT;
        buf = kvzalloc(compressed_size, GFP_KERNEL);
        if (!buf) {
                pr_err("Failed %zu byte compression buffer allocation for: %s\n",
                       psinfo->bufsize, compress);
                return;
        }

        compress_workspace =
                vmalloc(zlib_deflate_workspacesize(MAX_WBITS, DEF_MEM_LEVEL));
        if (!compress_workspace) {
                pr_err("Failed to allocate zlib deflate workspace\n");
                kvfree(buf);
                return;
        }

        /* A non-NULL big_oops_buf indicates compression is available. */
        big_oops_buf = buf;
        max_compressed_size = compressed_size;

        pr_info("Using crash dump compression: %s\n", compress);
}

static void free_buf_for_compression(void)
{
        if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && compress_workspace) {
                vfree(compress_workspace);
                compress_workspace = NULL;
        }

        kvfree(big_oops_buf);
        big_oops_buf = NULL;
        max_compressed_size = 0;
}

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,
                        struct kmsg_dump_detail *detail)
{
        struct kmsg_dump_iter iter;
        unsigned int    remaining = READ_ONCE(kmsg_bytes);
        unsigned long   total = 0;
        const char      *why;
        unsigned int    part = 1;
        unsigned long   flags = 0;
        int             saved_ret = 0;
        int             ret;

        why = kmsg_dump_reason_str(detail->reason);

        if (pstore_cannot_block_path(detail->reason)) {
                if (!raw_spin_trylock_irqsave(&psinfo->buf_lock, flags)) {
                        pr_err("dump skipped in %s path because of concurrent dump\n",
                                        in_nmi() ? "NMI" : why);
                        return;
                }
        } else {
                raw_spin_lock_irqsave(&psinfo->buf_lock, flags);
        }

        kmsg_dump_rewind(&iter);

        oopscount++;
        while (total < remaining) {
                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 = detail->reason;
                record.part = part;
                record.buf = psinfo->buf;

                dst = big_oops_buf ?: psinfo->buf;
                dst_size = max_compressed_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 {
                                /*
                                 * Compression failed, so the buffer is most
                                 * likely filled with binary data that does not
                                 * compress as well as ASCII text. Copy as much
                                 * of the uncompressed data as possible into
                                 * the pstore record, and discard the rest.
                                 */
                                record.size = psinfo->bufsize;
                                memcpy(psinfo->buf, dst, psinfo->bufsize);
                        }
                } else {
                        record.size = header_size + dump_size;
                }

                ret = psinfo->write(&record);
                if (ret == 0 && detail->reason == KMSG_DUMP_OOPS) {
                        pstore_new_entry = 1;
                        pstore_timer_kick();
                } else {
                        /* Preserve only the first non-zero returned value. */
                        if (!saved_ret)
                                saved_ret = ret;
                }

                total += record.size;
                part++;
        }
        raw_spin_unlock_irqrestore(&psinfo->buf_lock, flags);

        if (saved_ret) {
                pr_err_once("backend (%s) writing error (%d)\n", psinfo->name,
                            saved_ret);
        }
}

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

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

        kvfree(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)
{
        char *new_backend;

        if (backend && strcmp(backend, psi->name)) {
                pr_warn("backend '%s' already in use: ignoring '%s'\n",
                        backend, psi->name);
                return -EBUSY;
        }

        /* 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;
        }

        new_backend = kstrdup(psi->name, GFP_KERNEL);
        if (!new_backend)
                return -ENOMEM;

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

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

        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 = new_backend;

        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. */
        timer_delete_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;

        pr_info("Unregistered %s as persistent store backend\n", psi->name);
        mutex_unlock(&psinfo_lock);
}
EXPORT_SYMBOL_GPL(pstore_unregister);

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

        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 (!zstream->workspace) {
                pr_warn("no decompression method initialized!\n");
                return;
        }

        ret = zlib_inflateReset(zstream);
        if (ret != Z_OK) {
                pr_err("zlib_inflateReset() failed, ret = %d!\n", ret);
                return;
        }

        /* Allocate enough space to hold max decompression and ECC. */
        max_uncompressed_size = 3 * psinfo->bufsize;
        workspace = kvzalloc(max_uncompressed_size + record->ecc_notice_size,
                             GFP_KERNEL);
        if (!workspace)
                return;

        zstream->next_in        = record->buf;
        zstream->avail_in       = record->size;
        zstream->next_out       = workspace;
        zstream->avail_out      = max_uncompressed_size;

        ret = zlib_inflate(zstream, Z_FINISH);
        if (ret != Z_STREAM_END) {
                pr_err_ratelimited("zlib_inflate() failed, ret = %d!\n", ret);
                kvfree(workspace);
                return;
        }

        unzipped_len = zstream->total_out;

        /* 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 = kvmemdup(workspace, unzipped_len + record->ecc_notice_size,
                            GFP_KERNEL);
        kvfree(workspace);
        if (!unzipped)
                return;

        /* Swap out compressed contents with decompressed contents. */
        kvfree(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;
        struct z_stream_s zstream = {};

        if (!psi || !root)
                return;

        if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && compress) {
                zstream.workspace = kvmalloc(zlib_inflate_workspacesize(),
                                             GFP_KERNEL);
                zlib_inflateInit2(&zstream, -DEF_WBITS);
        }

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

        if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && compress) {
                if (zlib_inflateEnd(&zstream) != Z_OK)
                        pr_warn("zlib_inflateEnd() failed\n");
                kvfree(zstream.workspace);
        }

        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 int __init pstore_init(void)
{
        int ret;

        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_DESCRIPTION("Persistent Storage - platform driver interface");
MODULE_LICENSE("GPL");