#include <linux/efi.h>
#include <linux/module.h>
#include <linux/pstore.h>
#include <linux/slab.h>
#include <linux/ucs2_string.h>

#define DUMP_NAME_LEN 52

static bool efivars_pstore_disable =
        IS_ENABLED(CONFIG_EFI_VARS_PSTORE_DEFAULT_DISABLE);

module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644);

#define PSTORE_EFI_ATTRIBUTES \
        (EFI_VARIABLE_NON_VOLATILE | \
         EFI_VARIABLE_BOOTSERVICE_ACCESS | \
         EFI_VARIABLE_RUNTIME_ACCESS)

static int efi_pstore_open(struct pstore_info *psi)
{
        psi->data = NULL;
        return 0;
}

static int efi_pstore_close(struct pstore_info *psi)
{
        psi->data = NULL;
        return 0;
}

struct pstore_read_data {
        u64 *id;
        enum pstore_type_id *type;
        int *count;
        struct timespec *timespec;
        bool *compressed;
        char **buf;
};

static inline u64 generic_id(unsigned long timestamp,
                             unsigned int part, int count)
{
        return ((u64) timestamp * 100 + part) * 1000 + count;
}

static int efi_pstore_read_func(struct efivar_entry *entry, void *data)
{
        efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
        struct pstore_read_data *cb_data = data;
        char name[DUMP_NAME_LEN], data_type;
        int i;
        int cnt;
        unsigned int part;
        unsigned long time, size;

        if (efi_guidcmp(entry->var.VendorGuid, vendor))
                return 0;

        for (i = 0; i < DUMP_NAME_LEN; i++)
                name[i] = entry->var.VariableName[i];

        if (sscanf(name, "dump-type%u-%u-%d-%lu-%c",
                   cb_data->type, &part, &cnt, &time, &data_type) == 5) {
                *cb_data->id = generic_id(time, part, cnt);
                *cb_data->count = cnt;
                cb_data->timespec->tv_sec = time;
                cb_data->timespec->tv_nsec = 0;
                if (data_type == 'C')
                        *cb_data->compressed = true;
                else
                        *cb_data->compressed = false;
        } else if (sscanf(name, "dump-type%u-%u-%d-%lu",
                   cb_data->type, &part, &cnt, &time) == 4) {
                *cb_data->id = generic_id(time, part, cnt);
                *cb_data->count = cnt;
                cb_data->timespec->tv_sec = time;
                cb_data->timespec->tv_nsec = 0;
                *cb_data->compressed = false;
        } else if (sscanf(name, "dump-type%u-%u-%lu",
                          cb_data->type, &part, &time) == 3) {
                /*
                 * Check if an old format,
                 * which doesn't support holding
                 * multiple logs, remains.
                 */
                *cb_data->id = generic_id(time, part, 0);
                *cb_data->count = 0;
                cb_data->timespec->tv_sec = time;
                cb_data->timespec->tv_nsec = 0;
                *cb_data->compressed = false;
        } else
                return 0;

        entry->var.DataSize = 1024;
        __efivar_entry_get(entry, &entry->var.Attributes,
                           &entry->var.DataSize, entry->var.Data);
        size = entry->var.DataSize;
        memcpy(*cb_data->buf, entry->var.Data,
               (size_t)min_t(unsigned long, EFIVARS_DATA_SIZE_MAX, size));

        return size;
}

/**
 * efi_pstore_scan_sysfs_enter
 * @pos: scanning entry
 * @next: next entry
 * @head: list head
 */
static void efi_pstore_scan_sysfs_enter(struct efivar_entry *pos,
                                        struct efivar_entry *next,
                                        struct list_head *head)
{
        pos->scanning = true;
        if (&next->list != head)
                next->scanning = true;
}

/**
 * __efi_pstore_scan_sysfs_exit
 * @entry: deleting entry
 * @turn_off_scanning: Check if a scanning flag should be turned off
 */
static inline void __efi_pstore_scan_sysfs_exit(struct efivar_entry *entry,
                                                bool turn_off_scanning)
{
        if (entry->deleting) {
                list_del(&entry->list);
                efivar_entry_iter_end();
                efivar_unregister(entry);
                efivar_entry_iter_begin();
        } else if (turn_off_scanning)
                entry->scanning = false;
}

/**
 * efi_pstore_scan_sysfs_exit
 * @pos: scanning entry
 * @next: next entry
 * @head: list head
 * @stop: a flag checking if scanning will stop
 */
static void efi_pstore_scan_sysfs_exit(struct efivar_entry *pos,
                                       struct efivar_entry *next,
                                       struct list_head *head, bool stop)
{
        __efi_pstore_scan_sysfs_exit(pos, true);
        if (stop)
                __efi_pstore_scan_sysfs_exit(next, &next->list != head);
}

/**
 * efi_pstore_sysfs_entry_iter
 *
 * @data: function-specific data to pass to callback
 * @pos: entry to begin iterating from
 *
 * You MUST call efivar_enter_iter_begin() before this function, and
 * efivar_entry_iter_end() afterwards.
 *
 * It is possible to begin iteration from an arbitrary entry within
 * the list by passing @pos. @pos is updated on return to point to
 * the next entry of the last one passed to efi_pstore_read_func().
 * To begin iterating from the beginning of the list @pos must be %NULL.
 */
static int efi_pstore_sysfs_entry_iter(void *data, struct efivar_entry **pos)
{
        struct efivar_entry *entry, *n;
        struct list_head *head = &efivar_sysfs_list;
        int size = 0;

        if (!*pos) {
                list_for_each_entry_safe(entry, n, head, list) {
                        efi_pstore_scan_sysfs_enter(entry, n, head);

                        size = efi_pstore_read_func(entry, data);
                        efi_pstore_scan_sysfs_exit(entry, n, head, size < 0);
                        if (size)
                                break;
                }
                *pos = n;
                return size;
        }

        list_for_each_entry_safe_from((*pos), n, head, list) {
                efi_pstore_scan_sysfs_enter((*pos), n, head);

                size = efi_pstore_read_func((*pos), data);
                efi_pstore_scan_sysfs_exit((*pos), n, head, size < 0);
                if (size)
                        break;
        }
        *pos = n;
        return size;
}

/**
 * efi_pstore_read
 *
 * This function returns a size of NVRAM entry logged via efi_pstore_write().
 * The meaning and behavior of efi_pstore/pstore are as below.
 *
 * size > 0: Got data of an entry logged via efi_pstore_write() successfully,
 *           and pstore filesystem will continue reading subsequent entries.
 * size == 0: Entry was not logged via efi_pstore_write(),
 *            and efi_pstore driver will continue reading subsequent entries.
 * size < 0: Failed to get data of entry logging via efi_pstore_write(),
 *           and pstore will stop reading entry.
 */
static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
                               int *count, struct timespec *timespec,
                               char **buf, bool *compressed,
                               struct pstore_info *psi)
{
        struct pstore_read_data data;
        ssize_t size;

        data.id = id;
        data.type = type;
        data.count = count;
        data.timespec = timespec;
        data.compressed = compressed;
        data.buf = buf;

        *data.buf = kzalloc(EFIVARS_DATA_SIZE_MAX, GFP_KERNEL);
        if (!*data.buf)
                return -ENOMEM;

        efivar_entry_iter_begin();
        size = efi_pstore_sysfs_entry_iter(&data,
                                           (struct efivar_entry **)&psi->data);
        efivar_entry_iter_end();
        if (size <= 0)
                kfree(*data.buf);
        return size;
}

static int efi_pstore_write(enum pstore_type_id type,
                enum kmsg_dump_reason reason, u64 *id,
                unsigned int part, int count, bool compressed, size_t size,
                struct pstore_info *psi)
{
        char name[DUMP_NAME_LEN];
        efi_char16_t efi_name[DUMP_NAME_LEN];
        efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
        int i, ret = 0;

        sprintf(name, "dump-type%u-%u-%d-%lu-%c", type, part, count,
                get_seconds(), compressed ? 'C' : 'D');

        for (i = 0; i < DUMP_NAME_LEN; i++)
                efi_name[i] = name[i];

        efivar_entry_set_safe(efi_name, vendor, PSTORE_EFI_ATTRIBUTES,
                              !pstore_cannot_block_path(reason),
                              size, psi->buf);

        if (reason == KMSG_DUMP_OOPS)
                efivar_run_worker();

        *id = part;
        return ret;
};

struct pstore_erase_data {
        u64 id;
        enum pstore_type_id type;
        int count;
        struct timespec time;
        efi_char16_t *name;
};

/*
 * Clean up an entry with the same name
 */
static int efi_pstore_erase_func(struct efivar_entry *entry, void *data)
{
        struct pstore_erase_data *ed = data;
        efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
        efi_char16_t efi_name_old[DUMP_NAME_LEN];
        efi_char16_t *efi_name = ed->name;
        unsigned long ucs2_len = ucs2_strlen(ed->name);
        char name_old[DUMP_NAME_LEN];
        int i;

        if (efi_guidcmp(entry->var.VendorGuid, vendor))
                return 0;

        if (ucs2_strncmp(entry->var.VariableName,
                          efi_name, (size_t)ucs2_len)) {
                /*
                 * Check if an old format, which doesn't support
                 * holding multiple logs, remains.
                 */
                sprintf(name_old, "dump-type%u-%u-%lu", ed->type,
                        (unsigned int)ed->id, ed->time.tv_sec);

                for (i = 0; i < DUMP_NAME_LEN; i++)
                        efi_name_old[i] = name_old[i];

                if (ucs2_strncmp(entry->var.VariableName, efi_name_old,
                                  ucs2_strlen(efi_name_old)))
                        return 0;
        }

        if (entry->scanning) {
                /*
                 * Skip deletion because this entry will be deleted
                 * after scanning is completed.
                 */
                entry->deleting = true;
        } else
                list_del(&entry->list);

        /* found */
        __efivar_entry_delete(entry);

        return 1;
}

static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
                            struct timespec time, struct pstore_info *psi)
{
        struct pstore_erase_data edata;
        struct efivar_entry *entry = NULL;
        char name[DUMP_NAME_LEN];
        efi_char16_t efi_name[DUMP_NAME_LEN];
        int found, i;
        unsigned int part;

        do_div(id, 1000);
        part = do_div(id, 100);
        sprintf(name, "dump-type%u-%u-%d-%lu", type, part, count, time.tv_sec);

        for (i = 0; i < DUMP_NAME_LEN; i++)
                efi_name[i] = name[i];

        edata.id = part;
        edata.type = type;
        edata.count = count;
        edata.time = time;
        edata.name = efi_name;

        efivar_entry_iter_begin();
        found = __efivar_entry_iter(efi_pstore_erase_func, &efivar_sysfs_list, &edata, &entry);

        if (found && !entry->scanning) {
                efivar_entry_iter_end();
                efivar_unregister(entry);
        } else
                efivar_entry_iter_end();

        return 0;
}

static struct pstore_info efi_pstore_info = {
        .owner          = THIS_MODULE,
        .name           = "efi",
        .flags          = PSTORE_FLAGS_FRAGILE,
        .open           = efi_pstore_open,
        .close          = efi_pstore_close,
        .read           = efi_pstore_read,
        .write          = efi_pstore_write,
        .erase          = efi_pstore_erase,
};

static __init int efivars_pstore_init(void)
{
        if (!efi_enabled(EFI_RUNTIME_SERVICES))
                return 0;

        if (!efivars_kobject())
                return 0;

        if (efivars_pstore_disable)
                return 0;

        efi_pstore_info.buf = kmalloc(4096, GFP_KERNEL);
        if (!efi_pstore_info.buf)
                return -ENOMEM;

        efi_pstore_info.bufsize = 1024;
        spin_lock_init(&efi_pstore_info.buf_lock);

        if (pstore_register(&efi_pstore_info)) {
                kfree(efi_pstore_info.buf);
                efi_pstore_info.buf = NULL;
                efi_pstore_info.bufsize = 0;
        }

        return 0;
}

static __exit void efivars_pstore_exit(void)
{
}

module_init(efivars_pstore_init);
module_exit(efivars_pstore_exit);

MODULE_DESCRIPTION("EFI variable backend for pstore");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:efivars");