// SPDX-License-Identifier: GPL-2.0-only
/*
 * APEI Error Record Serialization Table support
 *
 * ERST is a way provided by APEI to save and retrieve hardware error
 * information to and from a persistent store.
 *
 * For more information about ERST, please refer to ACPI Specification
 * version 4.0, section 17.4.
 *
 * Copyright 2010 Intel Corp.
 *   Author: Huang Ying <ying.huang@intel.com>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/acpi.h>
#include <linux/uaccess.h>
#include <linux/cper.h>
#include <linux/nmi.h>
#include <linux/hardirq.h>
#include <linux/pstore.h>
#include <linux/vmalloc.h>
#include <linux/mm.h> /* kvfree() */
#include <acpi/apei.h>

#include "apei-internal.h"

#undef pr_fmt
#define pr_fmt(fmt) "ERST: " fmt

/* ERST command status */
#define ERST_STATUS_SUCCESS                     0x0
#define ERST_STATUS_NOT_ENOUGH_SPACE            0x1
#define ERST_STATUS_HARDWARE_NOT_AVAILABLE      0x2
#define ERST_STATUS_FAILED                      0x3
#define ERST_STATUS_RECORD_STORE_EMPTY          0x4
#define ERST_STATUS_RECORD_NOT_FOUND            0x5

#define ERST_TAB_ENTRY(tab)                                             \
        ((struct acpi_whea_header *)((char *)(tab) +                    \
                                     sizeof(struct acpi_table_erst)))

#define SPIN_UNIT               100                     /* 100ns */
/* Firmware should respond within 1 milliseconds */
#define FIRMWARE_TIMEOUT        (1 * NSEC_PER_MSEC)
#define FIRMWARE_MAX_STALL      50                      /* 50us */

int erst_disable;
EXPORT_SYMBOL_GPL(erst_disable);

static struct acpi_table_erst *erst_tab;

/* ERST Error Log Address Range attributes */
#define ERST_RANGE_RESERVED     0x0001
#define ERST_RANGE_NVRAM        0x0002
#define ERST_RANGE_SLOW         0x0004

/* ERST Exec max timings */
#define ERST_EXEC_TIMING_MAX_MASK      0xFFFFFFFF00000000
#define ERST_EXEC_TIMING_MAX_SHIFT     32

/*
 * ERST Error Log Address Range, used as buffer for reading/writing
 * error records.
 */
static struct erst_erange {
        u64 base;
        u64 size;
        void __iomem *vaddr;
        u32 attr;
        u64 timings;
} erst_erange;

/*
 * Prevent ERST interpreter to run simultaneously, because the
 * corresponding firmware implementation may not work properly when
 * invoked simultaneously.
 *
 * It is used to provide exclusive accessing for ERST Error Log
 * Address Range too.
 */
static DEFINE_RAW_SPINLOCK(erst_lock);

static inline int erst_errno(int command_status)
{
        switch (command_status) {
        case ERST_STATUS_SUCCESS:
                return 0;
        case ERST_STATUS_HARDWARE_NOT_AVAILABLE:
                return -ENODEV;
        case ERST_STATUS_NOT_ENOUGH_SPACE:
                return -ENOSPC;
        case ERST_STATUS_RECORD_STORE_EMPTY:
        case ERST_STATUS_RECORD_NOT_FOUND:
                return -ENOENT;
        default:
                return -EINVAL;
        }
}

static inline u64 erst_get_timeout(void)
{
        u64 timeout = FIRMWARE_TIMEOUT;

        if (erst_erange.attr & ERST_RANGE_SLOW) {
                timeout = ((erst_erange.timings & ERST_EXEC_TIMING_MAX_MASK) >>
                        ERST_EXEC_TIMING_MAX_SHIFT) * NSEC_PER_MSEC;
                if (timeout < FIRMWARE_TIMEOUT)
                        timeout = FIRMWARE_TIMEOUT;
        }
        return timeout;
}

static int erst_timedout(u64 *t, u64 spin_unit)
{
        if ((s64)*t < spin_unit) {
                pr_warn(FW_WARN "Firmware does not respond in time.\n");
                return 1;
        }
        *t -= spin_unit;
        ndelay(spin_unit);
        touch_nmi_watchdog();
        return 0;
}

static int erst_exec_load_var1(struct apei_exec_context *ctx,
                               struct acpi_whea_header *entry)
{
        return __apei_exec_read_register(entry, &ctx->var1);
}

static int erst_exec_load_var2(struct apei_exec_context *ctx,
                               struct acpi_whea_header *entry)
{
        return __apei_exec_read_register(entry, &ctx->var2);
}

static int erst_exec_store_var1(struct apei_exec_context *ctx,
                                struct acpi_whea_header *entry)
{
        return __apei_exec_write_register(entry, ctx->var1);
}

static int erst_exec_add(struct apei_exec_context *ctx,
                         struct acpi_whea_header *entry)
{
        ctx->var1 += ctx->var2;
        return 0;
}

static int erst_exec_subtract(struct apei_exec_context *ctx,
                              struct acpi_whea_header *entry)
{
        ctx->var1 -= ctx->var2;
        return 0;
}

static int erst_exec_add_value(struct apei_exec_context *ctx,
                               struct acpi_whea_header *entry)
{
        int rc;
        u64 val;

        rc = __apei_exec_read_register(entry, &val);
        if (rc)
                return rc;
        val += ctx->value;
        rc = __apei_exec_write_register(entry, val);
        return rc;
}

static int erst_exec_subtract_value(struct apei_exec_context *ctx,
                                    struct acpi_whea_header *entry)
{
        int rc;
        u64 val;

        rc = __apei_exec_read_register(entry, &val);
        if (rc)
                return rc;
        val -= ctx->value;
        rc = __apei_exec_write_register(entry, val);
        return rc;
}

static int erst_exec_stall(struct apei_exec_context *ctx,
                           struct acpi_whea_header *entry)
{
        u64 stall_time;

        if (ctx->value > FIRMWARE_MAX_STALL) {
                if (!in_nmi())
                        pr_warn(FW_WARN
                        "Too long stall time for stall instruction: 0x%llx.\n",
                                   ctx->value);
                stall_time = FIRMWARE_MAX_STALL;
        } else
                stall_time = ctx->value;
        udelay(stall_time);
        return 0;
}

static int erst_exec_stall_while_true(struct apei_exec_context *ctx,
                                      struct acpi_whea_header *entry)
{
        int rc;
        u64 val;
        u64 timeout;
        u64 stall_time;

        timeout = erst_get_timeout();

        if (ctx->var1 > FIRMWARE_MAX_STALL) {
                if (!in_nmi())
                        pr_warn(FW_WARN
                "Too long stall time for stall while true instruction: 0x%llx.\n",
                                   ctx->var1);
                stall_time = FIRMWARE_MAX_STALL;
        } else
                stall_time = ctx->var1;

        for (;;) {
                rc = __apei_exec_read_register(entry, &val);
                if (rc)
                        return rc;
                if (val != ctx->value)
                        break;
                if (erst_timedout(&timeout, stall_time * NSEC_PER_USEC))
                        return -EIO;
        }
        return 0;
}

static int erst_exec_skip_next_instruction_if_true(
        struct apei_exec_context *ctx,
        struct acpi_whea_header *entry)
{
        int rc;
        u64 val;

        rc = __apei_exec_read_register(entry, &val);
        if (rc)
                return rc;
        if (val == ctx->value) {
                ctx->ip += 2;
                return APEI_EXEC_SET_IP;
        }

        return 0;
}

static int erst_exec_goto(struct apei_exec_context *ctx,
                          struct acpi_whea_header *entry)
{
        ctx->ip = ctx->value;
        return APEI_EXEC_SET_IP;
}

static int erst_exec_set_src_address_base(struct apei_exec_context *ctx,
                                          struct acpi_whea_header *entry)
{
        return __apei_exec_read_register(entry, &ctx->src_base);
}

static int erst_exec_set_dst_address_base(struct apei_exec_context *ctx,
                                          struct acpi_whea_header *entry)
{
        return __apei_exec_read_register(entry, &ctx->dst_base);
}

static int erst_exec_move_data(struct apei_exec_context *ctx,
                               struct acpi_whea_header *entry)
{
        int rc;
        u64 offset;
        void *src, *dst;

        /* ioremap does not work in interrupt context */
        if (in_interrupt()) {
                pr_warn("MOVE_DATA can not be used in interrupt context.\n");
                return -EBUSY;
        }

        rc = __apei_exec_read_register(entry, &offset);
        if (rc)
                return rc;

        src = ioremap(ctx->src_base + offset, ctx->var2);
        if (!src)
                return -ENOMEM;
        dst = ioremap(ctx->dst_base + offset, ctx->var2);
        if (!dst) {
                iounmap(src);
                return -ENOMEM;
        }

        memmove(dst, src, ctx->var2);

        iounmap(src);
        iounmap(dst);

        return 0;
}

static struct apei_exec_ins_type erst_ins_type[] = {
        [ACPI_ERST_READ_REGISTER] = {
                .flags = APEI_EXEC_INS_ACCESS_REGISTER,
                .run = apei_exec_read_register,
        },
        [ACPI_ERST_READ_REGISTER_VALUE] = {
                .flags = APEI_EXEC_INS_ACCESS_REGISTER,
                .run = apei_exec_read_register_value,
        },
        [ACPI_ERST_WRITE_REGISTER] = {
                .flags = APEI_EXEC_INS_ACCESS_REGISTER,
                .run = apei_exec_write_register,
        },
        [ACPI_ERST_WRITE_REGISTER_VALUE] = {
                .flags = APEI_EXEC_INS_ACCESS_REGISTER,
                .run = apei_exec_write_register_value,
        },
        [ACPI_ERST_NOOP] = {
                .flags = 0,
                .run = apei_exec_noop,
        },
        [ACPI_ERST_LOAD_VAR1] = {
                .flags = APEI_EXEC_INS_ACCESS_REGISTER,
                .run = erst_exec_load_var1,
        },
        [ACPI_ERST_LOAD_VAR2] = {
                .flags = APEI_EXEC_INS_ACCESS_REGISTER,
                .run = erst_exec_load_var2,
        },
        [ACPI_ERST_STORE_VAR1] = {
                .flags = APEI_EXEC_INS_ACCESS_REGISTER,
                .run = erst_exec_store_var1,
        },
        [ACPI_ERST_ADD] = {
                .flags = 0,
                .run = erst_exec_add,
        },
        [ACPI_ERST_SUBTRACT] = {
                .flags = 0,
                .run = erst_exec_subtract,
        },
        [ACPI_ERST_ADD_VALUE] = {
                .flags = APEI_EXEC_INS_ACCESS_REGISTER,
                .run = erst_exec_add_value,
        },
        [ACPI_ERST_SUBTRACT_VALUE] = {
                .flags = APEI_EXEC_INS_ACCESS_REGISTER,
                .run = erst_exec_subtract_value,
        },
        [ACPI_ERST_STALL] = {
                .flags = 0,
                .run = erst_exec_stall,
        },
        [ACPI_ERST_STALL_WHILE_TRUE] = {
                .flags = APEI_EXEC_INS_ACCESS_REGISTER,
                .run = erst_exec_stall_while_true,
        },
        [ACPI_ERST_SKIP_NEXT_IF_TRUE] = {
                .flags = APEI_EXEC_INS_ACCESS_REGISTER,
                .run = erst_exec_skip_next_instruction_if_true,
        },
        [ACPI_ERST_GOTO] = {
                .flags = 0,
                .run = erst_exec_goto,
        },
        [ACPI_ERST_SET_SRC_ADDRESS_BASE] = {
                .flags = APEI_EXEC_INS_ACCESS_REGISTER,
                .run = erst_exec_set_src_address_base,
        },
        [ACPI_ERST_SET_DST_ADDRESS_BASE] = {
                .flags = APEI_EXEC_INS_ACCESS_REGISTER,
                .run = erst_exec_set_dst_address_base,
        },
        [ACPI_ERST_MOVE_DATA] = {
                .flags = APEI_EXEC_INS_ACCESS_REGISTER,
                .run = erst_exec_move_data,
        },
};

static inline void erst_exec_ctx_init(struct apei_exec_context *ctx)
{
        apei_exec_ctx_init(ctx, erst_ins_type, ARRAY_SIZE(erst_ins_type),
                           ERST_TAB_ENTRY(erst_tab), erst_tab->entries);
}

static int erst_get_erange(struct erst_erange *range)
{
        struct apei_exec_context ctx;
        int rc;

        erst_exec_ctx_init(&ctx);
        rc = apei_exec_run(&ctx, ACPI_ERST_GET_ERROR_RANGE);
        if (rc)
                return rc;
        range->base = apei_exec_ctx_get_output(&ctx);
        rc = apei_exec_run(&ctx, ACPI_ERST_GET_ERROR_LENGTH);
        if (rc)
                return rc;
        range->size = apei_exec_ctx_get_output(&ctx);
        rc = apei_exec_run(&ctx, ACPI_ERST_GET_ERROR_ATTRIBUTES);
        if (rc)
                return rc;
        range->attr = apei_exec_ctx_get_output(&ctx);
        rc = apei_exec_run(&ctx, ACPI_ERST_EXECUTE_TIMINGS);
        if (rc == 0)
                range->timings = apei_exec_ctx_get_output(&ctx);
        else if (rc == -ENOENT)
                range->timings = 0;
        else
                return rc;

        return 0;
}

static ssize_t __erst_get_record_count(void)
{
        struct apei_exec_context ctx;
        int rc;

        erst_exec_ctx_init(&ctx);
        rc = apei_exec_run(&ctx, ACPI_ERST_GET_RECORD_COUNT);
        if (rc)
                return rc;
        return apei_exec_ctx_get_output(&ctx);
}

ssize_t erst_get_record_count(void)
{
        ssize_t count;
        unsigned long flags;

        if (erst_disable)
                return -ENODEV;

        raw_spin_lock_irqsave(&erst_lock, flags);
        count = __erst_get_record_count();
        raw_spin_unlock_irqrestore(&erst_lock, flags);

        return count;
}
EXPORT_SYMBOL_GPL(erst_get_record_count);

#define ERST_RECORD_ID_CACHE_SIZE_MIN   16
#define ERST_RECORD_ID_CACHE_SIZE_MAX   1024

struct erst_record_id_cache {
        struct mutex lock;
        u64 *entries;
        int len;
        int size;
        int refcount;
};

static struct erst_record_id_cache erst_record_id_cache = {
        .lock = __MUTEX_INITIALIZER(erst_record_id_cache.lock),
        .refcount = 0,
};

static int __erst_get_next_record_id(u64 *record_id)
{
        struct apei_exec_context ctx;
        int rc;

        erst_exec_ctx_init(&ctx);
        rc = apei_exec_run(&ctx, ACPI_ERST_GET_RECORD_ID);
        if (rc)
                return rc;
        *record_id = apei_exec_ctx_get_output(&ctx);

        return 0;
}

int erst_get_record_id_begin(int *pos)
{
        int rc;

        if (erst_disable)
                return -ENODEV;

        rc = mutex_lock_interruptible(&erst_record_id_cache.lock);
        if (rc)
                return rc;
        erst_record_id_cache.refcount++;
        mutex_unlock(&erst_record_id_cache.lock);

        *pos = 0;

        return 0;
}
EXPORT_SYMBOL_GPL(erst_get_record_id_begin);

/* erst_record_id_cache.lock must be held by caller */
static int __erst_record_id_cache_add_one(void)
{
        u64 id, prev_id, first_id;
        int i, rc;
        u64 *entries;
        unsigned long flags;

        id = prev_id = first_id = APEI_ERST_INVALID_RECORD_ID;
retry:
        raw_spin_lock_irqsave(&erst_lock, flags);
        rc = __erst_get_next_record_id(&id);
        raw_spin_unlock_irqrestore(&erst_lock, flags);
        if (rc == -ENOENT)
                return 0;
        if (rc)
                return rc;
        if (id == APEI_ERST_INVALID_RECORD_ID)
                return 0;
        /* can not skip current ID, or loop back to first ID */
        if (id == prev_id || id == first_id)
                return 0;
        if (first_id == APEI_ERST_INVALID_RECORD_ID)
                first_id = id;
        prev_id = id;

        entries = erst_record_id_cache.entries;
        for (i = 0; i < erst_record_id_cache.len; i++) {
                if (entries[i] == id)
                        break;
        }
        /* record id already in cache, try next */
        if (i < erst_record_id_cache.len)
                goto retry;
        if (erst_record_id_cache.len >= erst_record_id_cache.size) {
                int new_size;
                u64 *new_entries;

                new_size = erst_record_id_cache.size * 2;
                new_size = clamp_val(new_size, ERST_RECORD_ID_CACHE_SIZE_MIN,
                                     ERST_RECORD_ID_CACHE_SIZE_MAX);
                if (new_size <= erst_record_id_cache.size) {
                        if (printk_ratelimit())
                                pr_warn(FW_WARN "too many record IDs!\n");
                        return 0;
                }
                new_entries = kvmalloc_array(new_size, sizeof(entries[0]),
                                             GFP_KERNEL);
                if (!new_entries)
                        return -ENOMEM;
                memcpy(new_entries, entries,
                       erst_record_id_cache.len * sizeof(entries[0]));
                kvfree(entries);
                erst_record_id_cache.entries = entries = new_entries;
                erst_record_id_cache.size = new_size;
        }
        entries[i] = id;
        erst_record_id_cache.len++;

        return 1;
}

/*
 * Get the record ID of an existing error record on the persistent
 * storage. If there is no error record on the persistent storage, the
 * returned record_id is APEI_ERST_INVALID_RECORD_ID.
 */
int erst_get_record_id_next(int *pos, u64 *record_id)
{
        int rc = 0;
        u64 *entries;

        if (erst_disable)
                return -ENODEV;

        /* must be enclosed by erst_get_record_id_begin/end */
        BUG_ON(!erst_record_id_cache.refcount);
        BUG_ON(*pos < 0 || *pos > erst_record_id_cache.len);

        mutex_lock(&erst_record_id_cache.lock);
        entries = erst_record_id_cache.entries;
        for (; *pos < erst_record_id_cache.len; (*pos)++)
                if (entries[*pos] != APEI_ERST_INVALID_RECORD_ID)
                        break;
        /* found next record id in cache */
        if (*pos < erst_record_id_cache.len) {
                *record_id = entries[*pos];
                (*pos)++;
                goto out_unlock;
        }

        /* Try to add one more record ID to cache */
        rc = __erst_record_id_cache_add_one();
        if (rc < 0)
                goto out_unlock;
        /* successfully add one new ID */
        if (rc == 1) {
                *record_id = erst_record_id_cache.entries[*pos];
                (*pos)++;
                rc = 0;
        } else {
                *pos = -1;
                *record_id = APEI_ERST_INVALID_RECORD_ID;
        }
out_unlock:
        mutex_unlock(&erst_record_id_cache.lock);

        return rc;
}
EXPORT_SYMBOL_GPL(erst_get_record_id_next);

/* erst_record_id_cache.lock must be held by caller */
static void __erst_record_id_cache_compact(void)
{
        int i, wpos = 0;
        u64 *entries;

        if (erst_record_id_cache.refcount)
                return;

        entries = erst_record_id_cache.entries;
        for (i = 0; i < erst_record_id_cache.len; i++) {
                if (entries[i] == APEI_ERST_INVALID_RECORD_ID)
                        continue;
                if (wpos != i)
                        entries[wpos] = entries[i];
                wpos++;
        }
        erst_record_id_cache.len = wpos;
}

void erst_get_record_id_end(void)
{
        /*
         * erst_disable != 0 should be detected by invoker via the
         * return value of erst_get_record_id_begin/next, so this
         * function should not be called for erst_disable != 0.
         */
        BUG_ON(erst_disable);

        mutex_lock(&erst_record_id_cache.lock);
        erst_record_id_cache.refcount--;
        BUG_ON(erst_record_id_cache.refcount < 0);
        __erst_record_id_cache_compact();
        mutex_unlock(&erst_record_id_cache.lock);
}
EXPORT_SYMBOL_GPL(erst_get_record_id_end);

static int __erst_write_to_storage(u64 offset)
{
        struct apei_exec_context ctx;
        u64 timeout;
        u64 val;
        int rc;

        timeout = erst_get_timeout();

        erst_exec_ctx_init(&ctx);
        rc = apei_exec_run_optional(&ctx, ACPI_ERST_BEGIN_WRITE);
        if (rc)
                return rc;
        apei_exec_ctx_set_input(&ctx, offset);
        rc = apei_exec_run(&ctx, ACPI_ERST_SET_RECORD_OFFSET);
        if (rc)
                return rc;
        rc = apei_exec_run(&ctx, ACPI_ERST_EXECUTE_OPERATION);
        if (rc)
                return rc;
        for (;;) {
                rc = apei_exec_run(&ctx, ACPI_ERST_CHECK_BUSY_STATUS);
                if (rc)
                        return rc;
                val = apei_exec_ctx_get_output(&ctx);
                if (!val)
                        break;
                if (erst_timedout(&timeout, SPIN_UNIT))
                        return -EIO;
        }
        rc = apei_exec_run(&ctx, ACPI_ERST_GET_COMMAND_STATUS);
        if (rc)
                return rc;
        val = apei_exec_ctx_get_output(&ctx);
        rc = apei_exec_run_optional(&ctx, ACPI_ERST_END);
        if (rc)
                return rc;

        return erst_errno(val);
}

static int __erst_read_from_storage(u64 record_id, u64 offset)
{
        struct apei_exec_context ctx;
        u64 timeout;
        u64 val;
        int rc;

        timeout = erst_get_timeout();

        erst_exec_ctx_init(&ctx);
        rc = apei_exec_run_optional(&ctx, ACPI_ERST_BEGIN_READ);
        if (rc)
                return rc;
        apei_exec_ctx_set_input(&ctx, offset);
        rc = apei_exec_run(&ctx, ACPI_ERST_SET_RECORD_OFFSET);
        if (rc)
                return rc;
        apei_exec_ctx_set_input(&ctx, record_id);
        rc = apei_exec_run(&ctx, ACPI_ERST_SET_RECORD_ID);
        if (rc)
                return rc;
        rc = apei_exec_run(&ctx, ACPI_ERST_EXECUTE_OPERATION);
        if (rc)
                return rc;
        for (;;) {
                rc = apei_exec_run(&ctx, ACPI_ERST_CHECK_BUSY_STATUS);
                if (rc)
                        return rc;
                val = apei_exec_ctx_get_output(&ctx);
                if (!val)
                        break;
                if (erst_timedout(&timeout, SPIN_UNIT))
                        return -EIO;
        }
        rc = apei_exec_run(&ctx, ACPI_ERST_GET_COMMAND_STATUS);
        if (rc)
                return rc;
        val = apei_exec_ctx_get_output(&ctx);
        rc = apei_exec_run_optional(&ctx, ACPI_ERST_END);
        if (rc)
                return rc;

        return erst_errno(val);
}

static int __erst_clear_from_storage(u64 record_id)
{
        struct apei_exec_context ctx;
        u64 timeout;
        u64 val;
        int rc;

        timeout = erst_get_timeout();

        erst_exec_ctx_init(&ctx);
        rc = apei_exec_run_optional(&ctx, ACPI_ERST_BEGIN_CLEAR);
        if (rc)
                return rc;
        apei_exec_ctx_set_input(&ctx, record_id);
        rc = apei_exec_run(&ctx, ACPI_ERST_SET_RECORD_ID);
        if (rc)
                return rc;
        rc = apei_exec_run(&ctx, ACPI_ERST_EXECUTE_OPERATION);
        if (rc)
                return rc;
        for (;;) {
                rc = apei_exec_run(&ctx, ACPI_ERST_CHECK_BUSY_STATUS);
                if (rc)
                        return rc;
                val = apei_exec_ctx_get_output(&ctx);
                if (!val)
                        break;
                if (erst_timedout(&timeout, SPIN_UNIT))
                        return -EIO;
        }
        rc = apei_exec_run(&ctx, ACPI_ERST_GET_COMMAND_STATUS);
        if (rc)
                return rc;
        val = apei_exec_ctx_get_output(&ctx);
        rc = apei_exec_run_optional(&ctx, ACPI_ERST_END);
        if (rc)
                return rc;

        return erst_errno(val);
}

/* NVRAM ERST Error Log Address Range is not supported yet */
static void pr_unimpl_nvram(void)
{
        if (printk_ratelimit())
                pr_warn("NVRAM ERST Log Address Range not implemented yet.\n");
}

static int __erst_write_to_nvram(const struct cper_record_header *record)
{
        /* do not print message, because printk is not safe for NMI */
        return -ENOSYS;
}

static int __erst_read_to_erange_from_nvram(u64 record_id, u64 *offset)
{
        pr_unimpl_nvram();
        return -ENOSYS;
}

static int __erst_clear_from_nvram(u64 record_id)
{
        pr_unimpl_nvram();
        return -ENOSYS;
}

int erst_write(const struct cper_record_header *record)
{
        int rc;
        unsigned long flags;
        struct cper_record_header *rcd_erange;

        if (erst_disable)
                return -ENODEV;

        if (memcmp(record->signature, CPER_SIG_RECORD, CPER_SIG_SIZE))
                return -EINVAL;

        if (erst_erange.attr & ERST_RANGE_NVRAM) {
                if (!raw_spin_trylock_irqsave(&erst_lock, flags))
                        return -EBUSY;
                rc = __erst_write_to_nvram(record);
                raw_spin_unlock_irqrestore(&erst_lock, flags);
                return rc;
        }

        if (record->record_length > erst_erange.size)
                return -EINVAL;

        if (!raw_spin_trylock_irqsave(&erst_lock, flags))
                return -EBUSY;
        memcpy(erst_erange.vaddr, record, record->record_length);
        rcd_erange = erst_erange.vaddr;
        /* signature for serialization system */
        memcpy(&rcd_erange->persistence_information, "ER", 2);

        rc = __erst_write_to_storage(0);
        raw_spin_unlock_irqrestore(&erst_lock, flags);

        return rc;
}
EXPORT_SYMBOL_GPL(erst_write);

static int __erst_read_to_erange(u64 record_id, u64 *offset)
{
        int rc;

        if (erst_erange.attr & ERST_RANGE_NVRAM)
                return __erst_read_to_erange_from_nvram(
                        record_id, offset);

        rc = __erst_read_from_storage(record_id, 0);
        if (rc)
                return rc;
        *offset = 0;

        return 0;
}

static ssize_t __erst_read(u64 record_id, struct cper_record_header *record,
                           size_t buflen)
{
        int rc;
        u64 offset, len = 0;
        struct cper_record_header *rcd_tmp;

        rc = __erst_read_to_erange(record_id, &offset);
        if (rc)
                return rc;
        rcd_tmp = erst_erange.vaddr + offset;
        len = rcd_tmp->record_length;
        if (len <= buflen)
                memcpy(record, rcd_tmp, len);

        return len;
}

/*
 * If return value > buflen, the buffer size is not big enough,
 * else if return value < 0, something goes wrong,
 * else everything is OK, and return value is record length
 */
ssize_t erst_read(u64 record_id, struct cper_record_header *record,
                  size_t buflen)
{
        ssize_t len;
        unsigned long flags;

        if (erst_disable)
                return -ENODEV;

        raw_spin_lock_irqsave(&erst_lock, flags);
        len = __erst_read(record_id, record, buflen);
        raw_spin_unlock_irqrestore(&erst_lock, flags);
        return len;
}
EXPORT_SYMBOL_GPL(erst_read);

static void erst_clear_cache(u64 record_id)
{
        int i;
        u64 *entries;

        mutex_lock(&erst_record_id_cache.lock);

        entries = erst_record_id_cache.entries;
        for (i = 0; i < erst_record_id_cache.len; i++) {
                if (entries[i] == record_id)
                        entries[i] = APEI_ERST_INVALID_RECORD_ID;
        }
        __erst_record_id_cache_compact();

        mutex_unlock(&erst_record_id_cache.lock);
}

ssize_t erst_read_record(u64 record_id, struct cper_record_header *record,
                size_t buflen, size_t recordlen, const guid_t *creatorid)
{
        ssize_t len;

        /*
         * if creatorid is NULL, read any record for erst-dbg module
         */
        if (creatorid == NULL) {
                len = erst_read(record_id, record, buflen);
                if (len == -ENOENT)
                        erst_clear_cache(record_id);

                return len;
        }

        len = erst_read(record_id, record, buflen);
        /*
         * if erst_read return value is -ENOENT skip to next record_id,
         * and clear the record_id cache.
         */
        if (len == -ENOENT) {
                erst_clear_cache(record_id);
                goto out;
        }

        if (len < 0)
                goto out;

        /*
         * if erst_read return value is less than record head length,
         * consider it as -EIO, and clear the record_id cache.
         */
        if (len < recordlen) {
                len = -EIO;
                erst_clear_cache(record_id);
                goto out;
        }

        /*
         * if creatorid is not wanted, consider it as not found,
         * for skipping to next record_id.
         */
        if (!guid_equal(&record->creator_id, creatorid))
                len = -ENOENT;

out:
        return len;
}
EXPORT_SYMBOL_GPL(erst_read_record);

int erst_clear(u64 record_id)
{
        int rc, i;
        unsigned long flags;
        u64 *entries;

        if (erst_disable)
                return -ENODEV;

        rc = mutex_lock_interruptible(&erst_record_id_cache.lock);
        if (rc)
                return rc;
        raw_spin_lock_irqsave(&erst_lock, flags);
        if (erst_erange.attr & ERST_RANGE_NVRAM)
                rc = __erst_clear_from_nvram(record_id);
        else
                rc = __erst_clear_from_storage(record_id);
        raw_spin_unlock_irqrestore(&erst_lock, flags);
        if (rc)
                goto out;
        entries = erst_record_id_cache.entries;
        for (i = 0; i < erst_record_id_cache.len; i++) {
                if (entries[i] == record_id)
                        entries[i] = APEI_ERST_INVALID_RECORD_ID;
        }
        __erst_record_id_cache_compact();
out:
        mutex_unlock(&erst_record_id_cache.lock);
        return rc;
}
EXPORT_SYMBOL_GPL(erst_clear);

static int __init setup_erst_disable(char *str)
{
        erst_disable = 1;
        return 1;
}

__setup("erst_disable", setup_erst_disable);

static int erst_check_table(struct acpi_table_erst *erst_tab)
{
        if ((erst_tab->header_length !=
             (sizeof(struct acpi_table_erst) - sizeof(erst_tab->header)))
            && (erst_tab->header_length != sizeof(struct acpi_table_erst)))
                return -EINVAL;
        if (erst_tab->header.length < sizeof(struct acpi_table_erst))
                return -EINVAL;
        if (erst_tab->entries !=
            (erst_tab->header.length - sizeof(struct acpi_table_erst)) /
            sizeof(struct acpi_erst_entry))
                return -EINVAL;

        return 0;
}

static int erst_open_pstore(struct pstore_info *psi);
static int erst_close_pstore(struct pstore_info *psi);
static ssize_t erst_reader(struct pstore_record *record);
static int erst_writer(struct pstore_record *record);
static int erst_clearer(struct pstore_record *record);

static struct pstore_info erst_info = {
        .owner          = THIS_MODULE,
        .name           = "erst",
        .flags          = PSTORE_FLAGS_DMESG,
        .open           = erst_open_pstore,
        .close          = erst_close_pstore,
        .read           = erst_reader,
        .write          = erst_writer,
        .erase          = erst_clearer
};

#define CPER_CREATOR_PSTORE                                             \
        GUID_INIT(0x75a574e3, 0x5052, 0x4b29, 0x8a, 0x8e, 0xbe, 0x2c,   \
                  0x64, 0x90, 0xb8, 0x9d)
#define CPER_SECTION_TYPE_DMESG                                         \
        GUID_INIT(0xc197e04e, 0xd545, 0x4a70, 0x9c, 0x17, 0xa5, 0x54,   \
                  0x94, 0x19, 0xeb, 0x12)
#define CPER_SECTION_TYPE_DMESG_Z                                       \
        GUID_INIT(0x4f118707, 0x04dd, 0x4055, 0xb5, 0xdd, 0x95, 0x6d,   \
                  0x34, 0xdd, 0xfa, 0xc6)
#define CPER_SECTION_TYPE_MCE                                           \
        GUID_INIT(0xfe08ffbe, 0x95e4, 0x4be7, 0xbc, 0x73, 0x40, 0x96,   \
                  0x04, 0x4a, 0x38, 0xfc)

struct cper_pstore_record {
        struct cper_record_header hdr;
        struct cper_section_descriptor sec_hdr;
        char data[];
} __packed;

static int reader_pos;

static int erst_open_pstore(struct pstore_info *psi)
{
        if (erst_disable)
                return -ENODEV;

        return erst_get_record_id_begin(&reader_pos);
}

static int erst_close_pstore(struct pstore_info *psi)
{
        erst_get_record_id_end();

        return 0;
}

static ssize_t erst_reader(struct pstore_record *record)
{
        int rc;
        ssize_t len = 0;
        u64 record_id;
        struct cper_pstore_record *rcd;
        size_t rcd_len = sizeof(*rcd) + erst_info.bufsize;

        if (erst_disable)
                return -ENODEV;

        rcd = kmalloc(rcd_len, GFP_KERNEL);
        if (!rcd) {
                rc = -ENOMEM;
                goto out;
        }
skip:
        rc = erst_get_record_id_next(&reader_pos, &record_id);
        if (rc)
                goto out;

        /* no more record */
        if (record_id == APEI_ERST_INVALID_RECORD_ID) {
                rc = -EINVAL;
                goto out;
        }

        len = erst_read_record(record_id, &rcd->hdr, rcd_len, sizeof(*rcd),
                        &CPER_CREATOR_PSTORE);
        /* The record may be cleared by others, try read next record */
        if (len == -ENOENT)
                goto skip;
        else if (len < 0)
                goto out;

        record->buf = kmalloc(len, GFP_KERNEL);
        if (record->buf == NULL) {
                rc = -ENOMEM;
                goto out;
        }
        memcpy(record->buf, rcd->data, len - sizeof(*rcd));
        record->id = record_id;
        record->compressed = false;
        record->ecc_notice_size = 0;
        if (guid_equal(&rcd->sec_hdr.section_type, &CPER_SECTION_TYPE_DMESG_Z)) {
                record->type = PSTORE_TYPE_DMESG;
                record->compressed = true;
        } else if (guid_equal(&rcd->sec_hdr.section_type, &CPER_SECTION_TYPE_DMESG))
                record->type = PSTORE_TYPE_DMESG;
        else if (guid_equal(&rcd->sec_hdr.section_type, &CPER_SECTION_TYPE_MCE))
                record->type = PSTORE_TYPE_MCE;
        else
                record->type = PSTORE_TYPE_MAX;

        if (rcd->hdr.validation_bits & CPER_VALID_TIMESTAMP)
                record->time.tv_sec = rcd->hdr.timestamp;
        else
                record->time.tv_sec = 0;
        record->time.tv_nsec = 0;

out:
        kfree(rcd);
        return (rc < 0) ? rc : (len - sizeof(*rcd));
}

static int erst_writer(struct pstore_record *record)
{
        struct cper_pstore_record *rcd = (struct cper_pstore_record *)
                                        (erst_info.buf - sizeof(*rcd));
        int ret;

        memset(rcd, 0, sizeof(*rcd));
        memcpy(rcd->hdr.signature, CPER_SIG_RECORD, CPER_SIG_SIZE);
        rcd->hdr.revision = CPER_RECORD_REV;
        rcd->hdr.signature_end = CPER_SIG_END;
        rcd->hdr.section_count = 1;
        rcd->hdr.error_severity = CPER_SEV_FATAL;
        /* timestamp valid. platform_id, partition_id are invalid */
        rcd->hdr.validation_bits = CPER_VALID_TIMESTAMP;
        rcd->hdr.timestamp = ktime_get_real_seconds();
        rcd->hdr.record_length = sizeof(*rcd) + record->size;
        rcd->hdr.creator_id = CPER_CREATOR_PSTORE;
        rcd->hdr.notification_type = CPER_NOTIFY_MCE;
        rcd->hdr.record_id = cper_next_record_id();
        rcd->hdr.flags = CPER_HW_ERROR_FLAGS_PREVERR;

        rcd->sec_hdr.section_offset = sizeof(*rcd);
        rcd->sec_hdr.section_length = record->size;
        rcd->sec_hdr.revision = CPER_SEC_REV;
        /* fru_id and fru_text is invalid */
        rcd->sec_hdr.validation_bits = 0;
        rcd->sec_hdr.flags = CPER_SEC_PRIMARY;
        switch (record->type) {
        case PSTORE_TYPE_DMESG:
                if (record->compressed)
                        rcd->sec_hdr.section_type = CPER_SECTION_TYPE_DMESG_Z;
                else
                        rcd->sec_hdr.section_type = CPER_SECTION_TYPE_DMESG;
                break;
        case PSTORE_TYPE_MCE:
                rcd->sec_hdr.section_type = CPER_SECTION_TYPE_MCE;
                break;
        default:
                return -EINVAL;
        }
        rcd->sec_hdr.section_severity = CPER_SEV_FATAL;

        ret = erst_write(&rcd->hdr);
        record->id = rcd->hdr.record_id;

        return ret;
}

static int erst_clearer(struct pstore_record *record)
{
        return erst_clear(record->id);
}

static int __init erst_init(void)
{
        int rc = 0;
        acpi_status status;
        struct apei_exec_context ctx;
        struct apei_resources erst_resources;
        struct resource *r;
        char *buf;

        if (acpi_disabled)
                goto err;

        if (erst_disable) {
                pr_info(
        "Error Record Serialization Table (ERST) support is disabled.\n");
                goto err;
        }

        status = acpi_get_table(ACPI_SIG_ERST, 0,
                                (struct acpi_table_header **)&erst_tab);
        if (status == AE_NOT_FOUND)
                goto err;
        else if (ACPI_FAILURE(status)) {
                const char *msg = acpi_format_exception(status);
                pr_err("Failed to get table, %s\n", msg);
                rc = -EINVAL;
                goto err;
        }

        rc = erst_check_table(erst_tab);
        if (rc) {
                pr_err(FW_BUG "ERST table is invalid.\n");
                goto err_put_erst_tab;
        }

        apei_resources_init(&erst_resources);
        erst_exec_ctx_init(&ctx);
        rc = apei_exec_collect_resources(&ctx, &erst_resources);
        if (rc)
                goto err_fini;
        rc = apei_resources_request(&erst_resources, "APEI ERST");
        if (rc)
                goto err_fini;
        rc = apei_exec_pre_map_gars(&ctx);
        if (rc)
                goto err_release;
        rc = erst_get_erange(&erst_erange);
        if (rc) {
                if (rc == -ENODEV)
                        pr_info(
        "The corresponding hardware device or firmware implementation "
        "is not available.\n");
                else
                        pr_err("Failed to get Error Log Address Range.\n");
                goto err_unmap_reg;
        }

        r = request_mem_region(erst_erange.base, erst_erange.size, "APEI ERST");
        if (!r) {
                pr_err("Can not request [mem %#010llx-%#010llx] for ERST.\n",
                       (unsigned long long)erst_erange.base,
                       (unsigned long long)erst_erange.base + erst_erange.size - 1);
                rc = -EIO;
                goto err_unmap_reg;
        }
        rc = -ENOMEM;
        erst_erange.vaddr = ioremap_cache(erst_erange.base,
                                          erst_erange.size);
        if (!erst_erange.vaddr)
                goto err_release_erange;

        pr_info(
        "Error Record Serialization Table (ERST) support is initialized.\n");

        buf = kmalloc(erst_erange.size, GFP_KERNEL);
        if (buf) {
                erst_info.buf = buf + sizeof(struct cper_pstore_record);
                erst_info.bufsize = erst_erange.size -
                                    sizeof(struct cper_pstore_record);
                rc = pstore_register(&erst_info);
                if (rc) {
                        if (rc != -EPERM)
                                pr_info(
                                "Could not register with persistent store.\n");
                        erst_info.buf = NULL;
                        erst_info.bufsize = 0;
                        kfree(buf);
                }
        } else
                pr_err(
                "Failed to allocate %lld bytes for persistent store error log.\n",
                erst_erange.size);

        /* Cleanup ERST Resources */
        apei_resources_fini(&erst_resources);

        return 0;

err_release_erange:
        release_mem_region(erst_erange.base, erst_erange.size);
err_unmap_reg:
        apei_exec_post_unmap_gars(&ctx);
err_release:
        apei_resources_release(&erst_resources);
err_fini:
        apei_resources_fini(&erst_resources);
err_put_erst_tab:
        acpi_put_table((struct acpi_table_header *)erst_tab);
err:
        erst_disable = 1;
        return rc;
}

device_initcall(erst_init);