// SPDX-License-Identifier: GPL-2.0-only
/*
 * dmi-sysfs.c
 *
 * This module exports the DMI tables read-only to userspace through the
 * sysfs file system.
 *
 * Data is currently found below
 *    /sys/firmware/dmi/...
 *
 * DMI attributes are presented in attribute files with names
 * formatted using %d-%d, so that the first integer indicates the
 * structure type (0-255), and the second field is the instance of that
 * entry.
 *
 * Copyright 2011 Google, Inc.
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kobject.h>
#include <linux/dmi.h>
#include <linux/capability.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/io.h>
#include <asm/dmi.h>

#define MAX_ENTRY_TYPE 255 /* Most of these aren't used, but we consider
                              the top entry type is only 8 bits */

struct dmi_sysfs_entry {
        struct dmi_header dh;
        struct kobject kobj;
        int instance;
        int position;
        struct list_head list;
        struct kobject *child;
};

/*
 * Global list of dmi_sysfs_entry.  Even though this should only be
 * manipulated at setup and teardown, the lazy nature of the kobject
 * system means we get lazy removes.
 */
static LIST_HEAD(entry_list);
static DEFINE_SPINLOCK(entry_list_lock);

/* dmi_sysfs_attribute - Top level attribute. used by all entries. */
struct dmi_sysfs_attribute {
        struct attribute attr;
        ssize_t (*show)(struct dmi_sysfs_entry *entry, char *buf);
};

#define DMI_SYSFS_ATTR(_entry, _name) \
struct dmi_sysfs_attribute dmi_sysfs_attr_##_entry##_##_name = { \
        .attr = {.name = __stringify(_name), .mode = 0400}, \
        .show = dmi_sysfs_##_entry##_##_name, \
}

/*
 * dmi_sysfs_mapped_attribute - Attribute where we require the entry be
 * mapped in.  Use in conjunction with dmi_sysfs_specialize_attr_ops.
 */
struct dmi_sysfs_mapped_attribute {
        struct attribute attr;
        ssize_t (*show)(struct dmi_sysfs_entry *entry,
                        const struct dmi_header *dh,
                        char *buf);
};

#define DMI_SYSFS_MAPPED_ATTR(_entry, _name) \
struct dmi_sysfs_mapped_attribute dmi_sysfs_attr_##_entry##_##_name = { \
        .attr = {.name = __stringify(_name), .mode = 0400}, \
        .show = dmi_sysfs_##_entry##_##_name, \
}

/*************************************************
 * Generic DMI entry support.
 *************************************************/
static void dmi_entry_free(struct kobject *kobj)
{
        kfree(kobj);
}

static struct dmi_sysfs_entry *to_entry(struct kobject *kobj)
{
        return container_of(kobj, struct dmi_sysfs_entry, kobj);
}

static struct dmi_sysfs_attribute *to_attr(struct attribute *attr)
{
        return container_of(attr, struct dmi_sysfs_attribute, attr);
}

static ssize_t dmi_sysfs_attr_show(struct kobject *kobj,
                                   struct attribute *_attr, char *buf)
{
        struct dmi_sysfs_entry *entry = to_entry(kobj);
        struct dmi_sysfs_attribute *attr = to_attr(_attr);

        /* DMI stuff is only ever admin visible */
        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        return attr->show(entry, buf);
}

static const struct sysfs_ops dmi_sysfs_attr_ops = {
        .show = dmi_sysfs_attr_show,
};

typedef ssize_t (*dmi_callback)(struct dmi_sysfs_entry *,
                                const struct dmi_header *dh, void *);

struct find_dmi_data {
        struct dmi_sysfs_entry  *entry;
        dmi_callback            callback;
        void                    *private;
        int                     instance_countdown;
        ssize_t                 ret;
};

static void find_dmi_entry_helper(const struct dmi_header *dh,
                                  void *_data)
{
        struct find_dmi_data *data = _data;
        struct dmi_sysfs_entry *entry = data->entry;

        /* Is this the entry we want? */
        if (dh->type != entry->dh.type)
                return;

        if (data->instance_countdown != 0) {
                /* try the next instance? */
                data->instance_countdown--;
                return;
        }

        /*
         * Don't ever revisit the instance.  Short circuit later
         * instances by letting the instance_countdown run negative
         */
        data->instance_countdown--;

        /* Found the entry */
        data->ret = data->callback(entry, dh, data->private);
}

/* State for passing the read parameters through dmi_find_entry() */
struct dmi_read_state {
        char *buf;
        loff_t pos;
        size_t count;
};

static ssize_t find_dmi_entry(struct dmi_sysfs_entry *entry,
                              dmi_callback callback, void *private)
{
        struct find_dmi_data data = {
                .entry = entry,
                .callback = callback,
                .private = private,
                .instance_countdown = entry->instance,
                .ret = -EIO,  /* To signal the entry disappeared */
        };
        int ret;

        ret = dmi_walk(find_dmi_entry_helper, &data);
        /* This shouldn't happen, but just in case. */
        if (ret)
                return -EINVAL;
        return data.ret;
}

/*
 * Calculate and return the byte length of the dmi entry identified by
 * dh.  This includes both the formatted portion as well as the
 * unformatted string space, including the two trailing nul characters.
 */
static size_t dmi_entry_length(const struct dmi_header *dh)
{
        const char *p = (const char *)dh;

        p += dh->length;

        while (p[0] || p[1])
                p++;

        return 2 + p - (const char *)dh;
}

/*************************************************
 * Support bits for specialized DMI entry support
 *************************************************/
struct dmi_entry_attr_show_data {
        struct attribute *attr;
        char *buf;
};

static ssize_t dmi_entry_attr_show_helper(struct dmi_sysfs_entry *entry,
                                          const struct dmi_header *dh,
                                          void *_data)
{
        struct dmi_entry_attr_show_data *data = _data;
        struct dmi_sysfs_mapped_attribute *attr;

        attr = container_of(data->attr,
                            struct dmi_sysfs_mapped_attribute, attr);
        return attr->show(entry, dh, data->buf);
}

static ssize_t dmi_entry_attr_show(struct kobject *kobj,
                                   struct attribute *attr,
                                   char *buf)
{
        struct dmi_entry_attr_show_data data = {
                .attr = attr,
                .buf  = buf,
        };
        /* Find the entry according to our parent and call the
         * normalized show method hanging off of the attribute */
        return find_dmi_entry(to_entry(kobj->parent),
                              dmi_entry_attr_show_helper, &data);
}

static const struct sysfs_ops dmi_sysfs_specialize_attr_ops = {
        .show = dmi_entry_attr_show,
};

/*************************************************
 * Specialized DMI entry support.
 *************************************************/

/*** Type 15 - System Event Table ***/

#define DMI_SEL_ACCESS_METHOD_IO8       0x00
#define DMI_SEL_ACCESS_METHOD_IO2x8     0x01
#define DMI_SEL_ACCESS_METHOD_IO16      0x02
#define DMI_SEL_ACCESS_METHOD_PHYS32    0x03
#define DMI_SEL_ACCESS_METHOD_GPNV      0x04

struct dmi_system_event_log {
        struct dmi_header header;
        u16     area_length;
        u16     header_start_offset;
        u16     data_start_offset;
        u8      access_method;
        u8      status;
        u32     change_token;
        union {
                struct {
                        u16 index_addr;
                        u16 data_addr;
                } io;
                u32     phys_addr32;
                u16     gpnv_handle;
                u32     access_method_address;
        };
        u8      header_format;
        u8      type_descriptors_supported_count;
        u8      per_log_type_descriptor_length;
        u8      supported_log_type_descriptos[];
} __packed;

#define DMI_SYSFS_SEL_FIELD(_field) \
static ssize_t dmi_sysfs_sel_##_field(struct dmi_sysfs_entry *entry, \
                                      const struct dmi_header *dh, \
                                      char *buf) \
{ \
        struct dmi_system_event_log sel; \
        if (sizeof(sel) > dmi_entry_length(dh)) \
                return -EIO; \
        memcpy(&sel, dh, sizeof(sel)); \
        return sprintf(buf, "%u\n", sel._field); \
} \
static DMI_SYSFS_MAPPED_ATTR(sel, _field)

DMI_SYSFS_SEL_FIELD(area_length);
DMI_SYSFS_SEL_FIELD(header_start_offset);
DMI_SYSFS_SEL_FIELD(data_start_offset);
DMI_SYSFS_SEL_FIELD(access_method);
DMI_SYSFS_SEL_FIELD(status);
DMI_SYSFS_SEL_FIELD(change_token);
DMI_SYSFS_SEL_FIELD(access_method_address);
DMI_SYSFS_SEL_FIELD(header_format);
DMI_SYSFS_SEL_FIELD(type_descriptors_supported_count);
DMI_SYSFS_SEL_FIELD(per_log_type_descriptor_length);

static struct attribute *dmi_sysfs_sel_attrs[] = {
        &dmi_sysfs_attr_sel_area_length.attr,
        &dmi_sysfs_attr_sel_header_start_offset.attr,
        &dmi_sysfs_attr_sel_data_start_offset.attr,
        &dmi_sysfs_attr_sel_access_method.attr,
        &dmi_sysfs_attr_sel_status.attr,
        &dmi_sysfs_attr_sel_change_token.attr,
        &dmi_sysfs_attr_sel_access_method_address.attr,
        &dmi_sysfs_attr_sel_header_format.attr,
        &dmi_sysfs_attr_sel_type_descriptors_supported_count.attr,
        &dmi_sysfs_attr_sel_per_log_type_descriptor_length.attr,
        NULL,
};


static struct kobj_type dmi_system_event_log_ktype = {
        .release = dmi_entry_free,
        .sysfs_ops = &dmi_sysfs_specialize_attr_ops,
        .default_attrs = dmi_sysfs_sel_attrs,
};

typedef u8 (*sel_io_reader)(const struct dmi_system_event_log *sel,
                            loff_t offset);

static DEFINE_MUTEX(io_port_lock);

static u8 read_sel_8bit_indexed_io(const struct dmi_system_event_log *sel,
                                   loff_t offset)
{
        u8 ret;

        mutex_lock(&io_port_lock);
        outb((u8)offset, sel->io.index_addr);
        ret = inb(sel->io.data_addr);
        mutex_unlock(&io_port_lock);
        return ret;
}

static u8 read_sel_2x8bit_indexed_io(const struct dmi_system_event_log *sel,
                                     loff_t offset)
{
        u8 ret;

        mutex_lock(&io_port_lock);
        outb((u8)offset, sel->io.index_addr);
        outb((u8)(offset >> 8), sel->io.index_addr + 1);
        ret = inb(sel->io.data_addr);
        mutex_unlock(&io_port_lock);
        return ret;
}

static u8 read_sel_16bit_indexed_io(const struct dmi_system_event_log *sel,
                                    loff_t offset)
{
        u8 ret;

        mutex_lock(&io_port_lock);
        outw((u16)offset, sel->io.index_addr);
        ret = inb(sel->io.data_addr);
        mutex_unlock(&io_port_lock);
        return ret;
}

static sel_io_reader sel_io_readers[] = {
        [DMI_SEL_ACCESS_METHOD_IO8]     = read_sel_8bit_indexed_io,
        [DMI_SEL_ACCESS_METHOD_IO2x8]   = read_sel_2x8bit_indexed_io,
        [DMI_SEL_ACCESS_METHOD_IO16]    = read_sel_16bit_indexed_io,
};

static ssize_t dmi_sel_raw_read_io(struct dmi_sysfs_entry *entry,
                                   const struct dmi_system_event_log *sel,
                                   char *buf, loff_t pos, size_t count)
{
        ssize_t wrote = 0;

        sel_io_reader io_reader = sel_io_readers[sel->access_method];

        while (count && pos < sel->area_length) {
                count--;
                *(buf++) = io_reader(sel, pos++);
                wrote++;
        }

        return wrote;
}

static ssize_t dmi_sel_raw_read_phys32(struct dmi_sysfs_entry *entry,
                                       const struct dmi_system_event_log *sel,
                                       char *buf, loff_t pos, size_t count)
{
        u8 __iomem *mapped;
        ssize_t wrote = 0;

        mapped = dmi_remap(sel->access_method_address, sel->area_length);
        if (!mapped)
                return -EIO;

        while (count && pos < sel->area_length) {
                count--;
                *(buf++) = readb(mapped + pos++);
                wrote++;
        }

        dmi_unmap(mapped);
        return wrote;
}

static ssize_t dmi_sel_raw_read_helper(struct dmi_sysfs_entry *entry,
                                       const struct dmi_header *dh,
                                       void *_state)
{
        struct dmi_read_state *state = _state;
        struct dmi_system_event_log sel;

        if (sizeof(sel) > dmi_entry_length(dh))
                return -EIO;

        memcpy(&sel, dh, sizeof(sel));

        switch (sel.access_method) {
        case DMI_SEL_ACCESS_METHOD_IO8:
        case DMI_SEL_ACCESS_METHOD_IO2x8:
        case DMI_SEL_ACCESS_METHOD_IO16:
                return dmi_sel_raw_read_io(entry, &sel, state->buf,
                                           state->pos, state->count);
        case DMI_SEL_ACCESS_METHOD_PHYS32:
                return dmi_sel_raw_read_phys32(entry, &sel, state->buf,
                                               state->pos, state->count);
        case DMI_SEL_ACCESS_METHOD_GPNV:
                pr_info("dmi-sysfs: GPNV support missing.\n");
                return -EIO;
        default:
                pr_info("dmi-sysfs: Unknown access method %02x\n",
                        sel.access_method);
                return -EIO;
        }
}

static ssize_t dmi_sel_raw_read(struct file *filp, struct kobject *kobj,
                                struct bin_attribute *bin_attr,
                                char *buf, loff_t pos, size_t count)
{
        struct dmi_sysfs_entry *entry = to_entry(kobj->parent);
        struct dmi_read_state state = {
                .buf = buf,
                .pos = pos,
                .count = count,
        };

        return find_dmi_entry(entry, dmi_sel_raw_read_helper, &state);
}

static struct bin_attribute dmi_sel_raw_attr = {
        .attr = {.name = "raw_event_log", .mode = 0400},
        .read = dmi_sel_raw_read,
};

static int dmi_system_event_log(struct dmi_sysfs_entry *entry)
{
        int ret;

        entry->child = kzalloc(sizeof(*entry->child), GFP_KERNEL);
        if (!entry->child)
                return -ENOMEM;
        ret = kobject_init_and_add(entry->child,
                                   &dmi_system_event_log_ktype,
                                   &entry->kobj,
                                   "system_event_log");
        if (ret)
                goto out_free;

        ret = sysfs_create_bin_file(entry->child, &dmi_sel_raw_attr);
        if (ret)
                goto out_del;

        return 0;

out_del:
        kobject_del(entry->child);
out_free:
        kfree(entry->child);
        return ret;
}

/*************************************************
 * Generic DMI entry support.
 *************************************************/

static ssize_t dmi_sysfs_entry_length(struct dmi_sysfs_entry *entry, char *buf)
{
        return sprintf(buf, "%d\n", entry->dh.length);
}

static ssize_t dmi_sysfs_entry_handle(struct dmi_sysfs_entry *entry, char *buf)
{
        return sprintf(buf, "%d\n", entry->dh.handle);
}

static ssize_t dmi_sysfs_entry_type(struct dmi_sysfs_entry *entry, char *buf)
{
        return sprintf(buf, "%d\n", entry->dh.type);
}

static ssize_t dmi_sysfs_entry_instance(struct dmi_sysfs_entry *entry,
                                        char *buf)
{
        return sprintf(buf, "%d\n", entry->instance);
}

static ssize_t dmi_sysfs_entry_position(struct dmi_sysfs_entry *entry,
                                        char *buf)
{
        return sprintf(buf, "%d\n", entry->position);
}

static DMI_SYSFS_ATTR(entry, length);
static DMI_SYSFS_ATTR(entry, handle);
static DMI_SYSFS_ATTR(entry, type);
static DMI_SYSFS_ATTR(entry, instance);
static DMI_SYSFS_ATTR(entry, position);

static struct attribute *dmi_sysfs_entry_attrs[] = {
        &dmi_sysfs_attr_entry_length.attr,
        &dmi_sysfs_attr_entry_handle.attr,
        &dmi_sysfs_attr_entry_type.attr,
        &dmi_sysfs_attr_entry_instance.attr,
        &dmi_sysfs_attr_entry_position.attr,
        NULL,
};

static ssize_t dmi_entry_raw_read_helper(struct dmi_sysfs_entry *entry,
                                         const struct dmi_header *dh,
                                         void *_state)
{
        struct dmi_read_state *state = _state;
        size_t entry_length;

        entry_length = dmi_entry_length(dh);

        return memory_read_from_buffer(state->buf, state->count,
                                       &state->pos, dh, entry_length);
}

static ssize_t dmi_entry_raw_read(struct file *filp,
                                  struct kobject *kobj,
                                  struct bin_attribute *bin_attr,
                                  char *buf, loff_t pos, size_t count)
{
        struct dmi_sysfs_entry *entry = to_entry(kobj);
        struct dmi_read_state state = {
                .buf = buf,
                .pos = pos,
                .count = count,
        };

        return find_dmi_entry(entry, dmi_entry_raw_read_helper, &state);
}

static const struct bin_attribute dmi_entry_raw_attr = {
        .attr = {.name = "raw", .mode = 0400},
        .read = dmi_entry_raw_read,
};

static void dmi_sysfs_entry_release(struct kobject *kobj)
{
        struct dmi_sysfs_entry *entry = to_entry(kobj);

        spin_lock(&entry_list_lock);
        list_del(&entry->list);
        spin_unlock(&entry_list_lock);
        kfree(entry);
}

static struct kobj_type dmi_sysfs_entry_ktype = {
        .release = dmi_sysfs_entry_release,
        .sysfs_ops = &dmi_sysfs_attr_ops,
        .default_attrs = dmi_sysfs_entry_attrs,
};

static struct kset *dmi_kset;

/* Global count of all instances seen.  Only for setup */
static int __initdata instance_counts[MAX_ENTRY_TYPE + 1];

/* Global positional count of all entries seen.  Only for setup */
static int __initdata position_count;

static void __init dmi_sysfs_register_handle(const struct dmi_header *dh,
                                             void *_ret)
{
        struct dmi_sysfs_entry *entry;
        int *ret = _ret;

        /* If a previous entry saw an error, short circuit */
        if (*ret)
                return;

        /* Allocate and register a new entry into the entries set */
        entry = kzalloc(sizeof(*entry), GFP_KERNEL);
        if (!entry) {
                *ret = -ENOMEM;
                return;
        }

        /* Set the key */
        memcpy(&entry->dh, dh, sizeof(*dh));
        entry->instance = instance_counts[dh->type]++;
        entry->position = position_count++;

        entry->kobj.kset = dmi_kset;
        *ret = kobject_init_and_add(&entry->kobj, &dmi_sysfs_entry_ktype, NULL,
                                    "%d-%d", dh->type, entry->instance);

        if (*ret) {
                kfree(entry);
                return;
        }

        /* Thread on the global list for cleanup */
        spin_lock(&entry_list_lock);
        list_add_tail(&entry->list, &entry_list);
        spin_unlock(&entry_list_lock);

        /* Handle specializations by type */
        switch (dh->type) {
        case DMI_ENTRY_SYSTEM_EVENT_LOG:
                *ret = dmi_system_event_log(entry);
                break;
        default:
                /* No specialization */
                break;
        }
        if (*ret)
                goto out_err;

        /* Create the raw binary file to access the entry */
        *ret = sysfs_create_bin_file(&entry->kobj, &dmi_entry_raw_attr);
        if (*ret)
                goto out_err;

        return;
out_err:
        kobject_put(entry->child);
        kobject_put(&entry->kobj);
        return;
}

static void cleanup_entry_list(void)
{
        struct dmi_sysfs_entry *entry, *next;

        /* No locks, we are on our way out */
        list_for_each_entry_safe(entry, next, &entry_list, list) {
                kobject_put(entry->child);
                kobject_put(&entry->kobj);
        }
}

static int __init dmi_sysfs_init(void)
{
        int error;
        int val;

        if (!dmi_kobj) {
                pr_debug("dmi-sysfs: dmi entry is absent.\n");
                error = -ENODATA;
                goto err;
        }

        dmi_kset = kset_create_and_add("entries", NULL, dmi_kobj);
        if (!dmi_kset) {
                error = -ENOMEM;
                goto err;
        }

        val = 0;
        error = dmi_walk(dmi_sysfs_register_handle, &val);
        if (error)
                goto err;
        if (val) {
                error = val;
                goto err;
        }

        pr_debug("dmi-sysfs: loaded.\n");

        return 0;
err:
        cleanup_entry_list();
        kset_unregister(dmi_kset);
        return error;
}

/* clean up everything. */
static void __exit dmi_sysfs_exit(void)
{
        pr_debug("dmi-sysfs: unloading.\n");
        cleanup_entry_list();
        kset_unregister(dmi_kset);
}

module_init(dmi_sysfs_init);
module_exit(dmi_sysfs_exit);

MODULE_AUTHOR("Mike Waychison <mikew@google.com>");
MODULE_DESCRIPTION("DMI sysfs support");
MODULE_LICENSE("GPL");