dmi-sysfs.c

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/*
 * 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>

#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[0];
} __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 = ioremap(sel->access_method_address, sel->area_length);
    if (!mapped)
        return -EIO;

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

    iounmap(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);
    sysfs_remove_bin_file(&entry->kobj, &dmi_entry_raw_attr);
    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 kobject *dmi_kobj;
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 = -ENOMEM;
    int val;

    /* Set up our directory */
    dmi_kobj = kobject_create_and_add("dmi", firmware_kobj);
    if (!dmi_kobj)
        goto err;

    dmi_kset = kset_create_and_add("entries", NULL, dmi_kobj);
    if (!dmi_kset)
        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);
    kobject_put(dmi_kobj);
    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);
    kobject_put(dmi_kobj);
}

module_init(dmi_sysfs_init);
module_exit(dmi_sysfs_exit);

MODULE_AUTHOR("Mike Waychison <[email protected]>");
MODULE_DESCRIPTION("DMI sysfs support");
MODULE_LICENSE("GPL");