/*
* 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;
};
/*
* 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 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;
}
/*************************************************
* 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 */
entry->dh = *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);
/* 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->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->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 <mikew@google.com>");
MODULE_DESCRIPTION("DMI sysfs support");
MODULE_LICENSE("GPL");
