efivars.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * Originally from efivars.c,
 *
 * Copyright (C) 2001,2003,2004 Dell <Matt_Domsch@dell.com>
 * Copyright (C) 2004 Intel Corporation <matthew.e.tolentino@intel.com>
 *
 * This code takes all variables accessible from EFI runtime and
 *  exports them via sysfs
 */

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

#define EFIVARS_VERSION "0.08"
#define EFIVARS_DATE "2004-May-17"

MODULE_AUTHOR("Matt Domsch <Matt_Domsch@Dell.com>");
MODULE_DESCRIPTION("sysfs interface to EFI Variables");
MODULE_LICENSE("GPL");
MODULE_VERSION(EFIVARS_VERSION);
MODULE_ALIAS("platform:efivars");

static LIST_HEAD(efivar_sysfs_list);

static struct kset *efivars_kset;

static struct bin_attribute *efivars_new_var;
static struct bin_attribute *efivars_del_var;

struct compat_efi_variable {
	efi_char16_t  VariableName[EFI_VAR_NAME_LEN/sizeof(efi_char16_t)];
	efi_guid_t    VendorGuid;
	__u32         DataSize;
	__u8          Data[1024];
	__u32         Status;
	__u32         Attributes;
} __packed;

struct efivar_attribute {
	struct attribute attr;
	ssize_t (*show) (struct efivar_entry *entry, char *buf);
	ssize_t (*store)(struct efivar_entry *entry, const char *buf, size_t count);
};

#define EFIVAR_ATTR(_name, _mode, _show, _store) \
struct efivar_attribute efivar_attr_##_name = { \
	.attr = {.name = __stringify(_name), .mode = _mode}, \
	.show = _show, \
	.store = _store, \
};

#define to_efivar_attr(_attr) container_of(_attr, struct efivar_attribute, attr)
#define to_efivar_entry(obj)  container_of(obj, struct efivar_entry, kobj)

/*
 * Prototype for sysfs creation function
 */
static int
efivar_create_sysfs_entry(struct efivar_entry *new_var);

static ssize_t
efivar_guid_read(struct efivar_entry *entry, char *buf)
{
	struct efi_variable *var = &entry->var;
	char *str = buf;

	if (!entry || !buf)
		return 0;

	efi_guid_to_str(&var->VendorGuid, str);
	str += strlen(str);
	str += sprintf(str, "\n");

	return str - buf;
}

static ssize_t
efivar_attr_read(struct efivar_entry *entry, char *buf)
{
	struct efi_variable *var = &entry->var;
	unsigned long size = sizeof(var->Data);
	char *str = buf;
	int ret;

	if (!entry || !buf)
		return -EINVAL;

	ret = efivar_entry_get(entry, &var->Attributes, &size, var->Data);
	var->DataSize = size;
	if (ret)
		return -EIO;

	if (var->Attributes & EFI_VARIABLE_NON_VOLATILE)
		str += sprintf(str, "EFI_VARIABLE_NON_VOLATILE\n");
	if (var->Attributes & EFI_VARIABLE_BOOTSERVICE_ACCESS)
		str += sprintf(str, "EFI_VARIABLE_BOOTSERVICE_ACCESS\n");
	if (var->Attributes & EFI_VARIABLE_RUNTIME_ACCESS)
		str += sprintf(str, "EFI_VARIABLE_RUNTIME_ACCESS\n");
	if (var->Attributes & EFI_VARIABLE_HARDWARE_ERROR_RECORD)
		str += sprintf(str, "EFI_VARIABLE_HARDWARE_ERROR_RECORD\n");
	if (var->Attributes & EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS)
		str += sprintf(str,
			"EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS\n");
	if (var->Attributes &
			EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS)
		str += sprintf(str,
			"EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS\n");
	if (var->Attributes & EFI_VARIABLE_APPEND_WRITE)
		str += sprintf(str, "EFI_VARIABLE_APPEND_WRITE\n");
	return str - buf;
}

static ssize_t
efivar_size_read(struct efivar_entry *entry, char *buf)
{
	struct efi_variable *var = &entry->var;
	unsigned long size = sizeof(var->Data);
	char *str = buf;
	int ret;

	if (!entry || !buf)
		return -EINVAL;

	ret = efivar_entry_get(entry, &var->Attributes, &size, var->Data);
	var->DataSize = size;
	if (ret)
		return -EIO;

	str += sprintf(str, "0x%lx\n", var->DataSize);
	return str - buf;
}

static ssize_t
efivar_data_read(struct efivar_entry *entry, char *buf)
{
	struct efi_variable *var = &entry->var;
	unsigned long size = sizeof(var->Data);
	int ret;

	if (!entry || !buf)
		return -EINVAL;

	ret = efivar_entry_get(entry, &var->Attributes, &size, var->Data);
	var->DataSize = size;
	if (ret)
		return -EIO;

	memcpy(buf, var->Data, var->DataSize);
	return var->DataSize;
}

static inline int
sanity_check(struct efi_variable *var, efi_char16_t *name, efi_guid_t vendor,
	     unsigned long size, u32 attributes, u8 *data)
{
	/*
	 * If only updating the variable data, then the name
	 * and guid should remain the same
	 */
	if (memcmp(name, var->VariableName, sizeof(var->VariableName)) ||
		efi_guidcmp(vendor, var->VendorGuid)) {
		printk(KERN_ERR "efivars: Cannot edit the wrong variable!\n");
		return -EINVAL;
	}

	if ((size <= 0) || (attributes == 0)){
		printk(KERN_ERR "efivars: DataSize & Attributes must be valid!\n");
		return -EINVAL;
	}

	if ((attributes & ~EFI_VARIABLE_MASK) != 0 ||
	    efivar_validate(vendor, name, data, size) == false) {
		printk(KERN_ERR "efivars: Malformed variable content\n");
		return -EINVAL;
	}

	return 0;
}

static void
copy_out_compat(struct efi_variable *dst, struct compat_efi_variable *src)
{
	memcpy(dst->VariableName, src->VariableName, EFI_VAR_NAME_LEN);
	memcpy(dst->Data, src->Data, sizeof(src->Data));

	dst->VendorGuid = src->VendorGuid;
	dst->DataSize = src->DataSize;
	dst->Attributes = src->Attributes;
}

/*
 * We allow each variable to be edited via rewriting the
 * entire efi variable structure.
 */
static ssize_t
efivar_store_raw(struct efivar_entry *entry, const char *buf, size_t count)
{
	struct efi_variable *new_var, *var = &entry->var;
	efi_char16_t *name;
	unsigned long size;
	efi_guid_t vendor;
	u32 attributes;
	u8 *data;
	int err;

	if (!entry || !buf)
		return -EINVAL;

	if (in_compat_syscall()) {
		struct compat_efi_variable *compat;

		if (count != sizeof(*compat))
			return -EINVAL;

		compat = (struct compat_efi_variable *)buf;
		attributes = compat->Attributes;
		vendor = compat->VendorGuid;
		name = compat->VariableName;
		size = compat->DataSize;
		data = compat->Data;

		err = sanity_check(var, name, vendor, size, attributes, data);
		if (err)
			return err;

		copy_out_compat(&entry->var, compat);
	} else {
		if (count != sizeof(struct efi_variable))
			return -EINVAL;

		new_var = (struct efi_variable *)buf;

		attributes = new_var->Attributes;
		vendor = new_var->VendorGuid;
		name = new_var->VariableName;
		size = new_var->DataSize;
		data = new_var->Data;

		err = sanity_check(var, name, vendor, size, attributes, data);
		if (err)
			return err;

		memcpy(&entry->var, new_var, count);
	}

	err = efivar_entry_set(entry, attributes, size, data, NULL);
	if (err) {
		printk(KERN_WARNING "efivars: set_variable() failed: status=%d\n", err);
		return -EIO;
	}

	return count;
}

static ssize_t
efivar_show_raw(struct efivar_entry *entry, char *buf)
{
	struct efi_variable *var = &entry->var;
	struct compat_efi_variable *compat;
	unsigned long datasize = sizeof(var->Data);
	size_t size;
	int ret;

	if (!entry || !buf)
		return 0;

	ret = efivar_entry_get(entry, &var->Attributes, &datasize, var->Data);
	var->DataSize = datasize;
	if (ret)
		return -EIO;

	if (in_compat_syscall()) {
		compat = (struct compat_efi_variable *)buf;

		size = sizeof(*compat);
		memcpy(compat->VariableName, var->VariableName,
			EFI_VAR_NAME_LEN);
		memcpy(compat->Data, var->Data, sizeof(compat->Data));

		compat->VendorGuid = var->VendorGuid;
		compat->DataSize = var->DataSize;
		compat->Attributes = var->Attributes;
	} else {
		size = sizeof(*var);
		memcpy(buf, var, size);
	}

	return size;
}

/*
 * Generic read/write functions that call the specific functions of
 * the attributes...
 */
static ssize_t efivar_attr_show(struct kobject *kobj, struct attribute *attr,
				char *buf)
{
	struct efivar_entry *var = to_efivar_entry(kobj);
	struct efivar_attribute *efivar_attr = to_efivar_attr(attr);
	ssize_t ret = -EIO;

	if (!capable(CAP_SYS_ADMIN))
		return -EACCES;

	if (efivar_attr->show) {
		ret = efivar_attr->show(var, buf);
	}
	return ret;
}

static ssize_t efivar_attr_store(struct kobject *kobj, struct attribute *attr,
				const char *buf, size_t count)
{
	struct efivar_entry *var = to_efivar_entry(kobj);
	struct efivar_attribute *efivar_attr = to_efivar_attr(attr);
	ssize_t ret = -EIO;

	if (!capable(CAP_SYS_ADMIN))
		return -EACCES;

	if (efivar_attr->store)
		ret = efivar_attr->store(var, buf, count);

	return ret;
}

static const struct sysfs_ops efivar_attr_ops = {
	.show = efivar_attr_show,
	.store = efivar_attr_store,
};

static void efivar_release(struct kobject *kobj)
{
	struct efivar_entry *var = to_efivar_entry(kobj);
	kfree(var);
}

static EFIVAR_ATTR(guid, 0400, efivar_guid_read, NULL);
static EFIVAR_ATTR(attributes, 0400, efivar_attr_read, NULL);
static EFIVAR_ATTR(size, 0400, efivar_size_read, NULL);
static EFIVAR_ATTR(data, 0400, efivar_data_read, NULL);
static EFIVAR_ATTR(raw_var, 0600, efivar_show_raw, efivar_store_raw);

static struct attribute *def_attrs[] = {
	&efivar_attr_guid.attr,
	&efivar_attr_size.attr,
	&efivar_attr_attributes.attr,
	&efivar_attr_data.attr,
	&efivar_attr_raw_var.attr,
	NULL,
};

static struct kobj_type efivar_ktype = {
	.release = efivar_release,
	.sysfs_ops = &efivar_attr_ops,
	.default_attrs = def_attrs,
};

static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
			     struct bin_attribute *bin_attr,
			     char *buf, loff_t pos, size_t count)
{
	struct compat_efi_variable *compat = (struct compat_efi_variable *)buf;
	struct efi_variable *new_var = (struct efi_variable *)buf;
	struct efivar_entry *new_entry;
	bool need_compat = in_compat_syscall();
	efi_char16_t *name;
	unsigned long size;
	u32 attributes;
	u8 *data;
	int err;

	if (!capable(CAP_SYS_ADMIN))
		return -EACCES;

	if (need_compat) {
		if (count != sizeof(*compat))
			return -EINVAL;

		attributes = compat->Attributes;
		name = compat->VariableName;
		size = compat->DataSize;
		data = compat->Data;
	} else {
		if (count != sizeof(*new_var))
			return -EINVAL;

		attributes = new_var->Attributes;
		name = new_var->VariableName;
		size = new_var->DataSize;
		data = new_var->Data;
	}

	if ((attributes & ~EFI_VARIABLE_MASK) != 0 ||
	    efivar_validate(new_var->VendorGuid, name, data,
			    size) == false) {
		printk(KERN_ERR "efivars: Malformed variable content\n");
		return -EINVAL;
	}

	new_entry = kzalloc(sizeof(*new_entry), GFP_KERNEL);
	if (!new_entry)
		return -ENOMEM;

	if (need_compat)
		copy_out_compat(&new_entry->var, compat);
	else
		memcpy(&new_entry->var, new_var, sizeof(*new_var));

	err = efivar_entry_set(new_entry, attributes, size,
			       data, &efivar_sysfs_list);
	if (err) {
		if (err == -EEXIST)
			err = -EINVAL;
		goto out;
	}

	if (efivar_create_sysfs_entry(new_entry)) {
		printk(KERN_WARNING "efivars: failed to create sysfs entry.\n");
		kfree(new_entry);
	}
	return count;

out:
	kfree(new_entry);
	return err;
}

static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
			     struct bin_attribute *bin_attr,
			     char *buf, loff_t pos, size_t count)
{
	struct efi_variable *del_var = (struct efi_variable *)buf;
	struct compat_efi_variable *compat;
	struct efivar_entry *entry;
	efi_char16_t *name;
	efi_guid_t vendor;
	int err = 0;

	if (!capable(CAP_SYS_ADMIN))
		return -EACCES;

	if (in_compat_syscall()) {
		if (count != sizeof(*compat))
			return -EINVAL;

		compat = (struct compat_efi_variable *)buf;
		name = compat->VariableName;
		vendor = compat->VendorGuid;
	} else {
		if (count != sizeof(*del_var))
			return -EINVAL;

		name = del_var->VariableName;
		vendor = del_var->VendorGuid;
	}

	if (efivar_entry_iter_begin())
		return -EINTR;
	entry = efivar_entry_find(name, vendor, &efivar_sysfs_list, true);
	if (!entry)
		err = -EINVAL;
	else if (__efivar_entry_delete(entry))
		err = -EIO;

	if (err) {
		efivar_entry_iter_end();
		return err;
	}

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

	/* It's dead Jim.... */
	return count;
}

/**
 * efivar_create_sysfs_entry - create a new entry in sysfs
 * @new_var: efivar entry to create
 *
 * Returns 0 on success, negative error code on failure
 */
static int
efivar_create_sysfs_entry(struct efivar_entry *new_var)
{
	int short_name_size;
	char *short_name;
	unsigned long utf8_name_size;
	efi_char16_t *variable_name = new_var->var.VariableName;
	int ret;

	/*
	 * Length of the variable bytes in UTF8, plus the '-' separator,
	 * plus the GUID, plus trailing NUL
	 */
	utf8_name_size = ucs2_utf8size(variable_name);
	short_name_size = utf8_name_size + 1 + EFI_VARIABLE_GUID_LEN + 1;

	short_name = kmalloc(short_name_size, GFP_KERNEL);
	if (!short_name)
		return -ENOMEM;

	ucs2_as_utf8(short_name, variable_name, short_name_size);

	/* This is ugly, but necessary to separate one vendor's
	   private variables from another's.         */
	short_name[utf8_name_size] = '-';
	efi_guid_to_str(&new_var->var.VendorGuid,
			 short_name + utf8_name_size + 1);

	new_var->kobj.kset = efivars_kset;

	ret = kobject_init_and_add(&new_var->kobj, &efivar_ktype,
				   NULL, "%s", short_name);
	kfree(short_name);
	if (ret) {
		kobject_put(&new_var->kobj);
		return ret;
	}

	kobject_uevent(&new_var->kobj, KOBJ_ADD);
	if (efivar_entry_add(new_var, &efivar_sysfs_list)) {
		efivar_unregister(new_var);
		return -EINTR;
	}

	return 0;
}

static int
create_efivars_bin_attributes(void)
{
	struct bin_attribute *attr;
	int error;

	/* new_var */
	attr = kzalloc(sizeof(*attr), GFP_KERNEL);
	if (!attr)
		return -ENOMEM;

	attr->attr.name = "new_var";
	attr->attr.mode = 0200;
	attr->write = efivar_create;
	efivars_new_var = attr;

	/* del_var */
	attr = kzalloc(sizeof(*attr), GFP_KERNEL);
	if (!attr) {
		error = -ENOMEM;
		goto out_free;
	}
	attr->attr.name = "del_var";
	attr->attr.mode = 0200;
	attr->write = efivar_delete;
	efivars_del_var = attr;

	sysfs_bin_attr_init(efivars_new_var);
	sysfs_bin_attr_init(efivars_del_var);

	/* Register */
	error = sysfs_create_bin_file(&efivars_kset->kobj, efivars_new_var);
	if (error) {
		printk(KERN_ERR "efivars: unable to create new_var sysfs file"
			" due to error %d\n", error);
		goto out_free;
	}

	error = sysfs_create_bin_file(&efivars_kset->kobj, efivars_del_var);
	if (error) {
		printk(KERN_ERR "efivars: unable to create del_var sysfs file"
			" due to error %d\n", error);
		sysfs_remove_bin_file(&efivars_kset->kobj, efivars_new_var);
		goto out_free;
	}

	return 0;
out_free:
	kfree(efivars_del_var);
	efivars_del_var = NULL;
	kfree(efivars_new_var);
	efivars_new_var = NULL;
	return error;
}

static int efivars_sysfs_callback(efi_char16_t *name, efi_guid_t vendor,
				  unsigned long name_size, void *data)
{
	struct efivar_entry *entry;

	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
	if (!entry)
		return -ENOMEM;

	memcpy(entry->var.VariableName, name, name_size);
	memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));

	efivar_create_sysfs_entry(entry);

	return 0;
}

static int efivar_sysfs_destroy(struct efivar_entry *entry, void *data)
{
	int err = efivar_entry_remove(entry);

	if (err)
		return err;
	efivar_unregister(entry);
	return 0;
}

static void efivars_sysfs_exit(void)
{
	/* Remove all entries and destroy */
	int err;

	err = __efivar_entry_iter(efivar_sysfs_destroy, &efivar_sysfs_list,
				  NULL, NULL);
	if (err) {
		pr_err("efivars: Failed to destroy sysfs entries\n");
		return;
	}

	if (efivars_new_var)
		sysfs_remove_bin_file(&efivars_kset->kobj, efivars_new_var);
	if (efivars_del_var)
		sysfs_remove_bin_file(&efivars_kset->kobj, efivars_del_var);
	kfree(efivars_new_var);
	kfree(efivars_del_var);
	kset_unregister(efivars_kset);
}

static int efivars_sysfs_init(void)
{
	struct kobject *parent_kobj = efivars_kobject();
	int error = 0;

	/* No efivars has been registered yet */
	if (!parent_kobj || !efivar_supports_writes())
		return 0;

	printk(KERN_INFO "EFI Variables Facility v%s %s\n", EFIVARS_VERSION,
	       EFIVARS_DATE);

	efivars_kset = kset_create_and_add("vars", NULL, parent_kobj);
	if (!efivars_kset) {
		printk(KERN_ERR "efivars: Subsystem registration failed.\n");
		return -ENOMEM;
	}

	efivar_init(efivars_sysfs_callback, NULL, true, &efivar_sysfs_list);

	error = create_efivars_bin_attributes();
	if (error) {
		efivars_sysfs_exit();
		return error;
	}

	return 0;
}

module_init(efivars_sysfs_init);
module_exit(efivars_sysfs_exit);