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// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright (C) 2019 IBM Corporation <nayna@linux.ibm.com>
*
* This code exposes secure variables to user via sysfs
*/
#define pr_fmt(fmt) "secvar-sysfs: "fmt
#include <linux/slab.h>
#include <linux/compat.h>
#include <linux/string.h>
#include <linux/of.h>
#include <asm/secvar.h>
#define NAME_MAX_SIZE 1024
static struct kobject *secvar_kobj;
static struct kset *secvar_kset;
static ssize_t format_show(struct kobject *kobj, struct kobj_attribute *attr,
char *buf)
{
ssize_t rc = 0;
struct device_node *node;
const char *format;
node = of_find_compatible_node(NULL, NULL, "ibm,secvar-backend");
if (!of_device_is_available(node)) {
rc = -ENODEV;
goto out;
}
rc = of_property_read_string(node, "format", &format);
if (rc)
goto out;
rc = sprintf(buf, "%s\n", format);
out:
of_node_put(node);
return rc;
}
static ssize_t size_show(struct kobject *kobj, struct kobj_attribute *attr,
char *buf)
{
uint64_t dsize;
int rc;
rc = secvar_ops->get(kobj->name, strlen(kobj->name) + 1, NULL, &dsize);
if (rc) {
pr_err("Error retrieving %s variable size %d\n", kobj->name,
rc);
return rc;
}
return sprintf(buf, "%llu\n", dsize);
}
static ssize_t data_read(struct file *filep, struct kobject *kobj,
struct bin_attribute *attr, char *buf, loff_t off,
size_t count)
{
uint64_t dsize;
char *data;
int rc;
rc = secvar_ops->get(kobj->name, strlen(kobj->name) + 1, NULL, &dsize);
if (rc) {
pr_err("Error getting %s variable size %d\n", kobj->name, rc);
return rc;
}
pr_debug("dsize is %llu\n", dsize);
data = kzalloc(dsize, GFP_KERNEL);
if (!data)
return -ENOMEM;
rc = secvar_ops->get(kobj->name, strlen(kobj->name) + 1, data, &dsize);
if (rc) {
pr_err("Error getting %s variable %d\n", kobj->name, rc);
goto data_fail;
}
rc = memory_read_from_buffer(buf, count, &off, data, dsize);
data_fail:
kfree(data);
return rc;
}
static ssize_t update_write(struct file *filep, struct kobject *kobj,
struct bin_attribute *attr, char *buf, loff_t off,
size_t count)
{
int rc;
pr_debug("count is %ld\n", count);
rc = secvar_ops->set(kobj->name, strlen(kobj->name) + 1, buf, count);
if (rc) {
pr_err("Error setting the %s variable %d\n", kobj->name, rc);
return rc;
}
return count;
}
static struct kobj_attribute format_attr = __ATTR_RO(format);
static struct kobj_attribute size_attr = __ATTR_RO(size);
static struct bin_attribute data_attr = __BIN_ATTR_RO(data, 0);
static struct bin_attribute update_attr = __BIN_ATTR_WO(update, 0);
static struct bin_attribute *secvar_bin_attrs[] = {
&data_attr,
&update_attr,
NULL,
};
static struct attribute *secvar_attrs[] = {
&size_attr.attr,
NULL,
};
static const struct attribute_group secvar_attr_group = {
.attrs = secvar_attrs,
.bin_attrs = secvar_bin_attrs,
};
__ATTRIBUTE_GROUPS(secvar_attr);
static struct kobj_type secvar_ktype = {
.sysfs_ops = &kobj_sysfs_ops,
.default_groups = secvar_attr_groups,
};
static int update_kobj_size(void)
{
struct device_node *node;
u64 varsize;
int rc = 0;
node = of_find_compatible_node(NULL, NULL, "ibm,secvar-backend");
if (!of_device_is_available(node)) {
rc = -ENODEV;
goto out;
}
rc = of_property_read_u64(node, "max-var-size", &varsize);
if (rc)
goto out;
data_attr.size = varsize;
update_attr.size = varsize;
out:
of_node_put(node);
return rc;
}
static int secvar_sysfs_load(void)
{
char *name;
uint64_t namesize = 0;
struct kobject *kobj;
int rc;
name = kzalloc(NAME_MAX_SIZE, GFP_KERNEL);
if (!name)
return -ENOMEM;
do {
rc = secvar_ops->get_next(name, &namesize, NAME_MAX_SIZE);
if (rc) {
if (rc != -ENOENT)
pr_err("error getting secvar from firmware %d\n",
rc);
break;
}
kobj = kzalloc(sizeof(*kobj), GFP_KERNEL);
if (!kobj) {
rc = -ENOMEM;
break;
}
kobject_init(kobj, &secvar_ktype);
rc = kobject_add(kobj, &secvar_kset->kobj, "%s", name);
if (rc) {
pr_warn("kobject_add error %d for attribute: %s\n", rc,
name);
kobject_put(kobj);
kobj = NULL;
}
if (kobj)
kobject_uevent(kobj, KOBJ_ADD);
} while (!rc);
kfree(name);
return rc;
}
static int secvar_sysfs_init(void)
{
int rc;
if (!secvar_ops) {
pr_warn("secvar: failed to retrieve secvar operations.\n");
return -ENODEV;
}
secvar_kobj = kobject_create_and_add("secvar", firmware_kobj);
if (!secvar_kobj) {
pr_err("secvar: Failed to create firmware kobj\n");
return -ENOMEM;
}
rc = sysfs_create_file(secvar_kobj, &format_attr.attr);
if (rc) {
kobject_put(secvar_kobj);
return -ENOMEM;
}
secvar_kset = kset_create_and_add("vars", NULL, secvar_kobj);
if (!secvar_kset) {
pr_err("secvar: sysfs kobject registration failed.\n");
kobject_put(secvar_kobj);
return -ENOMEM;
}
rc = update_kobj_size();
if (rc) {
pr_err("Cannot read the size of the attribute\n");
return rc;
}
secvar_sysfs_load();
return 0;
}
late_initcall(secvar_sysfs_init);
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