1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 * Copyright (C) 2019 IBM Corporation <nayna@linux.ibm.com>
  4 *
  5 * This code exposes secure variables to user via sysfs
  6 */
  7
  8#define pr_fmt(fmt) "secvar-sysfs: "fmt
  9
 10#include <linux/slab.h>
 11#include <linux/compat.h>
 12#include <linux/string.h>
 13#include <linux/of.h>
 14#include <asm/secvar.h>
 15
 16#define NAME_MAX_SIZE	   1024
 17
 18static struct kobject *secvar_kobj;
 19static struct kset *secvar_kset;
 20
 21static ssize_t format_show(struct kobject *kobj, struct kobj_attribute *attr,
 22			   char *buf)
 23{
 24	ssize_t rc = 0;
 25	struct device_node *node;
 26	const char *format;
 27
 28	node = of_find_compatible_node(NULL, NULL, "ibm,secvar-backend");
 29	if (!of_device_is_available(node))
 30		return -ENODEV;
 31
 32	rc = of_property_read_string(node, "format", &format);
 33	if (rc)
 34		return rc;
 35
 36	rc = sprintf(buf, "%s\n", format);
 37
 38	of_node_put(node);
 39
 40	return rc;
 41}
 42
 43
 44static ssize_t size_show(struct kobject *kobj, struct kobj_attribute *attr,
 45			 char *buf)
 46{
 47	uint64_t dsize;
 48	int rc;
 49
 50	rc = secvar_ops->get(kobj->name, strlen(kobj->name) + 1, NULL, &dsize);
 51	if (rc) {
 52		pr_err("Error retrieving %s variable size %d\n", kobj->name,
 53		       rc);
 54		return rc;
 55	}
 56
 57	return sprintf(buf, "%llu\n", dsize);
 58}
 59
 60static ssize_t data_read(struct file *filep, struct kobject *kobj,
 61			 struct bin_attribute *attr, char *buf, loff_t off,
 62			 size_t count)
 63{
 64	uint64_t dsize;
 65	char *data;
 66	int rc;
 67
 68	rc = secvar_ops->get(kobj->name, strlen(kobj->name) + 1, NULL, &dsize);
 69	if (rc) {
 70		pr_err("Error getting %s variable size %d\n", kobj->name, rc);
 71		return rc;
 72	}
 73	pr_debug("dsize is %llu\n", dsize);
 74
 75	data = kzalloc(dsize, GFP_KERNEL);
 76	if (!data)
 77		return -ENOMEM;
 78
 79	rc = secvar_ops->get(kobj->name, strlen(kobj->name) + 1, data, &dsize);
 80	if (rc) {
 81		pr_err("Error getting %s variable %d\n", kobj->name, rc);
 82		goto data_fail;
 83	}
 84
 85	rc = memory_read_from_buffer(buf, count, &off, data, dsize);
 86
 87data_fail:
 88	kfree(data);
 89	return rc;
 90}
 91
 92static ssize_t update_write(struct file *filep, struct kobject *kobj,
 93			    struct bin_attribute *attr, char *buf, loff_t off,
 94			    size_t count)
 95{
 96	int rc;
 97
 98	pr_debug("count is %ld\n", count);
 99	rc = secvar_ops->set(kobj->name, strlen(kobj->name) + 1, buf, count);
100	if (rc) {
101		pr_err("Error setting the %s variable %d\n", kobj->name, rc);
102		return rc;
103	}
104
105	return count;
106}
107
108static struct kobj_attribute format_attr = __ATTR_RO(format);
109
110static struct kobj_attribute size_attr = __ATTR_RO(size);
111
112static struct bin_attribute data_attr = __BIN_ATTR_RO(data, 0);
113
114static struct bin_attribute update_attr = __BIN_ATTR_WO(update, 0);
115
116static struct bin_attribute *secvar_bin_attrs[] = {
117	&data_attr,
118	&update_attr,
119	NULL,
120};
121
122static struct attribute *secvar_attrs[] = {
123	&size_attr.attr,
124	NULL,
125};
126
127static const struct attribute_group secvar_attr_group = {
128	.attrs = secvar_attrs,
129	.bin_attrs = secvar_bin_attrs,
130};
131__ATTRIBUTE_GROUPS(secvar_attr);
132
133static struct kobj_type secvar_ktype = {
134	.sysfs_ops	= &kobj_sysfs_ops,
135	.default_groups = secvar_attr_groups,
136};
137
138static int update_kobj_size(void)
139{
140
141	struct device_node *node;
142	u64 varsize;
143	int rc = 0;
144
145	node = of_find_compatible_node(NULL, NULL, "ibm,secvar-backend");
146	if (!of_device_is_available(node)) {
147		rc = -ENODEV;
148		goto out;
149	}
150
151	rc = of_property_read_u64(node, "max-var-size", &varsize);
152	if (rc)
153		goto out;
154
155	data_attr.size = varsize;
156	update_attr.size = varsize;
157
158out:
159	of_node_put(node);
160
161	return rc;
162}
163
164static int secvar_sysfs_load(void)
165{
166	char *name;
167	uint64_t namesize = 0;
168	struct kobject *kobj;
169	int rc;
170
171	name = kzalloc(NAME_MAX_SIZE, GFP_KERNEL);
172	if (!name)
173		return -ENOMEM;
174
175	do {
176		rc = secvar_ops->get_next(name, &namesize, NAME_MAX_SIZE);
177		if (rc) {
178			if (rc != -ENOENT)
179				pr_err("error getting secvar from firmware %d\n",
180				       rc);
181			break;
182		}
183
184		kobj = kzalloc(sizeof(*kobj), GFP_KERNEL);
185		if (!kobj) {
186			rc = -ENOMEM;
187			break;
188		}
189
190		kobject_init(kobj, &secvar_ktype);
191
192		rc = kobject_add(kobj, &secvar_kset->kobj, "%s", name);
193		if (rc) {
194			pr_warn("kobject_add error %d for attribute: %s\n", rc,
195				name);
196			kobject_put(kobj);
197			kobj = NULL;
198		}
199
200		if (kobj)
201			kobject_uevent(kobj, KOBJ_ADD);
202
203	} while (!rc);
204
205	kfree(name);
206	return rc;
207}
208
209static int secvar_sysfs_init(void)
210{
211	int rc;
212
213	if (!secvar_ops) {
214		pr_warn("secvar: failed to retrieve secvar operations.\n");
215		return -ENODEV;
216	}
217
218	secvar_kobj = kobject_create_and_add("secvar", firmware_kobj);
219	if (!secvar_kobj) {
220		pr_err("secvar: Failed to create firmware kobj\n");
221		return -ENOMEM;
222	}
223
224	rc = sysfs_create_file(secvar_kobj, &format_attr.attr);
225	if (rc) {
226		kobject_put(secvar_kobj);
227		return -ENOMEM;
228	}
229
230	secvar_kset = kset_create_and_add("vars", NULL, secvar_kobj);
231	if (!secvar_kset) {
232		pr_err("secvar: sysfs kobject registration failed.\n");
233		kobject_put(secvar_kobj);
234		return -ENOMEM;
235	}
236
237	rc = update_kobj_size();
238	if (rc) {
239		pr_err("Cannot read the size of the attribute\n");
240		return rc;
241	}
242
243	secvar_sysfs_load();
244
245	return 0;
246}
247
248late_initcall(secvar_sysfs_init);