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		rc = -ENODEV;
 31		goto out;
 32	}
 33
 34	rc = of_property_read_string(node, "format", &format);
 35	if (rc)
 36		goto out;
 37
 38	rc = sprintf(buf, "%s\n", format);
 39
 40out:
 41	of_node_put(node);
 42
 43	return rc;
 44}
 45
 46
 47static ssize_t size_show(struct kobject *kobj, struct kobj_attribute *attr,
 48			 char *buf)
 49{
 50	uint64_t dsize;
 51	int rc;
 52
 53	rc = secvar_ops->get(kobj->name, strlen(kobj->name) + 1, NULL, &dsize);
 54	if (rc) {
 55		pr_err("Error retrieving %s variable size %d\n", kobj->name,
 56		       rc);
 57		return rc;
 58	}
 59
 60	return sprintf(buf, "%llu\n", dsize);
 61}
 62
 63static ssize_t data_read(struct file *filep, struct kobject *kobj,
 64			 struct bin_attribute *attr, char *buf, loff_t off,
 65			 size_t count)
 66{
 67	uint64_t dsize;
 68	char *data;
 69	int rc;
 70
 71	rc = secvar_ops->get(kobj->name, strlen(kobj->name) + 1, NULL, &dsize);
 72	if (rc) {
 73		pr_err("Error getting %s variable size %d\n", kobj->name, rc);
 74		return rc;
 75	}
 76	pr_debug("dsize is %llu\n", dsize);
 77
 78	data = kzalloc(dsize, GFP_KERNEL);
 79	if (!data)
 80		return -ENOMEM;
 81
 82	rc = secvar_ops->get(kobj->name, strlen(kobj->name) + 1, data, &dsize);
 83	if (rc) {
 84		pr_err("Error getting %s variable %d\n", kobj->name, rc);
 85		goto data_fail;
 86	}
 87
 88	rc = memory_read_from_buffer(buf, count, &off, data, dsize);
 89
 90data_fail:
 91	kfree(data);
 92	return rc;
 93}
 94
 95static ssize_t update_write(struct file *filep, struct kobject *kobj,
 96			    struct bin_attribute *attr, char *buf, loff_t off,
 97			    size_t count)
 98{
 99	int rc;
100
101	pr_debug("count is %ld\n", count);
102	rc = secvar_ops->set(kobj->name, strlen(kobj->name) + 1, buf, count);
103	if (rc) {
104		pr_err("Error setting the %s variable %d\n", kobj->name, rc);
105		return rc;
106	}
107
108	return count;
109}
110
111static struct kobj_attribute format_attr = __ATTR_RO(format);
112
113static struct kobj_attribute size_attr = __ATTR_RO(size);
114
115static struct bin_attribute data_attr = __BIN_ATTR_RO(data, 0);
116
117static struct bin_attribute update_attr = __BIN_ATTR_WO(update, 0);
118
119static struct bin_attribute *secvar_bin_attrs[] = {
120	&data_attr,
121	&update_attr,
122	NULL,
123};
124
125static struct attribute *secvar_attrs[] = {
126	&size_attr.attr,
127	NULL,
128};
129
130static const struct attribute_group secvar_attr_group = {
131	.attrs = secvar_attrs,
132	.bin_attrs = secvar_bin_attrs,
133};
134__ATTRIBUTE_GROUPS(secvar_attr);
135
136static struct kobj_type secvar_ktype = {
137	.sysfs_ops	= &kobj_sysfs_ops,
138	.default_groups = secvar_attr_groups,
139};
140
141static int update_kobj_size(void)
142{
143
144	struct device_node *node;
145	u64 varsize;
146	int rc = 0;
147
148	node = of_find_compatible_node(NULL, NULL, "ibm,secvar-backend");
149	if (!of_device_is_available(node)) {
150		rc = -ENODEV;
151		goto out;
152	}
153
154	rc = of_property_read_u64(node, "max-var-size", &varsize);
155	if (rc)
156		goto out;
157
158	data_attr.size = varsize;
159	update_attr.size = varsize;
160
161out:
162	of_node_put(node);
163
164	return rc;
165}
166
167static int secvar_sysfs_load(void)
168{
169	char *name;
170	uint64_t namesize = 0;
171	struct kobject *kobj;
172	int rc;
173
174	name = kzalloc(NAME_MAX_SIZE, GFP_KERNEL);
175	if (!name)
176		return -ENOMEM;
177
178	do {
179		rc = secvar_ops->get_next(name, &namesize, NAME_MAX_SIZE);
180		if (rc) {
181			if (rc != -ENOENT)
182				pr_err("error getting secvar from firmware %d\n",
183				       rc);
184			break;
185		}
186
187		kobj = kzalloc(sizeof(*kobj), GFP_KERNEL);
188		if (!kobj) {
189			rc = -ENOMEM;
190			break;
191		}
192
193		kobject_init(kobj, &secvar_ktype);
194
195		rc = kobject_add(kobj, &secvar_kset->kobj, "%s", name);
196		if (rc) {
197			pr_warn("kobject_add error %d for attribute: %s\n", rc,
198				name);
199			kobject_put(kobj);
200			kobj = NULL;
201		}
202
203		if (kobj)
204			kobject_uevent(kobj, KOBJ_ADD);
205
206	} while (!rc);
207
208	kfree(name);
209	return rc;
210}
211
212static int secvar_sysfs_init(void)
213{
214	int rc;
215
216	if (!secvar_ops) {
217		pr_warn("secvar: failed to retrieve secvar operations.\n");
218		return -ENODEV;
219	}
220
221	secvar_kobj = kobject_create_and_add("secvar", firmware_kobj);
222	if (!secvar_kobj) {
223		pr_err("secvar: Failed to create firmware kobj\n");
224		return -ENOMEM;
225	}
226
227	rc = sysfs_create_file(secvar_kobj, &format_attr.attr);
228	if (rc) {
229		kobject_put(secvar_kobj);
230		return -ENOMEM;
231	}
232
233	secvar_kset = kset_create_and_add("vars", NULL, secvar_kobj);
234	if (!secvar_kset) {
235		pr_err("secvar: sysfs kobject registration failed.\n");
236		kobject_put(secvar_kobj);
237		return -ENOMEM;
238	}
239
240	rc = update_kobj_size();
241	if (rc) {
242		pr_err("Cannot read the size of the attribute\n");
243		return rc;
244	}
245
246	secvar_sysfs_load();
247
248	return 0;
249}
250
251late_initcall(secvar_sysfs_init);