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
18 static struct kobject *secvar_kobj;
19 static struct kset *secvar_kset;
20
format_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)21 static 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
40 out:
41 of_node_put(node);
42
43 return rc;
44 }
45
46
size_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)47 static 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
data_read(struct file * filep,struct kobject * kobj,struct bin_attribute * attr,char * buf,loff_t off,size_t count)63 static 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
90 data_fail:
91 kfree(data);
92 return rc;
93 }
94
update_write(struct file * filep,struct kobject * kobj,struct bin_attribute * attr,char * buf,loff_t off,size_t count)95 static 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
111 static struct kobj_attribute format_attr = __ATTR_RO(format);
112
113 static struct kobj_attribute size_attr = __ATTR_RO(size);
114
115 static struct bin_attribute data_attr = __BIN_ATTR_RO(data, 0);
116
117 static struct bin_attribute update_attr = __BIN_ATTR_WO(update, 0);
118
119 static struct bin_attribute *secvar_bin_attrs[] = {
120 &data_attr,
121 &update_attr,
122 NULL,
123 };
124
125 static struct attribute *secvar_attrs[] = {
126 &size_attr.attr,
127 NULL,
128 };
129
130 static const struct attribute_group secvar_attr_group = {
131 .attrs = secvar_attrs,
132 .bin_attrs = secvar_bin_attrs,
133 };
134 __ATTRIBUTE_GROUPS(secvar_attr);
135
136 static struct kobj_type secvar_ktype = {
137 .sysfs_ops = &kobj_sysfs_ops,
138 .default_groups = secvar_attr_groups,
139 };
140
update_kobj_size(void)141 static 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
161 out:
162 of_node_put(node);
163
164 return rc;
165 }
166
secvar_sysfs_load(void)167 static 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
secvar_sysfs_init(void)212 static 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
251 late_initcall(secvar_sysfs_init);
252