1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright(c) 2014 Intel Mobile Communications GmbH
4 * Copyright(c) 2015 Intel Deutschland GmbH
5 *
6 * Author: Johannes Berg <johannes@sipsolutions.net>
7 */
8 #include <linux/module.h>
9 #include <linux/device.h>
10 #include <linux/devcoredump.h>
11 #include <linux/list.h>
12 #include <linux/slab.h>
13 #include <linux/fs.h>
14 #include <linux/workqueue.h>
15
16 static struct class devcd_class;
17
18 /* global disable flag, for security purposes */
19 static bool devcd_disabled;
20
21 /* if data isn't read by userspace after 5 minutes then delete it */
22 #define DEVCD_TIMEOUT (HZ * 60 * 5)
23
24 struct devcd_entry {
25 struct device devcd_dev;
26 void *data;
27 size_t datalen;
28 struct module *owner;
29 ssize_t (*read)(char *buffer, loff_t offset, size_t count,
30 void *data, size_t datalen);
31 void (*free)(void *data);
32 struct delayed_work del_wk;
33 struct device *failing_dev;
34 };
35
dev_to_devcd(struct device * dev)36 static struct devcd_entry *dev_to_devcd(struct device *dev)
37 {
38 return container_of(dev, struct devcd_entry, devcd_dev);
39 }
40
devcd_dev_release(struct device * dev)41 static void devcd_dev_release(struct device *dev)
42 {
43 struct devcd_entry *devcd = dev_to_devcd(dev);
44
45 devcd->free(devcd->data);
46 module_put(devcd->owner);
47
48 /*
49 * this seems racy, but I don't see a notifier or such on
50 * a struct device to know when it goes away?
51 */
52 if (devcd->failing_dev->kobj.sd)
53 sysfs_delete_link(&devcd->failing_dev->kobj, &dev->kobj,
54 "devcoredump");
55
56 put_device(devcd->failing_dev);
57 kfree(devcd);
58 }
59
devcd_del(struct work_struct * wk)60 static void devcd_del(struct work_struct *wk)
61 {
62 struct devcd_entry *devcd;
63
64 devcd = container_of(wk, struct devcd_entry, del_wk.work);
65
66 device_del(&devcd->devcd_dev);
67 put_device(&devcd->devcd_dev);
68 }
69
devcd_data_read(struct file * filp,struct kobject * kobj,struct bin_attribute * bin_attr,char * buffer,loff_t offset,size_t count)70 static ssize_t devcd_data_read(struct file *filp, struct kobject *kobj,
71 struct bin_attribute *bin_attr,
72 char *buffer, loff_t offset, size_t count)
73 {
74 struct device *dev = kobj_to_dev(kobj);
75 struct devcd_entry *devcd = dev_to_devcd(dev);
76
77 return devcd->read(buffer, offset, count, devcd->data, devcd->datalen);
78 }
79
devcd_data_write(struct file * filp,struct kobject * kobj,struct bin_attribute * bin_attr,char * buffer,loff_t offset,size_t count)80 static ssize_t devcd_data_write(struct file *filp, struct kobject *kobj,
81 struct bin_attribute *bin_attr,
82 char *buffer, loff_t offset, size_t count)
83 {
84 struct device *dev = kobj_to_dev(kobj);
85 struct devcd_entry *devcd = dev_to_devcd(dev);
86
87 mod_delayed_work(system_wq, &devcd->del_wk, 0);
88
89 return count;
90 }
91
92 static struct bin_attribute devcd_attr_data = {
93 .attr = { .name = "data", .mode = S_IRUSR | S_IWUSR, },
94 .size = 0,
95 .read = devcd_data_read,
96 .write = devcd_data_write,
97 };
98
99 static struct bin_attribute *devcd_dev_bin_attrs[] = {
100 &devcd_attr_data, NULL,
101 };
102
103 static const struct attribute_group devcd_dev_group = {
104 .bin_attrs = devcd_dev_bin_attrs,
105 };
106
107 static const struct attribute_group *devcd_dev_groups[] = {
108 &devcd_dev_group, NULL,
109 };
110
devcd_free(struct device * dev,void * data)111 static int devcd_free(struct device *dev, void *data)
112 {
113 struct devcd_entry *devcd = dev_to_devcd(dev);
114
115 flush_delayed_work(&devcd->del_wk);
116 return 0;
117 }
118
disabled_show(struct class * class,struct class_attribute * attr,char * buf)119 static ssize_t disabled_show(struct class *class, struct class_attribute *attr,
120 char *buf)
121 {
122 return sysfs_emit(buf, "%d\n", devcd_disabled);
123 }
124
disabled_store(struct class * class,struct class_attribute * attr,const char * buf,size_t count)125 static ssize_t disabled_store(struct class *class, struct class_attribute *attr,
126 const char *buf, size_t count)
127 {
128 long tmp = simple_strtol(buf, NULL, 10);
129
130 /*
131 * This essentially makes the attribute write-once, since you can't
132 * go back to not having it disabled. This is intentional, it serves
133 * as a system lockdown feature.
134 */
135 if (tmp != 1)
136 return -EINVAL;
137
138 devcd_disabled = true;
139
140 class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
141
142 return count;
143 }
144 static CLASS_ATTR_RW(disabled);
145
146 static struct attribute *devcd_class_attrs[] = {
147 &class_attr_disabled.attr,
148 NULL,
149 };
150 ATTRIBUTE_GROUPS(devcd_class);
151
152 static struct class devcd_class = {
153 .name = "devcoredump",
154 .owner = THIS_MODULE,
155 .dev_release = devcd_dev_release,
156 .dev_groups = devcd_dev_groups,
157 .class_groups = devcd_class_groups,
158 };
159
devcd_readv(char * buffer,loff_t offset,size_t count,void * data,size_t datalen)160 static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count,
161 void *data, size_t datalen)
162 {
163 return memory_read_from_buffer(buffer, count, &offset, data, datalen);
164 }
165
devcd_freev(void * data)166 static void devcd_freev(void *data)
167 {
168 vfree(data);
169 }
170
171 /**
172 * dev_coredumpv - create device coredump with vmalloc data
173 * @dev: the struct device for the crashed device
174 * @data: vmalloc data containing the device coredump
175 * @datalen: length of the data
176 * @gfp: allocation flags
177 *
178 * This function takes ownership of the vmalloc'ed data and will free
179 * it when it is no longer used. See dev_coredumpm() for more information.
180 */
dev_coredumpv(struct device * dev,void * data,size_t datalen,gfp_t gfp)181 void dev_coredumpv(struct device *dev, void *data, size_t datalen,
182 gfp_t gfp)
183 {
184 dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, devcd_freev);
185 }
186 EXPORT_SYMBOL_GPL(dev_coredumpv);
187
devcd_match_failing(struct device * dev,const void * failing)188 static int devcd_match_failing(struct device *dev, const void *failing)
189 {
190 struct devcd_entry *devcd = dev_to_devcd(dev);
191
192 return devcd->failing_dev == failing;
193 }
194
195 /**
196 * devcd_free_sgtable - free all the memory of the given scatterlist table
197 * (i.e. both pages and scatterlist instances)
198 * NOTE: if two tables allocated with devcd_alloc_sgtable and then chained
199 * using the sg_chain function then that function should be called only once
200 * on the chained table
201 * @data: pointer to sg_table to free
202 */
devcd_free_sgtable(void * data)203 static void devcd_free_sgtable(void *data)
204 {
205 _devcd_free_sgtable(data);
206 }
207
208 /**
209 * devcd_read_from_sgtable - copy data from sg_table to a given buffer
210 * and return the number of bytes read
211 * @buffer: the buffer to copy the data to it
212 * @buf_len: the length of the buffer
213 * @data: the scatterlist table to copy from
214 * @offset: start copy from @offset@ bytes from the head of the data
215 * in the given scatterlist
216 * @data_len: the length of the data in the sg_table
217 */
devcd_read_from_sgtable(char * buffer,loff_t offset,size_t buf_len,void * data,size_t data_len)218 static ssize_t devcd_read_from_sgtable(char *buffer, loff_t offset,
219 size_t buf_len, void *data,
220 size_t data_len)
221 {
222 struct scatterlist *table = data;
223
224 if (offset > data_len)
225 return -EINVAL;
226
227 if (offset + buf_len > data_len)
228 buf_len = data_len - offset;
229 return sg_pcopy_to_buffer(table, sg_nents(table), buffer, buf_len,
230 offset);
231 }
232
233 /**
234 * dev_coredumpm - create device coredump with read/free methods
235 * @dev: the struct device for the crashed device
236 * @owner: the module that contains the read/free functions, use %THIS_MODULE
237 * @data: data cookie for the @read/@free functions
238 * @datalen: length of the data
239 * @gfp: allocation flags
240 * @read: function to read from the given buffer
241 * @free: function to free the given buffer
242 *
243 * Creates a new device coredump for the given device. If a previous one hasn't
244 * been read yet, the new coredump is discarded. The data lifetime is determined
245 * by the device coredump framework and when it is no longer needed the @free
246 * function will be called to free the data.
247 */
dev_coredumpm(struct device * dev,struct module * owner,void * data,size_t datalen,gfp_t gfp,ssize_t (* read)(char * buffer,loff_t offset,size_t count,void * data,size_t datalen),void (* free)(void * data))248 void dev_coredumpm(struct device *dev, struct module *owner,
249 void *data, size_t datalen, gfp_t gfp,
250 ssize_t (*read)(char *buffer, loff_t offset, size_t count,
251 void *data, size_t datalen),
252 void (*free)(void *data))
253 {
254 static atomic_t devcd_count = ATOMIC_INIT(0);
255 struct devcd_entry *devcd;
256 struct device *existing;
257
258 if (devcd_disabled)
259 goto free;
260
261 existing = class_find_device(&devcd_class, NULL, dev,
262 devcd_match_failing);
263 if (existing) {
264 put_device(existing);
265 goto free;
266 }
267
268 if (!try_module_get(owner))
269 goto free;
270
271 devcd = kzalloc(sizeof(*devcd), gfp);
272 if (!devcd)
273 goto put_module;
274
275 devcd->owner = owner;
276 devcd->data = data;
277 devcd->datalen = datalen;
278 devcd->read = read;
279 devcd->free = free;
280 devcd->failing_dev = get_device(dev);
281
282 device_initialize(&devcd->devcd_dev);
283
284 dev_set_name(&devcd->devcd_dev, "devcd%d",
285 atomic_inc_return(&devcd_count));
286 devcd->devcd_dev.class = &devcd_class;
287
288 if (device_add(&devcd->devcd_dev))
289 goto put_device;
290
291 /*
292 * These should normally not fail, but there is no problem
293 * continuing without the links, so just warn instead of
294 * failing.
295 */
296 if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj,
297 "failing_device") ||
298 sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj,
299 "devcoredump"))
300 dev_warn(dev, "devcoredump create_link failed\n");
301
302 INIT_DELAYED_WORK(&devcd->del_wk, devcd_del);
303 schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT);
304
305 return;
306 put_device:
307 put_device(&devcd->devcd_dev);
308 put_module:
309 module_put(owner);
310 free:
311 free(data);
312 }
313 EXPORT_SYMBOL_GPL(dev_coredumpm);
314
315 /**
316 * dev_coredumpsg - create device coredump that uses scatterlist as data
317 * parameter
318 * @dev: the struct device for the crashed device
319 * @table: the dump data
320 * @datalen: length of the data
321 * @gfp: allocation flags
322 *
323 * Creates a new device coredump for the given device. If a previous one hasn't
324 * been read yet, the new coredump is discarded. The data lifetime is determined
325 * by the device coredump framework and when it is no longer needed
326 * it will free the data.
327 */
dev_coredumpsg(struct device * dev,struct scatterlist * table,size_t datalen,gfp_t gfp)328 void dev_coredumpsg(struct device *dev, struct scatterlist *table,
329 size_t datalen, gfp_t gfp)
330 {
331 dev_coredumpm(dev, NULL, table, datalen, gfp, devcd_read_from_sgtable,
332 devcd_free_sgtable);
333 }
334 EXPORT_SYMBOL_GPL(dev_coredumpsg);
335
devcoredump_init(void)336 static int __init devcoredump_init(void)
337 {
338 return class_register(&devcd_class);
339 }
340 __initcall(devcoredump_init);
341
devcoredump_exit(void)342 static void __exit devcoredump_exit(void)
343 {
344 class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
345 class_unregister(&devcd_class);
346 }
347 __exitcall(devcoredump_exit);
348