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 * Contact Information:
  7 *  Intel Linux Wireless <ilw@linux.intel.com>
  8 * Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124-6497
  9 *
 10 * Author: Johannes Berg <johannes@sipsolutions.net>
 11 */
 12#include <linux/module.h>
 13#include <linux/device.h>
 14#include <linux/devcoredump.h>
 15#include <linux/list.h>
 16#include <linux/slab.h>
 17#include <linux/fs.h>
 18#include <linux/workqueue.h>
 19
 20static struct class devcd_class;
 21
 22/* global disable flag, for security purposes */
 23static bool devcd_disabled;
 24
 25/* if data isn't read by userspace after 5 minutes then delete it */
 26#define DEVCD_TIMEOUT	(HZ * 60 * 5)
 27
 28struct devcd_entry {
 29	struct device devcd_dev;
 30	void *data;
 31	size_t datalen;
 32	struct module *owner;
 33	ssize_t (*read)(char *buffer, loff_t offset, size_t count,
 34			void *data, size_t datalen);
 35	void (*free)(void *data);
 36	struct delayed_work del_wk;
 37	struct device *failing_dev;
 38};
 39
 40static struct devcd_entry *dev_to_devcd(struct device *dev)
 41{
 42	return container_of(dev, struct devcd_entry, devcd_dev);
 43}
 44
 45static void devcd_dev_release(struct device *dev)
 46{
 47	struct devcd_entry *devcd = dev_to_devcd(dev);
 48
 49	devcd->free(devcd->data);
 50	module_put(devcd->owner);
 51
 52	/*
 53	 * this seems racy, but I don't see a notifier or such on
 54	 * a struct device to know when it goes away?
 55	 */
 56	if (devcd->failing_dev->kobj.sd)
 57		sysfs_delete_link(&devcd->failing_dev->kobj, &dev->kobj,
 58				  "devcoredump");
 59
 60	put_device(devcd->failing_dev);
 61	kfree(devcd);
 62}
 63
 64static void devcd_del(struct work_struct *wk)
 65{
 66	struct devcd_entry *devcd;
 67
 68	devcd = container_of(wk, struct devcd_entry, del_wk.work);
 69
 70	device_del(&devcd->devcd_dev);
 71	put_device(&devcd->devcd_dev);
 72}
 73
 74static ssize_t devcd_data_read(struct file *filp, struct kobject *kobj,
 75			       struct bin_attribute *bin_attr,
 76			       char *buffer, loff_t offset, size_t count)
 77{
 78	struct device *dev = kobj_to_dev(kobj);
 79	struct devcd_entry *devcd = dev_to_devcd(dev);
 80
 81	return devcd->read(buffer, offset, count, devcd->data, devcd->datalen);
 82}
 83
 84static ssize_t devcd_data_write(struct file *filp, struct kobject *kobj,
 85				struct bin_attribute *bin_attr,
 86				char *buffer, loff_t offset, size_t count)
 87{
 88	struct device *dev = kobj_to_dev(kobj);
 89	struct devcd_entry *devcd = dev_to_devcd(dev);
 90
 91	mod_delayed_work(system_wq, &devcd->del_wk, 0);
 92
 93	return count;
 94}
 95
 96static struct bin_attribute devcd_attr_data = {
 97	.attr = { .name = "data", .mode = S_IRUSR | S_IWUSR, },
 98	.size = 0,
 99	.read = devcd_data_read,
100	.write = devcd_data_write,
101};
102
103static struct bin_attribute *devcd_dev_bin_attrs[] = {
104	&devcd_attr_data, NULL,
105};
106
107static const struct attribute_group devcd_dev_group = {
108	.bin_attrs = devcd_dev_bin_attrs,
109};
110
111static const struct attribute_group *devcd_dev_groups[] = {
112	&devcd_dev_group, NULL,
113};
114
115static int devcd_free(struct device *dev, void *data)
116{
117	struct devcd_entry *devcd = dev_to_devcd(dev);
118
119	flush_delayed_work(&devcd->del_wk);
120	return 0;
121}
122
123static ssize_t disabled_show(struct class *class, struct class_attribute *attr,
124			     char *buf)
125{
126	return sprintf(buf, "%d\n", devcd_disabled);
127}
128
129static ssize_t disabled_store(struct class *class, struct class_attribute *attr,
130			      const char *buf, size_t count)
131{
132	long tmp = simple_strtol(buf, NULL, 10);
133
134	/*
135	 * This essentially makes the attribute write-once, since you can't
136	 * go back to not having it disabled. This is intentional, it serves
137	 * as a system lockdown feature.
138	 */
139	if (tmp != 1)
140		return -EINVAL;
141
142	devcd_disabled = true;
143
144	class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
145
146	return count;
147}
148static CLASS_ATTR_RW(disabled);
149
150static struct attribute *devcd_class_attrs[] = {
151	&class_attr_disabled.attr,
152	NULL,
153};
154ATTRIBUTE_GROUPS(devcd_class);
155
156static struct class devcd_class = {
157	.name		= "devcoredump",
158	.owner		= THIS_MODULE,
159	.dev_release	= devcd_dev_release,
160	.dev_groups	= devcd_dev_groups,
161	.class_groups	= devcd_class_groups,
162};
163
164static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count,
165			   void *data, size_t datalen)
166{
167	if (offset > datalen)
168		return -EINVAL;
169
170	if (offset + count > datalen)
171		count = datalen - offset;
172
173	if (count)
174		memcpy(buffer, ((u8 *)data) + offset, count);
175
176	return count;
177}
178
179static void devcd_freev(void *data)
180{
181	vfree(data);
182}
183
184/**
185 * dev_coredumpv - create device coredump with vmalloc data
186 * @dev: the struct device for the crashed device
187 * @data: vmalloc data containing the device coredump
188 * @datalen: length of the data
189 * @gfp: allocation flags
190 *
191 * This function takes ownership of the vmalloc'ed data and will free
192 * it when it is no longer used. See dev_coredumpm() for more information.
193 */
194void dev_coredumpv(struct device *dev, void *data, size_t datalen,
195		   gfp_t gfp)
196{
197	dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, devcd_freev);
198}
199EXPORT_SYMBOL_GPL(dev_coredumpv);
200
201static int devcd_match_failing(struct device *dev, const void *failing)
202{
203	struct devcd_entry *devcd = dev_to_devcd(dev);
204
205	return devcd->failing_dev == failing;
206}
207
208/**
209 * devcd_free_sgtable - free all the memory of the given scatterlist table
210 * (i.e. both pages and scatterlist instances)
211 * NOTE: if two tables allocated with devcd_alloc_sgtable and then chained
212 * using the sg_chain function then that function should be called only once
213 * on the chained table
214 * @table: pointer to sg_table to free
215 */
216static void devcd_free_sgtable(void *data)
217{
218	_devcd_free_sgtable(data);
219}
220
221/**
222 * devcd_read_from_table - copy data from sg_table to a given buffer
223 * and return the number of bytes read
224 * @buffer: the buffer to copy the data to it
225 * @buf_len: the length of the buffer
226 * @data: the scatterlist table to copy from
227 * @offset: start copy from @offset@ bytes from the head of the data
228 *	in the given scatterlist
229 * @data_len: the length of the data in the sg_table
230 */
231static ssize_t devcd_read_from_sgtable(char *buffer, loff_t offset,
232				       size_t buf_len, void *data,
233				       size_t data_len)
234{
235	struct scatterlist *table = data;
236
237	if (offset > data_len)
238		return -EINVAL;
239
240	if (offset + buf_len > data_len)
241		buf_len = data_len - offset;
242	return sg_pcopy_to_buffer(table, sg_nents(table), buffer, buf_len,
243				  offset);
244}
245
246/**
247 * dev_coredumpm - create device coredump with read/free methods
248 * @dev: the struct device for the crashed device
249 * @owner: the module that contains the read/free functions, use %THIS_MODULE
250 * @data: data cookie for the @read/@free functions
251 * @datalen: length of the data
252 * @gfp: allocation flags
253 * @read: function to read from the given buffer
254 * @free: function to free the given buffer
255 *
256 * Creates a new device coredump for the given device. If a previous one hasn't
257 * been read yet, the new coredump is discarded. The data lifetime is determined
258 * by the device coredump framework and when it is no longer needed the @free
259 * function will be called to free the data.
260 */
261void dev_coredumpm(struct device *dev, struct module *owner,
262		   void *data, size_t datalen, gfp_t gfp,
263		   ssize_t (*read)(char *buffer, loff_t offset, size_t count,
264				   void *data, size_t datalen),
265		   void (*free)(void *data))
266{
267	static atomic_t devcd_count = ATOMIC_INIT(0);
268	struct devcd_entry *devcd;
269	struct device *existing;
270
271	if (devcd_disabled)
272		goto free;
273
274	existing = class_find_device(&devcd_class, NULL, dev,
275				     devcd_match_failing);
276	if (existing) {
277		put_device(existing);
278		goto free;
279	}
280
281	if (!try_module_get(owner))
282		goto free;
283
284	devcd = kzalloc(sizeof(*devcd), gfp);
285	if (!devcd)
286		goto put_module;
287
288	devcd->owner = owner;
289	devcd->data = data;
290	devcd->datalen = datalen;
291	devcd->read = read;
292	devcd->free = free;
293	devcd->failing_dev = get_device(dev);
294
295	device_initialize(&devcd->devcd_dev);
296
297	dev_set_name(&devcd->devcd_dev, "devcd%d",
298		     atomic_inc_return(&devcd_count));
299	devcd->devcd_dev.class = &devcd_class;
300
301	if (device_add(&devcd->devcd_dev))
302		goto put_device;
303
304	if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj,
305			      "failing_device"))
306		/* nothing - symlink will be missing */;
307
308	if (sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj,
309			      "devcoredump"))
310		/* nothing - symlink will be missing */;
311
312	INIT_DELAYED_WORK(&devcd->del_wk, devcd_del);
313	schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT);
314
315	return;
316 put_device:
317	put_device(&devcd->devcd_dev);
318 put_module:
319	module_put(owner);
320 free:
321	free(data);
322}
323EXPORT_SYMBOL_GPL(dev_coredumpm);
324
325/**
326 * dev_coredumpmsg - create device coredump that uses scatterlist as data
327 * parameter
328 * @dev: the struct device for the crashed device
329 * @table: the dump data
330 * @datalen: length of the data
331 * @gfp: allocation flags
332 *
333 * Creates a new device coredump for the given device. If a previous one hasn't
334 * been read yet, the new coredump is discarded. The data lifetime is determined
335 * by the device coredump framework and when it is no longer needed
336 * it will free the data.
337 */
338void dev_coredumpsg(struct device *dev, struct scatterlist *table,
339		    size_t datalen, gfp_t gfp)
340{
341	dev_coredumpm(dev, NULL, table, datalen, gfp, devcd_read_from_sgtable,
342		      devcd_free_sgtable);
343}
344EXPORT_SYMBOL_GPL(dev_coredumpsg);
345
346static int __init devcoredump_init(void)
347{
348	return class_register(&devcd_class);
349}
350__initcall(devcoredump_init);
351
352static void __exit devcoredump_exit(void)
353{
354	class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
355	class_unregister(&devcd_class);
356}
357__exitcall(devcoredump_exit);