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
 16static struct class devcd_class;
 17
 18/* global disable flag, for security purposes */
 19static 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
 24struct 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
 36static struct devcd_entry *dev_to_devcd(struct device *dev)
 37{
 38	return container_of(dev, struct devcd_entry, devcd_dev);
 39}
 40
 41static 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
 60static 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
 70static 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
 80static 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
 92static 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
 99static struct bin_attribute *devcd_dev_bin_attrs[] = {
100	&devcd_attr_data, NULL,
101};
102
103static const struct attribute_group devcd_dev_group = {
104	.bin_attrs = devcd_dev_bin_attrs,
105};
106
107static const struct attribute_group *devcd_dev_groups[] = {
108	&devcd_dev_group, NULL,
109};
110
111static 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
119static 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
125static 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}
144static CLASS_ATTR_RW(disabled);
145
146static struct attribute *devcd_class_attrs[] = {
147	&class_attr_disabled.attr,
148	NULL,
149};
150ATTRIBUTE_GROUPS(devcd_class);
151
152static 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
160static 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
166static 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 */
181void 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}
186EXPORT_SYMBOL_GPL(dev_coredumpv);
187
188static 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 */
203static 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 */
218static 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 */
248void 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}
313EXPORT_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 */
328void 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}
334EXPORT_SYMBOL_GPL(dev_coredumpsg);
335
336static int __init devcoredump_init(void)
337{
338	return class_register(&devcd_class);
339}
340__initcall(devcoredump_init);
341
342static 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);