drivers/base/devcoredump.c

   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
  20 static struct class devcd_class;
  21
  22 /* global disable flag, for security purposes */
  23 static 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
  28 struct 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
  40 static struct devcd_entry *dev_to_devcd(struct device *dev)
  41 {
  42         return container_of(dev, struct devcd_entry, devcd_dev);
  43 }
  44
  45 static 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
  64 static 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
  74 static 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
  84 static 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
  96 static 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
 103 static struct bin_attribute *devcd_dev_bin_attrs[] = {
 104         &devcd_attr_data, NULL,
 105 };
 106
 107 static const struct attribute_group devcd_dev_group = {
 108         .bin_attrs = devcd_dev_bin_attrs,
 109 };
 110
 111 static const struct attribute_group *devcd_dev_groups[] = {
 112         &devcd_dev_group, NULL,
 113 };
 114
 115 static 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
 123 static 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
 129 static 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 }
 148 static CLASS_ATTR_RW(disabled);
 149
 150 static struct attribute *devcd_class_attrs[] = {
 151         &class_attr_disabled.attr,
 152         NULL,
 153 };
 154 ATTRIBUTE_GROUPS(devcd_class);
 155
 156 static 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
 164 static 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
 179 static 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  */
 194 void 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 }
 199 EXPORT_SYMBOL_GPL(dev_coredumpv);
 200
 201 static 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  */
 216 static 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  */
 231 static 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  */
 261 void 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 }
 323 EXPORT_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  */
 338 void 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 }
 344 EXPORT_SYMBOL_GPL(dev_coredumpsg);
 345
 346 static int __init devcoredump_init(void)
 347 {
 348         return class_register(&devcd_class);
 349 }
 350 __initcall(devcoredump_init);
 351
 352 static 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);