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         return memory_read_from_buffer(buffer, count, &offset, data, datalen);
 168 }
 169
 170 static void devcd_freev(void *data)
 171 {
 172         vfree(data);
 173 }
 174
 175 /**
 176  * dev_coredumpv - create device coredump with vmalloc data
 177  * @dev: the struct device for the crashed device
 178  * @data: vmalloc data containing the device coredump
 179  * @datalen: length of the data
 180  * @gfp: allocation flags
 181  *
 182  * This function takes ownership of the vmalloc'ed data and will free
 183  * it when it is no longer used. See dev_coredumpm() for more information.
 184  */
 185 void dev_coredumpv(struct device *dev, void *data, size_t datalen,
 186                    gfp_t gfp)
 187 {
 188         dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, devcd_freev);
 189 }
 190 EXPORT_SYMBOL_GPL(dev_coredumpv);
 191
 192 static int devcd_match_failing(struct device *dev, const void *failing)
 193 {
 194         struct devcd_entry *devcd = dev_to_devcd(dev);
 195
 196         return devcd->failing_dev == failing;
 197 }
 198
 199 /**
 200  * devcd_free_sgtable - free all the memory of the given scatterlist table
 201  * (i.e. both pages and scatterlist instances)
 202  * NOTE: if two tables allocated with devcd_alloc_sgtable and then chained
 203  * using the sg_chain function then that function should be called only once
 204  * on the chained table
 205  * @table: pointer to sg_table to free
 206  */
 207 static void devcd_free_sgtable(void *data)
 208 {
 209         _devcd_free_sgtable(data);
 210 }
 211
 212 /**
 213  * devcd_read_from_table - copy data from sg_table to a given buffer
 214  * and return the number of bytes read
 215  * @buffer: the buffer to copy the data to it
 216  * @buf_len: the length of the buffer
 217  * @data: the scatterlist table to copy from
 218  * @offset: start copy from @offset@ bytes from the head of the data
 219  *      in the given scatterlist
 220  * @data_len: the length of the data in the sg_table
 221  */
 222 static ssize_t devcd_read_from_sgtable(char *buffer, loff_t offset,
 223                                        size_t buf_len, void *data,
 224                                        size_t data_len)
 225 {
 226         struct scatterlist *table = data;
 227
 228         if (offset > data_len)
 229                 return -EINVAL;
 230
 231         if (offset + buf_len > data_len)
 232                 buf_len = data_len - offset;
 233         return sg_pcopy_to_buffer(table, sg_nents(table), buffer, buf_len,
 234                                   offset);
 235 }
 236
 237 /**
 238  * dev_coredumpm - create device coredump with read/free methods
 239  * @dev: the struct device for the crashed device
 240  * @owner: the module that contains the read/free functions, use %THIS_MODULE
 241  * @data: data cookie for the @read/@free functions
 242  * @datalen: length of the data
 243  * @gfp: allocation flags
 244  * @read: function to read from the given buffer
 245  * @free: function to free the given buffer
 246  *
 247  * Creates a new device coredump for the given device. If a previous one hasn't
 248  * been read yet, the new coredump is discarded. The data lifetime is determined
 249  * by the device coredump framework and when it is no longer needed the @free
 250  * function will be called to free the data.
 251  */
 252 void dev_coredumpm(struct device *dev, struct module *owner,
 253                    void *data, size_t datalen, gfp_t gfp,
 254                    ssize_t (*read)(char *buffer, loff_t offset, size_t count,
 255                                    void *data, size_t datalen),
 256                    void (*free)(void *data))
 257 {
 258         static atomic_t devcd_count = ATOMIC_INIT(0);
 259         struct devcd_entry *devcd;
 260         struct device *existing;
 261
 262         if (devcd_disabled)
 263                 goto free;
 264
 265         existing = class_find_device(&devcd_class, NULL, dev,
 266                                      devcd_match_failing);
 267         if (existing) {
 268                 put_device(existing);
 269                 goto free;
 270         }
 271
 272         if (!try_module_get(owner))
 273                 goto free;
 274
 275         devcd = kzalloc(sizeof(*devcd), gfp);
 276         if (!devcd)
 277                 goto put_module;
 278
 279         devcd->owner = owner;
 280         devcd->data = data;
 281         devcd->datalen = datalen;
 282         devcd->read = read;
 283         devcd->free = free;
 284         devcd->failing_dev = get_device(dev);
 285
 286         device_initialize(&devcd->devcd_dev);
 287
 288         dev_set_name(&devcd->devcd_dev, "devcd%d",
 289                      atomic_inc_return(&devcd_count));
 290         devcd->devcd_dev.class = &devcd_class;
 291
 292         if (device_add(&devcd->devcd_dev))
 293                 goto put_device;
 294
 295         if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj,
 296                               "failing_device"))
 297                 /* nothing - symlink will be missing */;
 298
 299         if (sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj,
 300                               "devcoredump"))
 301                 /* nothing - symlink will be missing */;
 302
 303         INIT_DELAYED_WORK(&devcd->del_wk, devcd_del);
 304         schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT);
 305
 306         return;
 307  put_device:
 308         put_device(&devcd->devcd_dev);
 309  put_module:
 310         module_put(owner);
 311  free:
 312         free(data);
 313 }
 314 EXPORT_SYMBOL_GPL(dev_coredumpm);
 315
 316 /**
 317  * dev_coredumpsg - create device coredump that uses scatterlist as data
 318  * parameter
 319  * @dev: the struct device for the crashed device
 320  * @table: the dump data
 321  * @datalen: length of the data
 322  * @gfp: allocation flags
 323  *
 324  * Creates a new device coredump for the given device. If a previous one hasn't
 325  * been read yet, the new coredump is discarded. The data lifetime is determined
 326  * by the device coredump framework and when it is no longer needed
 327  * it will free the data.
 328  */
 329 void dev_coredumpsg(struct device *dev, struct scatterlist *table,
 330                     size_t datalen, gfp_t gfp)
 331 {
 332         dev_coredumpm(dev, NULL, table, datalen, gfp, devcd_read_from_sgtable,
 333                       devcd_free_sgtable);
 334 }
 335 EXPORT_SYMBOL_GPL(dev_coredumpsg);
 336
 337 static int __init devcoredump_init(void)
 338 {
 339         return class_register(&devcd_class);
 340 }
 341 __initcall(devcoredump_init);
 342
 343 static void __exit devcoredump_exit(void)
 344 {
 345         class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
 346         class_unregister(&devcd_class);
 347 }
 348 __exitcall(devcoredump_exit);