drivers/base/devcoredump.c

   1 /*
   2  * This file is provided under the GPLv2 license.
   3  *
   4  * GPL LICENSE SUMMARY
   5  *
   6  * Copyright(c) 2014 Intel Mobile Communications GmbH
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of version 2 of the GNU General Public License as
  10  * published by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * General Public License for more details.
  16  *
  17  * The full GNU General Public License is included in this distribution
  18  * in the file called COPYING.
  19  *
  20  * Contact Information:
  21  *  Intel Linux Wireless <ilw@linux.intel.com>
  22  * Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124-6497
  23  *
  24  * Author: Johannes Berg <johannes@sipsolutions.net>
  25  */
  26 #include <linux/module.h>
  27 #include <linux/device.h>
  28 #include <linux/devcoredump.h>
  29 #include <linux/list.h>
  30 #include <linux/slab.h>
  31 #include <linux/fs.h>
  32 #include <linux/workqueue.h>
  33
  34 static struct class devcd_class;
  35
  36 /* global disable flag, for security purposes */
  37 static bool devcd_disabled;
  38
  39 /* if data isn't read by userspace after 5 minutes then delete it */
  40 #define DEVCD_TIMEOUT   (HZ * 60 * 5)
  41
  42 struct devcd_entry {
  43         struct device devcd_dev;
  44         const void *data;
  45         size_t datalen;
  46         struct module *owner;
  47         ssize_t (*read)(char *buffer, loff_t offset, size_t count,
  48                         const void *data, size_t datalen);
  49         void (*free)(const void *data);
  50         struct delayed_work del_wk;
  51         struct device *failing_dev;
  52 };
  53
  54 static struct devcd_entry *dev_to_devcd(struct device *dev)
  55 {
  56         return container_of(dev, struct devcd_entry, devcd_dev);
  57 }
  58
  59 static void devcd_dev_release(struct device *dev)
  60 {
  61         struct devcd_entry *devcd = dev_to_devcd(dev);
  62
  63         devcd->free(devcd->data);
  64         module_put(devcd->owner);
  65
  66         /*
  67          * this seems racy, but I don't see a notifier or such on
  68          * a struct device to know when it goes away?
  69          */
  70         if (devcd->failing_dev->kobj.sd)
  71                 sysfs_delete_link(&devcd->failing_dev->kobj, &dev->kobj,
  72                                   "devcoredump");
  73
  74         put_device(devcd->failing_dev);
  75         kfree(devcd);
  76 }
  77
  78 static void devcd_del(struct work_struct *wk)
  79 {
  80         struct devcd_entry *devcd;
  81
  82         devcd = container_of(wk, struct devcd_entry, del_wk.work);
  83
  84         device_del(&devcd->devcd_dev);
  85         put_device(&devcd->devcd_dev);
  86 }
  87
  88 static ssize_t devcd_data_read(struct file *filp, struct kobject *kobj,
  89                                struct bin_attribute *bin_attr,
  90                                char *buffer, loff_t offset, size_t count)
  91 {
  92         struct device *dev = kobj_to_dev(kobj);
  93         struct devcd_entry *devcd = dev_to_devcd(dev);
  94
  95         return devcd->read(buffer, offset, count, devcd->data, devcd->datalen);
  96 }
  97
  98 static ssize_t devcd_data_write(struct file *filp, struct kobject *kobj,
  99                                 struct bin_attribute *bin_attr,
 100                                 char *buffer, loff_t offset, size_t count)
 101 {
 102         struct device *dev = kobj_to_dev(kobj);
 103         struct devcd_entry *devcd = dev_to_devcd(dev);
 104
 105         mod_delayed_work(system_wq, &devcd->del_wk, 0);
 106
 107         return count;
 108 }
 109
 110 static struct bin_attribute devcd_attr_data = {
 111         .attr = { .name = "data", .mode = S_IRUSR | S_IWUSR, },
 112         .size = 0,
 113         .read = devcd_data_read,
 114         .write = devcd_data_write,
 115 };
 116
 117 static struct bin_attribute *devcd_dev_bin_attrs[] = {
 118         &devcd_attr_data, NULL,
 119 };
 120
 121 static const struct attribute_group devcd_dev_group = {
 122         .bin_attrs = devcd_dev_bin_attrs,
 123 };
 124
 125 static const struct attribute_group *devcd_dev_groups[] = {
 126         &devcd_dev_group, NULL,
 127 };
 128
 129 static int devcd_free(struct device *dev, void *data)
 130 {
 131         struct devcd_entry *devcd = dev_to_devcd(dev);
 132
 133         flush_delayed_work(&devcd->del_wk);
 134         return 0;
 135 }
 136
 137 static ssize_t disabled_show(struct class *class, struct class_attribute *attr,
 138                              char *buf)
 139 {
 140         return sprintf(buf, "%d\n", devcd_disabled);
 141 }
 142
 143 static ssize_t disabled_store(struct class *class, struct class_attribute *attr,
 144                               const char *buf, size_t count)
 145 {
 146         long tmp = simple_strtol(buf, NULL, 10);
 147
 148         /*
 149          * This essentially makes the attribute write-once, since you can't
 150          * go back to not having it disabled. This is intentional, it serves
 151          * as a system lockdown feature.
 152          */
 153         if (tmp != 1)
 154                 return -EINVAL;
 155
 156         devcd_disabled = true;
 157
 158         class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
 159
 160         return count;
 161 }
 162
 163 static struct class_attribute devcd_class_attrs[] = {
 164         __ATTR_RW(disabled),
 165         __ATTR_NULL
 166 };
 167
 168 static struct class devcd_class = {
 169         .name           = "devcoredump",
 170         .owner          = THIS_MODULE,
 171         .dev_release    = devcd_dev_release,
 172         .dev_groups     = devcd_dev_groups,
 173         .class_attrs    = devcd_class_attrs,
 174 };
 175
 176 static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count,
 177                            const void *data, size_t datalen)
 178 {
 179         if (offset > datalen)
 180                 return -EINVAL;
 181
 182         if (offset + count > datalen)
 183                 count = datalen - offset;
 184
 185         if (count)
 186                 memcpy(buffer, ((u8 *)data) + offset, count);
 187
 188         return count;
 189 }
 190
 191 /**
 192  * dev_coredumpv - create device coredump with vmalloc data
 193  * @dev: the struct device for the crashed device
 194  * @data: vmalloc data containing the device coredump
 195  * @datalen: length of the data
 196  * @gfp: allocation flags
 197  *
 198  * This function takes ownership of the vmalloc'ed data and will free
 199  * it when it is no longer used. See dev_coredumpm() for more information.
 200  */
 201 void dev_coredumpv(struct device *dev, const void *data, size_t datalen,
 202                    gfp_t gfp)
 203 {
 204         dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, vfree);
 205 }
 206 EXPORT_SYMBOL_GPL(dev_coredumpv);
 207
 208 static int devcd_match_failing(struct device *dev, const void *failing)
 209 {
 210         struct devcd_entry *devcd = dev_to_devcd(dev);
 211
 212         return devcd->failing_dev == failing;
 213 }
 214
 215 /**
 216  * dev_coredumpm - create device coredump with read/free methods
 217  * @dev: the struct device for the crashed device
 218  * @owner: the module that contains the read/free functions, use %THIS_MODULE
 219  * @data: data cookie for the @read/@free functions
 220  * @datalen: length of the data
 221  * @gfp: allocation flags
 222  * @read: function to read from the given buffer
 223  * @free: function to free the given buffer
 224  *
 225  * Creates a new device coredump for the given device. If a previous one hasn't
 226  * been read yet, the new coredump is discarded. The data lifetime is determined
 227  * by the device coredump framework and when it is no longer needed the @free
 228  * function will be called to free the data.
 229  */
 230 void dev_coredumpm(struct device *dev, struct module *owner,
 231                    const void *data, size_t datalen, gfp_t gfp,
 232                    ssize_t (*read)(char *buffer, loff_t offset, size_t count,
 233                                    const void *data, size_t datalen),
 234                    void (*free)(const void *data))
 235 {
 236         static atomic_t devcd_count = ATOMIC_INIT(0);
 237         struct devcd_entry *devcd;
 238         struct device *existing;
 239
 240         if (devcd_disabled)
 241                 goto free;
 242
 243         existing = class_find_device(&devcd_class, NULL, dev,
 244                                      devcd_match_failing);
 245         if (existing) {
 246                 put_device(existing);
 247                 goto free;
 248         }
 249
 250         if (!try_module_get(owner))
 251                 goto free;
 252
 253         devcd = kzalloc(sizeof(*devcd), gfp);
 254         if (!devcd)
 255                 goto put_module;
 256
 257         devcd->owner = owner;
 258         devcd->data = data;
 259         devcd->datalen = datalen;
 260         devcd->read = read;
 261         devcd->free = free;
 262         devcd->failing_dev = get_device(dev);
 263
 264         device_initialize(&devcd->devcd_dev);
 265
 266         dev_set_name(&devcd->devcd_dev, "devcd%d",
 267                      atomic_inc_return(&devcd_count));
 268         devcd->devcd_dev.class = &devcd_class;
 269
 270         if (device_add(&devcd->devcd_dev))
 271                 goto put_device;
 272
 273         if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj,
 274                               "failing_device"))
 275                 /* nothing - symlink will be missing */;
 276
 277         if (sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj,
 278                               "devcoredump"))
 279                 /* nothing - symlink will be missing */;
 280
 281         INIT_DELAYED_WORK(&devcd->del_wk, devcd_del);
 282         schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT);
 283
 284         return;
 285  put_device:
 286         put_device(&devcd->devcd_dev);
 287  put_module:
 288         module_put(owner);
 289  free:
 290         free(data);
 291 }
 292 EXPORT_SYMBOL_GPL(dev_coredumpm);
 293
 294 static int __init devcoredump_init(void)
 295 {
 296         return class_register(&devcd_class);
 297 }
 298 __initcall(devcoredump_init);
 299
 300 static void __exit devcoredump_exit(void)
 301 {
 302         class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
 303         class_unregister(&devcd_class);
 304 }
 305 __exitcall(devcoredump_exit);