diff options
Diffstat (limited to 'drivers/base/devcoredump.c')
| -rw-r--r-- | drivers/base/devcoredump.c | 429 |
1 files changed, 429 insertions, 0 deletions
diff --git a/drivers/base/devcoredump.c b/drivers/base/devcoredump.c new file mode 100644 index 000000000..f3bd9f104 --- /dev/null +++ b/drivers/base/devcoredump.c @@ -0,0 +1,429 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright(c) 2014 Intel Mobile Communications GmbH + * Copyright(c) 2015 Intel Deutschland GmbH + * + * Author: Johannes Berg <johannes@sipsolutions.net> + */ +#include <linux/module.h> +#include <linux/device.h> +#include <linux/devcoredump.h> +#include <linux/list.h> +#include <linux/slab.h> +#include <linux/fs.h> +#include <linux/workqueue.h> + +static struct class devcd_class; + +/* global disable flag, for security purposes */ +static bool devcd_disabled; + +/* if data isn't read by userspace after 5 minutes then delete it */ +#define DEVCD_TIMEOUT (HZ * 60 * 5) + +struct devcd_entry { + struct device devcd_dev; + void *data; + size_t datalen; + /* + * Here, mutex is required to serialize the calls to del_wk work between + * user/kernel space which happens when devcd is added with device_add() + * and that sends uevent to user space. User space reads the uevents, + * and calls to devcd_data_write() which try to modify the work which is + * not even initialized/queued from devcoredump. + * + * + * + * cpu0(X) cpu1(Y) + * + * dev_coredump() uevent sent to user space + * device_add() ======================> user space process Y reads the + * uevents writes to devcd fd + * which results into writes to + * + * devcd_data_write() + * mod_delayed_work() + * try_to_grab_pending() + * del_timer() + * debug_assert_init() + * INIT_DELAYED_WORK() + * schedule_delayed_work() + * + * + * Also, mutex alone would not be enough to avoid scheduling of + * del_wk work after it get flush from a call to devcd_free() + * mentioned as below. + * + * disabled_store() + * devcd_free() + * mutex_lock() devcd_data_write() + * flush_delayed_work() + * mutex_unlock() + * mutex_lock() + * mod_delayed_work() + * mutex_unlock() + * So, delete_work flag is required. + */ + struct mutex mutex; + bool delete_work; + struct module *owner; + ssize_t (*read)(char *buffer, loff_t offset, size_t count, + void *data, size_t datalen); + void (*free)(void *data); + struct delayed_work del_wk; + struct device *failing_dev; +}; + +static struct devcd_entry *dev_to_devcd(struct device *dev) +{ + return container_of(dev, struct devcd_entry, devcd_dev); +} + +static void devcd_dev_release(struct device *dev) +{ + struct devcd_entry *devcd = dev_to_devcd(dev); + + devcd->free(devcd->data); + module_put(devcd->owner); + + /* + * this seems racy, but I don't see a notifier or such on + * a struct device to know when it goes away? + */ + if (devcd->failing_dev->kobj.sd) + sysfs_delete_link(&devcd->failing_dev->kobj, &dev->kobj, + "devcoredump"); + + put_device(devcd->failing_dev); + kfree(devcd); +} + +static void devcd_del(struct work_struct *wk) +{ + struct devcd_entry *devcd; + + devcd = container_of(wk, struct devcd_entry, del_wk.work); + + device_del(&devcd->devcd_dev); + put_device(&devcd->devcd_dev); +} + +static ssize_t devcd_data_read(struct file *filp, struct kobject *kobj, + struct bin_attribute *bin_attr, + char *buffer, loff_t offset, size_t count) +{ + struct device *dev = kobj_to_dev(kobj); + struct devcd_entry *devcd = dev_to_devcd(dev); + + return devcd->read(buffer, offset, count, devcd->data, devcd->datalen); +} + +static ssize_t devcd_data_write(struct file *filp, struct kobject *kobj, + struct bin_attribute *bin_attr, + char *buffer, loff_t offset, size_t count) +{ + struct device *dev = kobj_to_dev(kobj); + struct devcd_entry *devcd = dev_to_devcd(dev); + + mutex_lock(&devcd->mutex); + if (!devcd->delete_work) { + devcd->delete_work = true; + mod_delayed_work(system_wq, &devcd->del_wk, 0); + } + mutex_unlock(&devcd->mutex); + + return count; +} + +static struct bin_attribute devcd_attr_data = { + .attr = { .name = "data", .mode = S_IRUSR | S_IWUSR, }, + .size = 0, + .read = devcd_data_read, + .write = devcd_data_write, +}; + +static struct bin_attribute *devcd_dev_bin_attrs[] = { + &devcd_attr_data, NULL, +}; + +static const struct attribute_group devcd_dev_group = { + .bin_attrs = devcd_dev_bin_attrs, +}; + +static const struct attribute_group *devcd_dev_groups[] = { + &devcd_dev_group, NULL, +}; + +static int devcd_free(struct device *dev, void *data) +{ + struct devcd_entry *devcd = dev_to_devcd(dev); + + mutex_lock(&devcd->mutex); + if (!devcd->delete_work) + devcd->delete_work = true; + + flush_delayed_work(&devcd->del_wk); + mutex_unlock(&devcd->mutex); + return 0; +} + +static ssize_t disabled_show(struct class *class, struct class_attribute *attr, + char *buf) +{ + return sysfs_emit(buf, "%d\n", devcd_disabled); +} + +/* + * + * disabled_store() worker() + * class_for_each_device(&devcd_class, + * NULL, NULL, devcd_free) + * ... + * ... + * while ((dev = class_dev_iter_next(&iter)) + * devcd_del() + * device_del() + * put_device() <- last reference + * error = fn(dev, data) devcd_dev_release() + * devcd_free(dev, data) kfree(devcd) + * mutex_lock(&devcd->mutex); + * + * + * In the above diagram, It looks like disabled_store() would be racing with parallely + * running devcd_del() and result in memory abort while acquiring devcd->mutex which + * is called after kfree of devcd memory after dropping its last reference with + * put_device(). However, this will not happens as fn(dev, data) runs + * with its own reference to device via klist_node so it is not its last reference. + * so, above situation would not occur. + */ + +static ssize_t disabled_store(struct class *class, struct class_attribute *attr, + const char *buf, size_t count) +{ + long tmp = simple_strtol(buf, NULL, 10); + + /* + * This essentially makes the attribute write-once, since you can't + * go back to not having it disabled. This is intentional, it serves + * as a system lockdown feature. + */ + if (tmp != 1) + return -EINVAL; + + devcd_disabled = true; + + class_for_each_device(&devcd_class, NULL, NULL, devcd_free); + + return count; +} +static CLASS_ATTR_RW(disabled); + +static struct attribute *devcd_class_attrs[] = { + &class_attr_disabled.attr, + NULL, +}; +ATTRIBUTE_GROUPS(devcd_class); + +static struct class devcd_class = { + .name = "devcoredump", + .owner = THIS_MODULE, + .dev_release = devcd_dev_release, + .dev_groups = devcd_dev_groups, + .class_groups = devcd_class_groups, +}; + +static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count, + void *data, size_t datalen) +{ + return memory_read_from_buffer(buffer, count, &offset, data, datalen); +} + +static void devcd_freev(void *data) +{ + vfree(data); +} + +/** + * dev_coredumpv - create device coredump with vmalloc data + * @dev: the struct device for the crashed device + * @data: vmalloc data containing the device coredump + * @datalen: length of the data + * @gfp: allocation flags + * + * This function takes ownership of the vmalloc'ed data and will free + * it when it is no longer used. See dev_coredumpm() for more information. + */ +void dev_coredumpv(struct device *dev, void *data, size_t datalen, + gfp_t gfp) +{ + dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, devcd_freev); +} +EXPORT_SYMBOL_GPL(dev_coredumpv); + +static int devcd_match_failing(struct device *dev, const void *failing) +{ + struct devcd_entry *devcd = dev_to_devcd(dev); + + return devcd->failing_dev == failing; +} + +/** + * devcd_free_sgtable - free all the memory of the given scatterlist table + * (i.e. both pages and scatterlist instances) + * NOTE: if two tables allocated with devcd_alloc_sgtable and then chained + * using the sg_chain function then that function should be called only once + * on the chained table + * @data: pointer to sg_table to free + */ +static void devcd_free_sgtable(void *data) +{ + _devcd_free_sgtable(data); +} + +/** + * devcd_read_from_sgtable - copy data from sg_table to a given buffer + * and return the number of bytes read + * @buffer: the buffer to copy the data to it + * @buf_len: the length of the buffer + * @data: the scatterlist table to copy from + * @offset: start copy from @offset@ bytes from the head of the data + * in the given scatterlist + * @data_len: the length of the data in the sg_table + */ +static ssize_t devcd_read_from_sgtable(char *buffer, loff_t offset, + size_t buf_len, void *data, + size_t data_len) +{ + struct scatterlist *table = data; + + if (offset > data_len) + return -EINVAL; + + if (offset + buf_len > data_len) + buf_len = data_len - offset; + return sg_pcopy_to_buffer(table, sg_nents(table), buffer, buf_len, + offset); +} + +/** + * dev_coredumpm - create device coredump with read/free methods + * @dev: the struct device for the crashed device + * @owner: the module that contains the read/free functions, use %THIS_MODULE + * @data: data cookie for the @read/@free functions + * @datalen: length of the data + * @gfp: allocation flags + * @read: function to read from the given buffer + * @free: function to free the given buffer + * + * Creates a new device coredump for the given device. If a previous one hasn't + * been read yet, the new coredump is discarded. The data lifetime is determined + * by the device coredump framework and when it is no longer needed the @free + * function will be called to free the data. + */ +void dev_coredumpm(struct device *dev, struct module *owner, + void *data, size_t datalen, gfp_t gfp, + ssize_t (*read)(char *buffer, loff_t offset, size_t count, + void *data, size_t datalen), + void (*free)(void *data)) +{ + static atomic_t devcd_count = ATOMIC_INIT(0); + struct devcd_entry *devcd; + struct device *existing; + + if (devcd_disabled) + goto free; + + existing = class_find_device(&devcd_class, NULL, dev, + devcd_match_failing); + if (existing) { + put_device(existing); + goto free; + } + + if (!try_module_get(owner)) + goto free; + + devcd = kzalloc(sizeof(*devcd), gfp); + if (!devcd) + goto put_module; + + devcd->owner = owner; + devcd->data = data; + devcd->datalen = datalen; + devcd->read = read; + devcd->free = free; + devcd->failing_dev = get_device(dev); + devcd->delete_work = false; + + mutex_init(&devcd->mutex); + device_initialize(&devcd->devcd_dev); + + dev_set_name(&devcd->devcd_dev, "devcd%d", + atomic_inc_return(&devcd_count)); + devcd->devcd_dev.class = &devcd_class; + + mutex_lock(&devcd->mutex); + dev_set_uevent_suppress(&devcd->devcd_dev, true); + if (device_add(&devcd->devcd_dev)) + goto put_device; + + /* + * These should normally not fail, but there is no problem + * continuing without the links, so just warn instead of + * failing. + */ + if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj, + "failing_device") || + sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj, + "devcoredump")) + dev_warn(dev, "devcoredump create_link failed\n"); + + dev_set_uevent_suppress(&devcd->devcd_dev, false); + kobject_uevent(&devcd->devcd_dev.kobj, KOBJ_ADD); + INIT_DELAYED_WORK(&devcd->del_wk, devcd_del); + schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT); + mutex_unlock(&devcd->mutex); + return; + put_device: + put_device(&devcd->devcd_dev); + mutex_unlock(&devcd->mutex); + put_module: + module_put(owner); + free: + free(data); +} +EXPORT_SYMBOL_GPL(dev_coredumpm); + +/** + * dev_coredumpsg - create device coredump that uses scatterlist as data + * parameter + * @dev: the struct device for the crashed device + * @table: the dump data + * @datalen: length of the data + * @gfp: allocation flags + * + * Creates a new device coredump for the given device. If a previous one hasn't + * been read yet, the new coredump is discarded. The data lifetime is determined + * by the device coredump framework and when it is no longer needed + * it will free the data. + */ +void dev_coredumpsg(struct device *dev, struct scatterlist *table, + size_t datalen, gfp_t gfp) +{ + dev_coredumpm(dev, NULL, table, datalen, gfp, devcd_read_from_sgtable, + devcd_free_sgtable); +} +EXPORT_SYMBOL_GPL(dev_coredumpsg); + +static int __init devcoredump_init(void) +{ + return class_register(&devcd_class); +} +__initcall(devcoredump_init); + +static void __exit devcoredump_exit(void) +{ + class_for_each_device(&devcd_class, NULL, NULL, devcd_free); + class_unregister(&devcd_class); +} +__exitcall(devcoredump_exit); |