device coredump: add new device coredump class

Many devices run firmware and/or complex hardware, and most of that
can have bugs. When it misbehaves, however, it is often much harder
to debug than software running on the host.

Introduce a "device coredump" mechanism to allow dumping internal
device/firmware state through a generalized mechanism. As devices
are different and information needed can vary accordingly, this
doesn't prescribe a file format - it just provides mechanism to
get data to be able to capture it in a generalized way (e.g. in
distributions.)

The dumped data will be readable in sysfs in the virtual device's
data file under /sys/class/devcoredump/devcd*/. Writing to it will
free the data and remove the device, as does a 5-minute timeout.

Note that generalized capturing of such data may result in privacy
issues, so users generally need to be involved. In order to allow
certain users/system integrators/... to disable the feature at all,
introduce a Kconfig option to override the drivers that would like
to have the feature.

For now, this provides two ways of dumping data:
 1) with a vmalloc'ed area, that is then given to the subsystem
    and freed after retrieval or timeout
 2) with a generalized reader/free function method

We could/should add more options, e.g. a list of pages, since the
vmalloc area is very limited on some architectures.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

5 files changed, 329 insertions, 0 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index 809ecd680d88..d810a6fa8276 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2859,6 +2859,13 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git
 S:      Maintained
 F:      drivers/usb/dwc3/
 
+DEVICE COREDUMP (DEV_COREDUMP)
+M:      Johannes Berg <johannes@sipsolutions.net>
+L:      linux-kernel@vger.kernel.org
+S:      Maintained
+F:      drivers/base/devcoredump.c
+F:      include/linux/devcoredump.h
+
 DEVICE FREQUENCY (DEVFREQ)
 M:      MyungJoo Ham <myungjoo.ham@samsung.com>
 M:      Kyungmin Park <kyungmin.park@samsung.com>
diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 4e7f0ff83ae7..134f763d90fd 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -165,6 +165,27 @@ config FW_LOADER_USER_HELPER_FALLBACK
 
           If you are unsure about this, say N here.
 
+config WANT_DEV_COREDUMP
+        bool
+        help
+          Drivers should "select" this option if they desire to use the
+          device coredump mechanism.
+
+config DISABLE_DEV_COREDUMP
+        bool "Disable device coredump" if EXPERT
+        help
+          Disable the device coredump mechanism despite drivers wanting to
+          use it; this allows for more sensitive systems or systems that
+          don't want to ever access the information to not have the code,
+          nor keep any data.
+
+          If unsure, say N.
+
+config DEV_COREDUMP
+        bool
+        default y if WANT_DEV_COREDUMP
+        depends on !DISABLE_DEV_COREDUMP
+
 config DEBUG_DRIVER
         bool "Driver Core verbose debug messages"
         depends on DEBUG_KERNEL
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 4aab26ec0292..6922cd6850a2 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -21,6 +21,7 @@ obj-$(CONFIG_SYS_HYPERVISOR) += hypervisor.o
 obj-$(CONFIG_REGMAP)    += regmap/
 obj-$(CONFIG_SOC_BUS) += soc.o
 obj-$(CONFIG_PINCTRL) += pinctrl.o
+obj-$(CONFIG_DEV_COREDUMP) += devcoredump.o
 
 ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
 
diff --git a/drivers/base/devcoredump.c b/drivers/base/devcoredump.c
new file mode 100644
index 000000000000..96614b04544c
--- /dev/null
+++ b/drivers/base/devcoredump.c
@@ -0,0 +1,265 @@
+/*
+ * This file is provided under the GPLv2 license.
+ *
+ * GPL LICENSE SUMMARY
+ *
+ * Copyright(c) 2014 Intel Mobile Communications GmbH
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * The full GNU General Public License is included in this distribution
+ * in the file called COPYING.
+ *
+ * Contact Information:
+ *  Intel Linux Wireless <ilw@linux.intel.com>
+ * Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124-6497
+ *
+ * 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>
+
+/* 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;
+        const void *data;
+        size_t datalen;
+        struct module *owner;
+        ssize_t (*read)(char *buffer, loff_t offset, size_t count,
+                        const void *data, size_t datalen);
+        void (*free)(const 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);
+
+        mod_delayed_work(system_wq, &devcd->del_wk, 0);
+
+        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 struct class devcd_class = {
+        .name           = "devcoredump",
+        .owner          = THIS_MODULE,
+        .dev_release    = devcd_dev_release,
+        .dev_groups     = devcd_dev_groups,
+};
+
+static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count,
+                           const void *data, size_t datalen)
+{
+        if (offset > datalen)
+                return -EINVAL;
+
+        if (offset + count > datalen)
+                count = datalen - offset;
+
+        if (count)
+                memcpy(buffer, ((u8 *)data) + offset, count);
+
+        return count;
+}
+
+/**
+ * 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, const void *data, size_t datalen,
+                   gfp_t gfp)
+{
+        dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, vfree);
+}
+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;
+}
+
+/**
+ * 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,
+                   const void *data, size_t datalen, gfp_t gfp,
+                   ssize_t (*read)(char *buffer, loff_t offset, size_t count,
+                                   const void *data, size_t datalen),
+                   void (*free)(const void *data))
+{
+        static atomic_t devcd_count = ATOMIC_INIT(0);
+        struct devcd_entry *devcd;
+        struct device *existing;
+
+        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);
+
+        device_initialize(&devcd->devcd_dev);
+
+        dev_set_name(&devcd->devcd_dev, "devcd%d",
+                     atomic_inc_return(&devcd_count));
+        devcd->devcd_dev.class = &devcd_class;
+
+        if (device_add(&devcd->devcd_dev))
+                goto put_device;
+
+        if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj,
+                              "failing_device"))
+                /* nothing - symlink will be missing */;
+
+        if (sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj,
+                              "devcoredump"))
+                /* nothing - symlink will be missing */;
+
+        INIT_DELAYED_WORK(&devcd->del_wk, devcd_del);
+        schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT);
+
+        return;
+ put_device:
+        put_device(&devcd->devcd_dev);
+ put_module:
+        module_put(owner);
+ free:
+        free(data);
+}
+EXPORT_SYMBOL_GPL(dev_coredumpm);
+
+static int __init devcoredump_init(void)
+{
+        return class_register(&devcd_class);
+}
+__initcall(devcoredump_init);
+
+static int devcd_free(struct device *dev, void *data)
+{
+        struct devcd_entry *devcd = dev_to_devcd(dev);
+
+        flush_delayed_work(&devcd->del_wk);
+        return 0;
+}
+
+static void __exit devcoredump_exit(void)
+{
+        class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
+        class_unregister(&devcd_class);
+}
+__exitcall(devcoredump_exit);
diff --git a/include/linux/devcoredump.h b/include/linux/devcoredump.h
new file mode 100644
index 000000000000..c0a360e99f64
--- /dev/null
+++ b/include/linux/devcoredump.h
@@ -0,0 +1,35 @@
+#ifndef __DEVCOREDUMP_H
+#define __DEVCOREDUMP_H
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/vmalloc.h>
+
+#ifdef CONFIG_DEV_COREDUMP
+void dev_coredumpv(struct device *dev, const void *data, size_t datalen,
+                   gfp_t gfp);
+
+void dev_coredumpm(struct device *dev, struct module *owner,
+                   const void *data, size_t datalen, gfp_t gfp,
+                   ssize_t (*read)(char *buffer, loff_t offset, size_t count,
+                                   const void *data, size_t datalen),
+                   void (*free)(const void *data));
+#else
+static inline void dev_coredumpv(struct device *dev, const void *data,
+                                 size_t datalen, gfp_t gfp)
+{
+        vfree(data);
+}
+
+static inline void
+dev_coredumpm(struct device *dev, struct module *owner,
+              const void *data, size_t datalen, gfp_t gfp,
+              ssize_t (*read)(char *buffer, loff_t offset, size_t count,
+                              const void *data, size_t datalen),
+              void (*free)(const void *data))
+{
+        free(data);
+}
+#endif /* CONFIG_DEV_COREDUMP */
+
+#endif /* __DEVCOREDUMP_H */