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linux-next/drivers/iio/industrialio-event.c
Lars-Peter Clausen 4b1a9380a6 iio: iio_push_event(): Don't crash if the event interface is not registered
iio_push_event() operates on a struct iio_dev. This struct can be allocated
using iio_device_alloc() which returns a valid struct iio_dev pointer. But
iio_push_event() is not safe to use on such a iio_dev until
iio_device_register() for the same device has successfully completed.

This restriction is not documented anywhere and most drivers are written
with the assumption that this restriction does not exist. The basic pattern
that is followed by all drivers looks like the following:

	irqreturn_t event_callback(int irq, void *devid)
	{
		struct iio_dev *indio_dev = devid;
		...
		iio_push_event(indio_dev, ...);

		return IRQ_HANDLED;
	}

	int driver_probe(struct device *dev)
	{
		struct iio_dev *indio_dev;

		indio_dev = iio_device_alloc(...);

		request_irq(event_irq, event_callback, ..., indio_dev);

		return iio_device_register(indio_dev);
	}

And while it is unlikely that the IRQ fires before iio_device_register()
completes (e.g. because the IRQ is disabled in the device) it is not
impossible and might be triggered by glitches on the signal line or
incorrect hardware configuration.

To avoid undefined behaviour in such a case extend iio_push_event() to
check if the event has been registered and discard generated events if it
has not.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
2016-09-10 16:40:44 +01:00

558 lines
14 KiB
C

/* Industrial I/O event handling
*
* Copyright (c) 2008 Jonathan Cameron
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published by
* the Free Software Foundation.
*
* Based on elements of hwmon and input subsystems.
*/
#include <linux/anon_inodes.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/kfifo.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/wait.h>
#include <linux/iio/iio.h>
#include "iio_core.h"
#include <linux/iio/sysfs.h>
#include <linux/iio/events.h>
/**
* struct iio_event_interface - chrdev interface for an event line
* @wait: wait queue to allow blocking reads of events
* @det_events: list of detected events
* @dev_attr_list: list of event interface sysfs attribute
* @flags: file operations related flags including busy flag.
* @group: event interface sysfs attribute group
* @read_lock: lock to protect kfifo read operations
*/
struct iio_event_interface {
wait_queue_head_t wait;
DECLARE_KFIFO(det_events, struct iio_event_data, 16);
struct list_head dev_attr_list;
unsigned long flags;
struct attribute_group group;
struct mutex read_lock;
};
bool iio_event_enabled(const struct iio_event_interface *ev_int)
{
return !!test_bit(IIO_BUSY_BIT_POS, &ev_int->flags);
}
/**
* iio_push_event() - try to add event to the list for userspace reading
* @indio_dev: IIO device structure
* @ev_code: What event
* @timestamp: When the event occurred
*
* Note: The caller must make sure that this function is not running
* concurrently for the same indio_dev more than once.
*
* This function may be safely used as soon as a valid reference to iio_dev has
* been obtained via iio_device_alloc(), but any events that are submitted
* before iio_device_register() has successfully completed will be silently
* discarded.
**/
int iio_push_event(struct iio_dev *indio_dev, u64 ev_code, s64 timestamp)
{
struct iio_event_interface *ev_int = indio_dev->event_interface;
struct iio_event_data ev;
int copied;
if (!ev_int)
return 0;
/* Does anyone care? */
if (iio_event_enabled(ev_int)) {
ev.id = ev_code;
ev.timestamp = timestamp;
copied = kfifo_put(&ev_int->det_events, ev);
if (copied != 0)
wake_up_poll(&ev_int->wait, POLLIN);
}
return 0;
}
EXPORT_SYMBOL(iio_push_event);
/**
* iio_event_poll() - poll the event queue to find out if it has data
* @filep: File structure pointer to identify the device
* @wait: Poll table pointer to add the wait queue on
*
* Return: (POLLIN | POLLRDNORM) if data is available for reading
* or a negative error code on failure
*/
static unsigned int iio_event_poll(struct file *filep,
struct poll_table_struct *wait)
{
struct iio_dev *indio_dev = filep->private_data;
struct iio_event_interface *ev_int = indio_dev->event_interface;
unsigned int events = 0;
if (!indio_dev->info)
return events;
poll_wait(filep, &ev_int->wait, wait);
if (!kfifo_is_empty(&ev_int->det_events))
events = POLLIN | POLLRDNORM;
return events;
}
static ssize_t iio_event_chrdev_read(struct file *filep,
char __user *buf,
size_t count,
loff_t *f_ps)
{
struct iio_dev *indio_dev = filep->private_data;
struct iio_event_interface *ev_int = indio_dev->event_interface;
unsigned int copied;
int ret;
if (!indio_dev->info)
return -ENODEV;
if (count < sizeof(struct iio_event_data))
return -EINVAL;
do {
if (kfifo_is_empty(&ev_int->det_events)) {
if (filep->f_flags & O_NONBLOCK)
return -EAGAIN;
ret = wait_event_interruptible(ev_int->wait,
!kfifo_is_empty(&ev_int->det_events) ||
indio_dev->info == NULL);
if (ret)
return ret;
if (indio_dev->info == NULL)
return -ENODEV;
}
if (mutex_lock_interruptible(&ev_int->read_lock))
return -ERESTARTSYS;
ret = kfifo_to_user(&ev_int->det_events, buf, count, &copied);
mutex_unlock(&ev_int->read_lock);
if (ret)
return ret;
/*
* If we couldn't read anything from the fifo (a different
* thread might have been faster) we either return -EAGAIN if
* the file descriptor is non-blocking, otherwise we go back to
* sleep and wait for more data to arrive.
*/
if (copied == 0 && (filep->f_flags & O_NONBLOCK))
return -EAGAIN;
} while (copied == 0);
return copied;
}
static int iio_event_chrdev_release(struct inode *inode, struct file *filep)
{
struct iio_dev *indio_dev = filep->private_data;
struct iio_event_interface *ev_int = indio_dev->event_interface;
clear_bit(IIO_BUSY_BIT_POS, &ev_int->flags);
iio_device_put(indio_dev);
return 0;
}
static const struct file_operations iio_event_chrdev_fileops = {
.read = iio_event_chrdev_read,
.poll = iio_event_poll,
.release = iio_event_chrdev_release,
.owner = THIS_MODULE,
.llseek = noop_llseek,
};
int iio_event_getfd(struct iio_dev *indio_dev)
{
struct iio_event_interface *ev_int = indio_dev->event_interface;
int fd;
if (ev_int == NULL)
return -ENODEV;
fd = mutex_lock_interruptible(&indio_dev->mlock);
if (fd)
return fd;
if (test_and_set_bit(IIO_BUSY_BIT_POS, &ev_int->flags)) {
fd = -EBUSY;
goto unlock;
}
iio_device_get(indio_dev);
fd = anon_inode_getfd("iio:event", &iio_event_chrdev_fileops,
indio_dev, O_RDONLY | O_CLOEXEC);
if (fd < 0) {
clear_bit(IIO_BUSY_BIT_POS, &ev_int->flags);
iio_device_put(indio_dev);
} else {
kfifo_reset_out(&ev_int->det_events);
}
unlock:
mutex_unlock(&indio_dev->mlock);
return fd;
}
static const char * const iio_ev_type_text[] = {
[IIO_EV_TYPE_THRESH] = "thresh",
[IIO_EV_TYPE_MAG] = "mag",
[IIO_EV_TYPE_ROC] = "roc",
[IIO_EV_TYPE_THRESH_ADAPTIVE] = "thresh_adaptive",
[IIO_EV_TYPE_MAG_ADAPTIVE] = "mag_adaptive",
[IIO_EV_TYPE_CHANGE] = "change",
};
static const char * const iio_ev_dir_text[] = {
[IIO_EV_DIR_EITHER] = "either",
[IIO_EV_DIR_RISING] = "rising",
[IIO_EV_DIR_FALLING] = "falling"
};
static const char * const iio_ev_info_text[] = {
[IIO_EV_INFO_ENABLE] = "en",
[IIO_EV_INFO_VALUE] = "value",
[IIO_EV_INFO_HYSTERESIS] = "hysteresis",
[IIO_EV_INFO_PERIOD] = "period",
[IIO_EV_INFO_HIGH_PASS_FILTER_3DB] = "high_pass_filter_3db",
[IIO_EV_INFO_LOW_PASS_FILTER_3DB] = "low_pass_filter_3db",
};
static enum iio_event_direction iio_ev_attr_dir(struct iio_dev_attr *attr)
{
return attr->c->event_spec[attr->address & 0xffff].dir;
}
static enum iio_event_type iio_ev_attr_type(struct iio_dev_attr *attr)
{
return attr->c->event_spec[attr->address & 0xffff].type;
}
static enum iio_event_info iio_ev_attr_info(struct iio_dev_attr *attr)
{
return (attr->address >> 16) & 0xffff;
}
static ssize_t iio_ev_state_store(struct device *dev,
struct device_attribute *attr,
const char *buf,
size_t len)
{
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
int ret;
bool val;
ret = strtobool(buf, &val);
if (ret < 0)
return ret;
ret = indio_dev->info->write_event_config(indio_dev,
this_attr->c, iio_ev_attr_type(this_attr),
iio_ev_attr_dir(this_attr), val);
return (ret < 0) ? ret : len;
}
static ssize_t iio_ev_state_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
int val;
val = indio_dev->info->read_event_config(indio_dev,
this_attr->c, iio_ev_attr_type(this_attr),
iio_ev_attr_dir(this_attr));
if (val < 0)
return val;
else
return sprintf(buf, "%d\n", val);
}
static ssize_t iio_ev_value_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
int val, val2, val_arr[2];
int ret;
ret = indio_dev->info->read_event_value(indio_dev,
this_attr->c, iio_ev_attr_type(this_attr),
iio_ev_attr_dir(this_attr), iio_ev_attr_info(this_attr),
&val, &val2);
if (ret < 0)
return ret;
val_arr[0] = val;
val_arr[1] = val2;
return iio_format_value(buf, ret, 2, val_arr);
}
static ssize_t iio_ev_value_store(struct device *dev,
struct device_attribute *attr,
const char *buf,
size_t len)
{
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
int val, val2;
int ret;
if (!indio_dev->info->write_event_value)
return -EINVAL;
ret = iio_str_to_fixpoint(buf, 100000, &val, &val2);
if (ret)
return ret;
ret = indio_dev->info->write_event_value(indio_dev,
this_attr->c, iio_ev_attr_type(this_attr),
iio_ev_attr_dir(this_attr), iio_ev_attr_info(this_attr),
val, val2);
if (ret < 0)
return ret;
return len;
}
static int iio_device_add_event(struct iio_dev *indio_dev,
const struct iio_chan_spec *chan, unsigned int spec_index,
enum iio_event_type type, enum iio_event_direction dir,
enum iio_shared_by shared_by, const unsigned long *mask)
{
ssize_t (*show)(struct device *, struct device_attribute *, char *);
ssize_t (*store)(struct device *, struct device_attribute *,
const char *, size_t);
unsigned int attrcount = 0;
unsigned int i;
char *postfix;
int ret;
for_each_set_bit(i, mask, sizeof(*mask)*8) {
if (i >= ARRAY_SIZE(iio_ev_info_text))
return -EINVAL;
if (dir != IIO_EV_DIR_NONE)
postfix = kasprintf(GFP_KERNEL, "%s_%s_%s",
iio_ev_type_text[type],
iio_ev_dir_text[dir],
iio_ev_info_text[i]);
else
postfix = kasprintf(GFP_KERNEL, "%s_%s",
iio_ev_type_text[type],
iio_ev_info_text[i]);
if (postfix == NULL)
return -ENOMEM;
if (i == IIO_EV_INFO_ENABLE) {
show = iio_ev_state_show;
store = iio_ev_state_store;
} else {
show = iio_ev_value_show;
store = iio_ev_value_store;
}
ret = __iio_add_chan_devattr(postfix, chan, show, store,
(i << 16) | spec_index, shared_by, &indio_dev->dev,
&indio_dev->event_interface->dev_attr_list);
kfree(postfix);
if ((ret == -EBUSY) && (shared_by != IIO_SEPARATE))
continue;
if (ret)
return ret;
attrcount++;
}
return attrcount;
}
static int iio_device_add_event_sysfs(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan)
{
int ret = 0, i, attrcount = 0;
enum iio_event_direction dir;
enum iio_event_type type;
for (i = 0; i < chan->num_event_specs; i++) {
type = chan->event_spec[i].type;
dir = chan->event_spec[i].dir;
ret = iio_device_add_event(indio_dev, chan, i, type, dir,
IIO_SEPARATE, &chan->event_spec[i].mask_separate);
if (ret < 0)
return ret;
attrcount += ret;
ret = iio_device_add_event(indio_dev, chan, i, type, dir,
IIO_SHARED_BY_TYPE,
&chan->event_spec[i].mask_shared_by_type);
if (ret < 0)
return ret;
attrcount += ret;
ret = iio_device_add_event(indio_dev, chan, i, type, dir,
IIO_SHARED_BY_DIR,
&chan->event_spec[i].mask_shared_by_dir);
if (ret < 0)
return ret;
attrcount += ret;
ret = iio_device_add_event(indio_dev, chan, i, type, dir,
IIO_SHARED_BY_ALL,
&chan->event_spec[i].mask_shared_by_all);
if (ret < 0)
return ret;
attrcount += ret;
}
ret = attrcount;
return ret;
}
static inline int __iio_add_event_config_attrs(struct iio_dev *indio_dev)
{
int j, ret, attrcount = 0;
/* Dynamically created from the channels array */
for (j = 0; j < indio_dev->num_channels; j++) {
ret = iio_device_add_event_sysfs(indio_dev,
&indio_dev->channels[j]);
if (ret < 0)
return ret;
attrcount += ret;
}
return attrcount;
}
static bool iio_check_for_dynamic_events(struct iio_dev *indio_dev)
{
int j;
for (j = 0; j < indio_dev->num_channels; j++) {
if (indio_dev->channels[j].num_event_specs != 0)
return true;
}
return false;
}
static void iio_setup_ev_int(struct iio_event_interface *ev_int)
{
INIT_KFIFO(ev_int->det_events);
init_waitqueue_head(&ev_int->wait);
mutex_init(&ev_int->read_lock);
}
static const char *iio_event_group_name = "events";
int iio_device_register_eventset(struct iio_dev *indio_dev)
{
struct iio_dev_attr *p;
int ret = 0, attrcount_orig = 0, attrcount, attrn;
struct attribute **attr;
if (!(indio_dev->info->event_attrs ||
iio_check_for_dynamic_events(indio_dev)))
return 0;
indio_dev->event_interface =
kzalloc(sizeof(struct iio_event_interface), GFP_KERNEL);
if (indio_dev->event_interface == NULL)
return -ENOMEM;
INIT_LIST_HEAD(&indio_dev->event_interface->dev_attr_list);
iio_setup_ev_int(indio_dev->event_interface);
if (indio_dev->info->event_attrs != NULL) {
attr = indio_dev->info->event_attrs->attrs;
while (*attr++ != NULL)
attrcount_orig++;
}
attrcount = attrcount_orig;
if (indio_dev->channels) {
ret = __iio_add_event_config_attrs(indio_dev);
if (ret < 0)
goto error_free_setup_event_lines;
attrcount += ret;
}
indio_dev->event_interface->group.name = iio_event_group_name;
indio_dev->event_interface->group.attrs = kcalloc(attrcount + 1,
sizeof(indio_dev->event_interface->group.attrs[0]),
GFP_KERNEL);
if (indio_dev->event_interface->group.attrs == NULL) {
ret = -ENOMEM;
goto error_free_setup_event_lines;
}
if (indio_dev->info->event_attrs)
memcpy(indio_dev->event_interface->group.attrs,
indio_dev->info->event_attrs->attrs,
sizeof(indio_dev->event_interface->group.attrs[0])
*attrcount_orig);
attrn = attrcount_orig;
/* Add all elements from the list. */
list_for_each_entry(p,
&indio_dev->event_interface->dev_attr_list,
l)
indio_dev->event_interface->group.attrs[attrn++] =
&p->dev_attr.attr;
indio_dev->groups[indio_dev->groupcounter++] =
&indio_dev->event_interface->group;
return 0;
error_free_setup_event_lines:
iio_free_chan_devattr_list(&indio_dev->event_interface->dev_attr_list);
kfree(indio_dev->event_interface);
indio_dev->event_interface = NULL;
return ret;
}
/**
* iio_device_wakeup_eventset - Wakes up the event waitqueue
* @indio_dev: The IIO device
*
* Wakes up the event waitqueue used for poll() and blocking read().
* Should usually be called when the device is unregistered.
*/
void iio_device_wakeup_eventset(struct iio_dev *indio_dev)
{
if (indio_dev->event_interface == NULL)
return;
wake_up(&indio_dev->event_interface->wait);
}
void iio_device_unregister_eventset(struct iio_dev *indio_dev)
{
if (indio_dev->event_interface == NULL)
return;
iio_free_chan_devattr_list(&indio_dev->event_interface->dev_attr_list);
kfree(indio_dev->event_interface->group.attrs);
kfree(indio_dev->event_interface);
}