Hardware manufacturers group keys in the weirdest way possible. This may
cause a power-key to be grouped together with normal keyboard keys and
thus be reported on the same kernel interface.
However, user-space is often only interested in specific sets of events.
For instance, daemons dealing with system-reboot (like systemd-logind)
listen for KEY_POWER, but are not interested in any main keyboard keys.
Usually, power keys are reported via separate interfaces, however,
some i8042 boards report it in the AT matrix. To avoid waking up those
system daemons on each key-press, we had two ideas:
- split off KEY_POWER into a separate interface unconditionally
- allow masking a specific set of events on evdev FDs
Splitting of KEY_POWER is a rather weird way to deal with this and may
break backwards-compatibility. It is also specific to KEY_POWER and might
be required for other stuff, too. Moreover, we might end up with a huge
set of input-devices just to have them properly split.
Hence, this patchset implements the second idea: An event-mask to specify
which events you're interested in. Two ioctls allow setting this mask for
each event-type. If not set, all events are reported. The type==0 entry is
used same as in EVIOCGBIT to set the actual EV_* mask of masked events.
This way, you have a two-level filter.
We are heavily forward-compatible to new event-types and event-codes. So
new user-space will be able to run on an old kernel which doesn't know the
given event-codes or event event-types.
Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
---
drivers/input/evdev.c | 155 +++++++++++++++++++++++++++++++++++++++++++++
include/uapi/linux/input.h | 8 +++
2 files changed, 163 insertions(+)
diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 398648b..86778c3 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -51,10 +51,139 @@ struct evdev_client {
struct list_head node;
int clkid;
bool revoked;
+ unsigned long *evmasks[EV_CNT];
unsigned int bufsize;
struct input_event buffer[];
};
+static size_t evdev_get_mask_cnt(unsigned int type)
+{
+ switch (type) {
+ case 0:
+ /* 0 is special (EV-bits instead of EV_SYN) like EVIOCGBIT */
+ return EV_CNT;
+ case EV_KEY:
+ return KEY_CNT;
+ case EV_REL:
+ return REL_CNT;
+ case EV_ABS:
+ return ABS_CNT;
+ case EV_MSC:
+ return MSC_CNT;
+ case EV_SW:
+ return SW_CNT;
+ case EV_LED:
+ return LED_CNT;
+ case EV_SND:
+ return SND_CNT;
+ case EV_FF:
+ return FF_CNT;
+ }
+
+ return 0;
+}
+
+/* must be called with evdev-mutex held */
+static int evdev_set_mask(struct evdev_client *client,
+ unsigned int type,
+ const void __user *codes,
+ u32 codes_size)
+{
+ unsigned long flags, *mask, *oldmask;
+ size_t cnt, size;
+
+ /* unknown masks are simply ignored for forward-compat */
+ cnt = evdev_get_mask_cnt(type);
+ if (!cnt)
+ return 0;
+
+ /* we allow 'codes_size > size' for forward-compat */
+ size = sizeof(unsigned long) * BITS_TO_LONGS(cnt);
+
+ mask = kzalloc(size, GFP_KERNEL);
+ if (!mask)
+ return -ENOMEM;
+
+ if (copy_from_user(mask, codes, min_t(size_t, codes_size, size))) {
+ kfree(mask);
+ return -EFAULT;
+ }
+
+ spin_lock_irqsave(&client->buffer_lock, flags);
+ oldmask = client->evmasks[type];
+ client->evmasks[type] = mask;
+ spin_unlock_irqrestore(&client->buffer_lock, flags);
+
+ kfree(oldmask);
+
+ return 0;
+}
+
+/* must be called with evdev-mutex held */
+static int evdev_get_mask(struct evdev_client *client,
+ unsigned int type,
+ void __user *codes,
+ u32 codes_size)
+{
+ unsigned long *mask;
+ size_t cnt, size, min, i;
+ u8 __user *out;
+
+ /* we allow unknown types and 'codes_size > size' for forward-compat */
+ cnt = evdev_get_mask_cnt(type);
+ size = sizeof(unsigned long) * BITS_TO_LONGS(cnt);
+ min = min_t(size_t, codes_size, size);
+
+ if (cnt > 0) {
+ mask = client->evmasks[type];
+ if (mask) {
+ if (copy_to_user(codes, mask, min))
+ return -EFAULT;
+ } else {
+ /* fake mask with all bits set */
+ out = (u8 __user*)codes;
+ for (i = 0; i < min; ++i) {
+ if (put_user((u8)0xff, out + i))
+ return -EFAULT;
+ }
+ }
+ }
+
+ codes = (u8 __user*)codes + min;
+ codes_size -= min;
+
+ if (codes_size > 0 && clear_user(codes, codes_size))
+ return -EFAULT;
+
+ return 0;
+}
+
+/* requires the buffer lock to be held */
+static bool __evdev_is_masked(struct evdev_client *client,
+ unsigned int type,
+ unsigned int code)
+{
+ unsigned long *mask;
+ size_t cnt;
+
+ /* EV_SYN and unknown codes are never masked */
+ if (!type || type >= EV_CNT)
+ return false;
+
+ /* first test whether the type is masked */
+ mask = client->evmasks[0];
+ if (mask && !test_bit(type, mask))
+ return true;
+
+ /* unknown values are never masked */
+ cnt = evdev_get_mask_cnt(type);
+ if (!cnt || code >= cnt)
+ return false;
+
+ mask = client->evmasks[type];
+ return mask && !test_bit(code, mask);
+}
+
/* Flush queued events of given type @type and code @code. A negative code
* is interpreted as catch-all. Caller must hold client->buffer_lock. */
static void __evdev_flush_queue(struct evdev_client *client,
@@ -137,6 +266,9 @@ static void evdev_queue_syn_dropped(struct evdev_client *client)
static void __pass_event(struct evdev_client *client,
const struct input_event *event)
{
+ if (__evdev_is_masked(client, event->type, event->code))
+ return;
+
client->buffer[client->head++] = *event;
client->head &= client->bufsize - 1;
@@ -368,6 +500,7 @@ static int evdev_release(struct inode *inode, struct file *file)
{
struct evdev_client *client = file->private_data;
struct evdev *evdev = client->evdev;
+ unsigned int i;
mutex_lock(&evdev->mutex);
evdev_ungrab(evdev, client);
@@ -375,6 +508,9 @@ static int evdev_release(struct inode *inode, struct file *file)
evdev_detach_client(evdev, client);
+ for (i = 0; i < EV_CNT; ++i)
+ kfree(client->evmasks[i]);
+
if (is_vmalloc_addr(client))
vfree(client);
else
@@ -866,6 +1002,7 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,
struct evdev *evdev = client->evdev;
struct input_dev *dev = evdev->handle.dev;
struct input_absinfo abs;
+ struct input_mask mask;
struct ff_effect effect;
int __user *ip = (int __user *)p;
unsigned int i, t, u, v;
@@ -927,6 +1064,24 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,
else
return evdev_revoke(evdev, client, file);
+ case EVIOCGMASK:
+ if (copy_from_user(&mask, p, sizeof(mask)))
+ return -EFAULT;
+
+ return evdev_get_mask(client,
+ mask.type,
+ (void*)(long)mask.codes_ptr,
+ mask.codes_size);
+
+ case EVIOCSMASK:
+ if (copy_from_user(&mask, p, sizeof(mask)))
+ return -EFAULT;
+
+ return evdev_set_mask(client,
+ mask.type,
+ (const void*)(long)mask.codes_ptr,
+ mask.codes_size);
+
case EVIOCSCLOCKID:
if (copy_from_user(&i, p, sizeof(unsigned int)))
return -EFAULT;
diff --git a/include/uapi/linux/input.h b/include/uapi/linux/input.h
index bd24470..5b73712 100644
--- a/include/uapi/linux/input.h
+++ b/include/uapi/linux/input.h
@@ -97,6 +97,12 @@ struct input_keymap_entry {
__u8 scancode[32];
};
+struct input_mask {
+ u32 type;
+ u32 codes_size;
+ u64 codes_ptr;
+};
+
#define EVIOCGVERSION _IOR('E', 0x01, int) /* get driver version */
#define EVIOCGID _IOR('E', 0x02, struct input_id) /* get device ID */
#define EVIOCGREP _IOR('E', 0x03, unsigned int[2]) /* get repeat settings */
@@ -153,6 +159,8 @@ struct input_keymap_entry {
#define EVIOCGRAB _IOW('E', 0x90, int) /* Grab/Release device */
#define EVIOCREVOKE _IOW('E', 0x91, int) /* Revoke device access */
+#define EVIOCGMASK _IOR('E', 0x92, struct input_mask) /* Get event-masks */
+#define EVIOCSMASK _IOW('E', 0x93, struct input_mask) /* Set event-masks */
#define EVIOCSCLOCKID _IOW('E', 0xa0, int) /* Set clockid to be used for timestamps */
--
1.9.2
--
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