[PATCH 2/4] Input: introduce ABS_MAX2/CNT2 and friends

From: David Herrmann
Date: Tue Dec 17 2013 - 10:49:35 EST

As we painfully noticed during the 3.12 merge-window our
EVIOCGABS/EVIOCSABS API is limited to ABS_MAX<=0x3f. We tried several
hacks to work around it but if we ever decide to increase ABS_MAX, the
EVIOCSABS ioctl ABI might overflow into the next byte causing horrible
misinterpretations in the kernel that we cannot catch.

Therefore, we decided to go with ABS_MAX2/CNT2 and introduce two new
ioctls to get/set abs-params. They no longer encode the ABS code in the
ioctl number and thus allow up to 4 billion ABS codes.

The new API also allows to query multiple ABS values with one call. To
allow EVIOCSABS2(code = 0, cnt = ABS_CNT2) we need to silently ignore
writes to ABS_MT_SLOT. Furthermore, for better compatibility with
newer user-space, we ignore writes to unknown codes. Hence, if we ever
increase ABS_MAX2, new user-space will work with code=0,cnt=ABS_CNT2 just
fine even on old kernels.

Note that we also need to increase EV_VERSION so user-space can reliably
know whether ABS2 is supported. Unfortunately, we return EINVAL instead of
ENOSYS for unknown evdev ioctls so it's nearly impossible to catch
reliably without EVIOCGVERSION.

Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
---
drivers/hid/hid-debug.c | 2 +-
drivers/hid/hid-input.c | 2 +-
drivers/input/evdev.c | 95 +++++++++++++++++++++++++++++++-
drivers/input/input.c | 14 ++---
drivers/input/keyboard/goldfish_events.c | 6 +-
drivers/input/keyboard/hil_kbd.c | 2 +-
drivers/input/misc/uinput.c | 6 +-
include/linux/hid.h | 2 +-
include/linux/input.h | 6 +-
include/uapi/linux/input.h | 42 +++++++++++++-
include/uapi/linux/uinput.h | 2 +-
11 files changed, 155 insertions(+), 24 deletions(-)

diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c
index 8453214..d32fa30 100644
--- a/drivers/hid/hid-debug.c
+++ b/drivers/hid/hid-debug.c
@@ -862,7 +862,7 @@ static const char *relatives[REL_MAX + 1] = {
[REL_WHEEL] = "Wheel", [REL_MISC] = "Misc",
};

-static const char *absolutes[ABS_CNT] = {
+static const char *absolutes[ABS_CNT2] = {
[ABS_X] = "X", [ABS_Y] = "Y",
[ABS_Z] = "Z", [ABS_RX] = "Rx",
[ABS_RY] = "Ry", [ABS_RZ] = "Rz",
diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index d97f232..a02721c 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -1300,7 +1300,7 @@ static bool hidinput_has_been_populated(struct hid_input *hidinput)
for (i = 0; i < BITS_TO_LONGS(REL_CNT); i++)
r |= hidinput->input->relbit[i];

- for (i = 0; i < BITS_TO_LONGS(ABS_CNT); i++)
+ for (i = 0; i < BITS_TO_LONGS(ABS_CNT2); i++)
r |= hidinput->input->absbit[i];

for (i = 0; i < BITS_TO_LONGS(MSC_CNT); i++)
diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index a06e125..32b74e5 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -643,7 +643,7 @@ static int handle_eviocgbit(struct input_dev *dev,
case 0: bits = dev->evbit; len = EV_MAX; break;
case EV_KEY: bits = dev->keybit; len = KEY_MAX; break;
case EV_REL: bits = dev->relbit; len = REL_MAX; break;
- case EV_ABS: bits = dev->absbit; len = ABS_MAX; break;
+ case EV_ABS: bits = dev->absbit; len = ABS_MAX2; break;
case EV_MSC: bits = dev->mscbit; len = MSC_MAX; break;
case EV_LED: bits = dev->ledbit; len = LED_MAX; break;
case EV_SND: bits = dev->sndbit; len = SND_MAX; break;
@@ -671,6 +671,93 @@ static int handle_eviocgbit(struct input_dev *dev,
}
#undef OLD_KEY_MAX

+static int evdev_handle_get_abs2(struct input_dev *dev, void __user *p)
+{
+ u32 code, cnt, valid_cnt, i;
+ struct input_absinfo2 __user *pinfo = p;
+ struct input_absinfo abs;
+
+ if (copy_from_user(&code, &pinfo->code, sizeof(code)))
+ return -EFAULT;
+ if (copy_from_user(&cnt, &pinfo->cnt, sizeof(cnt)))
+ return -EFAULT;
+ if (!cnt)
+ return 0;
+
+ if (!dev->absinfo)
+ valid_cnt = 0;
+ else if (code > ABS_MAX2)
+ valid_cnt = 0;
+ else if (code + cnt <= code || code + cnt > ABS_MAX2)
+ valid_cnt = ABS_MAX2 - code + 1;
+ else
+ valid_cnt = cnt;
+
+ for (i = 0; i < valid_cnt; ++i) {
+ /*
+ * Take event lock to ensure that we are not
+ * copying data while EVIOCSABS2 changes it.
+ * Might be inconsistent, otherwise.
+ */
+ spin_lock_irq(&dev->event_lock);
+ abs = dev->absinfo[code + i];
+ spin_unlock_irq(&dev->event_lock);
+
+ if (copy_to_user(&pinfo->info[i], &abs, sizeof(abs)))
+ return -EFAULT;
+ }
+
+ memset(&abs, 0, sizeof(abs));
+ for (i = valid_cnt; i < cnt; ++i)
+ if (copy_to_user(&pinfo->info[i], &abs, sizeof(abs)))
+ return -EFAULT;
+
+ return 0;
+}
+
+static int evdev_handle_set_abs2(struct input_dev *dev, void __user *p)
+{
+ struct input_absinfo2 __user *pinfo = p;
+ struct input_absinfo *abs;
+ u32 code, cnt, i;
+ size_t size;
+
+ if (!dev->absinfo)
+ return 0;
+ if (copy_from_user(&code, &pinfo->code, sizeof(code)))
+ return -EFAULT;
+ if (copy_from_user(&cnt, &pinfo->cnt, sizeof(cnt)))
+ return -EFAULT;
+ if (!cnt || code > ABS_MAX2)
+ return 0;
+
+ if (code + cnt <= code || code + cnt > ABS_MAX2)
+ cnt = ABS_MAX2 - code + 1;
+
+ size = cnt * sizeof(*abs);
+ abs = memdup_user(pinfo->info, size);
+ if (IS_ERR(abs))
+ return PTR_ERR(abs);
+
+ /*
+ * Take event lock to ensure that we are not
+ * changing device parameters in the middle
+ * of event.
+ */
+ spin_lock_irq(&dev->event_lock);
+ for (i = 0; i < cnt; ++i) {
+ /* silently drop ABS_MT_SLOT */
+ if (code + i == ABS_MT_SLOT)
+ continue;
+
+ dev->absinfo[code + i] = abs[i];
+ }
+ spin_unlock_irq(&dev->event_lock);
+
+ kfree(abs);
+ return 0;
+}
+
static int evdev_handle_get_keycode(struct input_dev *dev, void __user *p)
{
struct input_keymap_entry ke = {
@@ -898,6 +985,12 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,
client->clkid = i;
return 0;

+ case EVIOCGABS2:
+ return evdev_handle_get_abs2(dev, p);
+
+ case EVIOCSABS2:
+ return evdev_handle_set_abs2(dev, p);
+
case EVIOCGKEYCODE:
return evdev_handle_get_keycode(dev, p);

diff --git a/drivers/input/input.c b/drivers/input/input.c
index 846ccdd..042157c 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -305,7 +305,7 @@ static int input_get_disposition(struct input_dev *dev,
break;

case EV_ABS:
- if (is_event_supported(code, dev->absbit, ABS_MAX))
+ if (is_event_supported(code, dev->absbit, ABS_MAX2))
disposition = input_handle_abs_event(dev, code, &value);

break;
@@ -474,7 +474,7 @@ EXPORT_SYMBOL(input_inject_event);
void input_alloc_absinfo(struct input_dev *dev)
{
if (!dev->absinfo)
- dev->absinfo = kcalloc(ABS_CNT, sizeof(struct input_absinfo),
+ dev->absinfo = kcalloc(ABS_CNT2, sizeof(struct input_absinfo),
GFP_KERNEL);

WARN(!dev->absinfo, "%s(): kcalloc() failed?\n", __func__);
@@ -954,7 +954,7 @@ static const struct input_device_id *input_match_device(struct input_handler *ha
if (!bitmap_subset(id->relbit, dev->relbit, REL_MAX))
continue;

- if (!bitmap_subset(id->absbit, dev->absbit, ABS_MAX))
+ if (!bitmap_subset(id->absbit, dev->absbit, ABS_MAX2))
continue;

if (!bitmap_subset(id->mscbit, dev->mscbit, MSC_MAX))
@@ -1147,7 +1147,7 @@ static int input_devices_seq_show(struct seq_file *seq, void *v)
if (test_bit(EV_REL, dev->evbit))
input_seq_print_bitmap(seq, "REL", dev->relbit, REL_MAX);
if (test_bit(EV_ABS, dev->evbit))
- input_seq_print_bitmap(seq, "ABS", dev->absbit, ABS_MAX);
+ input_seq_print_bitmap(seq, "ABS", dev->absbit, ABS_MAX2);
if (test_bit(EV_MSC, dev->evbit))
input_seq_print_bitmap(seq, "MSC", dev->mscbit, MSC_MAX);
if (test_bit(EV_LED, dev->evbit))
@@ -1333,7 +1333,7 @@ static int input_print_modalias(char *buf, int size, struct input_dev *id,
len += input_print_modalias_bits(buf + len, size - len,
'r', id->relbit, 0, REL_MAX);
len += input_print_modalias_bits(buf + len, size - len,
- 'a', id->absbit, 0, ABS_MAX);
+ 'a', id->absbit, 0, ABS_MAX2);
len += input_print_modalias_bits(buf + len, size - len,
'm', id->mscbit, 0, MSC_MAX);
len += input_print_modalias_bits(buf + len, size - len,
@@ -1592,7 +1592,7 @@ static int input_dev_uevent(struct device *device, struct kobj_uevent_env *env)
if (test_bit(EV_REL, dev->evbit))
INPUT_ADD_HOTPLUG_BM_VAR("REL=", dev->relbit, REL_MAX);
if (test_bit(EV_ABS, dev->evbit))
- INPUT_ADD_HOTPLUG_BM_VAR("ABS=", dev->absbit, ABS_MAX);
+ INPUT_ADD_HOTPLUG_BM_VAR("ABS=", dev->absbit, ABS_MAX2);
if (test_bit(EV_MSC, dev->evbit))
INPUT_ADD_HOTPLUG_BM_VAR("MSC=", dev->mscbit, MSC_MAX);
if (test_bit(EV_LED, dev->evbit))
@@ -1929,7 +1929,7 @@ static unsigned int input_estimate_events_per_packet(struct input_dev *dev)

events = mt_slots + 1; /* count SYN_MT_REPORT and SYN_REPORT */

- for (i = 0; i < ABS_CNT; i++) {
+ for (i = 0; i < ABS_CNT2; i++) {
if (test_bit(i, dev->absbit)) {
if (input_is_mt_axis(i))
events += mt_slots;
diff --git a/drivers/input/keyboard/goldfish_events.c b/drivers/input/keyboard/goldfish_events.c
index 9f60a2e..9999cea 100644
--- a/drivers/input/keyboard/goldfish_events.c
+++ b/drivers/input/keyboard/goldfish_events.c
@@ -90,8 +90,8 @@ static void events_import_abs_params(struct event_dev *edev)
__raw_writel(PAGE_ABSDATA, addr + REG_SET_PAGE);

count = __raw_readl(addr + REG_LEN) / sizeof(val);
- if (count > ABS_MAX)
- count = ABS_MAX;
+ if (count > ABS_MAX2)
+ count = ABS_MAX2;

for (i = 0; i < count; i++) {
if (!test_bit(i, input_dev->absbit))
@@ -158,7 +158,7 @@ static int events_probe(struct platform_device *pdev)
events_import_bits(edev, input_dev->evbit, EV_SYN, EV_MAX);
events_import_bits(edev, input_dev->keybit, EV_KEY, KEY_MAX);
events_import_bits(edev, input_dev->relbit, EV_REL, REL_MAX);
- events_import_bits(edev, input_dev->absbit, EV_ABS, ABS_MAX);
+ events_import_bits(edev, input_dev->absbit, EV_ABS, ABS_MAX2);
events_import_bits(edev, input_dev->mscbit, EV_MSC, MSC_MAX);
events_import_bits(edev, input_dev->ledbit, EV_LED, LED_MAX);
events_import_bits(edev, input_dev->sndbit, EV_SND, SND_MAX);
diff --git a/drivers/input/keyboard/hil_kbd.c b/drivers/input/keyboard/hil_kbd.c
index 589e3c2..4e4e010 100644
--- a/drivers/input/keyboard/hil_kbd.c
+++ b/drivers/input/keyboard/hil_kbd.c
@@ -387,7 +387,7 @@ static void hil_dev_pointer_setup(struct hil_dev *ptr)
0, HIL_IDD_AXIS_MAX(idd, i - 3), 0, 0);

#ifdef TABLET_AUTOADJUST
- for (i = 0; i < ABS_MAX; i++) {
+ for (i = 0; i < ABS_MAX2; i++) {
int diff = input_abs_get_max(input_dev, ABS_X + i) / 10;
input_abs_set_min(input_dev, ABS_X + i,
input_abs_get_min(input_dev, ABS_X + i) + diff);
diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
index 927ad9a..4660ed1 100644
--- a/drivers/input/misc/uinput.c
+++ b/drivers/input/misc/uinput.c
@@ -311,7 +311,7 @@ static int uinput_validate_absbits(struct input_dev *dev)
unsigned int cnt;
int retval = 0;

- for (cnt = 0; cnt < ABS_CNT; cnt++) {
+ for (cnt = 0; cnt < ABS_CNT2; cnt++) {
int min, max;
if (!test_bit(cnt, dev->absbit))
continue;
@@ -474,7 +474,7 @@ static int uinput_setup_device2(struct uinput_device *udev,
return -EINVAL;

/* rough check to avoid huge kernel space allocations */
- max = ABS_CNT * sizeof(*user_dev2->abs) + sizeof(*user_dev2);
+ max = ABS_CNT2 * sizeof(*user_dev2->abs) + sizeof(*user_dev2);
if (count > max)
return -EINVAL;

@@ -780,7 +780,7 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
break;

case UI_SET_ABSBIT:
- retval = uinput_set_bit(arg, absbit, ABS_MAX);
+ retval = uinput_set_bit(arg, absbit, ABS_MAX2);
break;

case UI_SET_MSCBIT:
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 31b9d29..c21d8bb 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -828,7 +828,7 @@ static inline void hid_map_usage(struct hid_input *hidinput,
switch (type) {
case EV_ABS:
*bit = input->absbit;
- *max = ABS_MAX;
+ *max = ABS_MAX2;
break;
case EV_REL:
*bit = input->relbit;
diff --git a/include/linux/input.h b/include/linux/input.h
index 82ce323..c6add6f 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -129,7 +129,7 @@ struct input_dev {
unsigned long evbit[BITS_TO_LONGS(EV_CNT)];
unsigned long keybit[BITS_TO_LONGS(KEY_CNT)];
unsigned long relbit[BITS_TO_LONGS(REL_CNT)];
- unsigned long absbit[BITS_TO_LONGS(ABS_CNT)];
+ unsigned long absbit[BITS_TO_LONGS(ABS_CNT2)];
unsigned long mscbit[BITS_TO_LONGS(MSC_CNT)];
unsigned long ledbit[BITS_TO_LONGS(LED_CNT)];
unsigned long sndbit[BITS_TO_LONGS(SND_CNT)];
@@ -210,8 +210,8 @@ struct input_dev {
#error "REL_MAX and INPUT_DEVICE_ID_REL_MAX do not match"
#endif

-#if ABS_MAX != INPUT_DEVICE_ID_ABS_MAX
-#error "ABS_MAX and INPUT_DEVICE_ID_ABS_MAX do not match"
+#if ABS_MAX2 != INPUT_DEVICE_ID_ABS_MAX
+#error "ABS_MAX2 and INPUT_DEVICE_ID_ABS_MAX do not match"
#endif

#if MSC_MAX != INPUT_DEVICE_ID_MSC_MAX
diff --git a/include/uapi/linux/input.h b/include/uapi/linux/input.h
index bd24470..1856461 100644
--- a/include/uapi/linux/input.h
+++ b/include/uapi/linux/input.h
@@ -32,7 +32,7 @@ struct input_event {
* Protocol version.
*/

-#define EV_VERSION 0x010001
+#define EV_VERSION 0x010002

/*
* IOCTLs (0x00 - 0x7f)
@@ -74,6 +74,30 @@ struct input_absinfo {
};

/**
+ * struct input_absinfo2 - used by EVIOC[G/S]ABS2 ioctls
+ * @code: First ABS code to query
+ * @cnt: Number of ABS codes to query starting at @code
+ * @info: #@cnt absinfo structures to get/set abs parameters for all codes
+ *
+ * This structure is used by the new EVIOC[G/S]ABS2 ioctls which
+ * do the same as the old EVIOC[G/S]ABS ioctls but avoid encoding
+ * the ABS code in the ioctl number. This allows a much wider
+ * range of ABS codes. Furthermore, it allows to query multiple codes with a
+ * single call.
+ *
+ * Note that this silently drops any requests to set ABS_MT_SLOT. Hence, it is
+ * allowed to call this with code=0 cnt=ABS_CNT2. Furthermore, retrieving
+ * invalid codes returns all 0, setting them does nothing. So you must check
+ * with EVIOCGBIT first if you want reliable results. This behavior is needed
+ * to allow forward compatibility to new ABS codes.
+ */
+struct input_absinfo2 {
+ __u32 code;
+ __u32 cnt;
+ struct input_absinfo info[1];
+};
+
+/**
* struct input_keymap_entry - used by EVIOCGKEYCODE/EVIOCSKEYCODE ioctls
* @scancode: scancode represented in machine-endian form.
* @len: length of the scancode that resides in @scancode buffer.
@@ -153,6 +177,8 @@ struct input_keymap_entry {

#define EVIOCGRAB _IOW('E', 0x90, int) /* Grab/Release device */
#define EVIOCREVOKE _IOW('E', 0x91, int) /* Revoke device access */
+#define EVIOCGABS2 _IOR('E', 0x92, struct input_absinfo2) /* get abs value/limits */
+#define EVIOCSABS2 _IOW('E', 0x93, struct input_absinfo2) /* set abs value/limits */

#define EVIOCSCLOCKID _IOW('E', 0xa0, int) /* Set clockid to be used for timestamps */

@@ -835,11 +861,23 @@ struct input_keymap_entry {
#define ABS_MT_TOOL_X 0x3c /* Center X tool position */
#define ABS_MT_TOOL_Y 0x3d /* Center Y tool position */

-
+/*
+ * ABS_MAX/CNT is limited to a maximum of 0x3f due to the design of EVIOCGABS
+ * and EVIOCSABS ioctls. Other kernel APIs like uinput also hardcoded it. Do
+ * not modify this value and instead use the extended ABS_MAX2/CNT2 API.
+ */
#define ABS_MAX 0x3f
#define ABS_CNT (ABS_MAX+1)

/*
+ * Due to API restrictions the legacy evdev API only supports ABS values up to
+ * ABS_MAX/CNT. Use the extended *ABS2 ioctls to operate on any ABS values in
+ * between ABS_MAX and ABS_MAX2.
+ */
+#define ABS_MAX2 0x3f
+#define ABS_CNT2 (ABS_MAX2+1)
+
+/*
* Switch events
*/

diff --git a/include/uapi/linux/uinput.h b/include/uapi/linux/uinput.h
index c2e8710..27ee521 100644
--- a/include/uapi/linux/uinput.h
+++ b/include/uapi/linux/uinput.h
@@ -140,7 +140,7 @@ struct uinput_user_dev2 {
char name[UINPUT_MAX_NAME_SIZE];
struct input_id id;
__u32 ff_effects_max;
- struct input_absinfo abs[ABS_CNT];
+ struct input_absinfo abs[ABS_CNT2];
};

#endif /* _UAPI__UINPUT_H_ */
--
1.8.5.1

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