On Tue, Dec 17, 2013 at 04:48:52PM +0100, David Herrmann wrote:
> 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;
why don't you return the number of valid copied axes to the user?
that seems better even than forcing the remainder to 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/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);
hmm, if you ever up the value of ABS_CNT2 and you don't have it query-able,
userspace won't be able to create a uinput device on a kernel with a smaller
ABS_CNT2. worst of all, the only error you get is EINVAL, which is also
used for invalid axis ranges, etc.
> 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
A history in the comments would be nice. something like
/**
* 0x010000: original version
* 0x010001: support for long scancodes
* 0x010002: added ABS_CNT2/ABS_MAX2, EVIOCSABS2, EVIOCGABS2
*/
> /*
> * IOCTLs (0x00 - 0x7f)
> @@ -74,6 +74,30 @@ struct input_absinfo {
> };
>
> /**
> + * struct input_absinfo2 - used by EVIOC[G/S]ABS2 ioctls
please spell the two out (at least once in this paragraph), it makes it grep-able.
> + * @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.
"new" and "old" have a tendency to become "old" and "before old" quickly,
just skip both. A simple "use of EVIOCGABS/EVIOCSABS is discouraged except on kernels
without EVIOCGABS2/EVIOCSABS2 support" is enough to signal which one is preferred.
> + *
> + * 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.
I think this needs rewording, I was quite confused reading this. How about:
"For axes not present on the device and for axes exceeding the kernel's
built-in ABS_CNT2 maximum, EVIOCGABS2 sets all values in the struct absinfo
to 0. EVIOCGSABS2 silently ignores write requests to these axes.
ABS_MT_SlOT is an immutable axis and cannot be modified by EVIOCSABS2,
the respective value is silently ignored."
also, please document the return value of the ioctl.
Cheers,
Peter
> + */
> +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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