On 10/28/23 19:32, Jonathan Cameron wrote:
On Sat, 21 Oct 2023 19:03:15 +0300
Matti Vaittinen <mazziesaccount@xxxxxxxxx> wrote:
On 10/21/23 18:55, Jonathan Cameron wrote:
On Mon, 16 Oct 2023 14:04:11 +0300
Matti Vaittinen <mazziesaccount@xxxxxxxxx> wrote:
Sanity-check available_scan_masks array
The available_scan_masks is an array of bitmasks representing the
channels which can be simultaneously(*) scanned by a driver from the
device. Following special characteristics apply:
- When IIO is scanning through the array it will use the first mask
which can be used to scan all enabled channels. This means drivers
should order the array in the order of the preference. This does also
mean that a mask which is a subset of a mask located earler in array
will never be used because the earlier one will be picked by the core.
- Masks wider than size of long are supported only to some extent. The
code scanning through the array will interpret the first mask with
first long zeroed as end-of-array terminator. Changing this behaviour
would make mask-arrays for multi-long masks to be terminated by more
than one zero long. Failure to do so would result kernel to read
beyond the array generating a potentially hazardous bug.
Add a sanity-check to IIO-device registration emitting a warning if
available_scan_mask array is misordered or if mask width is larger than
a long while available_scan_mask-array is populated. Currently there
should be no in-tree drivers with available_scan_mask populated and mask
wider than a long.
Revision history:
v1 => v2:
- Add patch 2/2 documenting why iio_scan_mask_match() checks only
a long worth of bits while searching for the end of the
available_scan_mask-array.
- Styling of patch 1/2 as per comments from Jonathan
v1 and related discussion here:
https://lore.kernel.org/lkml/ZRvjuZaQWdZw1U1I@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Matti Vaittinen (2):
iio: sanity check available_scan_masks array
iio: buffer: document known issue
...
I've started queuing stuff up for rebasing post merge window, so I've
added this as well. For now will only be exposed as the testing branch
that 0-day pokes at.
Thanks Jonathan!
--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland
~~ When things go utterly wrong vim users can always type :help! ~~
