Re: [PATCH] iio: adc: qcom-adc5-gen3: Annotate struct adc5_device_data with __counted_by_ptr

["Gustavo A. R. Silva" <gustavo@embeddedor.com>]

On 9/23/26 07:09, Bill Wendling wrote:
> Under compiler-supported bounds checking (via KASAN or UBSAN), pointer
> fields inside structures can be annotated with the '__counted_by_ptr'
> attribute to specify which field in the same structure holds the element
> count. This enables the compiler to perform runtime bounds checking on
> the pointer.
> 
> Annotate the "base" pointer field in "struct adc5_device_data" with the
> "__counted_by_ptr" attribute pointing to "num_sdams". The number of
> SDAMs is determined from the device property and assigned to "num_sdams"
> which is then used to initialize "base" via "devm_kcalloc".
> 
> By ensuring "num_sdams" is set to the correct element count prior to
> the "base" pointer allocation, and since the size of "base" is never
> reallocated or changed, this annotation is safe and will not cause any
> false-positive runtime bounds check panics or KASAN issues.
> 
> Cc: codemender-patching+linux@google.com
> Assisted-by: LLM
> Signed-off-by: Bill Wendling <morbo@google.com>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
-Gustavo

> ---
>   include/linux/iio/adc/qcom-adc5-gen3-common.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/iio/adc/qcom-adc5-gen3-common.h b/include/linux/iio/adc/qcom-adc5-gen3-common.h
> index 39cbfcbdb101..b3e2c2f50e8f 100644
> --- a/include/linux/iio/adc/qcom-adc5-gen3-common.h
> +++ b/include/linux/iio/adc/qcom-adc5-gen3-common.h
> @@ -137,7 +137,7 @@ struct adc5_sdam_data {
>    */
>   struct adc5_device_data {
>   	struct regmap *regmap;
> -	struct adc5_sdam_data *base;
> +	struct adc5_sdam_data *base __counted_by_ptr(num_sdams);
>   	int num_sdams;
>   };
>