Re: [PATCH RFC] drm/msm: move VM_BIND op validation to Rust

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 10/26/26 4:26 PM, Rob Clark wrote:
> On Mon, Oct 26, 2026 at 4:40 AM Konrad Dybcio <konradybcio@kernel.org> wrote:
>>
>> From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
>>
>> Much of the VM handling code is a headache to read and maintain.
>> There's a soup of mixed-signedness/size types which need to be compared
>> and added and getting that wrong in C is very easy.
>>
>> The "(range + obj_offset) > obj->size" check could wrap for a large
>> obj_offset, which let an out-of-range map be accepted and then mapped
>> as nothing. Oxidize it and use checked_add() to fix that.
>>
>> This commit is a "get the foot in the door" type change to make sure
>> that folks building kernels for Qualcomm SoCs have their Rust setup
>> ready. It may/should be extended to the wider mm code once the
>> appropriate abstractions are finalized.
>>
>> Worth noting, the C UERR() macro expands to dev_dbg() and the Rust
>> implementation for that currently doesn't support dynamic_debug.
>>
>> The DRM_BRIDGE dependency is dropped because including RUST exposed
>> some spaghetti dependencies ending at DEBUGFS and it's enabled anyway.
>>
>> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
>> ---
>> (if this is rejected we may just patch the C code).
>>
>> Notably, this will regress some ancient configurations:
>> -- arch/arm/Kconfig
>>     select HAVE_RUST if CPU_LITTLE_ENDIAN && CPU_32v7 && !KASAN
> 
> Side note, I'm ok w/ drm/msm (or at least the gpu part) depending on
> CPU_LITTLE_ENDIAN.  The combination of BE CPU and LE GPU would be a
> mess.  I'll actively ignore bug reports, patches, etc related to BE.
> So please, no BE!

arm64 is free of it now!

134b0fbc5c24 ("arm64: Kbuild: Remove vestigial big-endian support")

Konrad