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

[Rob Clark]

On Mon, Oct 26, 2026 at 8:30 AM Konrad Dybcio
<konrad.dybcio@xxxxxxxxxxxxxxxx> wrote:
>
> On 10/26/26 4:26 PM, Rob Clark wrote:
> > On Mon, Oct 26, 2026 at 4:40 AM Konrad Dybcio <konradybcio@xxxxxxxxxx> wrote:
> >>
> >> From: Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxxxx>
> >>
> >> 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@xxxxxxxxxxxxxxxx>
> >> ---
> >> (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")

And there was much rejoicing :-)

BR,
-R