Re: [linux-next:master 13069/13300] error[E0425]: cannot find value `VM_MERGEABLE` in crate `bindings`

[Alice Ryhl <aliceryhl@google.com>]

On Tue, Oct 7, 2025 at 9:07 AM Jakub Acs <acsjakub@amazon.de> wrote:
>
> On Thu, Oct 02, 2025 at 05:24:48PM -0700, John Hubbard wrote:
> > On 10/2/25 3:43 PM, Andrew Morton wrote:
> > > On Fri, 3 Oct 2025 00:39:16 +0200 Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> wrote:
> > >> On Fri, Oct 3, 2025 at 12:27 AM Andrew Morton <akpm@linux-foundation.org> wrote:
> > ...
> > > From: Andrew Morton <akpm@linux-foundation.org>
> > > Subject: mm-ksm-fix-flag-dropping-behavior-in-ksm_madvise-fix
> > > Date: Thu Oct  2 03:37:47 PM PDT 2025
> > >
> > > Rust bindgen wasn't able to handle the BIT() macro.  Add a helper (from
> > > Miguel) to fix this.
> > >
> > > Reported-by: kernel test robot <lkp@intel.com>
> > > Closes: https://lore.kernel.org/oe-kbuild-all/202510030449.VfSaAjvd-lkp@intel.com/
> > > Cc: Axel Rasmussen <axelrasmussen@google.com>
> > > Cc: Chengming Zhou <chengming.zhou@linux.dev>
> > > Cc: David Hildenbrand <david@redhat.com>
> > > Cc: Jakub Acs <acsjakub@amazon.de>
> > > Cc: Peter Xu <peterx@redhat.com>
> > > Cc: SeongJae Park <sj@kernel.org>
> > > Cc: Xu Xin <xu.xin16@zte.com.cn>
> > > Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
> > > Cc: Alice Ryhl <aliceryhl@google.com>
> > > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> > > ---
> > >
> > >  rust/bindings/bindings_helper.h |    1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > --- a/rust/bindings/bindings_helper.h~mm-ksm-fix-flag-dropping-behavior-in-ksm_madvise-fix
> > > +++ a/rust/bindings/bindings_helper.h
> > > @@ -99,3 +99,4 @@ const xa_mark_t RUST_CONST_HELPER_XA_PRE
> > >
> > >  const gfp_t RUST_CONST_HELPER_XA_FLAGS_ALLOC = XA_FLAGS_ALLOC;
> > >  const gfp_t RUST_CONST_HELPER_XA_FLAGS_ALLOC1 = XA_FLAGS_ALLOC1;
> > > +const vm_flags_t RUST_CONST_HELPER_VM_MERGEABLE = VM_MERGEABLE;
> > > _
> >
> > Yes, this fixes the build on my system too, so:
> >
> > Tested-by: John Hubbard <jhubbard@nvidia.com>
> >
> > ...of course, we'll have to undo this later, as part of the fix
> > for the Rust for Linux build system, to handle BIT() and similar
> > macros in bindgen.
> >
>
> Hi,
>
> sorry for the issues this has caused. We're also changing the other
> defines to BIT() for consistency, it was applied to mm-new in [1]. I
> assume this will have the same breaking effect. Not sure what is the
> solution - whether to wait for the fix mentioned by John or add similar
> defintions to a/rust/bindings/bindings_helper.h for all consts?
>
> [1]: https://lore.kernel.org/all/20251002202112.C2293C4CEF4@smtp.kernel.org/

You have two options: either add all of the constants to
bindings_helper.h, or use an enum similar to commit 3634783be125
("binder: use enum for binder ioctls").

Regarding John's mention, don't expect that for a while. It requires
support in bindgen, which is shipped by your distribution, not Linux.
Therefore, it takes time for improvements to become available to
everyone.

Alice