Re: [PATCH 1/2] rust: pass correct target to bindgen on Usermode Linux

Re: [PATCH 1/2] rust: pass correct target to bindgen on Usermode Linux

[David Gow]

On Sat, 8 Feb 2025 at 21:32, Thomas Weißschuh <linux@weissschuh.net> wrote:
>
> Usermode Linux uses "um" as primary architecture name and the underlying
> physical architecture is provided in "SUBARCH".
> Resolve the target architecture flags through that underlying architecture.
> This is the same pattern as used by scripts/Makefile.clang from which
> the bindgen flags are derived.
>
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> ---

(+cc linux-um, but I assume this will probably go in via the Rust tree, anyway.)

Thanks very much: this is enough to get Rust-for-Linux working with
gcc under 64-bit UML on my system.

However, this is actually a bit of a coincidence -- and there are
still some issues with 32-bit UML -- as the UML Rust flags are
currently conditionally set if CC_IS_CLANG. This is my fault (it was
to work around some bugs with older gcc), and I've sent a patch[1] to
fix it. (Though note that 32-bit UML/Rust still hits issues with
atomics in the block driver, so you'll need to disable that for now.)

Regardless, this is a significant improvement, thanks!

Reviewed-by: David Gow <davidgow@googl.ecom>

Thanks,
-- David

[1]: https://lore.kernel.org/rust-for-linux/20250210105353.2238769-2-davidgow@google.com/


>  rust/Makefile | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/rust/Makefile b/rust/Makefile
> index 8fcfd60447bc89ba2c66a4f341288db2387b0956..a94fafb91d7d743c6c1b2248479c0d723964e5c4 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -245,6 +245,7 @@ bindgen_skip_c_flags := -mno-fp-ret-in-387 -mpreferred-stack-boundary=% \
>  # Derived from `scripts/Makefile.clang`.
>  BINDGEN_TARGET_x86     := x86_64-linux-gnu
>  BINDGEN_TARGET_arm64   := aarch64-linux-gnu
> +BINDGEN_TARGET_um      := $(BINDGEN_TARGET_$(SUBARCH))
>  BINDGEN_TARGET         := $(BINDGEN_TARGET_$(SRCARCH))
>
>  # All warnings are inhibited since GCC builds are very experimental,
>
> --
> 2.48.1
>
>

Re: [PATCH 1/2] rust: pass correct target to bindgen on Usermode Linux

[David Gow]

[-- Attachment #1: Type: text/plain, Size: 788 bytes --]

On Sat, 8 Feb 2025 at 21:32, Thomas Weißschuh <linux@weissschuh.net> wrote:
>
> Usermode Linux uses "um" as primary architecture name and the underlying
> physical architecture is provided in "SUBARCH".
> Resolve the target architecture flags through that underlying architecture.
> This is the same pattern as used by scripts/Makefile.clang from which
> the bindgen flags are derived.
>
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> ---

Is there anything holding this up for the upcoming merge window?

Miguel: I'm assuming you'd rather take this (and possibly [1] as well)
via Rust, but if it goes in via the uml tree, that'd be fine by me,
too.

Cheers,
-- David

[1]: https://lore.kernel.org/linux-um/20250210105353.2238769-2-davidgow@google.com/

[-- Attachment #2: S/MIME Cryptographic Signature --]
[-- Type: application/pkcs7-signature, Size: 5281 bytes --]

Re: [PATCH 1/2] rust: pass correct target to bindgen on Usermode Linux

[Miguel Ojeda]

On Tue, Mar 18, 2025 at 9:07 AM David Gow <davidgow@google.com> wrote:
>
> Is there anything holding this up for the upcoming merge window?
>
> Miguel: I'm assuming you'd rather take this (and possibly [1] as well)
> via Rust, but if it goes in via the uml tree, that'd be fine by me,
> too.

We try to get arch maintainers involved (and everyone else, of
course), i.e. it is up to them. But I see only the list was Cc'd, not
them directly, for some reason -- doing it here.

Ideally, maintainers get involved and pick their own Rust-related
patches, but I can also do so with an Acked-by from them, which would
be nice.

If they don't say anything, then since you have tested it (and you are
a main um user due to KUnit), that should be enough, but then I would
suggest we do it after -rc1 to give them time to react.

Thanks!

Cheers,
Miguel

Re: [PATCH 1/2] rust: pass correct target to bindgen on Usermode Linux

[Johannes Berg]

On Tue, 2025-03-18 at 11:10 +0100, Miguel Ojeda wrote:
> On Tue, Mar 18, 2025 at 9:07 AM David Gow <davidgow@google.com> wrote:
> > 
> > Is there anything holding this up for the upcoming merge window?
> > 
> > Miguel: I'm assuming you'd rather take this (and possibly [1] as well)
> > via Rust, but if it goes in via the uml tree, that'd be fine by me,
> > too.
> 
> We try to get arch maintainers involved (and everyone else, of
> course), i.e. it is up to them. But I see only the list was Cc'd, not
> them directly, for some reason -- doing it here.

The list is fine, but the patch wasn't even CC'ed there, so we don't
have it in our patchwork:
https://patchwork.ozlabs.org/project/linux-um/list/

> Ideally, maintainers get involved and pick their own Rust-related
> patches, but I can also do so with an Acked-by from them, which would
> be nice.

I was just picking up um patches, but given that it was a series, and
changes rust/ rather than arch/um/, I think it's probably better if you
do it, so:

Acked-by: Johannes Berg <johannes@sipsolutions.net>

johannes

Re: [PATCH 1/2] rust: pass correct target to bindgen on Usermode Linux

[Miguel Ojeda]

On Tue, Mar 18, 2025 at 11:14 AM Johannes Berg
<johannes@sipsolutions.net> wrote:
>
> The list is fine, but the patch wasn't even CC'ed there, so we don't
> have it in our patchwork:
> https://patchwork.ozlabs.org/project/linux-um/list/

Ah, right, David added it.

> I was just picking up um patches, but given that it was a series, and
> changes rust/ rather than arch/um/, I think it's probably better if you
> do it, so:
>
> Acked-by: Johannes Berg <johannes@sipsolutions.net>

Thanks for the very quick reply!

I guess they could be picked independently, but I am happy to pick both.

Cheers,
Miguel