Currently randstruct does not support rust so we have Kconfig dependencies
which prevent rust being enabled when randstruct is. Unfortunately this
prevents rust being enabled in allmodconfig, our standard coverage build.
randstruct gets turned on by default, then the dependency on !RANDSTRUCT
causes rust to get disabled.

Work around this by disabling randstruct by default if we have a usable
rust toolchain and rust support for the architecture, circular
dependencies prevent us directly depending on !RUST. This means we might
end up with a configuration that disables both rust and randstruct but
hopefully it's more likely go give the expected result.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
Changes in v4:
- Rebase onto v7.3-rc1.
- Link to v3: https://patch.msgid.link/20260702-rust-reverse-randstruct-dep-v3-1-e4e09c50014e@kernel.org

Changes in v3:
- Rebase onto v7.2-rc1.
- Link to v2: https://patch.msgid.link/20260605-rust-reverse-randstruct-dep-v2-1-93d38023b6f9@kernel.org

Changes in v2:
- Add a HAVE_RUST in there too.
- Link to v1: https://patch.msgid.link/20260605-rust-reverse-randstruct-dep-v1-1-45ce9ee8d0d1@kernel.org
---
 security/Kconfig.hardening | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
index 6923036e1a2f..81c81ad983ad 100644
--- a/security/Kconfig.hardening
+++ b/security/Kconfig.hardening
@@ -278,7 +278,7 @@ config CC_HAS_RANDSTRUCT
 
 choice
 	prompt "Randomize layout of sensitive kernel structures"
-	default RANDSTRUCT_FULL if COMPILE_TEST && (GCC_PLUGINS || CC_HAS_RANDSTRUCT)
+	default RANDSTRUCT_FULL if !(RUST_IS_AVAILABLE && HAVE_RUST) && COMPILE_TEST && (GCC_PLUGINS || CC_HAS_RANDSTRUCT)
 	default RANDSTRUCT_NONE
 	help
 	  If you enable this, the layouts of structures that are entirely

---
base-commit: cee9395acd8043be0644b25c34bfa86623f2b935
change-id: 20260605-rust-reverse-randstruct-dep-5a504c861128

Best regards,
--  
Mark Brown <broonie@kernel.org>

On Tue, 01 Sep 2026 23:50:02 +0100, Mark Brown wrote:
> Currently randstruct does not support rust so we have Kconfig dependencies
> which prevent rust being enabled when randstruct is. Unfortunately this
> prevents rust being enabled in allmodconfig, our standard coverage build.
> randstruct gets turned on by default, then the dependency on !RANDSTRUCT
> causes rust to get disabled.
> 
> Work around this by disabling randstruct by default if we have a usable
> rust toolchain and rust support for the architecture, circular
> dependencies prevent us directly depending on !RUST. This means we might
> end up with a configuration that disables both rust and randstruct but
> hopefully it's more likely go give the expected result.
> 
> [...]

Applied to for-linus/hardening, thanks!

[1/1] hardening: Default randstruct off with rust for better allmodconfig support
      https://git.kernel.org/kees/c/2625480a1bf7

Take care,

-- 
Kees Cook

On Wed, Sep 2, 2026 at 12:52 AM Mark Brown <broonie@kernel.org> wrote:
>
> Currently randstruct does not support rust so we have Kconfig dependencies
> which prevent rust being enabled when randstruct is. Unfortunately this
> prevents rust being enabled in allmodconfig, our standard coverage build.
> randstruct gets turned on by default, then the dependency on !RANDSTRUCT
> causes rust to get disabled.
>
> Work around this by disabling randstruct by default if we have a usable
> rust toolchain and rust support for the architecture, circular
> dependencies prevent us directly depending on !RUST. This means we might
> end up with a configuration that disables both rust and randstruct but
> hopefully it's more likely go give the expected result.
>
> Signed-off-by: Mark Brown <broonie@kernel.org>

I thought this was already applied:

  https://git.kernel.org/kees/c/3844a38c9c4a

  https://lore.kernel.org/rust-for-linux/178733378275.2181196.3186172911325132761.b4-ty@kernel.org/

But it doesn't seem to be in -next -- that branch isn't merged there I think.

Cheers,
Miguel

On Wed, Sep 02, 2026 at 12:59:59AM +0200, Miguel Ojeda wrote:
> On Wed, Sep 2, 2026 at 12:52 AM Mark Brown <broonie@kernel.org> wrote:
> >
> > Currently randstruct does not support rust so we have Kconfig dependencies
> > which prevent rust being enabled when randstruct is. Unfortunately this
> > prevents rust being enabled in allmodconfig, our standard coverage build.
> > randstruct gets turned on by default, then the dependency on !RANDSTRUCT
> > causes rust to get disabled.
> >
> > Work around this by disabling randstruct by default if we have a usable
> > rust toolchain and rust support for the architecture, circular
> > dependencies prevent us directly depending on !RUST. This means we might
> > end up with a configuration that disables both rust and randstruct but
> > hopefully it's more likely go give the expected result.
> >
> > Signed-off-by: Mark Brown <broonie@kernel.org>
> 
> I thought this was already applied:
> 
>   https://git.kernel.org/kees/c/3844a38c9c4a
> 
>   https://lore.kernel.org/rust-for-linux/178733378275.2181196.3186172911325132761.b4-ty@kernel.org/
> 
> But it doesn't seem to be in -next -- that branch isn't merged there I think.

I applied it but the push broke. I've re-arranged things now and push
it; I'll get this sent to Linus this week :)

-- 
Kees Cook

On Wed, Sep 02, 2026 at 12:59:59AM +0200, Miguel Ojeda wrote:
> On Wed, Sep 2, 2026 at 12:52 AM Mark Brown <broonie@kernel.org> wrote:

> > Work around this by disabling randstruct by default if we have a usable
> > rust toolchain and rust support for the architecture, circular
> > dependencies prevent us directly depending on !RUST. This means we might
> > end up with a configuration that disables both rust and randstruct but
> > hopefully it's more likely go give the expected result.

> I thought this was already applied:

>   https://git.kernel.org/kees/c/3844a38c9c4a

>   https://lore.kernel.org/rust-for-linux/178733378275.2181196.3186172911325132761.b4-ty@kernel.org/

> But it doesn't seem to be in -next -- that branch isn't merged there I think.

Yes, I had thought I'd seen something saying it was applied but as you
did I checked -next, didn't find it and figured I must have been
confused.  The link in the mail above to the commit says it's missing
too.