kernel/rust, branch linux-6.15.y

rust: workaround `rustdoc` target modifiers bug

2025-08-20T16:36:27Z

commit abbf9a44944171ca99c150adad9361a2f517d3b6 upstream. Starting with Rust 1.88.0 (released 2025-06-26), `rustdoc` complains about a target modifier mismatch in configurations where `-Zfixed-x18` is passed: error: mixing `-Zfixed-x18` will cause an ABI mismatch in crate `rust_out` | = help: the `-Zfixed-x18` flag modifies the ABI so Rust crates compiled with different values of this flag cannot be used together safely = note: unset `-Zfixed-x18` in this crate is incompatible with `-Zfixed-x18=` in dependency `core` = help: set `-Zfixed-x18=` in this crate or unset `-Zfixed-x18` in `core` = help: if you are sure this will not cause problems, you may use `-Cunsafe-allow-abi-mismatch=fixed-x18` to silence this error The reason is that `rustdoc` was not passing the target modifiers when configuring the session options, and thus it would report a mismatch that did not exist as soon as a target modifier is used in a dependency. We did not notice it in the kernel until now because `-Zfixed-x18` has been a target modifier only since 1.88.0 (and it is the only one we use so far). The issue has been reported upstream [1] and a fix has been submitted [2], including a test similar to the kernel case. [ This is now fixed upstream (thanks Guillaume for the quick review), so it will be fixed in Rust 1.90.0 (expected 2025-09-18). - Miguel ] Meanwhile, conditionally pass `-Cunsafe-allow-abi-mismatch=fixed-x18` to workaround the issue on our side. Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs). Reported-by: Konrad Dybcio Closes: https://lore.kernel.org/rust-for-linux/36cdc798-524f-4910-8b77-d7b9fac08d77@oss.qualcomm.com/ Link: https://github.com/rust-lang/rust/issues/144521 [1] Link: https://github.com/rust-lang/rust/pull/144523 [2] Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20250727092317.2930617-1-ojeda@kernel.org Signed-off-by: Miguel Ojeda Signed-off-by: Greg Kroah-Hartman

rust: kbuild: clean output before running `rustdoc`

2025-08-20T16:36:27Z

commit 252fea131e15aba2cd487119d1a8f546471199e2 upstream. `rustdoc` can get confused when generating documentation into a folder that contains generated files from other `rustdoc` versions. For instance, running something like: rustup default 1.78.0 make LLVM=1 rustdoc rustup default 1.88.0 make LLVM=1 rustdoc may generate errors like: error: couldn't generate documentation: invalid template: last line expected to start with a comment | = note: failed to create or modify "./Documentation/output/rust/rustdoc/src-files.js" Thus just always clean the output folder before generating the documentation -- we are anyway regenerating it every time the `rustdoc` target gets called, at least for the time being. Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs). Reported-by: Daniel Almeida Closes: https://rust-for-linux.zulipchat.com/#narrow/channel/288089/topic/x/near/527201113 Reviewed-by: Tamir Duberstein Link: https://lore.kernel.org/r/20250726133435.2460085-1-ojeda@kernel.org Signed-off-by: Miguel Ojeda Signed-off-by: Greg Kroah-Hartman

rust: miscdevice: clarify invariant for `MiscDeviceRegistration`

2025-08-15T10:16:19Z

[ Upstream commit b9ff1c2a26fa31216be18e9b14c419ff8fe39e72 ] Reword and expand the invariant documentation for `MiscDeviceRegistration` to clarify what it means for the inner device to be "registered". It expands to explain: - `inner` points to a `miscdevice` registered via `misc_register`. - This registration stays valid for the entire lifetime of the object. - Deregistration is guaranteed on `Drop`, via `misc_deregister`. Reported-by: Benno Lossin Closes: https://github.com/Rust-for-Linux/linux/issues/1168 Fixes: f893691e7426 ("rust: miscdevice: add base miscdevice abstraction") Signed-off-by: Shankari Anand Link: https://lore.kernel.org/r/20250626104520.563036-1-shankari.ak0208@gmail.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

rust: use `#[used(compiler)]` to fix build and `modpost` with Rust >= 1.89.0

2025-07-24T06:58:41Z

commit 7498159226772d66f150dd406be462d75964a366 upstream. Starting with Rust 1.89.0 (expected 2025-08-07), the Rust compiler fails to build the `rusttest` target due to undefined references such as: kernel...-cgu.0:(.text....+0x116): undefined reference to `rust_helper_kunit_get_current_test' Moreover, tooling like `modpost` gets confused: WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/gpu/drm/nova/nova.o ERROR: modpost: missing MODULE_LICENSE() in drivers/gpu/nova-core/nova_core.o The reason behind both issues is that the Rust compiler will now [1] treat `#[used]` as `#[used(linker)]` instead of `#[used(compiler)]` for our targets. This means that the retain section flag (`R`, `SHF_GNU_RETAIN`) will be used and that they will be marked as `unique` too, with different IDs. In turn, that means we end up with undefined references that did not get discarded in `rusttest` and that multiple `.modinfo` sections are generated, which confuse tooling like `modpost` because they only expect one. Thus start using `#[used(compiler)]` to keep the previous behavior and to be explicit about what we want. Sadly, it is an unstable feature (`used_with_arg`) [2] -- we will talk to upstream Rust about it. The good news is that it has been available for a long time (Rust >= 1.60) [3]. The changes should also be fine for previous Rust versions, since they behave the same way as before [4]. Alternatively, we could use `#[no_mangle]` or `#[export_name = ...]` since those still behave like `#[used(compiler)]`, but of course it is not really what we want to express, and it requires other changes to avoid symbol conflicts. Cc: David Wood Cc: Wesley Wiser Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs). Link: https://github.com/rust-lang/rust/pull/140872 [1] Link: https://github.com/rust-lang/rust/issues/93798 [2] Link: https://github.com/rust-lang/rust/pull/91504 [3] Link: https://godbolt.org/z/sxzWTMfzW [4] Reviewed-by: Alice Ryhl Acked-by: Björn Roy Baron Link: https://lore.kernel.org/r/20250712160103.1244945-3-ojeda@kernel.org Signed-off-by: Miguel Ojeda Signed-off-by: Greg Kroah-Hartman

rust: init: Fix generics in *_init! macros

2025-07-24T06:58:24Z

commit fe49aae0fcb348b656bbde2eb1d1c75d8a1a5c3c upstream. The match pattern for a optional trailing comma in the list of generics is erroneously repeated in the code block resulting in following error: | error: attempted to repeat an expression containing no syntax variables matched as repeating at this depth | --> rust/kernel/init.rs:301:73 | | | 301 | ::pin_init::try_pin_init!($(&$this in)? $t $(::<$($generics),* $(,)?>)? { | | ^^^ Remove "$(,)?" from all code blocks in the try_init! and try_pin_init! definitions. Cc: stable@vger.kernel.org Fixes: 578eb8b6db13 ("rust: pin-init: move the default error behavior of `try_[pin_]init`") Signed-off-by: Janne Grunau Reviewed-by: Benno Lossin Link: https://lore.kernel.org/r/20250628-rust_init_trailing_comma-v1-1-2d162ae1a757@jannau.net Signed-off-by: Miguel Ojeda Signed-off-by: Greg Kroah-Hartman

rust: devres: do not dereference to the internal Revocable

2025-07-06T09:04:25Z

commit 20c96ed278e362ae4e324ed7d8c69fb48c508d3c upstream. We can't expose direct access to the internal Revocable, since this allows users to directly revoke the internal Revocable without Devres having the chance to synchronize with the devres callback -- we have to guarantee that the internal Revocable has been fully revoked before the device is fully unbound. Hence, remove the corresponding Deref implementation and, instead, provide indirect accessors for the internal Revocable. Note that we can still support Devres::revoke() by implementing the required synchronization (which would be almost identical to the synchronization in Devres::drop()). Fixes: 76c01ded724b ("rust: add devres abstraction") Reviewed-by: Benno Lossin Link: https://lore.kernel.org/r/20250611174827.380555-1-dakr@kernel.org Signed-off-by: Danilo Krummrich Signed-off-by: Greg Kroah-Hartman

rust: devres: fix race in Devres::drop()

2025-07-06T09:04:25Z

commit f744201c6159fc7323c40936fd079525f7063598 upstream. In Devres::drop() we first remove the devres action and then drop the wrapped device resource. The design goal is to give the owner of a Devres object control over when the device resource is dropped, but limit the overall scope to the corresponding device being bound to a driver. However, there's a race that was introduced with commit 8ff656643d30 ("rust: devres: remove action in `Devres::drop`"), but also has been (partially) present from the initial version on. In Devres::drop(), the devres action is removed successfully and subsequently the destructor of the wrapped device resource runs. However, there is no guarantee that the destructor of the wrapped device resource completes before the driver core is done unbinding the corresponding device. If in Devres::drop(), the devres action can't be removed, it means that the devres callback has been executed already, or is still running concurrently. In case of the latter, either Devres::drop() wins revoking the Revocable or the devres callback wins revoking the Revocable. If Devres::drop() wins, we (again) have no guarantee that the destructor of the wrapped device resource completes before the driver core is done unbinding the corresponding device. CPU0 CPU1 ------------------------------------------------------------------------ Devres::drop() { Devres::devres_callback() { self.data.revoke() { this.data.revoke() { is_available.swap() == true is_available.swap == false } } // [...] // device fully unbound drop_in_place() { // release device resource } } } Depending on the specific device resource, this can potentially lead to user-after-free bugs. In order to fix this, implement the following logic. In the devres callback, we're always good when we get to revoke the device resource ourselves, i.e. Revocable::revoke() returns true. If Revocable::revoke() returns false, it means that Devres::drop(), concurrently, already drops the device resource and we have to wait for Devres::drop() to signal that it finished dropping the device resource. Note that if we hit the case where we need to wait for the completion of Devres::drop() in the devres callback, it means that we're actually racing with a concurrent Devres::drop() call, which already started revoking the device resource for us. This is rather unlikely and means that the concurrent Devres::drop() already started doing our work and we just need to wait for it to complete it for us. Hence, there should not be any additional overhead from that. (Actually, for now it's even better if Devres::drop() does the work for us, since it can bypass the synchronize_rcu() call implied by Revocable::revoke(), but this goes away anyways once I get to implement the split devres callback approach, which allows us to first flip the atomics of all registered Devres objects of a certain device, execute a single synchronize_rcu() and then drop all revocable objects.) In Devres::drop() we try to revoke the device resource. If that is *not* successful, it means that the devres callback already did and we're good. Otherwise, we try to remove the devres action, which, if successful, means that we're good, since the device resource has just been revoked by us *before* we removed the devres action successfully. If the devres action could not be removed, it means that the devres callback must be running concurrently, hence we signal that the device resource has been revoked by us, using the completion. This makes it safe to drop a Devres object from any task and at any point of time, which is one of the design goals. Fixes: 76c01ded724b ("rust: add devres abstraction") Reported-by: Alice Ryhl Closes: https://lore.kernel.org/lkml/aD64YNuqbPPZHAa5@google.com/ Reviewed-by: Benno Lossin Link: https://lore.kernel.org/r/20250612121817.1621-4-dakr@kernel.org Signed-off-by: Danilo Krummrich Signed-off-by: Greg Kroah-Hartman

rust: revocable: indicate whether `data` has been revoked already

2025-07-06T09:04:25Z

commit 4b76fafb20dd4a2becb94949d78e86bc88006509 upstream. Return a boolean from Revocable::revoke() and Revocable::revoke_nosync() to indicate whether the data has been revoked already. Return true if the data hasn't been revoked yet (i.e. this call revoked the data), false otherwise. This is required by Devres in order to synchronize the completion of the revoke process. Reviewed-by: Benno Lossin Acked-by: Miguel Ojeda Link: https://lore.kernel.org/r/20250612121817.1621-3-dakr@kernel.org Signed-off-by: Danilo Krummrich Signed-off-by: Greg Kroah-Hartman

rust: completion: implement initial abstraction

2025-07-06T09:04:25Z

commit 1b56e765bf8990f1f60e124926c11fc4ac63d752 upstream. Implement a minimal abstraction for the completion synchronization primitive. This initial abstraction only adds complete_all() and wait_for_completion(), since that is what is required for the subsequent Devres patch. Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Steven Rostedt Cc: Ben Segall Cc: Mel Gorman Cc: Valentin Schneider Reviewed-by: Alice Ryhl Reviewed-by: Boqun Feng Reviewed-by: Benno Lossin Acked-by: Miguel Ojeda Link: https://lore.kernel.org/r/20250612121817.1621-2-dakr@kernel.org Signed-off-by: Danilo Krummrich Signed-off-by: Greg Kroah-Hartman

rust: arm: fix unknown (to Clang) argument '-mno-fdpic'

2025-07-06T09:04:05Z

[ Upstream commit 977c4308ee4270cf46e2c66b37de8e04670daa0c ] Currently rust on arm fails to compile due to '-mno-fdpic'. This flag disables a GCC feature that we don't want for kernel builds, so let's skip it as it doesn't apply to Clang. UPD include/generated/asm-offsets.h CALL scripts/checksyscalls.sh RUSTC L rust/core.o BINDGEN rust/bindings/bindings_generated.rs BINDGEN rust/bindings/bindings_helpers_generated.rs CC rust/helpers/helpers.o Unable to generate bindings: clang diagnosed error: error: unknown argument: '-mno-fdpic' make[2]: *** [rust/Makefile:369: rust/bindings/bindings_helpers_generated.rs] Error 1 make[2]: *** Deleting file 'rust/bindings/bindings_helpers_generated.rs' make[2]: *** Waiting for unfinished jobs.... Unable to generate bindings: clang diagnosed error: error: unknown argument: '-mno-fdpic' make[2]: *** [rust/Makefile:349: rust/bindings/bindings_generated.rs] Error 1 make[2]: *** Deleting file 'rust/bindings/bindings_generated.rs' make[1]: *** [/home/pmos/build/src/linux-next-next-20250521/Makefile:1285: prepare] Error 2 make: *** [Makefile:248: __sub-make] Error 2 [ Naresh provided the draft diff [1]. Ben explained [2]: FDPIC is only relevant with no-MMU targets, and then only for userspace. When configured for the arm-*-uclinuxfdpiceabi target, GCC enables FDPIC by default to facilitate compiling userspace programs. FDPIC is never used for the kernel, and we pass -mno-fdpic when building the kernel to override the default and make sure FDPIC is disabled. and [3]: -mno-fdpic disables a GCC feature that we don't want for kernel builds. clang does not support this feature, so it always behaves as though -mno-fdpic is passed. Therefore, it should be fine to mix the two, at least as far as FDPIC is concerned. [1] https://lore.kernel.org/rust-for-linux/CA+G9fYt4otQK4pHv8pJBW9e28yHSGCDncKquwuJiJ_1ou0pq0w@mail.gmail.com/ [2] https://lore.kernel.org/rust-for-linux/aAKrq2InExQk7f_k@dell-precision-5540/ [3] https://lore.kernel.org/rust-for-linux/aAo_F_UP1Gd4jHlZ@dell-precision-5540/ - Miguel ] Reported-by: Linux Kernel Functional Testing Closes: https://lore.kernel.org/all/CA+G9fYvOanQBYXKSg7C6EU30k8sTRC0JRPJXYu7wWK51w38QUQ@mail.gmail.com/ Suggested-by: Miguel Ojeda Acked-by: Naresh Kamboju Signed-off-by: Rudraksha Gupta Link: https://lore.kernel.org/r/20250522-rust-mno-fdpic-arm-fix-v2-1-a6f691d9c198@gmail.com [ Reworded title. - Miguel ] Signed-off-by: Miguel Ojeda Signed-off-by: Sasha Levin