In order to synchronize with C or external memory, atomic operations
over raw pointers are need. Although there is already an
`Atomic::from_ptr()` to provide a `&Atomic<T>`, it's more convenient to
have helpers that directly perform atomic operations on raw pointers.
Hence a few are added, which are basically an `Atomic::from_ptr().op()`
wrapper.
Note: for naming, since `atomic_xchg()` and `atomic_cmpxchg()` have a
conflict naming to 32bit C atomic xchg/cmpxchg, hence the helpers are
just named as `xchg()` and `cmpxchg()`. For `atomic_load()` and
`atomic_store()`, their 32bit C counterparts are `atomic_read()` and
`atomic_set()`, so keep the `atomic_` prefix.
[boqun: Fix typo spotted by Alice and fix broken sentence spotted by
Gary]
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260120115207.55318-3-boqun.feng@gmail.com
Link: https://patch.msgid.link/20260303201701.12204-11-boqun@kernel.org
Atomic pointer support is an important piece of synchronization
algorithm, e.g. RCU, hence provide the support for that.
Note that instead of relying on atomic_long or the implementation of
`Atomic<usize>`, a new set of helpers (atomic_ptr_*) is introduced for
atomic pointer specifically, this is because ptr2int casting would
lose the provenance of a pointer and even though in theory there are a
few tricks the provenance can be restored, it'll still be a simpler
implementation if C could provide atomic pointers directly. The side
effects of this approach are: we don't have the arithmetic and logical
operations for pointers yet and the current implementation only works
on ARCH_SUPPORTS_ATOMIC_RMW architectures, but these are implementation
issues and can be added later.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Link: https://patch.msgid.link/20260120140503.62804-3-boqun.feng@gmail.com
Link: https://patch.msgid.link/20260303201701.12204-8-boqun@kernel.org
Currently, since all the architectures that support Rust all have
CONFIG_ARCH_SUPPORTS_ATOMIC_RMW selected, the helpers of atomic
load/store on i8 and i16 relies on CONFIG_ARCH_SUPPORTS_ATOMIC_RMW=y.
It's generally fine since most of architectures support that.
The plan for CONFIG_ARCH_SUPPORTS_ATOMIC_RMW=n architectures is adding
their (probably lock-based) atomic load/store for i8 and i16 as their
atomic_{read,set}() and atomic64_{read,set}() counterpart when they
plans to support Rust.
Hence use a statis_assert!() to check this and remind the future us the
need of the helpers. This is more clear than the #[cfg] on impl blocks
of i8 and i16.
Suggested-by: Dirk Behme <dirk.behme@gmail.com>
Suggested-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260120140503.62804-2-boqun.feng@gmail.com
Link: https://patch.msgid.link/20260303201701.12204-7-boqun@kernel.org
Originally, `Atomic::from_ptr()` requires `T` being a `Sync` because I
thought having the ability to do `from_ptr()` meant multiplle
`&Atomic<T>`s shared by different threads, which was identical (or
similar) to multiple `&T`s shared by different threads. Hence `T` was
required to be `Sync`. However this is not true, since `&Atomic<T>` is
not the same at `&T`. Moreover, having this bound makes `Atomic::<*mut
T>::from_ptr()` impossible, which is definitely not intended. Therefore
remove the `T: Sync` bound.
[boqun: Fix title typo spotted by Alice & Gary]
Fixes: 29c32c405e ("rust: sync: atomic: Add generic atomics")
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260120115207.55318-2-boqun.feng@gmail.com
Link: https://patch.msgid.link/20260303201701.12204-2-boqun@kernel.org
Current `dma_read!`, `dma_write!` macros also use a custom
`addr_of!()`-based implementation for projecting pointers, which has
soundness issue as it relies on absence of `Deref` implementation on types.
It also has a soundness issue where it does not protect against unaligned
fields (when `#[repr(packed)]` is used) so it can generate misaligned
accesses.
This commit migrates them to use the general pointer projection
infrastructure, which handles these cases correctly.
As part of migration, the macro is updated to have an improved surface
syntax. The current macro have
dma_read!(a.b.c[d].e.f)
to mean `a.b.c` is a DMA coherent allocation and it should project into it
with `[d].e.f` and do a read, which is confusing as it makes the indexing
operator integral to the macro (so it will break if you have an array of
`CoherentAllocation`, for example).
This also is problematic as we would like to generalize
`CoherentAllocation` from just slices to arbitrary types.
Make the macro expects `dma_read!(path.to.dma, .path.inside.dma)` as the
canonical syntax. The index operator is no longer special and is just one
type of projection (in additional to field projection). Similarly, make
`dma_write!(path.to.dma, .path.inside.dma, value)` become the canonical
syntax for writing.
Another issue of the current macro is that it is always fallible. This
makes sense with existing design of `CoherentAllocation`, but once we
support fixed size arrays with `CoherentAllocation`, it is desirable to
have the ability to perform infallible indexing as well, e.g. doing a `[0]`
index of `[Foo; 2]` is okay and can be checked at build-time, so forcing
falliblity is non-ideal. To capture this, the macro is changed to use
`[idx]` as infallible projection and `[idx]?` as fallible index projection
(those syntax are part of the general projection infra). A benefit of this
is that while individual indexing operation may fail, the overall
read/write operation is not fallible.
Fixes: ad2907b4e3 ("rust: add dma coherent allocator abstraction")
Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260302164239.284084-4-gary@kernel.org
[ Capitalize safety comments; slightly improve wording in doc-comments.
- Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Add a generic infrastructure for performing field and index projections on
raw pointers. This will form the basis of performing I/O projections.
Pointers manipulations are intentionally using the safe wrapping variants
instead of the unsafe variants, as the latter requires pointers to be
inside an allocation which is not necessarily true for I/O pointers.
This projection macro protects against rogue `Deref` implementation, which
can causes the projected pointer to be outside the bounds of starting
pointer. This is extremely unlikely and Rust has a lint to catch this, but
is unsoundness regardless. The protection works by inducing type inference
ambiguity when `Deref` is implemented.
This projection macro also stops projecting into unaligned fields (i.e.
fields of `#[repr(packed)]` structs), as misaligned pointers require
special handling. This is implemented by attempting to create reference to
projected field inside a `if false` block. Despite being unreachable, Rust
still checks that they're not unaligned fields.
The projection macro supports both fallible and infallible index
projections. These are described in detail inside the documentation.
Signed-off-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://patch.msgid.link/20260302164239.284084-3-gary@kernel.org
[ * Add intro-doc links where possible,
* Fix typos and slightly improve wording, e.g. "as documentation
describes" -> "as the documentation of [`Self::proj`] describes",
* Add an empty line between regular and safety comments, before
examples, and between logically independent comments,
* Capitalize various safety comments.
- Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Add a `KnownSize` trait which is used obtain a size from a raw pointer's
metadata. This makes it possible to obtain size information on a raw slice
pointer. This is similar to Rust `core::mem::size_of_val_raw` which is not
yet stable.
Signed-off-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://patch.msgid.link/20260302164239.284084-2-gary@kernel.org
[ Fix wording in doc-comment. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Pull kunit fixes from Shuah Khan:
- Fix rust warnings when CONFIG_PRINTK is disabled
- Reduce stack usage in kunit_run_tests() to fix warnings when
CONFIG_FRAME_WARN is set to a relatively low value
- Update email address for David Gow
- Copy caller args in kunit tool in run_kernel to prevent mutation
* tag 'linux_kselftest-kunit-fixes-7.0-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest:
kunit: reduce stack usage in kunit_run_tests()
kunit: tool: copy caller args in run_kernel to prevent mutation
rust: kunit: fix warning when !CONFIG_PRINTK
MAINTAINERS: Update email address for David Gow
If `CONFIG_BLOCK` is disabled, the following warnings are displayed
during build:
warning: struct `NullTerminatedFormatter` is never constructed
--> ../rust/kernel/str.rs:667:19
|
667 | pub(crate) struct NullTerminatedFormatter<'a> {
| ^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default
warning: associated function `new` is never used
--> ../rust/kernel/str.rs:673:19
|
671 | impl<'a> NullTerminatedFormatter<'a> {
| ------------------------------------ associated function in this implementation
672 | /// Create a new [`Self`] instance.
673 | pub(crate) fn new(buffer: &'a mut [u8]) -> Option<NullTerminatedFormatter<'a>> {
Fix them by making `NullTerminatedFormatter` public, as it could be
useful for drivers anyway.
Fixes: cdde7a1951 ("rust: str: introduce `NullTerminatedFormatter`")
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260224-nullterminatedformatter-v1-1-5bef7b9b3d4c@nvidia.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
If `CONFIG_PRINTK` is not set, then the following warnings are issued
during build:
warning: unused variable: `args`
--> ../rust/kernel/kunit.rs:16:12
|
16 | pub fn err(args: fmt::Arguments<'_>) {
| ^^^^ help: if this is intentional, prefix it with an underscore: `_args`
|
= note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default
warning: unused variable: `args`
--> ../rust/kernel/kunit.rs:32:13
|
32 | pub fn info(args: fmt::Arguments<'_>) {
| ^^^^ help: if this is intentional, prefix it with an underscore: `_args`
Fix this by adding a no-op assignment using `args` when `CONFIG_PRINTK`
is not set.
Fixes: a66d733da8 ("rust: support running Rust documentation tests as KUnit ones")
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: David Gow <david@davidgow.net>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Add comprehensive KUnit tests for the shrink_to method for KVVec.
The tests verify:
- Basic shrinking from multiple pages to fewer pages with data integrity
preservation
- Empty vector shrinking to zero capacity
- No-op behavior when shrinking to a larger capacity than current
- Respect for min_capacity parameter when larger than vector length
These tests ensure that the shrinking logic correctly identifies when
memory can be reclaimed (by freeing at least one page) and that data
integrity is maintained throughout shrink operations.
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>
Link: https://patch.msgid.link/20260216-binder-shrink-vec-v3-v6-2-ece8e8593e53@zohomail.in
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Implement shrink_to method specifically for `KVVec` (i.e.,
`Vec<T, KVmalloc>`). `shrink_to` reduces the vector's capacity to a
specified minimum.
For kmalloc-backed allocations, the method delegates to realloc(),
letting the allocator decide whether shrinking is worthwhile. For
vmalloc-backed allocations (detected via is_vmalloc_addr), shrinking
only occurs if at least one page of memory can be freed, using an
explicit alloc+copy+free since vrealloc does not yet support in-place
shrinking.
A TODO note marks this for future replacement with a generic shrink_to
for all allocators that uses A::realloc() once the underlying allocators
properly support shrinking via realloc.
Suggested-by: Alice Ryhl <aliceryhl@google.com>
Suggested-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>
Link: https://patch.msgid.link/20260216-binder-shrink-vec-v3-v6-1-ece8e8593e53@zohomail.in
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Currently, the define_read!() and define_write!() I/O macros are crate
public. The only user outside of the I/O module is PCI (for the
configurations space I/O backend). Consequently, when CONFIG_PCI=n this
causes a compile time warning [1].
In order to fix this, rename the macros to io_define_read!() and
io_define_write!() and use #[macro_export] to export them.
This is better than making the crate public visibility conditional, as
eventually subsystems will have their own crate.
Also, I/O backends are valid to be implemented by drivers as well. For
instance, there are devices (such as GPUs) that run firmware which
allows to program other devices only accessible through the primary
device through indirect I/O.
Since the macros are now public, also add the corresponding
documentation.
Fixes: 121d87b28e ("rust: io: separate generic I/O helpers from MMIO implementation")
Reported-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Closes: https://lore.kernel.org/driver-core/CANiq72khOYkt6t5zwMvSiyZvWWHMZuNCMERXu=7K=_5tT-8Pgg@mail.gmail.com/ [1]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://patch.msgid.link/20260216131534.65008-1-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Pull rust fixes from Miguel Ojeda:
"Toolchain and infrastructure:
- Pass '-Zunstable-options' flag required by the future Rust 1.95.0
- Fix 'objtool' warning for Rust 1.84.0
'kernel' crate:
- 'irq' module: add missing bound detected by the future Rust 1.95.0
- 'list' module: add missing 'unsafe' blocks and placeholder safety
comments to macros (an issue for future callers within the crate)
'pin-init' crate:
- Clean Clippy warning that changed behavior in the future Rust
1.95.0"
* tag 'rust-fixes-7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux:
rust: list: Add unsafe blocks for container_of and safety comments
rust: pin-init: replace clippy `expect` with `allow`
rust: irq: add `'static` bounds to irq callbacks
objtool/rust: add one more `noreturn` Rust function
rust: kbuild: pass `-Zunstable-options` for Rust 1.95.0
impl_list_item_mod.rs calls container_of! without unsafe blocks at a
couple of places. Since container_of! is unsafe, the blocks are strictly
necessary.
The problem was so far not visible because the "unsafe-op-in-unsafe-fn"
check is a lint rather than a hard compiler error, and Rust suppresses
lints triggered inside of a macro from another crate.
Thus, the error becomes only visible once someone from within the kernel
crate tries to use linked lists:
error[E0133]: call to unsafe function `core::ptr::mut_ptr::<impl *mut T>::byte_sub`
is unsafe and requires unsafe block
--> rust/kernel/lib.rs:252:29
|
252 | let container_ptr = field_ptr.byte_sub(offset).cast::<$Container>();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
|
::: rust/kernel/drm/jq.rs:98:1
|
98 | / impl_list_item! {
99 | | impl ListItem<0> for BasicItem { using ListLinks { self.links }; }
100 | | }
| |_- in this macro invocation
|
note: an unsafe function restricts its caller, but its body is safe by default
--> rust/kernel/list/impl_list_item_mod.rs:216:13
|
216 | unsafe fn view_value(me: *mut $crate::list::ListLinks<$num>) -> *const Self {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
::: rust/kernel/drm/jq.rs:98:1
|
98 | / impl_list_item! {
99 | | impl ListItem<0> for BasicItem { using ListLinks { self.links }; }
100 | | }
| |_- in this macro invocation
= note: requested on the command line with `-D unsafe-op-in-unsafe-fn`
= note: this error originates in the macro `$crate::container_of` which comes
from the expansion of the macro `impl_list_item`
Therefore, add unsafe blocks to container_of! calls to fix the issue.
[ As discussed, let's fix the build for those that want to use the
macro within the `kernel` crate now and we can discuss the proper
safety comments afterwards. Thus I removed the ones from the patch.
However, we cannot just avoid the comments with `CLIPPY=1`, so I
provided placeholders for now, like we did in the past. They were
also needed for an `unsafe impl`.
While I am not happy about it, it isn't worse than the current
status (the comments were meant to be there), and at least this
shows what is missing -- our pre-existing "good first issue" [1]
may motivate new contributors to complete them properly.
Finally, I moved one of the existing safety comments one line down
so that Clippy could locate it.
Link: https://github.com/Rust-for-Linux/linux/issues/351 [1]
- Miguel ]
Cc: stable@vger.kernel.org
Fixes: c77f85b347 ("rust: list: remove OFFSET constants")
Suggested-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260216131613.45344-3-phasta@kernel.org
[ Fixed formatting. Reworded to fix the lint suppression
explanation. Indent build error. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
These callback functions take a generic `T` that is used in the body as
the generic argument in `Registration` and `ThreadedRegistration`. Those
types require `T: 'static`, but due to a compiler bug this requirement
isn't propagated to the function. Thus add the bound. This was caught in
the upstream Rust CI [1].
[ The three errors looked similar and will start appearing with Rust
1.95.0 (expected 2026-04-16). The first one was:
error[E0310]: the parameter type `T` may not live long enough
Error: --> rust/kernel/irq/request.rs:266:43
|
266 | let registration = unsafe { &*(ptr as *const Registration<T>) };
| ^^^^^^^^^^^^^^^^^^^^^^
| |
| the parameter type `T` must be valid for the static lifetime...
| ...so that the type `T` will meet its required lifetime bounds
|
help: consider adding an explicit lifetime bound
|
264 | unsafe extern "C" fn handle_irq_callback<T: Handler + 'static>(_irq: i32, ptr: *mut c_void) -> c_uint {
| +++++++++
- Miguel ]
Link: https://github.com/rust-lang/rust/pull/149389 [1]
Signed-off-by: Benno Lossin <lossin@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 29e16fcd67 ("rust: irq: add &Device<Bound> argument to irq callbacks")
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/rust-for-linux/20260217222425.8755-1-cole@unwrap.rs/
Link: https://patch.msgid.link/20260214092740.3201946-1-lossin@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Pull USB / Thunderbolt updates from Greg KH:
"Here is the "big" set of USB and Thunderbolt driver updates for
7.0-rc1. Overall more lines were removed than added, thanks to
dropping the obsolete isp1362 USB host controller driver, always a
nice change.
Other than that, nothing major happening here, highlights are:
- lots of dwc3 driver updates and new hardware support added
- usb gadget function driver updates
- usb phy driver updates
- typec driver updates and additions
- USB rust binding updates for syntax and formatting changes
- more usb serial device ids added
- other smaller USB core and driver updates and additions
All of these have been in linux-next for a long time, with no reported
problems"
* tag 'usb-7.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb: (77 commits)
usb: typec: ucsi: Add Thunderbolt alternate mode support
usb: typec: hd3ss3220: Check if regulator needs to be switched
usb: phy: tegra: parametrize PORTSC1 register offset
usb: phy: tegra: parametrize HSIC PTS value
usb: phy: tegra: return error value from utmi_wait_register
usb: phy: tegra: cosmetic fixes
dt-bindings: usb: renesas,usbhs: Add RZ/G3E SoC support
usb: dwc2: fix resume failure if dr_mode is host
usb: cdns3: fix role switching during resume
usb: dwc3: gadget: Move vbus draw to workqueue context
USB: serial: option: add Telit FN920C04 RNDIS compositions
usb: dwc3: Log dwc3 address in traces
usb: gadget: tegra-xudc: Add handling for BLCG_COREPLL_PWRDN
usb: phy: tegra: add HSIC support
usb: phy: tegra: use phy type directly
usb: typec: ucsi: Enforce mode selection for cros_ec_ucsi
usb: typec: ucsi: Support mode selection to activate altmodes
usb: typec: Introduce mode_selection bit
usb: typec: Implement mode selection
usb: typec: Expose alternate mode priority via sysfs
...
