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8 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Linus Torvalds
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f468cf53c5 |
Merge tag 'bitmap-for-6.19' of github.com:/norov/linux
Pull bitmap updates from Yury Norov:
- Runtime field_{get,prep}() (Geert)
- Rust ID pool updates (Alice)
- min_t() simplification (David)
- __sw_hweightN kernel-doc fixes (Andy)
- cpumask.h headers cleanup (Andy)
* tag 'bitmap-for-6.19' of github.com:/norov/linux: (32 commits)
rust_binder: use bitmap for allocation of handles
rust: id_pool: do not immediately acquire new ids
rust: id_pool: do not supply starting capacity
rust: id_pool: rename IdPool::new() to with_capacity()
rust: bitmap: add BitmapVec::new_inline()
rust: bitmap: add MAX_LEN and MAX_INLINE_LEN constants
cpumask: Don't use "proxy" headers
soc: renesas: Use bitfield helpers
clk: renesas: Use bitfield helpers
ALSA: usb-audio: Convert to common field_{get,prep}() helpers
soc: renesas: rz-sysc: Convert to common field_get() helper
pinctrl: ma35: Convert to common field_{get,prep}() helpers
iio: mlx90614: Convert to common field_{get,prep}() helpers
iio: dac: Convert to common field_prep() helper
gpio: aspeed: Convert to common field_{get,prep}() helpers
EDAC/ie31200: Convert to common field_get() helper
crypto: qat - convert to common field_get() helper
clk: at91: Convert to common field_{get,prep}() helpers
bitfield: Add non-constant field_{prep,get}() helpers
bitfield: Add less-checking __FIELD_{GET,PREP}()
...
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Linus Torvalds
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784faa8eca |
Merge tag 'rust-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux
Pull Rust updates from Miguel Ojeda:
"Toolchain and infrastructure:
- Add support for 'syn'.
Syn is a parsing library for parsing a stream of Rust tokens into a
syntax tree of Rust source code.
Currently this library is geared toward use in Rust procedural
macros, but contains some APIs that may be useful more generally.
'syn' allows us to greatly simplify writing complex macros such as
'pin-init' (Benno has already prepared the 'syn'-based version). We
will use it in the 'macros' crate too.
'syn' is the most downloaded Rust crate (according to crates.io),
and it is also used by the Rust compiler itself. While the amount
of code is substantial, there should not be many updates needed for
these crates, and even if there are, they should not be too big,
e.g. +7k -3k lines across the 3 crates in the last year.
'syn' requires two smaller dependencies: 'quote' and 'proc-macro2'.
I only modified their code to remove a third dependency
('unicode-ident') and to add the SPDX identifiers. The code can be
easily verified to exactly match upstream with the provided
scripts.
They are all licensed under "Apache-2.0 OR MIT", like the other
vendored 'alloc' crate we had for a while.
Please see the merge commit with the cover letter for more context.
- Allow 'unreachable_pub' and 'clippy::disallowed_names' for
doctests.
Examples (i.e. doctests) may want to do things like show public
items and use names such as 'foo'.
Nevertheless, we still try to keep examples as close to real code
as possible (this is part of why running Clippy on doctests is
important for us, e.g. for safety comments, which userspace Rust
does not support yet but we are stricter).
'kernel' crate:
- Replace our custom 'CStr' type with 'core::ffi::CStr'.
Using the standard library type reduces our custom code footprint,
and we retain needed custom functionality through an extension
trait and a new 'fmt!' macro which replaces the previous 'core'
import.
This started in 6.17 and continued in 6.18, and we finally land the
replacement now. This required quite some stamina from Tamir, who
split the changes in steps to prepare for the flag day change here.
- Replace 'kernel::c_str!' with C string literals.
C string literals were added in Rust 1.77, which produce '&CStr's
(the 'core' one), so now we can write:
c"hi"
instead of:
c_str!("hi")
- Add 'num' module for numerical features.
It includes the 'Integer' trait, implemented for all primitive
integer types.
It also includes the 'Bounded' integer wrapping type: an integer
value that requires only the 'N' least significant bits of the
wrapped type to be encoded:
// An unsigned 8-bit integer, of which only the 4 LSBs are used.
let v = Bounded::<u8, 4>::new::<15>();
assert_eq!(v.get(), 15);
'Bounded' is useful to e.g. enforce guarantees when working with
bitfields that have an arbitrary number of bits.
Values can also be constructed from simple non-constant expressions
or, for more complex ones, validated at runtime.
'Bounded' also comes with comparison and arithmetic operations
(with both their backing type and other 'Bounded's with a
compatible backing type), casts to change the backing type,
extending/shrinking and infallible/fallible conversions from/to
primitives as applicable.
- 'rbtree' module: add immutable cursor ('Cursor').
It enables to use just an immutable tree reference where
appropriate. The existing fully-featured mutable cursor is renamed
to 'CursorMut'.
kallsyms:
- Fix wrong "big" kernel symbol type read from procfs.
'pin-init' crate:
- A couple minor fixes (Benno asked me to pick these patches up for
him this cycle).
Documentation:
- Quick Start guide: add Debian 13 (Trixie).
Debian Stable is now able to build Linux, since Debian 13 (released
2025-08-09) packages Rust 1.85.0, which is recent enough.
We are planning to propose that the minimum supported Rust version
in Linux follows Debian Stable releases, with Debian 13 being the
first one we upgrade to, i.e. Rust 1.85.
MAINTAINERS:
- Add entry for the new 'num' module.
- Remove Alex as Rust maintainer: he hasn't had the time to
contribute for a few years now, so it is a no-op change in
practice.
And a few other cleanups and improvements"
* tag 'rust-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux: (53 commits)
rust: macros: support `proc-macro2`, `quote` and `syn`
rust: syn: enable support in kbuild
rust: syn: add `README.md`
rust: syn: remove `unicode-ident` dependency
rust: syn: add SPDX License Identifiers
rust: syn: import crate
rust: quote: enable support in kbuild
rust: quote: add `README.md`
rust: quote: add SPDX License Identifiers
rust: quote: import crate
rust: proc-macro2: enable support in kbuild
rust: proc-macro2: add `README.md`
rust: proc-macro2: remove `unicode_ident` dependency
rust: proc-macro2: add SPDX License Identifiers
rust: proc-macro2: import crate
rust: kbuild: support using libraries in `rustc_procmacro`
rust: kbuild: support skipping flags in `rustc_test_library`
rust: kbuild: add proc macro library support
rust: kbuild: simplify `--cfg` handling
rust: kbuild: introduce `core-flags` and `core-skip_flags`
...
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Alice Ryhl
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5ba71195a9 |
rust_binder: use bitmap for allocation of handles
To find an unused Binder handle, Rust Binder currently iterates the
red/black tree from the beginning until it finds a gap in the keys. This
is extremely slow.
To improve the performance, add a bitmap that keeps track of which
indices are actually in use. This allows us to quickly find an unused
key in the red/black tree.
For a benchmark, please see the below numbers that were obtained from
modifying binderThroughputTest to send a node with each transaction and
stashing it in the server. This results in the number of nodes
increasing by one for every transaction sent. I got the following table
of roundtrip latencies (in µs):
Transaction Range │ Baseline (Rust) │ Bitmap (Rust) │ Comparison (C)
0 - 10,000 │ 176.88 │ 92.93 │ 99.41
10,000 - 20,000 │ 437.37 │ 87.74 │ 98.55
20,000 - 30,000 │ 677.49 │ 76.24 │ 96.37
30,000 - 40,000 │ 901.76 │ 83.39 │ 96.73
40,000 - 50,000 │ 1126.62 │ 100.44 │ 94.57
50,000 - 60,000 │ 1288.98 │ 94.38 │ 96.64
60,000 - 70,000 │ 1588.74 │ 88.27 │ 96.36
70,000 - 80,000 │ 1812.97 │ 93.97 │ 91.24
80,000 - 90,000 │ 2062.95 │ 92.22 │ 102.01
90,000 - 100,000 │ 2330.03 │ 97.18 │ 100.31
It should be clear that the current Rust code becomes linearly slower
per insertion as the number of calls to rb_next() per transaction
increases. After this change, the time to find an ID number appears
constant. (Technically it is not constant-time as both insertion and
removal scan the entire bitmap. However, quick napkin math shows that
scanning the entire bitmap with N=100k takes ~1.5µs, which is neglible
in a benchmark where the rountrip latency is 100µs.)
I've included a comparison to the C driver, which uses the same bitmap
algorithm as this patch since commit
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Vitaly Wool
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f56b131723 |
rust: rbtree: add immutable cursor
Sometimes we may need to iterate over, or find an element in a read only (or read mostly) red-black tree, and in that case we don't need a mutable reference to the tree, which we'll however have to take to be able to use the current (mutable) cursor implementation. This patch adds a simple immutable cursor implementation to RBTree, which enables us to use an immutable tree reference. The existing (fully featured) cursor implementation is renamed to CursorMut, while retaining its functionality. The only existing user of the [mutable] cursor for RBTrees (binder) is updated to match the changes. Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.se> Reviewed-by: Alice Ryhl <aliceryhl@google.com> Link: https://patch.msgid.link/20251014123339.2492210-1-vitaly.wool@konsulko.se [ Applied `rustfmt`. Added intra-doc link. Fixed unclosed example. Fixed docs description. Fixed typo and other formatting nits. - Miguel ] Signed-off-by: Miguel Ojeda <ojeda@kernel.org> |
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Tamir Duberstein
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d9252f1be2 |
rust_binder: remove trailing comma
This prepares for a later commit in which we introduce a custom formatting macro; that macro doesn't handle trailing commas so just remove this one. Reviewed-by: Alice Ryhl <aliceryhl@google.com> Signed-off-by: Tamir Duberstein <tamird@gmail.com> Link: https://patch.msgid.link/20251018-cstr-core-v18-2-9378a54385f8@gmail.com Signed-off-by: Miguel Ojeda <ojeda@kernel.org> |
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Alice Ryhl
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b5ce7a5cc5 |
rust_binder: report freeze notification only when fully frozen
Binder only sends out freeze notifications when ioctl_freeze() completes and the process has become fully frozen. However, if a freeze notification is registered during the freeze operation, then it registers an initial state of 'frozen'. This is a problem because if the freeze operation fails, then the listener is not told about that state change, leading to lost updates. Signed-off-by: Alice Ryhl <aliceryhl@google.com> Acked-by: Carlos Llamas <cmllamas@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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Alice Ryhl
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c7c090af37 |
rust_binder: remove warning about orphan mappings
This condition occurs if a thread dies while processing a transaction. We should not print anything in this scenario. Signed-off-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com> Acked-by: Carlos Llamas <cmllamas@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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Alice Ryhl
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eafedbc7c0 |
rust_binder: add Rust Binder driver
We're generally not proponents of rewrites (nasty uncomfortable things that make you late for dinner!). So why rewrite Binder? Binder has been evolving over the past 15+ years to meet the evolving needs of Android. Its responsibilities, expectations, and complexity have grown considerably during that time. While we expect Binder to continue to evolve along with Android, there are a number of factors that currently constrain our ability to develop/maintain it. Briefly those are: 1. Complexity: Binder is at the intersection of everything in Android and fulfills many responsibilities beyond IPC. It has become many things to many people, and due to its many features and their interactions with each other, its complexity is quite high. In just 6kLOC it must deliver transactions to the right threads. It must correctly parse and translate the contents of transactions, which can contain several objects of different types (e.g., pointers, fds) that can interact with each other. It controls the size of thread pools in userspace, and ensures that transactions are assigned to threads in ways that avoid deadlocks where the threadpool has run out of threads. It must track refcounts of objects that are shared by several processes by forwarding refcount changes between the processes correctly. It must handle numerous error scenarios and it combines/nests 13 different locks, 7 reference counters, and atomic variables. Finally, It must do all of this as fast and efficiently as possible. Minor performance regressions can cause a noticeably degraded user experience. 2. Things to improve: Thousand-line functions [1], error-prone error handling [2], and confusing structure can occur as a code base grows organically. After more than a decade of development, this codebase could use an overhaul. [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/android/binder.c?h=v6.5#n2896 [2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/android/binder.c?h=v6.5#n3658 3. Security critical: Binder is a critical part of Android's sandboxing strategy. Even Android's most de-privileged sandboxes (e.g. the Chrome renderer, or SW Codec) have direct access to Binder. More than just about any other component, it's important that Binder provide robust security, and itself be robust against security vulnerabilities. It's #1 (high complexity) that has made continuing to evolve Binder and resolving #2 (tech debt) exceptionally difficult without causing #3 (security issues). For Binder to continue to meet Android's needs, we need better ways to manage (and reduce!) complexity without increasing the risk. The biggest change is obviously the choice of programming language. We decided to use Rust because it directly addresses a number of the challenges within Binder that we have faced during the last years. It prevents mistakes with ref counting, locking, bounds checking, and also does a lot to reduce the complexity of error handling. Additionally, we've been able to use the more expressive type system to encode the ownership semantics of the various structs and pointers, which takes the complexity of managing object lifetimes out of the hands of the programmer, reducing the risk of use-after-frees and similar problems. Rust has many different pointer types that it uses to encode ownership semantics into the type system, and this is probably one of the most important aspects of how it helps in Binder. The Binder driver has a lot of different objects that have complex ownership semantics; some pointers own a refcount, some pointers have exclusive ownership, and some pointers just reference the object and it is kept alive in some other manner. With Rust, we can use a different pointer type for each kind of pointer, which enables the compiler to enforce that the ownership semantics are implemented correctly. Another useful feature is Rust's error handling. Rust allows for more simplified error handling with features such as destructors, and you get compilation failures if errors are not properly handled. This means that even though Rust requires you to spend more lines of code than C on things such as writing down invariants that are left implicit in C, the Rust driver is still slightly smaller than C binder: Rust is 5.5kLOC and C is 5.8kLOC. (These numbers are excluding blank lines, comments, binderfs, and any debugging facilities in C that are not yet implemented in the Rust driver. The numbers include abstractions in rust/kernel/ that are unlikely to be used by other drivers than Binder.) Although this rewrite completely rethinks how the code is structured and how assumptions are enforced, we do not fundamentally change *how* the driver does the things it does. A lot of careful thought has gone into the existing design. The rewrite is aimed rather at improving code health, structure, readability, robustness, security, maintainability and extensibility. We also include more inline documentation, and improve how assumptions in the code are enforced. Furthermore, all unsafe code is annotated with a SAFETY comment that explains why it is correct. We have left the binderfs filesystem component in C. Rewriting it in Rust would be a large amount of work and requires a lot of bindings to the file system interfaces. Binderfs has not historically had the same challenges with security and complexity, so rewriting binderfs seems to have lower value than the rest of Binder. Correctness and feature parity ------------------------------ Rust binder passes all tests that validate the correctness of Binder in the Android Open Source Project. We can boot a device, and run a variety of apps and functionality without issues. We have performed this both on the Cuttlefish Android emulator device, and on a Pixel 6 Pro. As for feature parity, Rust binder currently implements all features that C binder supports, with the exception of some debugging facilities. The missing debugging facilities will be added before we submit the Rust implementation upstream. Tracepoints ----------- I did not include all of the tracepoints as I felt that the mechansim for making C access fields of Rust structs should be discussed on list separately. I also did not include the support for building Rust Binder as a module since that requires exporting a bunch of additional symbols on the C side. Original RFC Link with old benchmark numbers: https://lore.kernel.org/r/20231101-rust-binder-v1-0-08ba9197f637@google.com Co-developed-by: Wedson Almeida Filho <wedsonaf@gmail.com> Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com> Co-developed-by: Matt Gilbride <mattgilbride@google.com> Signed-off-by: Matt Gilbride <mattgilbride@google.com> Acked-by: Carlos Llamas <cmllamas@google.com> Acked-by: Paul Moore <paul@paul-moore.com> Signed-off-by: Alice Ryhl <aliceryhl@google.com> Link: https://lore.kernel.org/r/20250919-rust-binder-v2-1-a384b09f28dd@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |