linux/rust/helpers/helpers.c

108 lines
3.1 KiB

rust: helpers: #define __rust_helper Because of LLVM inling checks, it's generally not possible to inline a C helper into Rust code, even with LTO: * LLVM doesn't want to inline functions compiled with `-fno-delete-null-pointer-checks` with code compiled without. The C CGUs all have this enabled and Rust CGUs don't. Inlining is okay since this is one of the hardening features that does not change the ABI, and we shouldn't have null pointer dereferences in these helpers. * LLVM doesn't want to inline functions with different list of builtins. C side has `-fno-builtin-wcslen`; `wcslen` is not a Rust builtin, so they should be compatible, but LLVM does not perform inlining due to attributes mismatch. * clang and Rust doesn't have the exact target string. Clang generates `+cmov,+cx8,+fxsr` but Rust doesn't enable them (in fact, Rust will complain if `-Ctarget-feature=+cmov,+cx8,+fxsr` is used). x86-64 always enable these features, so they are in fact the same target string, but LLVM doesn't understand this and so inlining is inhibited. This can be bypassed with `--ignore-tti-inline-compatible`, but this is a hidden option. To fix this, we can add __always_inline on every helper, which skips these LLVM inlining checks. For this purpose, introduce a new __rust_helper macro that needs to be added to every helper. Most helpers already have __rust_helper specified, but there are a few missing. The only consequence of this is that those specific helpers do not get inlined. Signed-off-by: Gary Guo <gary@garyguo.net> Signed-off-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Andreas Hindborg <a.hindborg@kernel.org> Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org> Link: https://patch.msgid.link/20260203-inline-helpers-v2-2-beb8547a03c9@google.com Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2026-02-03 11:34:09 +00:00
rust: helpers: #define __rust_helper Because of LLVM inling checks, it's generally not possible to inline a C helper into Rust code, even with LTO: * LLVM doesn't want to inline functions compiled with `-fno-delete-null-pointer-checks` with code compiled without. The C CGUs all have this enabled and Rust CGUs don't. Inlining is okay since this is one of the hardening features that does not change the ABI, and we shouldn't have null pointer dereferences in these helpers. * LLVM doesn't want to inline functions with different list of builtins. C side has `-fno-builtin-wcslen`; `wcslen` is not a Rust builtin, so they should be compatible, but LLVM does not perform inlining due to attributes mismatch. * clang and Rust doesn't have the exact target string. Clang generates `+cmov,+cx8,+fxsr` but Rust doesn't enable them (in fact, Rust will complain if `-Ctarget-feature=+cmov,+cx8,+fxsr` is used). x86-64 always enable these features, so they are in fact the same target string, but LLVM doesn't understand this and so inlining is inhibited. This can be bypassed with `--ignore-tti-inline-compatible`, but this is a hidden option. To fix this, we can add __always_inline on every helper, which skips these LLVM inlining checks. For this purpose, introduce a new __rust_helper macro that needs to be added to every helper. Most helpers already have __rust_helper specified, but there are a few missing. The only consequence of this is that those specific helpers do not get inlined. Signed-off-by: Gary Guo <gary@garyguo.net> Signed-off-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Andreas Hindborg <a.hindborg@kernel.org> Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org> Link: https://patch.msgid.link/20260203-inline-helpers-v2-2-beb8547a03c9@google.com Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2026-02-03 11:34:09 +00:00
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>
2025-09-19 06:42:07 +00:00
2024-09-15 14:31:30 +00:00
rust: helpers: Add dma_alloc_attrs() and dma_free_attrs() Add dma_alloc_attrs() and dma_free_attrs() helpers to fix a build error when CONFIG_HAS_DMA is not enabled. Note that when CONFIG_HAS_DMA is enabled, dma_alloc_attrs() and dma_free_attrs() are included in both bindings_generated.rs and bindings_helpers_generated.rs. The former takes precedence so behavior remains unchanged in that case. This fixes the following build error on UML: error[E0425]: cannot find function `dma_alloc_attrs` in crate `bindings` --> rust/kernel/dma.rs:171:23 | 171 | bindings::dma_alloc_attrs( | ^^^^^^^^^^^^^^^ help: a function with a similar name exists: `dma_alloc_pages` | ::: rust/bindings/bindings_generated.rs:44568:5 | 44568 | / pub fn dma_alloc_pages( 44569 | | dev: *mut device, 44570 | | size: usize, 44571 | | dma_handle: *mut dma_addr_t, 44572 | | dir: dma_data_direction, 44573 | | gfp: gfp_t, 44574 | | ) -> *mut page; | |___________________- similarly named function `dma_alloc_pages` defined here error[E0425]: cannot find function `dma_free_attrs` in crate `bindings` --> rust/kernel/dma.rs:293:23 | 293 | bindings::dma_free_attrs( | ^^^^^^^^^^^^^^ help: a function with a similar name exists: `dma_free_pages` | ::: rust/bindings/bindings_generated.rs:44577:5 | 44577 | / pub fn dma_free_pages( 44578 | | dev: *mut device, 44579 | | size: usize, 44580 | | page: *mut page, 44581 | | dma_handle: dma_addr_t, 44582 | | dir: dma_data_direction, 44583 | | ); | |______- similarly named function `dma_free_pages` defined here Fixes: ad2907b4e308 ("rust: add dma coherent allocator abstraction") Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com> Acked-by: Danilo Krummrich <dakr@kernel.org> Link: https://lore.kernel.org/r/20250412000507.157000-1-fujita.tomonori@gmail.com [ Reworded for relative paths. - Miguel ] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2025-04-12 09:05:06 +09:00
rust: file: add Rust abstraction for `struct file` This abstraction makes it possible to manipulate the open files for a process. The new `File` struct wraps the C `struct file`. When accessing it using the smart pointer `ARef<File>`, the pointer will own a reference count to the file. When accessing it as `&File`, then the reference does not own a refcount, but the borrow checker will ensure that the reference count does not hit zero while the `&File` is live. Since this is intended to manipulate the open files of a process, we introduce an `fget` constructor that corresponds to the C `fget` method. In future patches, it will become possible to create a new fd in a process and bind it to a `File`. Rust Binder will use these to send fds from one process to another. We also provide a method for accessing the file's flags. Rust Binder will use this to access the flags of the Binder fd to check whether the non-blocking flag is set, which affects what the Binder ioctl does. This introduces a struct for the EBADF error type, rather than just using the Error type directly. This has two advantages: * `File::fget` returns a `Result<ARef<File>, BadFdError>`, which the compiler will represent as a single pointer, with null being an error. This is possible because the compiler understands that `BadFdError` has only one possible value, and it also understands that the `ARef<File>` smart pointer is guaranteed non-null. * Additionally, we promise to users of the method that the method can only fail with EBADF, which means that they can rely on this promise without having to inspect its implementation. That said, there are also two disadvantages: * Defining additional error types involves boilerplate. * The question mark operator will only utilize the `From` trait once, which prevents you from using the question mark operator on `BadFdError` in methods that return some third error type that the kernel `Error` is convertible into. (However, it works fine in methods that return `Error`.) Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com> Co-developed-by: Daniel Xu <dxu@dxuuu.xyz> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> Co-developed-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Benno Lossin <benno.lossin@proton.me> Signed-off-by: Alice Ryhl <aliceryhl@google.com> Link: https://lore.kernel.org/r/20240915-alice-file-v10-3-88484f7a3dcf@google.com Reviewed-by: Gary Guo <gary@garyguo.net> Signed-off-by: Christian Brauner <brauner@kernel.org>
2024-09-15 14:31:29 +00:00
rust: introduce abstractions for fwctl Introduce safe Rust wrappers around struct fwctl_device and struct fwctl_uctx. This lets Rust drivers register fwctl devices and implement firmware RPC callbacks through a typed trait interface. The abstraction keeps lifetime and reference-count handling inside the wrapper, exposes pinned per-FD user contexts to drivers, and validates the layout assumptions required by the C fwctl allocation model. Allocation sizes are padded so the kmalloc-backed C allocations also satisfy Rust alignment requirements. Registration owns driver private data with a lifetime tied to the bound parent device and verifies the parent identity before registration. Callbacks access that data through a higher-ranked closure, preventing its erased lifetime from escaping, while Device remains only the refcounted fwctl object. This avoids requiring Rust drop glue from the fwctl_device release path after unregister or module teardown. RPC callbacks receive typed scope information, a mutable request/response buffer, and the userspace output-buffer size. Response pointer conversion, length validation, and raw output-length handling remain inside the abstraction. Add the Rust sources to the FWCTL MAINTAINERS entry and add myself as the maintainer for the Rust abstractions. Link: https://patch.msgid.link/r/20260813152312.1311142-2-zhiw@nvidia.com Co-developed-by: Danilo Krummrich <dakr@kernel.org> Signed-off-by: Danilo Krummrich <dakr@kernel.org> Signed-off-by: Zhi Wang <zhiw@nvidia.com> Reviewed-by: Alexandre Courbot <acourbot@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2026-08-13 18:23:12 +03:00
rust: add `io::{Io, IoRaw}` base types I/O memory is typically either mapped through direct calls to ioremap() or subsystem / bus specific ones such as pci_iomap(). Even though subsystem / bus specific functions to map I/O memory are based on ioremap() / iounmap() it is not desirable to re-implement them in Rust. Instead, implement a base type for I/O mapped memory, which generically provides the corresponding accessors, such as `Io::readb` or `Io:try_readb`. `Io` supports an optional const generic, such that a driver can indicate the minimal expected and required size of the mapping at compile time. Correspondingly, calls to the 'non-try' accessors, support compile time checks of the I/O memory offset to read / write, while the 'try' accessors, provide boundary checks on runtime. `IoRaw` is meant to be embedded into a structure (e.g. pci::Bar or io::IoMem) which creates the actual I/O memory mapping and initializes `IoRaw` accordingly. To ensure that I/O mapped memory can't out-live the device it may be bound to, subsystems must embed the corresponding I/O memory type (e.g. pci::Bar) into a `Devres` container, such that it gets revoked once the device is unbound. Reviewed-by: Alice Ryhl <aliceryhl@google.com> Tested-by: Daniel Almeida <daniel.almeida@collabora.com> Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com> Signed-off-by: Danilo Krummrich <dakr@kernel.org> Tested-by: Dirk Behme <dirk.behme@de.bosch.com> Link: https://lore.kernel.org/r/20241219170425.12036-8-dakr@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-12-19 18:04:09 +01:00
rust: introduce abstractions for fwctl Introduce safe Rust wrappers around struct fwctl_device and struct fwctl_uctx. This lets Rust drivers register fwctl devices and implement firmware RPC callbacks through a typed trait interface. The abstraction keeps lifetime and reference-count handling inside the wrapper, exposes pinned per-FD user contexts to drivers, and validates the layout assumptions required by the C fwctl allocation model. Allocation sizes are padded so the kmalloc-backed C allocations also satisfy Rust alignment requirements. Registration owns driver private data with a lifetime tied to the bound parent device and verifies the parent identity before registration. Callbacks access that data through a higher-ranked closure, preventing its erased lifetime from escaping, while Device remains only the refcounted fwctl object. This avoids requiring Rust drop glue from the fwctl_device release path after unregister or module teardown. RPC callbacks receive typed scope information, a mutable request/response buffer, and the userspace output-buffer size. Response pointer conversion, length validation, and raw output-length handling remain inside the abstraction. Add the Rust sources to the FWCTL MAINTAINERS entry and add myself as the maintainer for the Rust abstractions. Link: https://patch.msgid.link/r/20260813152312.1311142-2-zhiw@nvidia.com Co-developed-by: Danilo Krummrich <dakr@kernel.org> Signed-off-by: Danilo Krummrich <dakr@kernel.org> Signed-off-by: Zhi Wang <zhiw@nvidia.com> Reviewed-by: Alexandre Courbot <acourbot@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2026-08-13 18:23:12 +03:00
rust: add static_branch_unlikely for static_key_false Add just enough support for static key so that we can use it from tracepoints. Tracepoints rely on `static_branch_unlikely` with a `struct static_key_false`, so we add the same functionality to Rust. This patch only provides a generic implementation without code patching (matching the one used when CONFIG_JUMP_LABEL is disabled). Later patches add support for inline asm implementations that use runtime patching. When CONFIG_JUMP_LABEL is unset, `static_key_count` is a static inline function, so a Rust helper is defined for `static_key_count` in this case. If Rust is compiled with LTO, this call should get inlined. The helper can be eliminated once we have the necessary inline asm to make atomic operations from Rust. Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Josh Poimboeuf <jpoimboe@kernel.org> Cc: Jason Baron <jbaron@akamai.com> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: Miguel Ojeda <ojeda@kernel.org> Cc: Alex Gaynor <alex.gaynor@gmail.com> Cc: Wedson Almeida Filho <wedsonaf@gmail.com> Cc: " =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= " <bjorn3_gh@protonmail.com> Cc: Benno Lossin <benno.lossin@proton.me> Cc: Andreas Hindborg <a.hindborg@kernel.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Sean Christopherson <seanjc@google.com> Cc: Uros Bizjak <ubizjak@gmail.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Marc Zyngier <maz@kernel.org> Cc: Oliver Upton <oliver.upton@linux.dev> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Fuad Tabba <tabba@google.com> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Anup Patel <apatel@ventanamicro.com> Cc: Andrew Jones <ajones@ventanamicro.com> Cc: Alexandre Ghiti <alexghiti@rivosinc.com> Cc: Conor Dooley <conor.dooley@microchip.com> Cc: Samuel Holland <samuel.holland@sifive.com> Cc: Huacai Chen <chenhuacai@kernel.org> Cc: WANG Xuerui <kernel@xen0n.name> Cc: Bibo Mao <maobibo@loongson.cn> Cc: Tiezhu Yang <yangtiezhu@loongson.cn> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Tianrui Zhao <zhaotianrui@loongson.cn> Link: https://lore.kernel.org/20241030-tracepoint-v12-1-eec7f0f8ad22@google.com Reviewed-by: Boqun Feng <boqun.feng@gmail.com> Reviewed-by: Gary Guo <gary@garyguo.net> Signed-off-by: Alice Ryhl <aliceryhl@google.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-10-30 16:04:24 +00:00
rust: maple_tree: add MapleTree Patch series "Add Rust abstraction for Maple Trees", v3. This will be used in the Tyr driver [1] to allocate from the GPU's VA space that is not owned by userspace, but by the kernel, for kernel GPU mappings. Danilo tells me that in nouveau, the maple tree is used for keeping track of "VM regions" on top of GPUVM, and that he will most likely end up doing the same in the Rust Nova driver as well. These abstractions intentionally do not expose any way to make use of external locking. You are required to use the internal spinlock. For now, we do not support loads that only utilize rcu for protection. This contains some parts taken from Andrew Ballance's RFC [2] from April. However, it has also been reworked significantly compared to that RFC taking the use-cases in Tyr into account. This patch (of 3): The maple tree will be used in the Tyr driver to allocate and keep track of GPU allocations created internally (i.e. not by userspace). It will likely also be used in the Nova driver eventually. This adds the simplest methods for additional and removal that do not require any special care with respect to concurrency. This implementation is based on the RFC by Andrew but with significant changes to simplify the implementation. [ojeda@kernel.org: fix intra-doc links] Link: https://lkml.kernel.org/r/20250910140212.997771-1-ojeda@kernel.org Link: https://lkml.kernel.org/r/20250902-maple-tree-v3-0-fb5c8958fb1e@google.com Link: https://lkml.kernel.org/r/20250902-maple-tree-v3-1-fb5c8958fb1e@google.com Link: https://lore.kernel.org/r/20250627-tyr-v1-1-cb5f4c6ced46@collabora.com [1] Link: https://lore.kernel.org/r/20250405060154.1550858-1-andrewjballance@gmail.com [2] Co-developed-by: Andrew Ballance <andrewjballance@gmail.com> Signed-off-by: Andrew Ballance <andrewjballance@gmail.com> Signed-off-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Danilo Krummrich <dakr@kernel.org> Cc: Andreas Hindborg <a.hindborg@kernel.org> Cc: Björn Roy Baron <bjorn3_gh@protonmail.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Daniel Almeida <daniel.almeida@collabora.com> Cc: Gary Guo <gary@garyguo.net> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Miguel Ojeda <ojeda@kernel.org> Cc: Trevor Gross <tmgross@umich.edu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2025-09-02 08:35:11 +00:00
mm: rust: add abstraction for struct mm_struct Patch series "Rust support for mm_struct, vm_area_struct, and mmap", v16. This updates the vm_area_struct support to use the approach we discussed at LPC where there are several different Rust wrappers for vm_area_struct depending on the kind of access you have to the vma. Each case allows a different set of operations on the vma. This includes an MM MAINTAINERS entry as proposed by Lorenzo: https://lore.kernel.org/all/33e64b12-aa07-4e78-933a-b07c37ff1d84@lucifer.local/ This patch (of 9): These abstractions allow you to reference a `struct mm_struct` using both mmgrab and mmget refcounts. This is done using two Rust types: * Mm - represents an mm_struct where you don't know anything about the value of mm_users. * MmWithUser - represents an mm_struct where you know at compile time that mm_users is non-zero. This allows us to encode in the type system whether a method requires that mm_users is non-zero or not. For instance, you can always call `mmget_not_zero` but you can only call `mmap_read_lock` when mm_users is non-zero. The struct is called Mm to keep consistency with the C side. The ability to obtain `current->mm` is added later in this series. The mm module is defined to only exist when CONFIG_MMU is set. This avoids various errors due to missing types and functions when CONFIG_MMU is disabled. More fine-grained cfgs can be considered in the future. See the thread at [1] for more info. Link: https://lkml.kernel.org/r/20250408-vma-v16-9-d8b446e885d9@google.com Link: https://lkml.kernel.org/r/20250408-vma-v16-1-d8b446e885d9@google.com Link: https://lore.kernel.org/all/202503091916.QousmtcY-lkp@intel.com/ Signed-off-by: Alice Ryhl <aliceryhl@google.com> Acked-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Acked-by: Liam R. Howlett <Liam.Howlett@Oracle.com> Acked-by: Balbir Singh <balbirs@nvidia.com> Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org> Reviewed-by: Gary Guo <gary@garyguo.net> Cc: Alex Gaynor <alex.gaynor@gmail.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Benno Lossin <benno.lossin@proton.me> Cc: Björn Roy Baron <bjorn3_gh@protonmail.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jann Horn <jannh@google.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Miguel Ojeda <ojeda@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Trevor Gross <tmgross@umich.edu> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2025-04-08 09:22:38 +00:00
rust: add PidNamespace The lifetime of `PidNamespace` is bound to `Task` and `struct pid`. The `PidNamespace` of a `Task` doesn't ever change once the `Task` is alive. A `unshare(CLONE_NEWPID)` or `setns(fd_pidns/pidfd, CLONE_NEWPID)` will not have an effect on the calling `Task`'s pid namespace. It will only effect the pid namespace of children created by the calling `Task`. This invariant guarantees that after having acquired a reference to a `Task`'s pid namespace it will remain unchanged. When a task has exited and been reaped `release_task()` will be called. This will set the `PidNamespace` of the task to `NULL`. So retrieving the `PidNamespace` of a task that is dead will return `NULL`. Note, that neither holding the RCU lock nor holding a referencing count to the `Task` will prevent `release_task()` being called. In order to retrieve the `PidNamespace` of a `Task` the `task_active_pid_ns()` function can be used. There are two cases to consider: (1) retrieving the `PidNamespace` of the `current` task (2) retrieving the `PidNamespace` of a non-`current` task From system call context retrieving the `PidNamespace` for case (1) is always safe and requires neither RCU locking nor a reference count to be held. Retrieving the `PidNamespace` after `release_task()` for current will return `NULL` but no codepath like that is exposed to Rust. Retrieving the `PidNamespace` from system call context for (2) requires RCU protection. Accessing `PidNamespace` outside of RCU protection requires a reference count that must've been acquired while holding the RCU lock. Note that accessing a non-`current` task means `NULL` can be returned as the non-`current` task could have already passed through `release_task()`. To retrieve (1) the `current_pid_ns!()` macro should be used which ensure that the returned `PidNamespace` cannot outlive the calling scope. The associated `current_pid_ns()` function should not be called directly as it could be abused to created an unbounded lifetime for `PidNamespace`. The `current_pid_ns!()` macro allows Rust to handle the common case of accessing `current`'s `PidNamespace` without RCU protection and without having to acquire a reference count. For (2) the `task_get_pid_ns()` method must be used. This will always acquire a reference on `PidNamespace` and will return an `Option` to force the caller to explicitly handle the case where `PidNamespace` is `None`, something that tends to be forgotten when doing the equivalent operation in `C`. Missing RCU primitives make it difficult to perform operations that are otherwise safe without holding a reference count as long as RCU protection is guaranteed. But it is not important currently. But we do want it in the future. Note for (2) the required RCU protection around calling `task_active_pid_ns()` synchronizes against putting the last reference of the associated `struct pid` of `task->thread_pid`. The `struct pid` stored in that field is used to retrieve the `PidNamespace` of the caller. When `release_task()` is called `task->thread_pid` will be `NULL`ed and `put_pid()` on said `struct pid` will be delayed in `free_pid()` via `call_rcu()` allowing everyone with an RCU protected access to the `struct pid` acquired from `task->thread_pid` to finish. Link: https://lore.kernel.org/r/20241002-brauner-rust-pid_namespace-v5-1-a90e70d44fde@kernel.org Reviewed-by: Alice Ryhl <aliceryhl@google.com> Signed-off-by: Christian Brauner <brauner@kernel.org>
2024-10-02 13:38:10 +02:00
Rust changes for v6.17 Toolchain and infrastructure: - Enable a set of Clippy lints: 'ptr_as_ptr', 'ptr_cast_constness', 'as_ptr_cast_mut', 'as_underscore', 'cast_lossless' and 'ref_as_ptr'. These are intended to avoid type casts with the 'as' operator, which are quite powerful, into restricted variants that are less powerful and thus should help to avoid mistakes. - Remove the 'author' key now that most instances were moved to the plural one in the previous cycle. 'kernel' crate: - New 'bug' module: add 'warn_on!' macro which reuses the existing 'BUG'/'WARN' infrastructure, i.e. it respects the usual sysctls and kernel parameters: warn_on!(value == 42); To avoid duplicating the assembly code, the same strategy is followed as for the static branch code in order to share the assembly between both C and Rust. This required a few rearrangements on C arch headers -- the existing C macros should still generate the same outputs, thus no functional change expected there. - 'workqueue' module: add delayed work items, including a 'DelayedWork' struct, a 'impl_has_delayed_work!' macro and an 'enqueue_delayed' method, e.g.: /// Enqueue the struct for execution on the system workqueue, /// where its value will be printed 42 jiffies later. fn print_later(value: Arc<MyStruct>) { let _ = workqueue::system().enqueue_delayed(value, 42); } - New 'bits' module: add support for 'bit' and 'genmask' functions, with runtime- and compile-time variants, e.g.: static_assert!(0b00010000 == bit_u8(4)); static_assert!(0b00011110 == genmask_u8(1..=4)); assert!(checked_bit_u32(u32::BITS).is_none()); - 'uaccess' module: add 'UserSliceReader::strcpy_into_buf', which reads NUL-terminated strings from userspace into a '&CStr'. Introduce 'UserPtr' newtype, similar in purpose to '__user' in C, to minimize mistakes handling userspace pointers, including mixing them up with integers and leaking them via the 'Debug' trait. Add it to the prelude, too. - Start preparations for the replacement of our custom 'CStr' type with the analogous type in the 'core' standard library. This will take place across several cycles to make it easier. For this one, it includes a new 'fmt' module, using upstream method names and some other cleanups. Replace 'fmt!' with a re-export, which helps Clippy lint properly, and clean up the found 'uninlined-format-args' instances. - 'dma' module: - Clarify wording and be consistent in 'coherent' nomenclature. - Convert the 'read!()' and 'write!()' macros to return a 'Result'. - Add 'as_slice()', 'write()' methods in 'CoherentAllocation'. - Expose 'count()' and 'size()' in 'CoherentAllocation' and add the corresponding type invariants. - Implement 'CoherentAllocation::dma_handle_with_offset()'. - 'time' module: - Make 'Instant' generic over clock source. This allows the compiler to assert that arithmetic expressions involving the 'Instant' use 'Instants' based on the same clock source. - Make 'HrTimer' generic over the timer mode. 'HrTimer' timers take a 'Duration' or an 'Instant' when setting the expiry time, depending on the timer mode. With this change, the compiler can check the type matches the timer mode. - Add an abstraction for 'fsleep'. 'fsleep' is a flexible sleep function that will select an appropriate sleep method depending on the requested sleep time. - Avoid 64-bit divisions on 32-bit hardware when calculating timestamps. - Seal the 'HrTimerMode' trait. This prevents users of the 'HrTimerMode' from implementing the trait on their own types. - Pass the correct timer mode ID to 'hrtimer_start_range_ns()'. - 'list' module: remove 'OFFSET' constants, allowing to remove pointer arithmetic; now 'impl_list_item!' invokes 'impl_has_list_links!' or 'impl_has_list_links_self_ptr!'. Other simplifications too. - 'types' module: remove 'ForeignOwnable::PointedTo' in favor of a constant, which avoids exposing the type of the opaque pointer, and require 'into_foreign' to return non-null. Remove the 'Either<L, R>' type as well. It is unused, and we want to encourage the use of custom enums for concrete use cases. - 'sync' module: implement 'Borrow' and 'BorrowMut' for 'Arc' types to allow them to be used in generic APIs. - 'alloc' module: implement 'Borrow' and 'BorrowMut' for 'Box<T, A>'; and 'Borrow', 'BorrowMut' and 'Default' for 'Vec<T, A>'. - 'Opaque' type: add 'cast_from' method to perform a restricted cast that cannot change the inner type and use it in callers of 'container_of!'. Rename 'raw_get' to 'cast_into' to match it. - 'rbtree' module: add 'is_empty' method. - 'sync' module: new 'aref' submodule to hold 'AlwaysRefCounted' and 'ARef', which are moved from the too general 'types' module which we want to reduce or eventually remove. Also fix a safety comment in 'static_lock_class'. 'pin-init' crate: - Add 'impl<T, E> [Pin]Init<T, E> for Result<T, E>', so results are now (pin-)initializers. - Add 'Zeroable::init_zeroed()' that delegates to 'init_zeroed()'. - New 'zeroed()', a safe version of 'mem::zeroed()' and also provide it via 'Zeroable::zeroed()'. - Implement 'Zeroable' for 'Option<&T>', 'Option<&mut T>' and for 'Option<[unsafe] [extern "abi"] fn(...args...) -> ret>' for '"Rust"' and '"C"' ABIs and up to 20 arguments. - Changed blanket impls of 'Init' and 'PinInit' from 'impl<T, E> [Pin]Init<T, E> for T' to 'impl<T> [Pin]Init<T> for T'. - Renamed 'zeroed()' to 'init_zeroed()'. - Upstream dev news: improve CI more to deny warnings, use '--all-targets'. Check the synchronization status of the two '-next' branches in upstream and the kernel. MAINTAINERS: - Add Vlastimil Babka, Liam R. Howlett, Uladzislau Rezki and Lorenzo Stoakes as reviewers (thanks everyone). And a few other cleanups and improvements. -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEPjU5OPd5QIZ9jqqOGXyLc2htIW0FAmiOWREACgkQGXyLc2ht IW39Ig/9E0ExSiBgNKdkCOaULMq31wAxnu3iWoVVisFndlh/Inv+JlaLrmA57BCi xXgBwVZ1GoMsG8Fzt6gT+gyhGYi8waNd+5KXr/WJZVTaJ9v1KpdvxuCnSz0DjCbk GaKfAfxvJ5GAOEwiIIX8X0TFu6kx911DCJY387/VrqZQ7Msh1QSM3tcZeir/EV4w lPjUdlOh1FnLJLI9CGuW20d1IhQUP7K3pdoywgJPpCZV0I8QCyMlMqCEael8Tw2S r/PzRaQtiIzk5HTx06V8paK+nEn0K2vQXqW2kV56Y6TNm1Zcv6dES/8hCITsISs2 nwney3vXEwvoZX+YkQRffZddY4i6YenWMrtLgVxZzdshBL3bn6eHqBL04Nfix+p7 pQe3qMH3G8UBtX1lugBE7RrWGWcz9ARN8sK12ClmpAUnKJOwTpo97kpqXP7pDme8 Buh/oV3voAMsqwooSbVBzuUUWnbGaQ5Oj6CiiosSadfNh6AxJLYLKHtRLKJHZEw3 0Ob/1HhoWS6JSvYKVjMyD19qcH7O8ThZE+83CfMAkI4KphXJarWhpSmN4cHkFn/v 0clQ7Y5m+up9v1XWTaEq0Biqa6CaxLQwm/qW5WU0Y/TiovmvxAFdCwsQqDkRoJNx 9kNfMJRvNl78KQxrjEDz9gl7/ajgqX1KkqP8CQbGjv29cGzFlVE= =5Wt9 -----END PGP SIGNATURE----- Merge tag 'rust-6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux Pull Rust updates from Miguel Ojeda: "Toolchain and infrastructure: - Enable a set of Clippy lints: 'ptr_as_ptr', 'ptr_cast_constness', 'as_ptr_cast_mut', 'as_underscore', 'cast_lossless' and 'ref_as_ptr' These are intended to avoid type casts with the 'as' operator, which are quite powerful, into restricted variants that are less powerful and thus should help to avoid mistakes - Remove the 'author' key now that most instances were moved to the plural one in the previous cycle 'kernel' crate: - New 'bug' module: add 'warn_on!' macro which reuses the existing 'BUG'/'WARN' infrastructure, i.e. it respects the usual sysctls and kernel parameters: warn_on!(value == 42); To avoid duplicating the assembly code, the same strategy is followed as for the static branch code in order to share the assembly between both C and Rust This required a few rearrangements on C arch headers -- the existing C macros should still generate the same outputs, thus no functional change expected there - 'workqueue' module: add delayed work items, including a 'DelayedWork' struct, a 'impl_has_delayed_work!' macro and an 'enqueue_delayed' method, e.g.: /// Enqueue the struct for execution on the system workqueue, /// where its value will be printed 42 jiffies later. fn print_later(value: Arc<MyStruct>) { let _ = workqueue::system().enqueue_delayed(value, 42); } - New 'bits' module: add support for 'bit' and 'genmask' functions, with runtime- and compile-time variants, e.g.: static_assert!(0b00010000 == bit_u8(4)); static_assert!(0b00011110 == genmask_u8(1..=4)); assert!(checked_bit_u32(u32::BITS).is_none()); - 'uaccess' module: add 'UserSliceReader::strcpy_into_buf', which reads NUL-terminated strings from userspace into a '&CStr' Introduce 'UserPtr' newtype, similar in purpose to '__user' in C, to minimize mistakes handling userspace pointers, including mixing them up with integers and leaking them via the 'Debug' trait. Add it to the prelude, too - Start preparations for the replacement of our custom 'CStr' type with the analogous type in the 'core' standard library. This will take place across several cycles to make it easier. For this one, it includes a new 'fmt' module, using upstream method names and some other cleanups Replace 'fmt!' with a re-export, which helps Clippy lint properly, and clean up the found 'uninlined-format-args' instances - 'dma' module: - Clarify wording and be consistent in 'coherent' nomenclature - Convert the 'read!()' and 'write!()' macros to return a 'Result' - Add 'as_slice()', 'write()' methods in 'CoherentAllocation' - Expose 'count()' and 'size()' in 'CoherentAllocation' and add the corresponding type invariants - Implement 'CoherentAllocation::dma_handle_with_offset()' - 'time' module: - Make 'Instant' generic over clock source. This allows the compiler to assert that arithmetic expressions involving the 'Instant' use 'Instants' based on the same clock source - Make 'HrTimer' generic over the timer mode. 'HrTimer' timers take a 'Duration' or an 'Instant' when setting the expiry time, depending on the timer mode. With this change, the compiler can check the type matches the timer mode - Add an abstraction for 'fsleep'. 'fsleep' is a flexible sleep function that will select an appropriate sleep method depending on the requested sleep time - Avoid 64-bit divisions on 32-bit hardware when calculating timestamps - Seal the 'HrTimerMode' trait. This prevents users of the 'HrTimerMode' from implementing the trait on their own types - Pass the correct timer mode ID to 'hrtimer_start_range_ns()' - 'list' module: remove 'OFFSET' constants, allowing to remove pointer arithmetic; now 'impl_list_item!' invokes 'impl_has_list_links!' or 'impl_has_list_links_self_ptr!'. Other simplifications too - 'types' module: remove 'ForeignOwnable::PointedTo' in favor of a constant, which avoids exposing the type of the opaque pointer, and require 'into_foreign' to return non-null Remove the 'Either<L, R>' type as well. It is unused, and we want to encourage the use of custom enums for concrete use cases - 'sync' module: implement 'Borrow' and 'BorrowMut' for 'Arc' types to allow them to be used in generic APIs - 'alloc' module: implement 'Borrow' and 'BorrowMut' for 'Box<T, A>'; and 'Borrow', 'BorrowMut' and 'Default' for 'Vec<T, A>' - 'Opaque' type: add 'cast_from' method to perform a restricted cast that cannot change the inner type and use it in callers of 'container_of!'. Rename 'raw_get' to 'cast_into' to match it - 'rbtree' module: add 'is_empty' method - 'sync' module: new 'aref' submodule to hold 'AlwaysRefCounted' and 'ARef', which are moved from the too general 'types' module which we want to reduce or eventually remove. Also fix a safety comment in 'static_lock_class' 'pin-init' crate: - Add 'impl<T, E> [Pin]Init<T, E> for Result<T, E>', so results are now (pin-)initializers - Add 'Zeroable::init_zeroed()' that delegates to 'init_zeroed()' - New 'zeroed()', a safe version of 'mem::zeroed()' and also provide it via 'Zeroable::zeroed()' - Implement 'Zeroable' for 'Option<&T>', 'Option<&mut T>' and for 'Option<[unsafe] [extern "abi"] fn(...args...) -> ret>' for '"Rust"' and '"C"' ABIs and up to 20 arguments - Changed blanket impls of 'Init' and 'PinInit' from 'impl<T, E> [Pin]Init<T, E> for T' to 'impl<T> [Pin]Init<T> for T' - Renamed 'zeroed()' to 'init_zeroed()' - Upstream dev news: improve CI more to deny warnings, use '--all-targets'. Check the synchronization status of the two '-next' branches in upstream and the kernel MAINTAINERS: - Add Vlastimil Babka, Liam R. Howlett, Uladzislau Rezki and Lorenzo Stoakes as reviewers (thanks everyone) And a few other cleanups and improvements" * tag 'rust-6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux: (76 commits) rust: Add warn_on macro arm64/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing with Rust riscv/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing with Rust x86/bug: Add ARCH_WARN_ASM macro for BUG/WARN asm code sharing with Rust rust: kernel: move ARef and AlwaysRefCounted to sync::aref rust: sync: fix safety comment for `static_lock_class` rust: types: remove `Either<L, R>` rust: kernel: use `core::ffi::CStr` method names rust: str: add `CStr` methods matching `core::ffi::CStr` rust: str: remove unnecessary qualification rust: use `kernel::{fmt,prelude::fmt!}` rust: kernel: add `fmt` module rust: kernel: remove `fmt!`, fix clippy::uninlined-format-args scripts: rust: emit path candidates in panic message scripts: rust: replace length checks with match rust: list: remove nonexistent generic parameter in link rust: bits: add support for bits/genmask macros rust: list: remove OFFSET constants rust: list: add `impl_list_item!` examples rust: list: use fully qualified path ...
2025-08-03 13:49:10 -07:00
rust: scatterlist: Add abstraction for sg_table Add a safe Rust abstraction for the kernel's scatter-gather list facilities (`struct scatterlist` and `struct sg_table`). This commit introduces `SGTable<T>`, a wrapper that uses a generic parameter to provide compile-time guarantees about ownership and lifetime. The abstraction provides two primary states: - `SGTable<Owned<P>>`: Represents a table whose resources are fully managed by Rust. It takes ownership of a page provider `P`, allocates the underlying `struct sg_table`, maps it for DMA, and handles all cleanup automatically upon drop. The DMA mapping's lifetime is tied to the associated device using `Devres`, ensuring it is correctly unmapped before the device is unbound. - `SGTable<Borrowed>` (or just `SGTable`): A zero-cost representation of an externally managed `struct sg_table`. It is created from a raw pointer using `SGTable::from_raw()` and provides a lifetime-bound reference (`&'a SGTable`) for operations like iteration. The API exposes a safe iterator that yields `&SGEntry` references, allowing drivers to easily access the DMA address and length of each segment in the list. Reviewed-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Alexandre Courbot <acourbot@nvidia.com> Tested-by: Alexandre Courbot <acourbot@nvidia.com> Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com> Reviewed-by: Lyude Paul <lyude@redhat.com> Co-developed-by: Abdiel Janulgue <abdiel.janulgue@gmail.com> Signed-off-by: Abdiel Janulgue <abdiel.janulgue@gmail.com> Link: https://lore.kernel.org/r/20250828133323.53311-4-dakr@kernel.org Signed-off-by: Danilo Krummrich <dakr@kernel.org>
2025-08-28 15:32:16 +02:00