[PATCH v7 0/6] rust: extend `module!` macro with integer parameter support

Andreas Hindborg
2025-02-18T13:02:38Z

This series extends the `module!` macro with support module parameters. It
also adds some string to integer parsing functions and updates `BStr` with
a method to strip a string prefix.

This series stated out as code by Adam Bratschi-Kaye lifted from the original
`rust` branch [1].

After a bit of discussion on v3 about whether or not module parameters
is a good idea, it seems that module parameters in Rust has a place
in the kernel for now. This series is a dependency for `rnull`, the Rust
null block driver [2].

---
Module subsystem people: how do you want to handle merging of the patches and
subsequent maintenance of code?

I think we discussed you guys taking this under the current module maintainer
entry? If that is correct, will you add the new files to your entry yourself, or
should I include an update to MAINTAINERS in this series?

If prefer another solution, let me know and we can figure that out.

To: Miguel Ojeda <ojeda@kernel.org>
To: Alex Gaynor <alex.gaynor@gmail.com>
To: Boqun Feng <boqun.feng@gmail.com>
To: Gary Guo <gary@garyguo.net>
To: Björn Roy Baron <bjorn3_gh@protonmail.com>
To: Benno Lossin <benno.lossin@proton.me>
To: Alice Ryhl <aliceryhl@google.com>
To: Masahiro Yamada <masahiroy@kernel.org>
To: Nathan Chancellor <nathan@kernel.org>
To: Nicolas Schier <nicolas@fjasle.eu>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: Trevor Gross <tmgross@umich.edu>
Cc: Adam Bratschi-Kaye <ark.email@gmail.com>
Cc: rust-for-linux@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-kbuild@vger.kernel.org
Cc: Petr Pavlu <petr.pavlu@suse.com>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Daniel Gomez <da.gomez@samsung.com>
Cc: Simona Vetter <simona.vetter@ffwll.ch>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: linux-modules@vger.kernel.org
Link: https://github.com/Rust-for-Linux/linux/tree/bc22545f38d74473cfef3e9fd65432733435b79f [1]
Link: https://git.kernel.org/pub/scm/linux/kernel/git/a.hindborg/linux.git/log/?h=rnull [2]
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>

---
Changes in v7:
- Remove dependency on `pr_warn_once` patches, replace with TODO.
- Rework `ParseInt::from_str` to avoid allocating.
- Add a comment explaining how we parse "0".
- Change trait bound on `Index` impl for `BStr` to match std library approach.
- Link to v6: https://lore.kernel.org/r/20250211-module-params-v3-v6-0-24b297ddc43d@kernel.org

Changes in v6:
- Fix a bug that prevented parsing of negative default values for
parameters in the `module!` macro.
- Fix a bug that prevented parsing zero in `strip_radix`. Also add a
test case for this.
- Add `AsRef<BStr>` for `[u8]` and `BStr`.
- Use `impl AsRef<BStr>` as type of prefix in `BStr::strip_prefix`.
- Link to v5: https://lore.kernel.org/r/20250204-module-params-v3-v5-0-bf5ec2041625@kernel.org

Changes in v5:
- Fix a typo in a safety comment in `set_param`.
- Use a match statement in `parse_int::strip_radix`.
- Add an implementation of `Index` for `BStr`.
- Fix a logic inversion bug where parameters would not be parsed.
- Use `kernel::ffi::c_char` in `set_param` rather than the one in `core`.
- Use `kernel::c_str!` rather than `c"..."` literal in module macro.
- Rebase on v6.14-rc1.
- Link to v4: https://lore.kernel.org/r/20250109-module-params-v3-v4-0-c208bcfbe11f@kernel.org

Changes in v4:
- Add module maintainers to Cc list (sorry)
- Add a few missing [`doc_links`]
- Add panic section to `expect_string_field`
- Fix a typo in safety requirement of `module_params::free`
- Change `assert!` to `pr_warn_once!` in `module_params::set_param`
- Remove `module_params::get_param` and install null pointer instead
- Remove use of the unstable feature `sync_unsafe_cell`
- Link to v3: https://lore.kernel.org/r/20241213-module-params-v3-v3-0-485a015ac2cf@kernel.org

Changes in v3:
- use `SyncUnsafeCell` rather than `static mut` and simplify parameter access
- remove `Display` bound from `ModuleParam`
- automatically generate documentation for `PARAM_OPS_.*`
- remove `as *const _ as *mut_` phrasing
- inline parameter name in struct instantiation in `emit_params`
- move `RacyKernelParam` out of macro template
- use C string literals rather than byte string literals with explicit null
- template out `__{name}_{param_name}` in `emit_param`
- indent template in `emit_params`
- use let-else expression in `emit_params` to get rid of an indentation level
- document `expect_string_field`
- move invication of `impl_int_module_param` to be closer to macro def
- move attributes after docs in `make_param_ops`
- rename `impl_module_param` to impl_int_module_param`
- use `ty` instead of `ident` in `impl_parse_int`
- use `BStr` instead of `&str` for string manipulation
- move string parsing functions to seperate patch and add examples, fix bugs
- degrade comment about future support from doc comment to regular comment
- remove std lib path from `Sized` marker
- update documentation for `trait ModuleParam`
- Link to v2: https://lore.kernel.org/all/20240819133345.3438739-1-nmi@metaspace.dk/

Changes in v2:
- Remove support for params without values (`NOARG_ALLOWED`).
- Improve documentation for `try_from_param_arg`.
- Use prelude import.
- Refactor `try_from_param_arg` to return `Result`.
- Refactor `ParseInt::from_str` to return `Result`.
- Move C callable functions out of `ModuleParam` trait.
- Rename literal string field parser to `expect_string_field`.
- Move parameter parsing from generation to parsing stage.
- Use absolute type paths in macro code.
- Inline `kparam`and `read_func` values.
- Resolve TODO regarding alignment attributes.
- Remove unnecessary unsafe blocks in macro code.
- Improve error message for unrecognized parameter types.
- Do not use `self` receiver when reading parameter value.
- Add parameter documentation to `module!` macro.
- Use empty `enum` for parameter type.
- Use `addr_of_mut` to get address of parameter value variable.
- Enabled building of docs for for `module_param` module.
- Link to v1: https://lore.kernel.org/rust-for-linux/20240705111455.142790-1-nmi@metaspace.dk/

---
Andreas Hindborg (6):
rust: str: implement `PartialEq` for `BStr`
rust: str: implement `Index` for `BStr`
rust: str: implement `AsRef<BStr>` for `[u8]` and `BStr`
rust: str: implement `strip_prefix` for `BStr`
rust: str: add radix prefixed integer parsing functions
rust: add parameter support to the `module!` macro

rust/kernel/lib.rs | 1 +
rust/kernel/module_param.rs | 226 +++++++++++++++++++++++++++++++++++++++++++
rust/kernel/str.rs | 163 +++++++++++++++++++++++++++++++
rust/macros/helpers.rs | 25 +++++
rust/macros/lib.rs | 31 ++++++
rust/macros/module.rs | 191 ++++++++++++++++++++++++++++++++----
samples/rust/rust_minimal.rs | 10 ++
7 files changed, 629 insertions(+), 18 deletions(-)
---
base-commit: 379487e17ca406b47392e7ab6cf35d1c3bacb371
change-id: 20241211-module-params-v3-ae7e5c8d8b5a

Best regards,
--
Andreas Hindborg <a.hindborg@kernel.org>