This crate contains all the procedural macros ("proc macros")
shared by all the kernel.
Procedural macros allow to create syntax extensions. They run at
compile-time and can consume as well as produce Rust syntax.
For instance, the `module!` macro that is used by Rust modules
is implemented here. It allows to easily declare the equivalent
information to the `MODULE_*` macros in C modules, e.g.:
module! {
type: RustMinimal,
name: b"rust_minimal",
author: b"Rust for Linux Contributors",
description: b"Rust minimal sample",
license: b"GPL",
}
Co-developed-by: Alex Gaynor <[email protected]>
Signed-off-by: Alex Gaynor <[email protected]>
Co-developed-by: Finn Behrens <[email protected]>
Signed-off-by: Finn Behrens <[email protected]>
Co-developed-by: Adam Bratschi-Kaye <[email protected]>
Signed-off-by: Adam Bratschi-Kaye <[email protected]>
Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Co-developed-by: Sumera Priyadarsini <[email protected]>
Signed-off-by: Sumera Priyadarsini <[email protected]>
Co-developed-by: Gary Guo <[email protected]>
Signed-off-by: Gary Guo <[email protected]>
Co-developed-by: Matthew Bakhtiari <[email protected]>
Signed-off-by: Matthew Bakhtiari <[email protected]>
Co-developed-by: Björn Roy Baron <[email protected]>
Signed-off-by: Björn Roy Baron <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
---
rust/macros/helpers.rs | 51 ++++++++
rust/macros/lib.rs | 72 +++++++++++
rust/macros/module.rs | 282 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 405 insertions(+)
create mode 100644 rust/macros/helpers.rs
create mode 100644 rust/macros/lib.rs
create mode 100644 rust/macros/module.rs
diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs
new file mode 100644
index 000000000000..cdc7dc6135d2
--- /dev/null
+++ b/rust/macros/helpers.rs
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use proc_macro::{token_stream, TokenTree};
+
+pub(crate) fn try_ident(it: &mut token_stream::IntoIter) -> Option<String> {
+ if let Some(TokenTree::Ident(ident)) = it.next() {
+ Some(ident.to_string())
+ } else {
+ None
+ }
+}
+
+pub(crate) fn try_literal(it: &mut token_stream::IntoIter) -> Option<String> {
+ if let Some(TokenTree::Literal(literal)) = it.next() {
+ Some(literal.to_string())
+ } else {
+ None
+ }
+}
+
+pub(crate) fn try_byte_string(it: &mut token_stream::IntoIter) -> Option<String> {
+ try_literal(it).and_then(|byte_string| {
+ if byte_string.starts_with("b\"") && byte_string.ends_with('\"') {
+ Some(byte_string[2..byte_string.len() - 1].to_string())
+ } else {
+ None
+ }
+ })
+}
+
+pub(crate) fn expect_ident(it: &mut token_stream::IntoIter) -> String {
+ try_ident(it).expect("Expected Ident")
+}
+
+pub(crate) fn expect_punct(it: &mut token_stream::IntoIter) -> char {
+ if let TokenTree::Punct(punct) = it.next().expect("Reached end of token stream for Punct") {
+ punct.as_char()
+ } else {
+ panic!("Expected Punct");
+ }
+}
+
+pub(crate) fn expect_byte_string(it: &mut token_stream::IntoIter) -> String {
+ try_byte_string(it).expect("Expected byte string")
+}
+
+pub(crate) fn expect_end(it: &mut token_stream::IntoIter) {
+ if it.next().is_some() {
+ panic!("Expected end");
+ }
+}
diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
new file mode 100644
index 000000000000..91764bfb1f89
--- /dev/null
+++ b/rust/macros/lib.rs
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Crate for all kernel procedural macros.
+
+mod helpers;
+mod module;
+
+use proc_macro::TokenStream;
+
+/// Declares a kernel module.
+///
+/// The `type` argument should be a type which implements the [`Module`]
+/// trait. Also accepts various forms of kernel metadata.
+///
+/// C header: [`include/linux/moduleparam.h`](../../../include/linux/moduleparam.h)
+///
+/// [`Module`]: ../kernel/trait.Module.html
+///
+/// # Examples
+///
+/// ```ignore
+/// use kernel::prelude::*;
+///
+/// module!{
+/// type: MyModule,
+/// name: b"my_kernel_module",
+/// author: b"Rust for Linux Contributors",
+/// description: b"My very own kernel module!",
+/// license: b"GPL",
+/// params: {
+/// my_i32: i32 {
+/// default: 42,
+/// permissions: 0o000,
+/// description: b"Example of i32",
+/// },
+/// writeable_i32: i32 {
+/// default: 42,
+/// permissions: 0o644,
+/// description: b"Example of i32",
+/// },
+/// },
+/// }
+///
+/// struct MyModule;
+///
+/// impl kernel::Module for MyModule {
+/// fn init() -> Result<Self> {
+/// // If the parameter is writeable, then the kparam lock must be
+/// // taken to read the parameter:
+/// {
+/// let lock = THIS_MODULE.kernel_param_lock();
+/// pr_info!("i32 param is: {}\n", writeable_i32.read(&lock));
+/// }
+/// // If the parameter is read only, it can be read without locking
+/// // the kernel parameters:
+/// pr_info!("i32 param is: {}\n", my_i32.read());
+/// Ok(Self)
+/// }
+/// }
+/// ```
+///
+/// # Supported argument types
+/// - `type`: type which implements the [`Module`] trait (required).
+/// - `name`: byte array of the name of the kernel module (required).
+/// - `author`: byte array of the author of the kernel module.
+/// - `description`: byte array of the description of the kernel module.
+/// - `license`: byte array of the license of the kernel module (required).
+/// - `alias`: byte array of alias name of the kernel module.
+#[proc_macro]
+pub fn module(ts: TokenStream) -> TokenStream {
+ module::module(ts)
+}
diff --git a/rust/macros/module.rs b/rust/macros/module.rs
new file mode 100644
index 000000000000..186a5b8be23c
--- /dev/null
+++ b/rust/macros/module.rs
@@ -0,0 +1,282 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use crate::helpers::*;
+use proc_macro::{token_stream, Literal, TokenStream, TokenTree};
+use std::fmt::Write;
+
+struct ModInfoBuilder<'a> {
+ module: &'a str,
+ counter: usize,
+ buffer: String,
+}
+
+impl<'a> ModInfoBuilder<'a> {
+ fn new(module: &'a str) -> Self {
+ ModInfoBuilder {
+ module,
+ counter: 0,
+ buffer: String::new(),
+ }
+ }
+
+ fn emit_base(&mut self, field: &str, content: &str, builtin: bool) {
+ let string = if builtin {
+ // Built-in modules prefix their modinfo strings by `module.`.
+ format!(
+ "{module}.{field}={content}\0",
+ module = self.module,
+ field = field,
+ content = content
+ )
+ } else {
+ // Loadable modules' modinfo strings go as-is.
+ format!("{field}={content}\0", field = field, content = content)
+ };
+
+ write!(
+ &mut self.buffer,
+ "
+ {cfg}
+ #[doc(hidden)]
+ #[link_section = \".modinfo\"]
+ #[used]
+ pub static __{module}_{counter}: [u8; {length}] = *{string};
+ ",
+ cfg = if builtin {
+ "#[cfg(not(MODULE))]"
+ } else {
+ "#[cfg(MODULE)]"
+ },
+ module = self.module.to_uppercase(),
+ counter = self.counter,
+ length = string.len(),
+ string = Literal::byte_string(string.as_bytes()),
+ )
+ .unwrap();
+
+ self.counter += 1;
+ }
+
+ fn emit_only_builtin(&mut self, field: &str, content: &str) {
+ self.emit_base(field, content, true)
+ }
+
+ fn emit_only_loadable(&mut self, field: &str, content: &str) {
+ self.emit_base(field, content, false)
+ }
+
+ fn emit(&mut self, field: &str, content: &str) {
+ self.emit_only_builtin(field, content);
+ self.emit_only_loadable(field, content);
+ }
+}
+
+#[derive(Debug, Default)]
+struct ModuleInfo {
+ type_: String,
+ license: String,
+ name: String,
+ author: Option<String>,
+ description: Option<String>,
+ alias: Option<String>,
+}
+
+impl ModuleInfo {
+ fn parse(it: &mut token_stream::IntoIter) -> Self {
+ let mut info = ModuleInfo::default();
+
+ const EXPECTED_KEYS: &[&str] =
+ &["type", "name", "author", "description", "license", "alias"];
+ const REQUIRED_KEYS: &[&str] = &["type", "name", "license"];
+ let mut seen_keys = Vec::new();
+
+ loop {
+ let key = match it.next() {
+ Some(TokenTree::Ident(ident)) => ident.to_string(),
+ Some(_) => panic!("Expected Ident or end"),
+ None => break,
+ };
+
+ if seen_keys.contains(&key) {
+ panic!(
+ "Duplicated key \"{}\". Keys can only be specified once.",
+ key
+ );
+ }
+
+ assert_eq!(expect_punct(it), ':');
+
+ match key.as_str() {
+ "type" => info.type_ = expect_ident(it),
+ "name" => info.name = expect_byte_string(it),
+ "author" => info.author = Some(expect_byte_string(it)),
+ "description" => info.description = Some(expect_byte_string(it)),
+ "license" => info.license = expect_byte_string(it),
+ "alias" => info.alias = Some(expect_byte_string(it)),
+ _ => panic!(
+ "Unknown key \"{}\". Valid keys are: {:?}.",
+ key, EXPECTED_KEYS
+ ),
+ }
+
+ assert_eq!(expect_punct(it), ',');
+
+ seen_keys.push(key);
+ }
+
+ expect_end(it);
+
+ for key in REQUIRED_KEYS {
+ if !seen_keys.iter().any(|e| e == key) {
+ panic!("Missing required key \"{}\".", key);
+ }
+ }
+
+ let mut ordered_keys: Vec<&str> = Vec::new();
+ for key in EXPECTED_KEYS {
+ if seen_keys.iter().any(|e| e == key) {
+ ordered_keys.push(key);
+ }
+ }
+
+ if seen_keys != ordered_keys {
+ panic!(
+ "Keys are not ordered as expected. Order them like: {:?}.",
+ ordered_keys
+ );
+ }
+
+ info
+ }
+}
+
+pub(crate) fn module(ts: TokenStream) -> TokenStream {
+ let mut it = ts.into_iter();
+
+ let info = ModuleInfo::parse(&mut it);
+
+ let mut modinfo = ModInfoBuilder::new(info.name.as_ref());
+ if let Some(author) = info.author {
+ modinfo.emit("author", &author);
+ }
+ if let Some(description) = info.description {
+ modinfo.emit("description", &description);
+ }
+ modinfo.emit("license", &info.license);
+ if let Some(alias) = info.alias {
+ modinfo.emit("alias", &alias);
+ }
+
+ // Built-in modules also export the `file` modinfo string.
+ let file =
+ std::env::var("RUST_MODFILE").expect("Unable to fetch RUST_MODFILE environmental variable");
+ modinfo.emit_only_builtin("file", &file);
+
+ format!(
+ "
+ /// The module name.
+ ///
+ /// Used by the printing macros, e.g. [`info!`].
+ const __LOG_PREFIX: &[u8] = b\"{name}\\0\";
+
+ /// The \"Rust loadable module\" mark, for `scripts/is_rust_module.sh`.
+ //
+ // This may be best done another way later on, e.g. as a new modinfo
+ // key or a new section. For the moment, keep it simple.
+ #[cfg(MODULE)]
+ #[doc(hidden)]
+ #[used]
+ static __IS_RUST_MODULE: () = ();
+
+ static mut __MOD: Option<{type_}> = None;
+
+ // SAFETY: `__this_module` is constructed by the kernel at load time and will not be
+ // freed until the module is unloaded.
+ #[cfg(MODULE)]
+ static THIS_MODULE: kernel::ThisModule = unsafe {{
+ kernel::ThisModule::from_ptr(&kernel::bindings::__this_module as *const _ as *mut _)
+ }};
+ #[cfg(not(MODULE))]
+ static THIS_MODULE: kernel::ThisModule = unsafe {{
+ kernel::ThisModule::from_ptr(core::ptr::null_mut())
+ }};
+
+ // Loadable modules need to export the `{{init,cleanup}}_module` identifiers.
+ #[cfg(MODULE)]
+ #[doc(hidden)]
+ #[no_mangle]
+ pub extern \"C\" fn init_module() -> core::ffi::c_int {{
+ __init()
+ }}
+
+ #[cfg(MODULE)]
+ #[doc(hidden)]
+ #[no_mangle]
+ pub extern \"C\" fn cleanup_module() {{
+ __exit()
+ }}
+
+ // Built-in modules are initialized through an initcall pointer
+ // and the identifiers need to be unique.
+ #[cfg(not(MODULE))]
+ #[cfg(not(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS))]
+ #[doc(hidden)]
+ #[link_section = \"{initcall_section}\"]
+ #[used]
+ pub static __{name}_initcall: extern \"C\" fn() -> core::ffi::c_int = __{name}_init;
+
+ #[cfg(not(MODULE))]
+ #[cfg(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)]
+ core::arch::global_asm!(
+ r#\".section \"{initcall_section}\", \"a\"
+ __{name}_initcall:
+ .long __{name}_init - .
+ .previous
+ \"#
+ );
+
+ #[cfg(not(MODULE))]
+ #[doc(hidden)]
+ #[no_mangle]
+ pub extern \"C\" fn __{name}_init() -> core::ffi::c_int {{
+ __init()
+ }}
+
+ #[cfg(not(MODULE))]
+ #[doc(hidden)]
+ #[no_mangle]
+ pub extern \"C\" fn __{name}_exit() {{
+ __exit()
+ }}
+
+ fn __init() -> core::ffi::c_int {{
+ match <{type_} as kernel::Module>::init(&THIS_MODULE) {{
+ Ok(m) => {{
+ unsafe {{
+ __MOD = Some(m);
+ }}
+ return 0;
+ }}
+ Err(e) => {{
+ return e.to_kernel_errno();
+ }}
+ }}
+ }}
+
+ fn __exit() {{
+ unsafe {{
+ // Invokes `drop()` on `__MOD`, which should be used for cleanup.
+ __MOD = None;
+ }}
+ }}
+
+ {modinfo}
+ ",
+ type_ = info.type_,
+ name = info.name,
+ modinfo = modinfo.buffer,
+ initcall_section = ".initcall6.init"
+ )
+ .parse()
+ .expect("Error parsing formatted string into token stream.")
+}
--
2.37.3
On Tue, Sep 27, 2022 at 03:14:41PM +0200, Miguel Ojeda wrote:
[...]
> For instance, the `module!` macro that is used by Rust modules
> is implemented here. It allows to easily declare the equivalent
> information to the `MODULE_*` macros in C modules, e.g.:
>
> module! {
> type: RustMinimal,
> name: b"rust_minimal",
> author: b"Rust for Linux Contributors",
> description: b"Rust minimal sample",
> license: b"GPL",
> }
[...]
I remember that there was a switch from &u8 to &str on master branch a
while ago. Why this patch was reverted? Strings are really better here.
On Tue, Sep 27, 2022 at 04:48:05PM +0300, Konstantin Shelekhin wrote:
> On Tue, Sep 27, 2022 at 03:14:41PM +0200, Miguel Ojeda wrote:
> [...]
> > For instance, the `module!` macro that is used by Rust modules
> > is implemented here. It allows to easily declare the equivalent
> > information to the `MODULE_*` macros in C modules, e.g.:
> >
> > module! {
> > type: RustMinimal,
> > name: b"rust_minimal",
> > author: b"Rust for Linux Contributors",
> > description: b"Rust minimal sample",
> > license: b"GPL",
> > }
> [...]
>
> I remember that there was a switch from &u8 to &str on master branch a
> while ago. Why this patch was reverted? Strings are really better here.
ASCII versus UTF8
Groeten
Geert Stappers
--
Silence is hard to parse
On Tue, Sep 27, 2022 at 3:48 PM Konstantin Shelekhin
<[email protected]> wrote:
>
> I remember that there was a switch from &u8 to &str on master branch a
> while ago. Why this patch was reverted? Strings are really better here.
It was not reverted; but it was merged right after v8. Then v9 was a
trimmed v8 and v10 is intended to resolve a few last nits from v9.
In other words, there are many changes (including the vast majority of
the `kernel` crate) that will come afterwards.
Please see the cover letter(s) for details.
Cheers,
Miguel
On Tue, Sep 27, 2022 at 03:14:41PM +0200, Miguel Ojeda wrote:
> This crate contains all the procedural macros ("proc macros")
> shared by all the kernel.
>
> Procedural macros allow to create syntax extensions. They run at
> compile-time and can consume as well as produce Rust syntax.
>
> For instance, the `module!` macro that is used by Rust modules
> is implemented here. It allows to easily declare the equivalent
> information to the `MODULE_*` macros in C modules, e.g.:
>
> module! {
> type: RustMinimal,
> name: b"rust_minimal",
> author: b"Rust for Linux Contributors",
> description: b"Rust minimal sample",
> license: b"GPL",
> }
I don't use / know much of procedural macros, so I don't feel like I'm
qualified to review this patch.
Just a general question: what is the house rule for adding new proc
macros? They are powerful tools. I can see their value in `module!`
because writing all that boilerplate by hand is just painful. Yet they
are not straightforward to understand. It is difficult, just by looking
at the macro, to fully grasp what the final code looks like (though the
rsi target will help). Is there a concern that proc macro gets abused?
Thanks,
Wei.
On Wed, Sep 28, 2022 at 5:29 PM Wei Liu <[email protected]> wrote:
>
> Just a general question: what is the house rule for adding new proc
> macros? They are powerful tools. I can see their value in `module!`
> because writing all that boilerplate by hand is just painful. Yet they
> are not straightforward to understand. It is difficult, just by looking
> at the macro, to fully grasp what the final code looks like (though the
> rsi target will help). Is there a concern that proc macro gets abused?
The rule is "use them as last resort". That is, they are not banned,
but they need to be justified: if there is an alternative that is not
too bad (e.g. in terms of ergonomics or implementation), then the
alternative should be used instead.
Nevertheless, sometimes they are very handy. Apart from `module!`
here, we are currently using them in the full repo for vtables [1] and
the Asahi M1 GPU driver is using them for versioning [2].
It is also possible to make proc macros easier to handle, for instance
if we end up deciding to allow utilities like the `syn` crate.
[1] https://github.com/Rust-for-Linux/linux/blob/fcad53ca9071c7bf6a412640a82e679bad6d1cd4/rust/macros/lib.rs#L99-L148
[2] https://github.com/AsahiLinux/linux/blob/3c8982e2c78c219bf96761445c8b73c2b3034fba/drivers/gpu/drm/asahi/fw/buffer.rs#L43-L56
Cheers,
Miguel