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rust: add macros crate

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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 <alex.gaynor@gmail.com>
Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com>
Co-developed-by: Finn Behrens <me@kloenk.de>
Signed-off-by: Finn Behrens <me@kloenk.de>
Co-developed-by: Adam Bratschi-Kaye <ark.email@gmail.com>
Signed-off-by: Adam Bratschi-Kaye <ark.email@gmail.com>
Co-developed-by: Wedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com>
Co-developed-by: Sumera Priyadarsini <sylphrenadin@gmail.com>
Signed-off-by: Sumera Priyadarsini <sylphrenadin@gmail.com>
Co-developed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Gary Guo <gary@garyguo.net>
Co-developed-by: Matthew Bakhtiari <dev@mtbk.me>
Signed-off-by: Matthew Bakhtiari <dev@mtbk.me>
Co-developed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Signed-off-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Miguel Ojeda 2021-07-03 16:56:17 +02:00
parent db958dcf88
commit 1fbde52bde
3 changed files with 405 additions and 0 deletions
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51
rust/macros/helpers.rs Normal file
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// 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");
}
}

72
rust/macros/lib.rs Normal file
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// 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)
}

282
rust/macros/module.rs Normal file
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// 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.")
}