Merge tag 'rust-v6.1-rc1' of https://github.com/Rust-for-Linux/linux

Pull Rust introductory support from Kees Cook:
 "The tree has a recent base, but has fundamentally been in linux-next
  for a year and a half[1]. It's been updated based on feedback from the
  Kernel Maintainer's Summit, and to gain recent Reviewed-by: tags.

  Miguel is the primary maintainer, with me helping where needed/wanted.
  Our plan is for the tree to switch to the standard non-rebasing
  practice once this initial infrastructure series lands.

  The contents are the absolute minimum to get Rust code building in the
  kernel, with many more interfaces[2] (and drivers - NVMe[3], 9p[4], M1
  GPU[5]) on the way.

  The initial support of Rust-for-Linux comes in roughly 4 areas:

   - Kernel internals (kallsyms expansion for Rust symbols, %pA format)

   - Kbuild infrastructure (Rust build rules and support scripts)

   - Rust crates and bindings for initial minimum viable build

   - Rust kernel documentation and samples

  Rust support has been in linux-next for a year and a half now, and the
  short log doesn't do justice to the number of people who have
  contributed both to the Linux kernel side but also to the upstream
  Rust side to support the kernel's needs. Thanks to these 173 people,
  and many more, who have been involved in all kinds of ways:

  Miguel Ojeda, Wedson Almeida Filho, Alex Gaynor, Boqun Feng, Gary Guo,
  Björn Roy Baron, Andreas Hindborg, Adam Bratschi-Kaye, Benno Lossin,
  Maciej Falkowski, Finn Behrens, Sven Van Asbroeck, Asahi Lina, FUJITA
  Tomonori, John Baublitz, Wei Liu, Geoffrey Thomas, Philip Herron,
  Arthur Cohen, David Faust, Antoni Boucher, Philip Li, Yujie Liu,
  Jonathan Corbet, Greg Kroah-Hartman, Paul E. McKenney, Josh Triplett,
  Kent Overstreet, David Gow, Alice Ryhl, Robin Randhawa, Kees Cook,
  Nick Desaulniers, Matthew Wilcox, Linus Walleij, Joe Perches, Michael
  Ellerman, Petr Mladek, Masahiro Yamada, Arnaldo Carvalho de Melo,
  Andrii Nakryiko, Konstantin Shelekhin, Rasmus Villemoes, Konstantin
  Ryabitsev, Stephen Rothwell, Andy Shevchenko, Sergey Senozhatsky, John
  Paul Adrian Glaubitz, David Laight, Nathan Chancellor, Jonathan
  Cameron, Daniel Latypov, Shuah Khan, Brendan Higgins, Julia Lawall,
  Laurent Pinchart, Geert Uytterhoeven, Akira Yokosawa, Pavel Machek,
  David S. Miller, John Hawley, James Bottomley, Arnd Bergmann,
  Christian Brauner, Dan Robertson, Nicholas Piggin, Zhouyi Zhou, Elena
  Zannoni, Jose E. Marchesi, Leon Romanovsky, Will Deacon, Richard
  Weinberger, Randy Dunlap, Paolo Bonzini, Roland Dreier, Mark Brown,
  Sasha Levin, Ted Ts'o, Steven Rostedt, Jarkko Sakkinen, Michal
  Kubecek, Marco Elver, Al Viro, Keith Busch, Johannes Berg, Jan Kara,
  David Sterba, Connor Kuehl, Andy Lutomirski, Andrew Lunn, Alexandre
  Belloni, Peter Zijlstra, Russell King, Eric W. Biederman, Willy
  Tarreau, Christoph Hellwig, Emilio Cobos Álvarez, Christian Poveda,
  Mark Rousskov, John Ericson, TennyZhuang, Xuanwo, Daniel Paoliello,
  Manish Goregaokar, comex, Josh Stone, Stephan Sokolow, Philipp Krones,
  Guillaume Gomez, Joshua Nelson, Mats Larsen, Marc Poulhiès, Samantha
  Miller, Esteban Blanc, Martin Schmidt, Martin Rodriguez Reboredo,
  Daniel Xu, Viresh Kumar, Bartosz Golaszewski, Vegard Nossum, Milan
  Landaverde, Dariusz Sosnowski, Yuki Okushi, Matthew Bakhtiari, Wu
  XiangCheng, Tiago Lam, Boris-Chengbiao Zhou, Sumera Priyadarsini,
  Viktor Garske, Niklas Mohrin, Nándor István Krácser, Morgan Bartlett,
  Miguel Cano, Léo Lanteri Thauvin, Julian Merkle, Andreas Reindl,
  Jiapeng Chong, Fox Chen, Douglas Su, Antonio Terceiro, SeongJae Park,
  Sergio González Collado, Ngo Iok Ui (Wu Yu Wei), Joshua Abraham,
  Milan, Daniel Kolsoi, ahomescu, Manas, Luis Gerhorst, Li Hongyu,
  Philipp Gesang, Russell Currey, Jalil David Salamé Messina, Jon Olson,
  Raghvender, Angelos, Kaviraj Kanagaraj, Paul Römer, Sladyn Nunes,
  Mauro Baladés, Hsiang-Cheng Yang, Abhik Jain, Hongyu Li, Sean Nash,
  Yuheng Su, Peng Hao, Anhad Singh, Roel Kluin, Sara Saa, Geert
  Stappers, Garrett LeSage, IFo Hancroft, and Linus Torvalds"

Link: https://lwn.net/Articles/849849/ [1]
Link: https://github.com/Rust-for-Linux/linux/commits/rust [2]
Link: https://github.com/metaspace/rust-linux/commit/d88c3744d6cbdf11767e08bad56cbfb67c4c96d0 [3]
Link: https://github.com/wedsonaf/linux/commit/9367032607f7670de0ba1537cf09ab0f4365a338 [4]
Link: https://github.com/AsahiLinux/linux/commits/gpu/rust-wip [5]

* tag 'rust-v6.1-rc1' of https://github.com/Rust-for-Linux/linux: (27 commits)
  MAINTAINERS: Rust
  samples: add first Rust examples
  x86: enable initial Rust support
  docs: add Rust documentation
  Kbuild: add Rust support
  rust: add `.rustfmt.toml`
  scripts: add `is_rust_module.sh`
  scripts: add `rust_is_available.sh`
  scripts: add `generate_rust_target.rs`
  scripts: add `generate_rust_analyzer.py`
  scripts: decode_stacktrace: demangle Rust symbols
  scripts: checkpatch: enable language-independent checks for Rust
  scripts: checkpatch: diagnose uses of `%pA` in the C side as errors
  vsprintf: add new `%pA` format specifier
  rust: export generated symbols
  rust: add `kernel` crate
  rust: add `bindings` crate
  rust: add `macros` crate
  rust: add `compiler_builtins` crate
  rust: adapt `alloc` crate to the kernel
  ...

1 files changed, 198 insertions, 0 deletions

diff --git a/rust/kernel/print.rs b/rust/kernel/print.rs
new file mode 100644
index 000000000000..55db5a1ba752
--- /dev/null
+++ b/rust/kernel/print.rs
@@ -0,0 +1,198 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Printing facilities.
+//!
+//! C header: [`include/linux/printk.h`](../../../../include/linux/printk.h)
+//!
+//! Reference: <https://www.kernel.org/doc/html/latest/core-api/printk-basics.html>
+
+use core::{
+    ffi::{c_char, c_void},
+    fmt,
+};
+
+use crate::str::RawFormatter;
+
+#[cfg(CONFIG_PRINTK)]
+use crate::bindings;
+
+// Called from `vsprintf` with format specifier `%pA`.
+#[no_mangle]
+unsafe fn rust_fmt_argument(buf: *mut c_char, end: *mut c_char, ptr: *const c_void) -> *mut c_char {
+    use fmt::Write;
+    // SAFETY: The C contract guarantees that `buf` is valid if it's less than `end`.
+    let mut w = unsafe { RawFormatter::from_ptrs(buf.cast(), end.cast()) };
+    let _ = w.write_fmt(unsafe { *(ptr as *const fmt::Arguments<'_>) });
+    w.pos().cast()
+}
+
+/// Format strings.
+///
+/// Public but hidden since it should only be used from public macros.
+#[doc(hidden)]
+pub mod format_strings {
+    use crate::bindings;
+
+    /// The length we copy from the `KERN_*` kernel prefixes.
+    const LENGTH_PREFIX: usize = 2;
+
+    /// The length of the fixed format strings.
+    pub const LENGTH: usize = 10;
+
+    /// Generates a fixed format string for the kernel's [`_printk`].
+    ///
+    /// The format string is always the same for a given level, i.e. for a
+    /// given `prefix`, which are the kernel's `KERN_*` constants.
+    ///
+    /// [`_printk`]: ../../../../include/linux/printk.h
+    const fn generate(is_cont: bool, prefix: &[u8; 3]) -> [u8; LENGTH] {
+        // Ensure the `KERN_*` macros are what we expect.
+        assert!(prefix[0] == b'\x01');
+        if is_cont {
+            assert!(prefix[1] == b'c');
+        } else {
+            assert!(prefix[1] >= b'0' && prefix[1] <= b'7');
+        }
+        assert!(prefix[2] == b'\x00');
+
+        let suffix: &[u8; LENGTH - LENGTH_PREFIX] = if is_cont {
+            b"%pA\0\0\0\0\0"
+        } else {
+            b"%s: %pA\0"
+        };
+
+        [
+            prefix[0], prefix[1], suffix[0], suffix[1], suffix[2], suffix[3], suffix[4], suffix[5],
+            suffix[6], suffix[7],
+        ]
+    }
+
+    // Generate the format strings at compile-time.
+    //
+    // This avoids the compiler generating the contents on the fly in the stack.
+    //
+    // Furthermore, `static` instead of `const` is used to share the strings
+    // for all the kernel.
+    pub static EMERG: [u8; LENGTH] = generate(false, bindings::KERN_EMERG);
+    pub static INFO: [u8; LENGTH] = generate(false, bindings::KERN_INFO);
+}
+
+/// Prints a message via the kernel's [`_printk`].
+///
+/// Public but hidden since it should only be used from public macros.
+///
+/// # Safety
+///
+/// The format string must be one of the ones in [`format_strings`], and
+/// the module name must be null-terminated.
+///
+/// [`_printk`]: ../../../../include/linux/_printk.h
+#[doc(hidden)]
+#[cfg_attr(not(CONFIG_PRINTK), allow(unused_variables))]
+pub unsafe fn call_printk(
+    format_string: &[u8; format_strings::LENGTH],
+    module_name: &[u8],
+    args: fmt::Arguments<'_>,
+) {
+    // `_printk` does not seem to fail in any path.
+    #[cfg(CONFIG_PRINTK)]
+    unsafe {
+        bindings::_printk(
+            format_string.as_ptr() as _,
+            module_name.as_ptr(),
+            &args as *const _ as *const c_void,
+        );
+    }
+}
+
+/// Performs formatting and forwards the string to [`call_printk`].
+///
+/// Public but hidden since it should only be used from public macros.
+#[doc(hidden)]
+#[cfg(not(testlib))]
+#[macro_export]
+#[allow(clippy::crate_in_macro_def)]
+macro_rules! print_macro (
+    // The non-continuation cases (most of them, e.g. `INFO`).
+    ($format_string:path, $($arg:tt)+) => (
+        // SAFETY: This hidden macro should only be called by the documented
+        // printing macros which ensure the format string is one of the fixed
+        // ones. All `__LOG_PREFIX`s are null-terminated as they are generated
+        // by the `module!` proc macro or fixed values defined in a kernel
+        // crate.
+        unsafe {
+            $crate::print::call_printk(
+                &$format_string,
+                crate::__LOG_PREFIX,
+                format_args!($($arg)+),
+            );
+        }
+    );
+);
+
+/// Stub for doctests
+#[cfg(testlib)]
+#[macro_export]
+macro_rules! print_macro (
+    ($format_string:path, $e:expr, $($arg:tt)+) => (
+        ()
+    );
+);
+
+// We could use a macro to generate these macros. However, doing so ends
+// up being a bit ugly: it requires the dollar token trick to escape `$` as
+// well as playing with the `doc` attribute. Furthermore, they cannot be easily
+// imported in the prelude due to [1]. So, for the moment, we just write them
+// manually, like in the C side; while keeping most of the logic in another
+// macro, i.e. [`print_macro`].
+//
+// [1]: https://github.com/rust-lang/rust/issues/52234
+
+/// Prints an emergency-level message (level 0).
+///
+/// Use this level if the system is unusable.
+///
+/// Equivalent to the kernel's [`pr_emerg`] macro.
+///
+/// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
+/// `alloc::format!` for information about the formatting syntax.
+///
+/// [`pr_emerg`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_emerg
+/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
+///
+/// # Examples
+///
+/// ```
+/// pr_emerg!("hello {}\n", "there");
+/// ```
+#[macro_export]
+macro_rules! pr_emerg (
+    ($($arg:tt)*) => (
+        $crate::print_macro!($crate::print::format_strings::EMERG, $($arg)*)
+    )
+);
+
+/// Prints an info-level message (level 6).
+///
+/// Use this level for informational messages.
+///
+/// Equivalent to the kernel's [`pr_info`] macro.
+///
+/// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
+/// `alloc::format!` for information about the formatting syntax.
+///
+/// [`pr_info`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_info
+/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
+///
+/// # Examples
+///
+/// ```
+/// pr_info!("hello {}\n", "there");
+/// ```
+#[macro_export]
+#[doc(alias = "print")]
+macro_rules! pr_info (
+    ($($arg:tt)*) => (
+        $crate::print_macro!($crate::print::format_strings::INFO, $($arg)*)
+    )
+);