Merge tag 'rust-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux

Pull Rust updates from Miguel Ojeda:
 "Toolchain and infrastructure:

   - Add support for 'syn'.

     Syn is a parsing library for parsing a stream of Rust tokens into a
     syntax tree of Rust source code.

     Currently this library is geared toward use in Rust procedural
     macros, but contains some APIs that may be useful more generally.

     'syn' allows us to greatly simplify writing complex macros such as
     'pin-init' (Benno has already prepared the 'syn'-based version). We
     will use it in the 'macros' crate too.

     'syn' is the most downloaded Rust crate (according to crates.io),
     and it is also used by the Rust compiler itself. While the amount
     of code is substantial, there should not be many updates needed for
     these crates, and even if there are, they should not be too big,
     e.g. +7k -3k lines across the 3 crates in the last year.

     'syn' requires two smaller dependencies: 'quote' and 'proc-macro2'.
     I only modified their code to remove a third dependency
     ('unicode-ident') and to add the SPDX identifiers. The code can be
     easily verified to exactly match upstream with the provided
     scripts.

     They are all licensed under "Apache-2.0 OR MIT", like the other
     vendored 'alloc' crate we had for a while.

     Please see the merge commit with the cover letter for more context.

   - Allow 'unreachable_pub' and 'clippy::disallowed_names' for
     doctests.

     Examples (i.e. doctests) may want to do things like show public
     items and use names such as 'foo'.

     Nevertheless, we still try to keep examples as close to real code
     as possible (this is part of why running Clippy on doctests is
     important for us, e.g. for safety comments, which userspace Rust
     does not support yet but we are stricter).

  'kernel' crate:

   - Replace our custom 'CStr' type with 'core::ffi::CStr'.

     Using the standard library type reduces our custom code footprint,
     and we retain needed custom functionality through an extension
     trait and a new 'fmt!' macro which replaces the previous 'core'
     import.

     This started in 6.17 and continued in 6.18, and we finally land the
     replacement now. This required quite some stamina from Tamir, who
     split the changes in steps to prepare for the flag day change here.

   - Replace 'kernel::c_str!' with C string literals.

     C string literals were added in Rust 1.77, which produce '&CStr's
     (the 'core' one), so now we can write:

         c"hi"

     instead of:

         c_str!("hi")

   - Add 'num' module for numerical features.

     It includes the 'Integer' trait, implemented for all primitive
     integer types.

     It also includes the 'Bounded' integer wrapping type: an integer
     value that requires only the 'N' least significant bits of the
     wrapped type to be encoded:

         // An unsigned 8-bit integer, of which only the 4 LSBs are used.
         let v = Bounded::<u8, 4>::new::<15>();
         assert_eq!(v.get(), 15);

     'Bounded' is useful to e.g. enforce guarantees when working with
     bitfields that have an arbitrary number of bits.

     Values can also be constructed from simple non-constant expressions
     or, for more complex ones, validated at runtime.

     'Bounded' also comes with comparison and arithmetic operations
     (with both their backing type and other 'Bounded's with a
     compatible backing type), casts to change the backing type,
     extending/shrinking and infallible/fallible conversions from/to
     primitives as applicable.

   - 'rbtree' module: add immutable cursor ('Cursor').

     It enables to use just an immutable tree reference where
     appropriate. The existing fully-featured mutable cursor is renamed
     to 'CursorMut'.

  kallsyms:

   - Fix wrong "big" kernel symbol type read from procfs.

  'pin-init' crate:

   - A couple minor fixes (Benno asked me to pick these patches up for
     him this cycle).

  Documentation:

   - Quick Start guide: add Debian 13 (Trixie).

     Debian Stable is now able to build Linux, since Debian 13 (released
     2025-08-09) packages Rust 1.85.0, which is recent enough.

     We are planning to propose that the minimum supported Rust version
     in Linux follows Debian Stable releases, with Debian 13 being the
     first one we upgrade to, i.e. Rust 1.85.

  MAINTAINERS:

   - Add entry for the new 'num' module.

   - Remove Alex as Rust maintainer: he hasn't had the time to
     contribute for a few years now, so it is a no-op change in
     practice.

  And a few other cleanups and improvements"

* tag 'rust-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux: (53 commits)
  rust: macros: support `proc-macro2`, `quote` and `syn`
  rust: syn: enable support in kbuild
  rust: syn: add `README.md`
  rust: syn: remove `unicode-ident` dependency
  rust: syn: add SPDX License Identifiers
  rust: syn: import crate
  rust: quote: enable support in kbuild
  rust: quote: add `README.md`
  rust: quote: add SPDX License Identifiers
  rust: quote: import crate
  rust: proc-macro2: enable support in kbuild
  rust: proc-macro2: add `README.md`
  rust: proc-macro2: remove `unicode_ident` dependency
  rust: proc-macro2: add SPDX License Identifiers
  rust: proc-macro2: import crate
  rust: kbuild: support using libraries in `rustc_procmacro`
  rust: kbuild: support skipping flags in `rustc_test_library`
  rust: kbuild: add proc macro library support
  rust: kbuild: simplify `--cfg` handling
  rust: kbuild: introduce `core-flags` and `core-skip_flags`
  ...

Author: torvalds

.gitignore

@@ -41,6 +41,7 @@
 *.o.*
 *.patch
 *.pyc
+*.rlib
 *.rmeta
 *.rpm
 *.rsi

Documentation/rust/quick-start.rst

@@ -39,8 +39,8 @@ of the box, e.g.::
 Debian
 ******
 
-Debian Testing and Debian Unstable (Sid), outside of the freeze period, provide
-recent Rust releases and thus they should generally work out of the box, e.g.::
+Debian 13 (Trixie), as well as Testing and Debian Unstable (Sid) provide recent
+Rust releases and thus they should generally work out of the box, e.g.::
 
 	apt install rustc rust-src bindgen rustfmt rust-clippy
 

MAINTAINERS

@@ -22524,7 +22524,6 @@ F:	tools/verification/
 
 RUST
 M:	Miguel Ojeda <[email protected]>
-M:	Alex Gaynor <[email protected]>
 R:	Boqun Feng <[email protected]>
 R:	Gary Guo <[email protected]>
 R:	Björn Roy Baron <[email protected]>
@@ -22561,6 +22560,14 @@ T:	git https://github.com/Rust-for-Linux/linux.git alloc-next
 F:	rust/kernel/alloc.rs
 F:	rust/kernel/alloc/
 
+RUST [NUM]
+M:	Alexandre Courbot <[email protected]>
+R:	Yury Norov <[email protected]>
+L:	[email protected]
+S:	Maintained
+F:	rust/kernel/num.rs
+F:	rust/kernel/num/
+
 RUST [PIN-INIT]
 M:	Benno Lossin <[email protected]>
 L:	[email protected]

Makefile

@@ -1830,10 +1830,17 @@ rusttest: prepare
 	$(Q)$(MAKE) $(build)=rust $@
 
 # Formatting targets
+#
+# Generated files as well as vendored crates are skipped.
 PHONY += rustfmt rustfmtcheck
 
 rustfmt:
 	$(Q)find $(srctree) $(RCS_FIND_IGNORE) \
+		\( \
+			-path $(srctree)/rust/proc-macro2 \
+			-o -path $(srctree)/rust/quote \
+			-o -path $(srctree)/rust/syn \
+		\) -prune -o \
 		-type f -a -name '*.rs' -a ! -name '*generated*' -print \
 		| xargs $(RUSTFMT) $(rustfmt_flags)
 

drivers/android/binder/error.rs

@@ -2,6 +2,7 @@
 
 // Copyright (C) 2025 Google LLC.
 
+use kernel::fmt;
 use kernel::prelude::*;
 
 use crate::defs::*;
@@ -76,8 +77,8 @@ impl From<kernel::alloc::AllocError> for BinderError {
     }
 }
 
-impl core::fmt::Debug for BinderError {
-    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+impl fmt::Debug for BinderError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self.reply {
             BR_FAILED_REPLY => match self.source.as_ref() {
                 Some(source) => f

drivers/android/binder/freeze.rs

@@ -331,7 +331,7 @@ impl Process {
             KVVec::with_capacity(8, GFP_KERNEL).unwrap_or_else(|_err| KVVec::new());
 
         let mut inner = self.lock_with_nodes();
-        let mut curr = inner.nodes.cursor_front();
+        let mut curr = inner.nodes.cursor_front_mut();
         while let Some(cursor) = curr {
             let (key, node) = cursor.current();
             let key = *key;
@@ -345,7 +345,7 @@ impl Process {
                 // Find the node we were looking at and try again. If the set of nodes was changed,
                 // then just proceed to the next node. This is ok because we don't guarantee the
                 // inclusion of nodes that are added or removed in parallel with this operation.
-                curr = inner.nodes.cursor_lower_bound(&key);
+                curr = inner.nodes.cursor_lower_bound_mut(&key);
                 continue;
             }
 

drivers/android/binder/process.rs

@@ -623,7 +623,7 @@ impl Process {
                     "  ref {}: desc {} {}node {debug_id} s {strong} w {weak}",
                     r.debug_id,
                     r.handle,
-                    if dead { "dead " } else { "" },
+                    if dead { "dead " } else { "" }
                 );
             }
         }
@@ -1320,7 +1320,7 @@ impl Process {
         {
             while let Some(node) = {
                 let mut lock = self.inner.lock();
-                lock.nodes.cursor_front().map(|c| c.remove_current().1)
+                lock.nodes.cursor_front_mut().map(|c| c.remove_current().1)
             } {
                 node.to_key_value().1.release();
             }

drivers/android/binder/range_alloc/tree.rs

@@ -207,7 +207,7 @@ impl<T> TreeRangeAllocator<T> {
     }
 
     pub(crate) fn reservation_abort(&mut self, offset: usize) -> Result<FreedRange> {
-        let mut cursor = self.tree.cursor_lower_bound(&offset).ok_or_else(|| {
+        let mut cursor = self.tree.cursor_lower_bound_mut(&offset).ok_or_else(|| {
             pr_warn!(
                 "EINVAL from range_alloc.reservation_abort - offset: {}",
                 offset

drivers/android/binder/stats.rs

@@ -61,7 +61,7 @@ impl BinderStats {
 
 mod strings {
     use core::str::from_utf8_unchecked;
-    use kernel::str::CStr;
+    use kernel::str::{CStr, CStrExt as _};
 
     extern "C" {
         static binder_command_strings: [*const u8; super::BC_COUNT];
@@ -72,7 +72,7 @@ mod strings {
         // SAFETY: Accessing `binder_command_strings` is always safe.
         let c_str_ptr = unsafe { binder_command_strings[i] };
         // SAFETY: The `binder_command_strings` array only contains nul-terminated strings.
-        let bytes = unsafe { CStr::from_char_ptr(c_str_ptr) }.as_bytes();
+        let bytes = unsafe { CStr::from_char_ptr(c_str_ptr) }.to_bytes();
         // SAFETY: The `binder_command_strings` array only contains strings with ascii-chars.
         unsafe { from_utf8_unchecked(bytes) }
     }
@@ -81,7 +81,7 @@ mod strings {
         // SAFETY: Accessing `binder_return_strings` is always safe.
         let c_str_ptr = unsafe { binder_return_strings[i] };
         // SAFETY: The `binder_command_strings` array only contains nul-terminated strings.
-        let bytes = unsafe { CStr::from_char_ptr(c_str_ptr) }.as_bytes();
+        let bytes = unsafe { CStr::from_char_ptr(c_str_ptr) }.to_bytes();
         // SAFETY: The `binder_command_strings` array only contains strings with ascii-chars.
         unsafe { from_utf8_unchecked(bytes) }
     }

drivers/block/rnull/configfs.rs

@@ -1,12 +1,13 @@
 // SPDX-License-Identifier: GPL-2.0
 
 use super::{NullBlkDevice, THIS_MODULE};
-use core::fmt::{Display, Write};
 use kernel::{
     block::mq::gen_disk::{GenDisk, GenDiskBuilder},
     c_str,
     configfs::{self, AttributeOperations},
-    configfs_attrs, new_mutex,
+    configfs_attrs,
+    fmt::{self, Write as _},
+    new_mutex,
     page::PAGE_SIZE,
     prelude::*,
     str::{kstrtobool_bytes, CString},
@@ -99,8 +100,8 @@ impl TryFrom<u8> for IRQMode {
     }
 }
 
-impl Display for IRQMode {
-    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+impl fmt::Display for IRQMode {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Self::None => f.write_str("0")?,
             Self::Soft => f.write_str("1")?,