Merge tag 'rust-6.10' of https://github.com/Rust-for-Linux/linux

Pull Rust updates from Miguel Ojeda:
 "The most notable change is the drop of the 'alloc' in-tree fork. This
  is nicely reflected in the diffstat as a ~10k lines drop. In turn,
  this makes the version upgrades way simpler and smaller in the future,
  e.g. the latest one in commit 56f64b3 ("rust: upgrade to Rust
  1.78.0").

  More importantly, this increases the chances that a newer compiler
  version just works, which in turn means supporting several compiler
  versions is easier now. Thus we will look into finally setting a
  minimum version in the near future.

  Toolchain and infrastructure:

   - Upgrade to Rust 1.78.0

     This time around, due to how the kernel and Rust schedules have
     aligned, there are two upgrades in fact. These allow us to remove
     one more unstable feature ('offset_of') from the list, among other
     improvements

   - Drop 'alloc' in-tree fork of the standard library crate, which
     means all the unstable features used by 'alloc' (~30 language ones,
     ~60 library ones) are not a concern anymore

   - Support DWARFv5 via the '-Zdwarf-version' flag

   - Support zlib and zstd debuginfo compression via the
     '-Zdebuginfo-compression' flag

  'kernel' crate:

   - Support allocation flags ('GFP_*'), particularly in 'Box' (via
     'BoxExt'), 'Vec' (via 'VecExt'), 'Arc' and 'UniqueArc', as well as
     in the 'init' module APIs

   - Remove usage of the 'allocator_api' unstable feature

   - Remove 'try_' prefix in allocation APIs' names

   - Add 'VecExt' (an extension trait) to be able to drop the 'alloc'
     fork

   - Add the '{make,to}_{upper,lower}case()' methods to 'CStr'/'CString'

   - Add the 'as_ptr' method to 'ThisModule'

   - Add the 'from_raw' method to 'ArcBorrow'

   - Add the 'into_unique_or_drop' method to 'Arc'

   - Display column number in the 'dbg!' macro output by applying the
     equivalent change done to the standard library one

   - Migrate 'Work' to '#[pin_data]' thanks to the changes in the
     'macros' crate, which allows to remove an unsafe call in its 'new'
     associated function

   - Prevent namespacing issues when using the '[try_][pin_]init!'
     macros by changing the generated name of guard variables

   - Make the 'get' method in 'Opaque' const

   - Implement the 'Default' trait for 'LockClassKey'

   - Remove unneeded 'kernel::prelude' imports from doctests

   - Remove redundant imports

  'macros' crate:

   - Add 'decl_generics' to 'parse_generics()' to support default
     values, and use that to allow them in '#[pin_data]'

  Helpers:

   - Trivial English grammar fix

  Documentation:

   - Add section on Rust Kselftests to the 'Testing' document

   - Expand the 'Abstractions vs. bindings' section of the 'General
     Information' document"

* tag 'rust-6.10' of https://github.com/Rust-for-Linux/linux: (31 commits)
  rust: alloc: fix dangling pointer in VecExt<T>::reserve()
  rust: upgrade to Rust 1.78.0
  rust: kernel: remove redundant imports
  rust: sync: implement `Default` for `LockClassKey`
  docs: rust: extend abstraction and binding documentation
  docs: rust: Add instructions for the Rust kselftest
  rust: remove unneeded `kernel::prelude` imports from doctests
  rust: update `dbg!()` to format column number
  rust: helpers: Fix grammar in comment
  rust: init: change the generated name of guard variables
  rust: sync: add `Arc::into_unique_or_drop`
  rust: sync: add `ArcBorrow::from_raw`
  rust: types: Make Opaque::get const
  rust: kernel: remove usage of `allocator_api` unstable feature
  rust: init: update `init` module to take allocation flags
  rust: sync: update `Arc` and `UniqueArc` to take allocation flags
  rust: alloc: update `VecExt` to take allocation flags
  rust: alloc: introduce the `BoxExt` trait
  rust: alloc: introduce allocation flags
  rust: alloc: remove our fork of the `alloc` crate
  ...

Author: torvalds

Documentation/process/changes.rst

@@ -31,7 +31,7 @@ you probably needn't concern yourself with pcmciautils.
 ====================== ===============  ========================================
 GNU C                  5.1              gcc --version
 Clang/LLVM (optional)  13.0.1           clang --version
-Rust (optional)        1.76.0           rustc --version
+Rust (optional)        1.78.0           rustc --version
 bindgen (optional)     0.65.1           bindgen --version
 GNU make               3.82             make --version
 bash                   4.2              bash --version

Documentation/rust/general-information.rst

@@ -64,6 +64,63 @@ but it is intended that coverage is expanded as time goes on. "Leaf" modules
 (e.g. drivers) should not use the C bindings directly. Instead, subsystems
 should provide as-safe-as-possible abstractions as needed.
 
+.. code-block::
+
+	                                                rust/bindings/
+	                                               (rust/helpers.c)
+
+	                                                   include/ -----+ <-+
+	                                                                 |   |
+	  drivers/              rust/kernel/              +----------+ <-+   |
+	    fs/                                           | bindgen  |       |
+	   .../            +-------------------+          +----------+ --+   |
+	                   |    Abstractions   |                         |   |
+	+---------+        | +------+ +------+ |          +----------+   |   |
+	| my_foo  | -----> | | foo  | | bar  | | -------> | Bindings | <-+   |
+	| driver  |  Safe  | | sub- | | sub- | |  Unsafe  |          |       |
+	+---------+        | |system| |system| |          | bindings | <-----+
+	     |             | +------+ +------+ |          |  crate   |       |
+	     |             |   kernel crate    |          +----------+       |
+	     |             +-------------------+                             |
+	     |                                                               |
+	     +------------------# FORBIDDEN #--------------------------------+
+
+The main idea is to encapsulate all direct interaction with the kernel's C APIs
+into carefully reviewed and documented abstractions. Then users of these
+abstractions cannot introduce undefined behavior (UB) as long as:
+
+#. The abstractions are correct ("sound").
+#. Any ``unsafe`` blocks respect the safety contract necessary to call the
+   operations inside the block. Similarly, any ``unsafe impl``\ s respect the
+   safety contract necessary to implement the trait.
+
+Bindings
+~~~~~~~~
+
+By including a C header from ``include/`` into
+``rust/bindings/bindings_helper.h``, the ``bindgen`` tool will auto-generate the
+bindings for the included subsystem. After building, see the ``*_generated.rs``
+output files in the ``rust/bindings/`` directory.
+
+For parts of the C header that ``bindgen`` does not auto generate, e.g. C
+``inline`` functions or non-trivial macros, it is acceptable to add a small
+wrapper function to ``rust/helpers.c`` to make it available for the Rust side as
+well.
+
+Abstractions
+~~~~~~~~~~~~
+
+Abstractions are the layer between the bindings and the in-kernel users. They
+are located in ``rust/kernel/`` and their role is to encapsulate the unsafe
+access to the bindings into an as-safe-as-possible API that they expose to their
+users. Users of the abstractions include things like drivers or file systems
+written in Rust.
+
+Besides the safety aspect, the abstractions are supposed to be "ergonomic", in
+the sense that they turn the C interfaces into "idiomatic" Rust code. Basic
+examples are to turn the C resource acquisition and release into Rust
+constructors and destructors or C integer error codes into Rust's ``Result``\ s.
+
 
 Conditional compilation
 -----------------------

Documentation/rust/testing.rst

@@ -6,10 +6,11 @@ Testing
 This document contains useful information how to test the Rust code in the
 kernel.
 
-There are two sorts of tests:
+There are three sorts of tests:
 
 - The KUnit tests.
 - The ``#[test]`` tests.
+- The Kselftests.
 
 The KUnit tests
 ---------------
@@ -133,3 +134,25 @@ Additionally, there are the ``#[test]`` tests. These can be run using the
 This requires the kernel ``.config`` and downloads external repositories. It
 runs the ``#[test]`` tests on the host (currently) and thus is fairly limited in
 what these tests can test.
+
+The Kselftests
+--------------
+
+Kselftests are also available in the ``tools/testing/selftests/rust`` folder.
+
+The kernel config options required for the tests are listed in the
+``tools/testing/selftests/rust/config`` file and can be included with the aid
+of the ``merge_config.sh`` script::
+
+	./scripts/kconfig/merge_config.sh .config tools/testing/selftests/rust/config
+
+The kselftests are built within the kernel source tree and are intended to
+be executed on a system that is running the same kernel.
+
+Once a kernel matching the source tree has been installed and booted, the
+tests can be compiled and executed using the following command::
+
+	make TARGETS="rust" kselftest
+
+Refer to Documentation/dev-tools/kselftest.rst for the general Kselftest
+documentation.

rust/Makefile

@@ -61,15 +61,9 @@ core-cfgs = \
     --cfg no_fp_fmt_parse
 
 alloc-cfgs = \
-    --cfg no_borrow \
-    --cfg no_fmt \
     --cfg no_global_oom_handling \
-    --cfg no_macros \
     --cfg no_rc \
-    --cfg no_str \
-    --cfg no_string \
-    --cfg no_sync \
-    --cfg no_thin
+    --cfg no_sync
 
 quiet_cmd_rustdoc = RUSTDOC $(if $(rustdoc_host),H, ) $<
       cmd_rustdoc = \
@@ -123,7 +117,7 @@ rustdoc-compiler_builtins: $(src)/compiler_builtins.rs rustdoc-core FORCE
 # due to things that are "configured out" vs. entirely non-existing ones.
 rustdoc-alloc: private rustc_target_flags = $(alloc-cfgs) \
     -Arustdoc::broken_intra_doc_links
-rustdoc-alloc: $(src)/alloc/lib.rs rustdoc-core rustdoc-compiler_builtins FORCE
+rustdoc-alloc: $(RUST_LIB_SRC)/alloc/src/lib.rs rustdoc-core rustdoc-compiler_builtins FORCE
 	+$(call if_changed,rustdoc)
 
 rustdoc-kernel: private rustc_target_flags = --extern alloc \
@@ -218,8 +212,6 @@ rusttest: rusttest-macros rusttest-kernel
 #   - `cargo` only considers the use case of building the standard library
 #     to use it in a given package. Thus we need to create a dummy package
 #     and pick the generated libraries from there.
-#   - Since we only keep a subset of upstream `alloc` in-tree, we need
-#     to recreate it on the fly by putting our sources on top.
 #   - The usual ways of modifying the dependency graph in `cargo` do not seem
 #     to apply for the `-Zbuild-std` steps, thus we have to mislead it
 #     by modifying the sources in the sysroot.
@@ -238,8 +230,6 @@ quiet_cmd_rustsysroot = RUSTSYSROOT
 	rm -rf $(objtree)/$(obj)/test; \
 	mkdir -p $(objtree)/$(obj)/test; \
 	cp -a $(rustc_sysroot) $(objtree)/$(obj)/test/sysroot; \
-	cp -r $(srctree)/$(src)/alloc/* \
-		$(objtree)/$(obj)/test/sysroot/lib/rustlib/src/rust/library/alloc/src; \
 	echo '\#!/bin/sh' > $(objtree)/$(obj)/test/rustc_sysroot; \
 	echo "$(RUSTC) --sysroot=$(abspath $(objtree)/$(obj)/test/sysroot) \"\$$@\"" \
 		>> $(objtree)/$(obj)/test/rustc_sysroot; \
@@ -447,7 +437,7 @@ $(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o FORCE
 $(obj)/alloc.o: private skip_clippy = 1
 $(obj)/alloc.o: private skip_flags = -Dunreachable_pub
 $(obj)/alloc.o: private rustc_target_flags = $(alloc-cfgs)
-$(obj)/alloc.o: $(src)/alloc/lib.rs $(obj)/compiler_builtins.o FORCE
+$(obj)/alloc.o: $(RUST_LIB_SRC)/alloc/src/lib.rs $(obj)/compiler_builtins.o FORCE
 	+$(call if_changed_dep,rustc_library)
 
 $(obj)/build_error.o: $(src)/build_error.rs $(obj)/compiler_builtins.o FORCE