[PATCH v2 00/13] Support several Rust toolchain versions

[PATCH v2 00/13] Support several Rust toolchain versions

[Miguel Ojeda]

Hi all,

A few things improved here and there, and rebased on top of `rust-next`.

The changelog is attached to each patch.

I kept the `Tested-by`s since most of the changes are on documentation
or comments, though I did remove them on the patch that changed the most
just in case (even for that one, I think Benno's and Andreas' setup
would not have made a difference).

I plan to put this series into `rust-next` very soon so that it goes
into the merge window.

Previous cover letter:

  v1: https://lore.kernel.org/rust-for-linux/20240701183625.665574-1-ojeda@kernel.org/

Thanks!

Cheers,
Miguel

Miguel Ojeda (13):
  rust: macros: indent list item in `paste!`'s docs
  rust: init: simplify from `map_err` to `inspect_err`
  rust: allow `dead_code` for never constructed bindings
  rust: relax most deny-level lints to warnings
  rust: simplify Clippy warning flags set
  rust: start supporting several compiler versions
  rust: avoid assuming a particular `bindgen` build
  rust: work around `bindgen` 0.69.0 issue
  rust: start supporting several `bindgen` versions
  rust: warn about `bindgen` versions 0.66.0 and 0.66.1
  kbuild: rust: add `rustc-version` support
  rust: support the new `-Zub-checks` flag
  docs: rust: quick-start: add section on Linux distributions

 Documentation/process/changes.rst        |   9 +-
 Documentation/rust/quick-start.rst       | 136 +++++++++++++++++------
 Makefile                                 |  31 +++---
 init/Kconfig                             |  11 +-
 lib/Kconfig.debug                        |  18 +++
 rust/Makefile                            |   4 +-
 rust/bindings/lib.rs                     |   1 +
 rust/kernel/init.rs                      |  13 +--
 rust/macros/lib.rs                       |   2 +-
 rust/uapi/lib.rs                         |   1 +
 scripts/Kconfig.include                  |   6 +
 scripts/Makefile.compiler                |   4 +
 scripts/rust_is_available.sh             |  33 +++---
 scripts/rust_is_available_bindgen_0_66.h |   2 +
 scripts/rust_is_available_test.py        |  59 ++++++----
 scripts/rustc-version.sh                 |  52 +++++++++
 16 files changed, 274 insertions(+), 108 deletions(-)
 create mode 100644 scripts/rust_is_available_bindgen_0_66.h
 create mode 100755 scripts/rustc-version.sh


base-commit: fc6e66f4696b63b8a2645a2bcea407cb04bd0666
--
2.45.2

[PATCH v2 01/13] rust: macros: indent list item in `paste!`'s docs

[Miguel Ojeda]

A new style lint, `doc_lazy_continuation` [1], has been introduced in the
upcoming Rust 1.80 (currently in beta), which detects missing indentation
in code documentation.

We have one such case:

    error: doc list item missing indentation
    --> rust/macros/lib.rs:315:5
        |
    315 | /// default the span of the `[< >]` group is used.
        |     ^
        |
        = help: if this is supposed to be its own paragraph, add a blank line
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#doc_lazy_continuation
        = note: `-D clippy::doc-lazy-continuation` implied by `-D clippy::style`
        = help: to override `-D clippy::style` add `#[allow(clippy::doc_lazy_continuation)]`
    help: indent this line
        |
    315 | ///   default the span of the `[< >]` group is used.
        |     ++

While the rendering of the docs by `rustdoc` is not affected, we apply
this kind of indentation elsewhere since it looks better.

Thus clean it up.

Link: https://rust-lang.github.io/rust-clippy/master/index.html#/doc_lazy_continuation [1]
Reviewed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Reviewed-by: Finn Behrens <me@kloenk.dev>
Tested-by: Benno Lossin <benno.lossin@proton.me>
Tested-by: Andreas Hindborg <a.hindborg@samsung.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 rust/macros/lib.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
index 6dcc72aff111..159e75292970 100644
--- a/rust/macros/lib.rs
+++ b/rust/macros/lib.rs
@@ -345,7 +345,7 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
 ///
 /// Currently supported modifiers are:
 /// * `span`: change the span of concatenated identifier to the span of the specified token. By
-/// default the span of the `[< >]` group is used.
+///   default the span of the `[< >]` group is used.
 /// * `lower`: change the identifier to lower case.
 /// * `upper`: change the identifier to upper case.
 ///
-- 
2.45.2

[PATCH v2 02/13] rust: init: simplify from `map_err` to `inspect_err`

[Miguel Ojeda]

A new complexity lint, `manual_inspect` [1], has been introduced in
the upcoming Rust 1.81 (currently in nightly), which checks for uses of
`map*` which return the original item:

    error:
    --> rust/kernel/init.rs:846:23
        |
    846 |         (self.1)(val).map_err(|e| {
        |                       ^^^^^^^
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#manual_inspect
        = note: `-D clippy::manual-inspect` implied by `-D warnings`
        = help: to override `-D warnings` add `#[allow(clippy::manual_inspect)]`
    help: try
        |
    846 ~         (self.1)(val).inspect_err(|e| {
    847 |             // SAFETY: `slot` was initialized above.
    848 ~             unsafe { core::ptr::drop_in_place(slot) };
        |

Thus clean them up.

Link: https://rust-lang.github.io/rust-clippy/master/index.html#/manual_inspect [1]
Tested-by: Benno Lossin <benno.lossin@proton.me>
Tested-by: Andreas Hindborg <a.hindborg@samsung.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
v2:
  - Moved `SAFETY` comment out of the closure, in one of the instances
    only. In the other, it would mean putting two `SAFETY` comments in
    a row, which is even more confusing. Open coding it may be clearer,
    though -- happy to get a patch for that later on (with some docs
    about guidelines for using or avoiding `inspect_*`). (Björn, Benno,
    Alice)

 rust/kernel/init.rs | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
index 68605b633e73..495c09ebe3a3 100644
--- a/rust/kernel/init.rs
+++ b/rust/kernel/init.rs
@@ -843,11 +843,8 @@ unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
         let val = unsafe { &mut *slot };
         // SAFETY: `slot` is considered pinned.
         let val = unsafe { Pin::new_unchecked(val) };
-        (self.1)(val).map_err(|e| {
-            // SAFETY: `slot` was initialized above.
-            unsafe { core::ptr::drop_in_place(slot) };
-            e
-        })
+        // SAFETY: `slot` was initialized above.
+        (self.1)(val).inspect_err(|_| unsafe { core::ptr::drop_in_place(slot) })
     }
 }

@@ -941,11 +938,9 @@ unsafe fn __init(self, slot: *mut T) -> Result<(), E> {
         // SAFETY: All requirements fulfilled since this function is `__init`.
         unsafe { self.0.__pinned_init(slot)? };
         // SAFETY: The above call initialized `slot` and we still have unique access.
-        (self.1)(unsafe { &mut *slot }).map_err(|e| {
+        (self.1)(unsafe { &mut *slot }).inspect_err(|_|
             // SAFETY: `slot` was initialized above.
-            unsafe { core::ptr::drop_in_place(slot) };
-            e
-        })
+            unsafe { core::ptr::drop_in_place(slot) })
     }
 }

--
2.45.2

[PATCH v2 03/13] rust: allow `dead_code` for never constructed bindings

[Miguel Ojeda]

Starting with the upcoming Rust 1.80.0 (since upstream commit 35130d7233e9
("Detect pub structs never constructed and unused associated constants
in traits")), the `dead_code` pass detects more cases, which triggers
in the `bindings` crate:

    warning: struct `boot_params` is never constructed
        --> rust/bindings/bindings_generated.rs:10684:12
        |
    10684 | pub struct boot_params {
        |            ^^^^^^^^^^^
        |
        = note: `#[warn(dead_code)]` on by default

As well as in the `uapi` one:

    warning: struct `boot_params` is never constructed
        --> rust/uapi/uapi_generated.rs:10392:12
        |
    10392 | pub struct boot_params {
        |            ^^^^^^^^^^^
        |
        = note: `#[warn(dead_code)]` on by default

These are all expected, since we do not use all the structs in the
bindings that `bindgen` generates from the C headers.

Therefore, allow them.

Reviewed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Reviewed-by: Finn Behrens <me@kloenk.dev>
Tested-by: Benno Lossin <benno.lossin@proton.me>
Tested-by: Andreas Hindborg <a.hindborg@samsung.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 rust/bindings/lib.rs | 1 +
 rust/uapi/lib.rs     | 1 +
 2 files changed, 2 insertions(+)

diff --git a/rust/bindings/lib.rs b/rust/bindings/lib.rs
index 40ddaee50d8b..93a1a3fc97bc 100644
--- a/rust/bindings/lib.rs
+++ b/rust/bindings/lib.rs
@@ -24,6 +24,7 @@
     unsafe_op_in_unsafe_fn
 )]
 
+#[allow(dead_code)]
 mod bindings_raw {
     // Use glob import here to expose all helpers.
     // Symbols defined within the module will take precedence to the glob import.
diff --git a/rust/uapi/lib.rs b/rust/uapi/lib.rs
index 0caad902ba40..80a00260e3e7 100644
--- a/rust/uapi/lib.rs
+++ b/rust/uapi/lib.rs
@@ -14,6 +14,7 @@
 #![cfg_attr(test, allow(unsafe_op_in_unsafe_fn))]
 #![allow(
     clippy::all,
+    dead_code,
     missing_docs,
     non_camel_case_types,
     non_upper_case_globals,
-- 
2.45.2

[PATCH v2 04/13] rust: relax most deny-level lints to warnings

[Miguel Ojeda]

Since we are starting to support several Rust toolchains, lints (including
Clippy ones) now may behave differently and lint groups may include
new lints.

Therefore, to maximize the chances a given version works, relax some
deny-level lints to warnings. It may also make our lives a bit easier
while developing new code or refactoring.

To be clear, the requirements for in-tree code are still the same, since
Rust code still needs to be warning-free (patches should be clean under
`WERROR=y`) and the set of lints is not changed.

`unsafe_op_in_unsafe_fn` is left unmodified, i.e. as an error, since it is
becoming the default in the language (warn-by-default in Rust 2024 [1] and
ideally an error later on) and thus it should also be very well tested. In
addition, it is simple enough that it should not have false positives
(unlike e.g. `rust_2018_idioms`'s `explicit_outlives_requirements`).

`non_ascii_idents` is left unmodified as well, i.e. as an error, since
it is unlikely one gains any productivity during development if it
were a warning (in fact, it may be worse, since it is likely one made
a typo). In addition, it should not have false positives.

Finally, put the two `-D` ones at the top and take the chance to do one
per line.

Link: https://github.com/rust-lang/rust/pull/112038 [1]
Reviewed-by: Finn Behrens <me@kloenk.dev>
Tested-by: Benno Lossin <benno.lossin@proton.me>
Tested-by: Andreas Hindborg <a.hindborg@samsung.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
v2:
  - Kept `non_ascii_idents` as an error. (Björn, Finn)

 Makefile      | 24 +++++++++++++-----------
 rust/Makefile |  4 ++--
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/Makefile b/Makefile
index fea263aaa492..7ea526814fdb 100644
--- a/Makefile
+++ b/Makefile
@@ -461,17 +461,19 @@ KBUILD_USERLDFLAGS := $(USERLDFLAGS)
 # host programs.
 export rust_common_flags := --edition=2021 \
 			    -Zbinary_dep_depinfo=y \
-			    -Dunsafe_op_in_unsafe_fn -Drust_2018_idioms \
-			    -Dunreachable_pub -Dnon_ascii_idents \
+			    -Dunsafe_op_in_unsafe_fn \
+			    -Dnon_ascii_idents \
+			    -Wrust_2018_idioms \
+			    -Wunreachable_pub \
 			    -Wmissing_docs \
-			    -Drustdoc::missing_crate_level_docs \
-			    -Dclippy::correctness -Dclippy::style \
-			    -Dclippy::suspicious -Dclippy::complexity \
-			    -Dclippy::perf \
-			    -Dclippy::let_unit_value -Dclippy::mut_mut \
-			    -Dclippy::needless_bitwise_bool \
-			    -Dclippy::needless_continue \
-			    -Dclippy::no_mangle_with_rust_abi \
+			    -Wrustdoc::missing_crate_level_docs \
+			    -Wclippy::correctness -Wclippy::style \
+			    -Wclippy::suspicious -Wclippy::complexity \
+			    -Wclippy::perf \
+			    -Wclippy::let_unit_value -Wclippy::mut_mut \
+			    -Wclippy::needless_bitwise_bool \
+			    -Wclippy::needless_continue \
+			    -Wclippy::no_mangle_with_rust_abi \
 			    -Wclippy::dbg_macro

 KBUILD_HOSTCFLAGS   := $(KBUILD_USERHOSTCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS)
@@ -572,7 +574,7 @@ KBUILD_RUSTFLAGS := $(rust_common_flags) \
 		    -Csymbol-mangling-version=v0 \
 		    -Crelocation-model=static \
 		    -Zfunction-sections=n \
-		    -Dclippy::float_arithmetic
+		    -Wclippy::float_arithmetic

 KBUILD_AFLAGS_KERNEL :=
 KBUILD_CFLAGS_KERNEL :=
diff --git a/rust/Makefile b/rust/Makefile
index 385378311322..bf05e65365da 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -367,7 +367,7 @@ ifneq ($(or $(CONFIG_ARM64),$(and $(CONFIG_RISCV),$(CONFIG_64BIT))),)
 endif

 $(obj)/core.o: private skip_clippy = 1
-$(obj)/core.o: private skip_flags = -Dunreachable_pub
+$(obj)/core.o: private skip_flags = -Wunreachable_pub
 $(obj)/core.o: private rustc_objcopy = $(foreach sym,$(redirect-intrinsics),--redefine-sym $(sym)=__rust$(sym))
 $(obj)/core.o: private rustc_target_flags = $(core-cfgs)
 $(obj)/core.o: $(RUST_LIB_SRC)/core/src/lib.rs FORCE
@@ -381,7 +381,7 @@ $(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o FORCE
 	+$(call if_changed_dep,rustc_library)

 $(obj)/alloc.o: private skip_clippy = 1
-$(obj)/alloc.o: private skip_flags = -Dunreachable_pub
+$(obj)/alloc.o: private skip_flags = -Wunreachable_pub
 $(obj)/alloc.o: private rustc_target_flags = $(alloc-cfgs)
 $(obj)/alloc.o: $(RUST_LIB_SRC)/alloc/src/lib.rs $(obj)/compiler_builtins.o FORCE
 	+$(call if_changed_dep,rustc_library)
--
2.45.2

[PATCH v2 05/13] rust: simplify Clippy warning flags set

[Miguel Ojeda]

All Clippy lint groups that we enable, except `correctness`, have a
default `warn` level, thus they may be removed now that we relaxed all
lints to `warn`.

Moreover, Clippy provides an `all` lint group that covers the groups
we enable by default. Thus just use `all` instead -- the only change is
that, if Clippy introduces a new lint group or splits an existing one,
we will cover that one automatically.

In addition, `let_unit_value` is in `style` since Rust 1.62.0, thus it
does not need to be enabled manually.

Reviewed-by: Finn Behrens <me@kloenk.dev>
Tested-by: Benno Lossin <benno.lossin@proton.me>
Tested-by: Andreas Hindborg <a.hindborg@samsung.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 Makefile | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/Makefile b/Makefile
index 7ea526814fdb..9044fdb9adb1 100644
--- a/Makefile
+++ b/Makefile
@@ -467,10 +467,8 @@ export rust_common_flags := --edition=2021 \
 			    -Wunreachable_pub \
 			    -Wmissing_docs \
 			    -Wrustdoc::missing_crate_level_docs \
-			    -Wclippy::correctness -Wclippy::style \
-			    -Wclippy::suspicious -Wclippy::complexity \
-			    -Wclippy::perf \
-			    -Wclippy::let_unit_value -Wclippy::mut_mut \
+			    -Wclippy::all \
+			    -Wclippy::mut_mut \
 			    -Wclippy::needless_bitwise_bool \
 			    -Wclippy::needless_continue \
 			    -Wclippy::no_mangle_with_rust_abi \
-- 
2.45.2

[PATCH v2 06/13] rust: start supporting several compiler versions

[Miguel Ojeda]

It is time to start supporting several Rust compiler versions and thus
establish a minimum Rust version.

We may still want to upgrade the minimum sometimes in the beginning since
there may be important features coming into the language that improve
how we write code (e.g. field projections), which may or may not make
sense to support conditionally.

We will start with a window of two stable releases, and widen it over
time. Thus this patch does not move the current minimum (1.78.0), but
instead adds support for the recently released 1.79.0.

This should already be enough for kernel developers in distributions that
provide recent Rust compiler versions routinely, such as Arch Linux,
Debian Unstable (outside the freeze period), Fedora Linux, Gentoo
Linux (especially the testing channel), Nix (unstable) and openSUSE
Tumbleweed. See the documentation patch about it later in this series.

In addition, Rust for Linux is now being built-tested in Rust's pre-merge
CI [1]. That is, every change that is attempting to land into the Rust
compiler is tested against the kernel, and it is merged only if it passes
-- thanks to the Rust project for that!

Thus, with the pre-merge CI in place, both projects hope to avoid
unintentional changes to Rust that break the kernel. This means that,
in general, apart from intentional changes on their side (that we will
need to workaround conditionally on our side), the upcoming Rust compiler
versions should generally work.

For instance, currently, the beta (1.80.0) and nightly (1.81.0) branches
work as well.

Of course, the Rust for Linux CI job in the Rust toolchain may still need
to be temporarily disabled for different reasons, but the intention is
to help bring Rust for Linux into stable Rust.

Link: https://github.com/rust-lang/rust/pull/125209 [1]
Reviewed-by: Finn Behrens <me@kloenk.dev>
Tested-by: Benno Lossin <benno.lossin@proton.me>
Tested-by: Andreas Hindborg <a.hindborg@samsung.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
v2:
  - Update suggested `rustup` command to just install `stable`. (Finn)
  - Update suggested command for installing manually the Rust standard
    library sources with the version that `rustc` reports, rather than
    the minimum (since now the user may have installed e.g. stable).

 Documentation/process/changes.rst  |  4 +---
 Documentation/rust/quick-start.rst | 15 +++++++--------
 scripts/rust_is_available.sh       |  8 --------
 scripts/rust_is_available_test.py  |  5 -----
 4 files changed, 8 insertions(+), 24 deletions(-)

diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
index 5685d7bfe4d0..0d0b7120792b 100644
--- a/Documentation/process/changes.rst
+++ b/Documentation/process/changes.rst
@@ -88,9 +88,7 @@ docs on :ref:`Building Linux with Clang/LLVM <kbuild_llvm>`.
 Rust (optional)
 ---------------

-A particular version of the Rust toolchain is required. Newer versions may or
-may not work because the kernel depends on some unstable Rust features, for
-the moment.
+A recent version of the Rust compiler is required.

 Each Rust toolchain comes with several "components", some of which are required
 (like ``rustc``) and some that are optional. The ``rust-src`` component (which
diff --git a/Documentation/rust/quick-start.rst b/Documentation/rust/quick-start.rst
index ac2f16288458..89bbfde8c96c 100644
--- a/Documentation/rust/quick-start.rst
+++ b/Documentation/rust/quick-start.rst
@@ -36,16 +36,15 @@ if that is the case.
 rustc
 *****

-A particular version of the Rust compiler is required. Newer versions may or
-may not work because, for the moment, the kernel depends on some unstable
-Rust features.
+A recent version of the Rust compiler is required.

 If ``rustup`` is being used, enter the kernel build directory (or use
-``--path=<build-dir>`` argument to the ``set`` sub-command) and run::
+``--path=<build-dir>`` argument to the ``set`` sub-command) and run,
+for instance::

-	rustup override set $(scripts/min-tool-version.sh rustc)
+	rustup override set stable

-This will configure your working directory to use the correct version of
+This will configure your working directory to use the given version of
 ``rustc`` without affecting your default toolchain.

 Note that the override applies to the current working directory (and its
@@ -72,9 +71,9 @@ version later on requires re-adding the component.
 Otherwise, if a standalone installer is used, the Rust source tree may be
 downloaded into the toolchain's installation folder::

-	curl -L "https://static.rust-lang.org/dist/rust-src-$(scripts/min-tool-version.sh rustc).tar.gz" |
+	curl -L "https://static.rust-lang.org/dist/rust-src-$(rustc --version | cut -d' ' -f2).tar.gz" |
 		tar -xzf - -C "$(rustc --print sysroot)/lib" \
-		"rust-src-$(scripts/min-tool-version.sh rustc)/rust-src/lib/" \
+		"rust-src-$(rustc --version | cut -d' ' -f2)/rust-src/lib/" \
 		--strip-components=3

 In this case, upgrading the Rust compiler version later on requires manually
diff --git a/scripts/rust_is_available.sh b/scripts/rust_is_available.sh
index 117018946b57..67cb900124cc 100755
--- a/scripts/rust_is_available.sh
+++ b/scripts/rust_is_available.sh
@@ -117,14 +117,6 @@ if [ "$rust_compiler_cversion" -lt "$rust_compiler_min_cversion" ]; then
 	echo >&2 "***"
 	exit 1
 fi
-if [ "$rust_compiler_cversion" -gt "$rust_compiler_min_cversion" ]; then
-	echo >&2 "***"
-	echo >&2 "*** Rust compiler '$RUSTC' is too new. This may or may not work."
-	echo >&2 "***   Your version:     $rust_compiler_version"
-	echo >&2 "***   Expected version: $rust_compiler_min_version"
-	echo >&2 "***"
-	warning=1
-fi

 # Check that the Rust bindings generator is suitable.
 #
diff --git a/scripts/rust_is_available_test.py b/scripts/rust_is_available_test.py
index 57613fe5ed75..a255f79aafc2 100755
--- a/scripts/rust_is_available_test.py
+++ b/scripts/rust_is_available_test.py
@@ -193,11 +193,6 @@ else:
         result = self.run_script(self.Expected.FAILURE, { "RUSTC": rustc })
         self.assertIn(f"Rust compiler '{rustc}' is too old.", result.stderr)

-    def test_rustc_new_version(self):
-        rustc = self.generate_rustc("rustc 1.999.0 (a8314ef7d 2099-06-27)")
-        result = self.run_script(self.Expected.SUCCESS_WITH_WARNINGS, { "RUSTC": rustc })
-        self.assertIn(f"Rust compiler '{rustc}' is too new. This may or may not work.", result.stderr)
-
     def test_bindgen_nonexecutable(self):
         result = self.run_script(self.Expected.FAILURE, { "BINDGEN": self.nonexecutable })
         self.assertIn(f"Running '{self.nonexecutable}' to check the Rust bindings generator version failed with", result.stderr)
--
2.45.2

[PATCH v2 07/13] rust: avoid assuming a particular `bindgen` build

[Miguel Ojeda]

`bindgen`'s logic to find `libclang` (via `clang-sys`) may change over
time, and depends on how it was built (e.g. Linux distributions may decide
to build it differently, and we are going to provide documentation on
installing it via distributions later in this series).

Therefore, clarify that `bindgen` may be built in several ways and
simplify the documentation by only mentioning the most prominent
environment variable (`LIBCLANG_PATH`) as an example on how to tweak the
search of the library at runtime (i.e. when `bindgen` is built as our
documentation explains). This also avoids duplicating the documentation,
like `bindgen` itself does (i.e. it refers to `clang-sys`).

Similarly, replace the test we had for this (which used the real program)
with a mocked one, to avoid depending on the particular build as well.

Tested-by: Benno Lossin <benno.lossin@proton.me>
Tested-by: Andreas Hindborg <a.hindborg@samsung.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 Documentation/rust/quick-start.rst | 23 +++++++++--------------
 scripts/rust_is_available_test.py  | 25 +++++++++++++++----------
 2 files changed, 24 insertions(+), 24 deletions(-)

diff --git a/Documentation/rust/quick-start.rst b/Documentation/rust/quick-start.rst
index 89bbfde8c96c..5ea8c8914942 100644
--- a/Documentation/rust/quick-start.rst
+++ b/Documentation/rust/quick-start.rst
@@ -113,20 +113,15 @@ Install it via (note that this will download and build the tool from source)::
 
 	cargo install --locked --version $(scripts/min-tool-version.sh bindgen) bindgen-cli
 
-``bindgen`` needs to find a suitable ``libclang`` in order to work. If it is
-not found (or a different ``libclang`` than the one found should be used),
-the process can be tweaked using the environment variables understood by
-``clang-sys`` (the Rust bindings crate that ``bindgen`` uses to access
-``libclang``):
-
-* ``LLVM_CONFIG_PATH`` can be pointed to an ``llvm-config`` executable.
-
-* Or ``LIBCLANG_PATH`` can be pointed to a ``libclang`` shared library
-  or to the directory containing it.
-
-* Or ``CLANG_PATH`` can be pointed to a ``clang`` executable.
-
-For details, please see ``clang-sys``'s documentation at:
+``bindgen`` uses the ``clang-sys`` crate to find a suitable ``libclang`` (which
+may be linked statically, dynamically or loaded at runtime). By default, the
+``cargo`` command above will produce a ``bindgen`` binary that will load
+``libclang`` at runtime. If it is not found (or a different ``libclang`` than
+the one found should be used), the process can be tweaked, e.g. by using the
+``LIBCLANG_PATH`` environment variable. For details, please see ``clang-sys``'s
+documentation at:
+
+	https://github.com/KyleMayes/clang-sys#linking
 
 	https://github.com/KyleMayes/clang-sys#environment-variables
 
diff --git a/scripts/rust_is_available_test.py b/scripts/rust_is_available_test.py
index a255f79aafc2..0481aab862ec 100755
--- a/scripts/rust_is_available_test.py
+++ b/scripts/rust_is_available_test.py
@@ -55,10 +55,15 @@ else:
 
     @classmethod
     def generate_bindgen(cls, version_stdout, libclang_stderr):
+        if libclang_stderr is None:
+            libclang_case = f"raise SystemExit({cls.bindgen_default_bindgen_libclang_failure_exit_code})"
+        else:
+            libclang_case = f"print({repr(libclang_stderr)}, file=sys.stderr)"
+
         return cls.generate_executable(f"""#!/usr/bin/env python3
 import sys
 if "rust_is_available_bindgen_libclang.h" in " ".join(sys.argv):
-    print({repr(libclang_stderr)}, file=sys.stderr)
+    {libclang_case}
 else:
     print({repr(version_stdout)})
 """)
@@ -67,6 +72,10 @@ else:
     def generate_bindgen_version(cls, stdout):
         return cls.generate_bindgen(stdout, cls.bindgen_default_bindgen_libclang_stderr)
 
+    @classmethod
+    def generate_bindgen_libclang_failure(cls):
+        return cls.generate_bindgen(cls.bindgen_default_bindgen_version_stdout, None)
+
     @classmethod
     def generate_bindgen_libclang(cls, stderr):
         return cls.generate_bindgen(cls.bindgen_default_bindgen_version_stdout, stderr)
@@ -89,6 +98,7 @@ else:
         cls.rust_default_sysroot = subprocess.check_output(("rustc", "--print", "sysroot")).decode().strip()
 
         cls.bindgen_default_bindgen_version_stdout = f"bindgen {cls.bindgen_default_version}"
+        cls.bindgen_default_bindgen_libclang_failure_exit_code = 42
         cls.bindgen_default_bindgen_libclang_stderr = f"scripts/rust_is_available_bindgen_libclang.h:2:9: warning: clang version {cls.llvm_default_version} [-W#pragma-messages], err: false"
 
         cls.default_rustc = cls.generate_rustc(f"rustc {cls.rustc_default_version}")
@@ -227,15 +237,10 @@ else:
         self.assertIn(f"Rust bindings generator '{bindgen}' is too new. This may or may not work.", result.stderr)
 
     def test_bindgen_libclang_failure(self):
-        for env in (
-            { "LLVM_CONFIG_PATH": self.missing },
-            { "LIBCLANG_PATH": self.missing },
-            { "CLANG_PATH": self.missing },
-        ):
-            with self.subTest(env=env):
-                result = self.run_script(self.Expected.FAILURE, env | { "PATH": os.environ["PATH"], "BINDGEN": "bindgen" })
-                self.assertIn("Running 'bindgen' to check the libclang version (used by the Rust", result.stderr)
-                self.assertIn("bindings generator) failed with code ", result.stderr)
+        bindgen = self.generate_bindgen_libclang_failure()
+        result = self.run_script(self.Expected.FAILURE, { "BINDGEN": bindgen })
+        self.assertIn(f"Running '{bindgen}' to check the libclang version (used by the Rust", result.stderr)
+        self.assertIn(f"bindings generator) failed with code {self.bindgen_default_bindgen_libclang_failure_exit_code}. This may be caused by", result.stderr)
 
     def test_bindgen_libclang_unexpected_version(self):
         bindgen = self.generate_bindgen_libclang("scripts/rust_is_available_bindgen_libclang.h:2:9: warning: clang version unexpected [-W#pragma-messages], err: false")
-- 
2.45.2

[PATCH v2 08/13] rust: work around `bindgen` 0.69.0 issue

[Miguel Ojeda]

`bindgen` 0.69.0 contains a bug: `--version` does not work without
providing a header [1]:

    error: the following required arguments were not provided:
      <HEADER>

    Usage: bindgen <FLAGS> <OPTIONS> <HEADER> -- <CLANG_ARGS>...

Thus, in preparation for supporting several `bindgen` versions, work
around the issue by passing a dummy argument.

Include a comment so that we can remove the workaround in the future.

Link: https://github.com/rust-lang/rust-bindgen/pull/2678 [1]
Reviewed-by: Finn Behrens <me@kloenk.dev>
Tested-by: Benno Lossin <benno.lossin@proton.me>
Tested-by: Andreas Hindborg <a.hindborg@samsung.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 init/Kconfig                 | 5 ++++-
 scripts/rust_is_available.sh | 6 +++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index febdea2afc3b..94e20d3b99d4 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1928,7 +1928,10 @@ config RUSTC_VERSION_TEXT
 config BINDGEN_VERSION_TEXT
 	string
 	depends on RUST
-	default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version || echo n)
+	# The dummy parameter `workaround-for-0.69.0` is required to support 0.69.0
+	# (https://github.com/rust-lang/rust-bindgen/pull/2678). It can be removed when
+	# the minimum version is upgraded past that (0.69.1 already fixed the issue).
+	default $(shell,command -v $(BINDGEN) >/dev/null 2>&1 && $(BINDGEN) --version workaround-for-0.69.0 || echo n)
 
 #
 # Place an empty function call at each tracepoint site. Can be
diff --git a/scripts/rust_is_available.sh b/scripts/rust_is_available.sh
index 67cb900124cc..1881e8f2a2b9 100755
--- a/scripts/rust_is_available.sh
+++ b/scripts/rust_is_available.sh
@@ -121,8 +121,12 @@ fi
 # Check that the Rust bindings generator is suitable.
 #
 # Non-stable and distributions' versions may have a version suffix, e.g. `-dev`.
+#
+# The dummy parameter `workaround-for-0.69.0` is required to support 0.69.0
+# (https://github.com/rust-lang/rust-bindgen/pull/2678). It can be removed when
+# the minimum version is upgraded past that (0.69.1 already fixed the issue).
 rust_bindings_generator_output=$( \
-	LC_ALL=C "$BINDGEN" --version 2>/dev/null
+	LC_ALL=C "$BINDGEN" --version workaround-for-0.69.0 2>/dev/null
 ) || rust_bindings_generator_code=$?
 if [ -n "$rust_bindings_generator_code" ]; then
 	echo >&2 "***"
-- 
2.45.2

[PATCH v2 09/13] rust: start supporting several `bindgen` versions

[Miguel Ojeda]

With both the workaround for `bindgen` 0.69.0 and the warning about
0.66.0 and 0.66.1 in place, start supporting several `bindgen` versions,
like it was done for the Rust compiler in a previous patch.

All other versions, including the latest 0.69.4, build without errors.

The `bindgen` project, like Rust, has also agreed to have the kernel
in their CI [1] -- thanks! This should help both projects: `bindgen`
will be able to detect early issues like those mentioned above, and the
kernel will be very likely build with new releases (at least for the
basic configuration being tested).

Link: https://github.com/rust-lang/rust-bindgen/pull/2851 [1]
Tested-by: Benno Lossin <benno.lossin@proton.me>
Tested-by: Andreas Hindborg <a.hindborg@samsung.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
v2:
  - Update suggested `cargo` command to just install the latest, i.e.
    removing the `--version` flag, following the same pattern as Finn's
    suggestion to use `stable `for the `rustup` command.

 Documentation/rust/quick-start.rst | 7 ++++---
 scripts/rust_is_available.sh       | 8 --------
 scripts/rust_is_available_test.py  | 5 -----
 3 files changed, 4 insertions(+), 16 deletions(-)

diff --git a/Documentation/rust/quick-start.rst b/Documentation/rust/quick-start.rst
index 5ea8c8914942..66cefbab8f9a 100644
--- a/Documentation/rust/quick-start.rst
+++ b/Documentation/rust/quick-start.rst
@@ -107,11 +107,12 @@ bindgen
 *******

 The bindings to the C side of the kernel are generated at build time using
-the ``bindgen`` tool. A particular version is required.
+the ``bindgen`` tool.

-Install it via (note that this will download and build the tool from source)::
+Install it, for instance, via (note that this will download and build the tool
+from source)::

-	cargo install --locked --version $(scripts/min-tool-version.sh bindgen) bindgen-cli
+	cargo install --locked bindgen-cli

 ``bindgen`` uses the ``clang-sys`` crate to find a suitable ``libclang`` (which
 may be linked statically, dynamically or loaded at runtime). By default, the
diff --git a/scripts/rust_is_available.sh b/scripts/rust_is_available.sh
index 1881e8f2a2b9..4531f9dd19d3 100755
--- a/scripts/rust_is_available.sh
+++ b/scripts/rust_is_available.sh
@@ -161,14 +161,6 @@ if [ "$rust_bindings_generator_cversion" -lt "$rust_bindings_generator_min_cvers
 	echo >&2 "***"
 	exit 1
 fi
-if [ "$rust_bindings_generator_cversion" -gt "$rust_bindings_generator_min_cversion" ]; then
-	echo >&2 "***"
-	echo >&2 "*** Rust bindings generator '$BINDGEN' is too new. This may or may not work."
-	echo >&2 "***   Your version:     $rust_bindings_generator_version"
-	echo >&2 "***   Expected version: $rust_bindings_generator_min_version"
-	echo >&2 "***"
-	warning=1
-fi

 # Check that the `libclang` used by the Rust bindings generator is suitable.
 #
diff --git a/scripts/rust_is_available_test.py b/scripts/rust_is_available_test.py
index 0481aab862ec..d6d54b7ea42a 100755
--- a/scripts/rust_is_available_test.py
+++ b/scripts/rust_is_available_test.py
@@ -231,11 +231,6 @@ else:
         result = self.run_script(self.Expected.FAILURE, { "BINDGEN": bindgen })
         self.assertIn(f"Rust bindings generator '{bindgen}' is too old.", result.stderr)

-    def test_bindgen_new_version(self):
-        bindgen = self.generate_bindgen_version("bindgen 0.999.0")
-        result = self.run_script(self.Expected.SUCCESS_WITH_WARNINGS, { "BINDGEN": bindgen })
-        self.assertIn(f"Rust bindings generator '{bindgen}' is too new. This may or may not work.", result.stderr)
-
     def test_bindgen_libclang_failure(self):
         bindgen = self.generate_bindgen_libclang_failure()
         result = self.run_script(self.Expected.FAILURE, { "BINDGEN": bindgen })
--
2.45.2

[PATCH v2 10/13] rust: warn about `bindgen` versions 0.66.0 and 0.66.1

[Miguel Ojeda]

`bindgen` versions 0.66.0 and 0.66.1 panic due to C string literals with
NUL characters [1]:

    panicked at .cargo/registry/src/index.crates.io-6f17d22bba15001f/bindgen-0.66.0/codegen/mod.rs:717:71:
    called `Result::unwrap()` on an `Err` value: FromBytesWithNulError { kind: InteriorNul(4) }

Thus, in preparation for supporting several `bindgen` versions, add a
version check to warn the user about it.

Since some distributions may have patched it (e.g. Debian did [2]),
check if that seems to be the case (after the version check matches),
in order to avoid printing a warning in that case.

We could make it an error, but 1) it is going to fail anyway later
in the build, 2) we would disable `RUST`, which is also painful, 3)
someone could have patched it in a way that still makes our extra check
fail (however unlikely), 4) the interior NUL may go away in the headers
(however unlikely). Thus just warn about it so that users know why it
is failing.

In addition, add a couple tests for the new cases.

Link: https://github.com/rust-lang/rust-bindgen/pull/2567 [1]
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1069047 [2]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
v2:
  - If the version matches, then also check whether the `bindgen` binary
    fails with a simple interior NUL case, so that we can avoid the
    warning if it has been patched (like Debian's). Update the comment
    for the warning as well, and add a test for it too.
  - Move test later in the series so that the new test does not fail due
    to the "too new" check.
  - Split `if` condition in 2 lines.

 scripts/rust_is_available.sh             | 13 ++++++++++++
 scripts/rust_is_available_bindgen_0_66.h |  2 ++
 scripts/rust_is_available_test.py        | 26 +++++++++++++++++++++---
 3 files changed, 38 insertions(+), 3 deletions(-)
 create mode 100644 scripts/rust_is_available_bindgen_0_66.h

diff --git a/scripts/rust_is_available.sh b/scripts/rust_is_available.sh
index 4531f9dd19d3..5262c56dd674 100755
--- a/scripts/rust_is_available.sh
+++ b/scripts/rust_is_available.sh
@@ -161,6 +161,19 @@ if [ "$rust_bindings_generator_cversion" -lt "$rust_bindings_generator_min_cvers
 	echo >&2 "***"
 	exit 1
 fi
+if [ "$rust_bindings_generator_cversion" -eq 6600 ] ||
+	[ "$rust_bindings_generator_cversion" -eq 6601 ]; then
+	# Distributions may have patched the issue (e.g. Debian did).
+	if ! "$BINDGEN" $(dirname $0)/rust_is_available_bindgen_0_66.h >/dev/null; then
+		echo >&2 "***"
+		echo >&2 "*** Rust bindings generator '$BINDGEN' versions 0.66.0 and 0.66.1 may not"
+		echo >&2 "*** work due to a bug (https://github.com/rust-lang/rust-bindgen/pull/2567),"
+		echo >&2 "*** unless patched (like Debian's)."
+		echo >&2 "***   Your version:     $rust_bindings_generator_version"
+		echo >&2 "***"
+		warning=1
+	fi
+fi

 # Check that the `libclang` used by the Rust bindings generator is suitable.
 #
diff --git a/scripts/rust_is_available_bindgen_0_66.h b/scripts/rust_is_available_bindgen_0_66.h
new file mode 100644
index 000000000000..c0431293421c
--- /dev/null
+++ b/scripts/rust_is_available_bindgen_0_66.h
@@ -0,0 +1,2 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#define A "\0"
diff --git a/scripts/rust_is_available_test.py b/scripts/rust_is_available_test.py
index d6d54b7ea42a..413741037fb3 100755
--- a/scripts/rust_is_available_test.py
+++ b/scripts/rust_is_available_test.py
@@ -54,23 +54,30 @@ else:
 """)

     @classmethod
-    def generate_bindgen(cls, version_stdout, libclang_stderr):
+    def generate_bindgen(cls, version_stdout, libclang_stderr, version_0_66_patched=False):
         if libclang_stderr is None:
             libclang_case = f"raise SystemExit({cls.bindgen_default_bindgen_libclang_failure_exit_code})"
         else:
             libclang_case = f"print({repr(libclang_stderr)}, file=sys.stderr)"

+        if version_0_66_patched:
+            version_0_66_case = "pass"
+        else:
+            version_0_66_case = "raise SystemExit(1)"
+
         return cls.generate_executable(f"""#!/usr/bin/env python3
 import sys
 if "rust_is_available_bindgen_libclang.h" in " ".join(sys.argv):
     {libclang_case}
+elif "rust_is_available_bindgen_0_66.h" in " ".join(sys.argv):
+    {version_0_66_case}
 else:
     print({repr(version_stdout)})
 """)

     @classmethod
-    def generate_bindgen_version(cls, stdout):
-        return cls.generate_bindgen(stdout, cls.bindgen_default_bindgen_libclang_stderr)
+    def generate_bindgen_version(cls, stdout, version_0_66_patched=False):
+        return cls.generate_bindgen(stdout, cls.bindgen_default_bindgen_libclang_stderr, version_0_66_patched)

     @classmethod
     def generate_bindgen_libclang_failure(cls):
@@ -231,6 +238,19 @@ else:
         result = self.run_script(self.Expected.FAILURE, { "BINDGEN": bindgen })
         self.assertIn(f"Rust bindings generator '{bindgen}' is too old.", result.stderr)

+    def test_bindgen_bad_version_0_66_0_and_0_66_1(self):
+        for version in ("0.66.0", "0.66.1"):
+            with self.subTest(version=version):
+                bindgen = self.generate_bindgen_version(f"bindgen {version}")
+                result = self.run_script(self.Expected.SUCCESS_WITH_WARNINGS, { "BINDGEN": bindgen })
+                self.assertIn(f"Rust bindings generator '{bindgen}' versions 0.66.0 and 0.66.1 may not", result.stderr)
+
+    def test_bindgen_bad_version_0_66_0_and_0_66_1_patched(self):
+        for version in ("0.66.0", "0.66.1"):
+            with self.subTest(version=version):
+                bindgen = self.generate_bindgen_version(f"bindgen {version}", True)
+                result = self.run_script(self.Expected.SUCCESS, { "BINDGEN": bindgen })
+
     def test_bindgen_libclang_failure(self):
         bindgen = self.generate_bindgen_libclang_failure()
         result = self.run_script(self.Expected.FAILURE, { "BINDGEN": bindgen })
--
2.45.2

[PATCH v2 11/13] kbuild: rust: add `rustc-version` support

[Miguel Ojeda]

Now that we are starting to support several Rust versions, introduce
`rustc-version` support, mimicking the C side:

  - `scripts/rustc-version.sh`, that mimics the other version scripts
     (with one more digit, e.g. Rust 1.79.0 is 107900).

  - `rustc-{info,name,version}` Kbuild macros.

  - `CONFIG_RUSTC_VERSION` Kconfig symbol that calls `rustc-version`.

  - `rustc-min-version` Kbuild macro that uses `CONFIG_RUSTC_VERSION`.

With these, we can easily support flags conditionally depending on
`rustc`'s version -- a user comes in the next patch.

Another user will be the `-Ctarget-feature=+reserve-x18`/`-Zfixed-x18`
arm64 flags [1].

Link: https://lore.kernel.org/rust-for-linux/20240305-shadow-call-stack-v2-1-c7b4a3f4d616@google.com/ [1]
Reviewed-by: Finn Behrens <me@kloenk.dev>
Tested-by: Benno Lossin <benno.lossin@proton.me>
Tested-by: Andreas Hindborg <a.hindborg@samsung.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
v2:
  - Fix comment from "5 or 6-digit" to "6 to 7-digit".

 init/Kconfig              |  6 +++++
 scripts/Kconfig.include   |  6 +++++
 scripts/Makefile.compiler |  4 +++
 scripts/rustc-version.sh  | 52 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 68 insertions(+)
 create mode 100755 scripts/rustc-version.sh

diff --git a/init/Kconfig b/init/Kconfig
index 94e20d3b99d4..7d344f248785 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1920,6 +1920,12 @@ config RUST

 	  If unsure, say N.

+config RUSTC_VERSION
+	int
+	depends on RUST
+	default $(rustc-version)
+	default 0
+
 config RUSTC_VERSION_TEXT
 	string
 	depends on RUST
diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index 3ee8ecfb8c04..82ab889725db 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -45,6 +45,12 @@ $(error-if,$(success,test -z "$(cc-info)"),Sorry$(comma) this C compiler is not
 cc-name := $(shell,set -- $(cc-info) && echo $1)
 cc-version := $(shell,set -- $(cc-info) && echo $2)

+# Get the Rust compiler name, version, and error out if it is not supported.
+rustc-info := $(shell,$(srctree)/scripts/rustc-version.sh $(RUSTC))
+$(error-if,$(success,test -z "$(rustc-info)"),Sorry$(comma) this Rust compiler is not supported.)
+rustc-name := $(shell,set -- $(rustc-info) && echo $1)
+rustc-version := $(shell,set -- $(rustc-info) && echo $2)
+
 # Get the assembler name, version, and error out if it is not supported.
 as-info := $(shell,$(srctree)/scripts/as-version.sh $(CC) $(CLANG_FLAGS))
 $(error-if,$(success,test -z "$(as-info)"),Sorry$(comma) this assembler is not supported.)
diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
index 92be0c9a13ee..17eaa085b59c 100644
--- a/scripts/Makefile.compiler
+++ b/scripts/Makefile.compiler
@@ -69,6 +69,10 @@ gcc-min-version = $(call test-ge, $(CONFIG_GCC_VERSION), $1)
 # Usage: cflags-$(call clang-min-version, 110000) += -foo
 clang-min-version = $(call test-ge, $(CONFIG_CLANG_VERSION), $1)

+# rustc-min-version
+# Usage: rustflags-$(call rustc-min-version, 107900) += -foo
+rustc-min-version = $(call test-ge, $(CONFIG_RUSTC_VERSION), $1)
+
 # ld-option
 # Usage: KBUILD_LDFLAGS += $(call ld-option, -X, -Y)
 ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3))
diff --git a/scripts/rustc-version.sh b/scripts/rustc-version.sh
new file mode 100755
index 000000000000..7b27ab5d4ecd
--- /dev/null
+++ b/scripts/rustc-version.sh
@@ -0,0 +1,52 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# Print the Rust compiler name and its version in a 6 or 7-digit form.
+# Also, perform the minimum version check.
+
+set -e
+
+# Convert the version string x.y.z to a canonical up-to-7-digits form.
+#
+# Note that this function uses one more digit (compared to other
+# instances in other version scripts) to give a bit more space to
+# `rustc` since it will reach 1.100.0 in late 2026.
+get_canonical_version()
+{
+	IFS=.
+	set -- $1
+	echo $((100000 * $1 + 100 * $2 + $3))
+}
+
+orig_args="$@"
+
+set -- $("$@" --version)
+
+name=$1
+
+min_tool_version=$(dirname $0)/min-tool-version.sh
+
+case "$name" in
+rustc)
+	version=$2
+	min_version=$($min_tool_version rustc)
+	;;
+*)
+	echo "$orig_args: unknown Rust compiler" >&2
+	exit 1
+	;;
+esac
+
+rustcversion=$(get_canonical_version $version)
+min_rustcversion=$(get_canonical_version $min_version)
+
+if [ "$rustcversion" -lt "$min_rustcversion" ]; then
+	echo >&2 "***"
+	echo >&2 "*** Rust compiler is too old."
+	echo >&2 "***   Your $name version:    $version"
+	echo >&2 "***   Minimum $name version: $min_version"
+	echo >&2 "***"
+	exit 1
+fi
+
+echo $name $rustcversion
--
2.45.2

[PATCH v2 12/13] rust: support the new `-Zub-checks` flag

[Miguel Ojeda]

Rust 1.79.0 has introduced a new codegen flag, `-Zub-checks` [1], to
allow to independently configure (from `-Cdebug-assertions`) whether the
extra runtime checks for UB are emitted, in a similar fashion to
`-Coverflow-checks`.

This allows to configure the kernel with only the UB checks enabled,
but not the `debug_assert!`s; or vice versa, e.g. [2].

It also showcases how `RUSTC_VERSION` and the Kbuild macros, introduced
in the previous commit, can be used.

Link: https://github.com/rust-lang/compiler-team/issues/725 [1]
Link: https://godbolt.org/z/jY69ezx5K [2]
Reviewed-by: Finn Behrens <me@kloenk.dev>
Tested-by: Benno Lossin <benno.lossin@proton.me>
Tested-by: Andreas Hindborg <a.hindborg@samsung.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 Makefile          |  9 +++++++--
 lib/Kconfig.debug | 18 ++++++++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 9044fdb9adb1..4cf3b9799ec9 100644
--- a/Makefile
+++ b/Makefile
@@ -821,10 +821,15 @@ KBUILD_CFLAGS += -Os
 KBUILD_RUSTFLAGS += -Copt-level=s
 endif
 
-# Always set `debug-assertions` and `overflow-checks` because their default
-# depends on `opt-level` and `debug-assertions`, respectively.
+# Always set `debug-assertions` because its default depends on `opt-level`.
 KBUILD_RUSTFLAGS += -Cdebug-assertions=$(if $(CONFIG_RUST_DEBUG_ASSERTIONS),y,n)
+
+# Always set `overflow-checks` and `ub-checks` because their default depends on
+# `debug-assertions`.
 KBUILD_RUSTFLAGS += -Coverflow-checks=$(if $(CONFIG_RUST_OVERFLOW_CHECKS),y,n)
+ifeq ($(call rustc-min-version, 107900),y)
+KBUILD_RUSTFLAGS += -Zub-checks=$(if $(CONFIG_RUST_UNDEFINED_BEHAVIOR_CHECKS),y,n)
+endif
 
 # Tell gcc to never replace conditional load with a non-conditional one
 ifdef CONFIG_CC_IS_GCC
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 59b6765d86b8..6b4f512f9e13 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -3020,6 +3020,24 @@ config RUST_OVERFLOW_CHECKS
 
 	  If unsure, say Y.
 
+config RUST_UNDEFINED_BEHAVIOR_CHECKS
+	bool "Undefined Behavior checks"
+	depends on RUST && RUSTC_VERSION >= 107900
+	help
+	  Enables rustc's `-Zub-checks` codegen option.
+
+	  This flag allows you to control whether additional runtime checks that
+	  detect some causes of Undefined Behavior at runtime will be emitted.
+	  When enabled, a Rust panic will occur if UB is detected.
+
+	  All checks are generated on a best-effort basis; even if there is a check
+	  implemented for some cause of Undefined Behavior, it may be possible for
+	  the check to not fire.
+
+	  Note that this will apply to all Rust code, including `core`.
+
+	  If unsure, say N.
+
 config RUST_BUILD_ASSERT_ALLOW
 	bool "Allow unoptimized build-time assertions"
 	depends on RUST
-- 
2.45.2

[PATCH v2 13/13] docs: rust: quick-start: add section on Linux distributions

[Miguel Ojeda]

Now that we are starting to support several Rust compiler and `bindgen`
versions, there is a good chance some Linux distributions work out of
the box.

Thus, provide some instructions on how to set the toolchain up for a
few major Linux distributions. This simplifies the setup users need to
build the kernel.

In addition, add an introduction to the document so that it is easier
to understand its structure and move the LLVM+Rust kernel.org toolchains
paragraph there (removing "depending on the Linux version"). We may want
to reorganize the document or split it in the future, but I wanted to
focus this commit on the new information added about each particular
distribution.

Finally, remove the `rustup`'s components mention in `changes.rst` since
users do not need it if they install the toolchain via the distributions
(and anyway it was too detailed for that main document).

Cc: Jan Alexander Steffens <heftig@archlinux.org>
Cc: Johannes Löthberg <johannes@kyriasis.com>
Cc: Fabian Grünbichler <debian@fabian.gruenbichler.email>
Cc: Josh Stone <jistone@redhat.com>
Cc: Randy Barlow <randy@electronsweatshop.com>
Cc: Anna (navi) Figueiredo Gomes <navi@vlhl.dev>
Cc: Matoro Mahri <matoro_gentoo@matoro.tk>
Cc: Ryan Scheel <ryan.havvy@gmail.com>
Cc: figsoda <figsoda@pm.me>
Cc: Jörg Thalheim <joerg@thalheim.io>
Cc: Theodore Ni <43ngvg@masqt.com>
Cc: Winter <nixos@winter.cafe>
Cc: William Brown <wbrown@suse.de>
Cc: Xiaoguang Wang <xiaoguang.wang@suse.com>
Cc: Andrea Righi <andrea.righi@canonical.com>
Cc: Zixing Liu <zixing.liu@canonical.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Tested-by: Benno Lossin <benno.lossin@proton.me>
Tested-by: Andreas Hindborg <a.hindborg@samsung.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
v2:
  - Add openSUSE Slowroll.
  - Update openSUSE docs: both Slowroll and Tumbleweed now provide
    `rustfmt`, Clippy and the Rust standard library sources, so the
    comment about those can be dropped. (William)
  - I ended up leaving the Debian/Ubuntu docs as-is for the time being.
    Happy to get a patch for that later. We should definitely add them
    if they start working for the current kernel (currently: Ubuntu's
    latest versioned package is 1.76, and Debian's `web` one is 1.70).
    (Andrea, Fabian)
  - Move the LLVM+Rust kernel.org toolchains paragraph to the
    introduction that this commit adds, now that we have access to that
    paragraph since the series is rebased on top of `rust-next`.
  - Use plural for "release".

 Documentation/process/changes.rst  |  5 --
 Documentation/rust/quick-start.rst | 93 ++++++++++++++++++++++++++----
 2 files changed, 81 insertions(+), 17 deletions(-)

diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
index 0d0b7120792b..0ce96ae2588c 100644
--- a/Documentation/process/changes.rst
+++ b/Documentation/process/changes.rst
@@ -90,11 +90,6 @@ Rust (optional)

 A recent version of the Rust compiler is required.

-Each Rust toolchain comes with several "components", some of which are required
-(like ``rustc``) and some that are optional. The ``rust-src`` component (which
-is optional) needs to be installed to build the kernel. Other components are
-useful for developing.
-
 Please see Documentation/rust/quick-start.rst for instructions on how to
 satisfy the build requirements of Rust support. In particular, the ``Makefile``
 target ``rustavailable`` is useful to check why the Rust toolchain may not
diff --git a/Documentation/rust/quick-start.rst b/Documentation/rust/quick-start.rst
index 66cefbab8f9a..d06a36106cd4 100644
--- a/Documentation/rust/quick-start.rst
+++ b/Documentation/rust/quick-start.rst
@@ -5,24 +5,93 @@ Quick Start

 This document describes how to get started with kernel development in Rust.

+There are a few ways to install a Rust toolchain needed for kernel development.
+A simple way is to use the packages from your Linux distribution if they are
+suitable -- the first section below explains this approach. An advantage of this
+approach is that, typically, the distribution will match the LLVM used by Rust
+and Clang.
+
+Another way is using the prebuilt stable versions of LLVM+Rust provided on
+`kernel.org <https://kernel.org/pub/tools/llvm/rust/>`_. These are the same slim
+and fast LLVM toolchains from :ref:`Getting LLVM <getting_llvm>` with versions
+of Rust added to them that Rust for Linux supports. Two sets are provided: the
+"latest LLVM" and "matching LLVM" (please see the link for more information).
+
+Alternatively, the next two "Requirements" sections explain each component and
+how to install them through ``rustup``, the standalone installers from Rust
+and/or building them.
+
+The rest of the document explains other aspects on how to get started.
+
+
+Distributions
+-------------
+
+Arch Linux
+**********
+
+Arch Linux provides recent Rust releases and thus it should generally work out
+of the box, e.g.::
+
+	pacman -S rust rust-src rust-bindgen
+
+
+Debian
+******
+
+Debian Unstable (Sid), outside of the freeze period, provides recent Rust
+releases and thus it should generally work out of the box, e.g.::
+
+	apt install rustc rust-src bindgen rustfmt rust-clippy
+
+
+Fedora Linux
+************
+
+Fedora Linux provides recent Rust releases and thus it should generally work out
+of the box, e.g.::
+
+	dnf install rust rust-src bindgen-cli rustfmt clippy
+
+
+Gentoo Linux
+************
+
+Gentoo Linux (and especially the testing branch) provides recent Rust releases
+and thus it should generally work out of the box, e.g.::
+
+	USE='rust-src rustfmt clippy' emerge dev-lang/rust dev-util/bindgen
+
+``LIBCLANG_PATH`` may need to be set.
+
+
+Nix
+***
+
+Nix (unstable channel) provides recent Rust releases and thus it should
+generally work out of the box, e.g.::
+
+	{ pkgs ? import <nixpkgs> {} }:
+	pkgs.mkShell {
+	  nativeBuildInputs = with pkgs; [ rustc rust-bindgen rustfmt clippy ];
+	  RUST_LIB_SRC = "${pkgs.rust.packages.stable.rustPlatform.rustLibSrc}";
+	}
+
+
+openSUSE
+********
+
+openSUSE Slowroll and openSUSE Tumbleweed provide recent Rust releases and thus
+they should generally work out of the box, e.g.::
+
+	zypper install rust rust1.79-src rust-bindgen clang
+

 Requirements: Building
 ----------------------

 This section explains how to fetch the tools needed for building.

-Some of these requirements might be available from Linux distributions
-under names like ``rustc``, ``rust-src``, ``rust-bindgen``, etc. However,
-at the time of writing, they are likely not to be recent enough unless
-the distribution tracks the latest releases.
-
-Prebuilt stable versions of LLVM+Rust are provided on `kernel.org
-<https://kernel.org/pub/tools/llvm/rust/>`_. These are the same slim and fast
-LLVM toolchains from :ref:`Getting LLVM <getting_llvm>` with versions of Rust
-added to them that Rust for Linux supports, depending on the Linux version. Two
-sets are provided: the "latest LLVM" and "matching LLVM" (please see the link
-for more information).
-
 To easily check whether the requirements are met, the following target
 can be used::

--
2.45.2

Re: [PATCH v2 11/13] kbuild: rust: add `rustc-version` support

[Miguel Ojeda]

On Tue, Jul 9, 2024 at 6:07 PM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> +$(error-if,$(success,test -z "$(rustc-info)"),Sorry$(comma) this Rust compiler is not supported.)

Bah, this is broken, I just noticed in my CI that I didn't handle the
"Rust not installed" case.

Anyway, this patch (and the next one) are not important for the
series, I will just drop them and send them independently next cycle
to Kbuild instead. I should have done that anyway, even if they were
correct.

Cheers,
Miguel

Re: [PATCH v2 00/13] Support several Rust toolchain versions

[Miguel Ojeda]

On Tue, Jul 9, 2024 at 6:06 PM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> A few things improved here and there, and rebased on top of `rust-next`.
>
> The changelog is attached to each patch.
>
> I kept the `Tested-by`s since most of the changes are on documentation
> or comments, though I did remove them on the patch that changed the most
> just in case (even for that one, I think Benno's and Andreas' setup
> would not have made a difference).
>
> I plan to put this series into `rust-next` very soon so that it goes
> into the merge window.

Applied into `rust-next` -- thanks everyone!

Cheers,
Miguel