Rust fixes for v6.3

- Build: Rust + GCC build fix and 'grep' warning fix.
 
  - Code: Missing 'extern "C"' fix.
 
  - Scripts: 'is_rust_module.sh' and 'generate_rust_analyzer.py' fixes.
 
  - A couple trivial fixes.
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Merge tag 'rust-fixes-6.3' of https://github.com/Rust-for-Linux/linux

Pull Rust fixes from Miguel Ojeda:
 "Most of these are straightforward.

  The last one is more complex, but it only touches Rust + GCC builds
  which are for the moment best-effort.

   - Code: Missing 'extern "C"' fix.

   - Scripts: 'is_rust_module.sh' and 'generate_rust_analyzer.py' fixes.

   - A couple trivial fixes

   - Build: Rust + GCC build fix and 'grep' warning fix"

* tag 'rust-fixes-6.3' of https://github.com/Rust-for-Linux/linux:
  rust: allow to use INIT_STACK_ALL_ZERO
  rust: fix regexp in scripts/is_rust_module.sh
  rust: build: Fix grep warning
  scripts: generate_rust_analyzer: Handle sub-modules with no Makefile
  rust: kernel: Mark rust_fmt_argument as extern "C"
  rust: sort uml documentation arch support table
  rust: str: fix requierments->requirements typo

Documentation/rust/arch-support.rst

@@ -15,7 +15,7 @@ support corresponds to ``S`` values in the ``MAINTAINERS`` file.
 ============  ================  ==============================================
 Architecture  Level of support  Constraints
 ============  ================  ==============================================
-``x86``       Maintained        ``x86_64`` only.
 ``um``        Maintained        ``x86_64`` only.
+``x86``       Maintained        ``x86_64`` only.
 ============  ================  ==============================================
 

rust/Makefile

@@ -262,6 +262,20 @@ BINDGEN_TARGET		:= $(BINDGEN_TARGET_$(SRCARCH))
 # some configurations, with new GCC versions, etc.
 bindgen_extra_c_flags = -w --target=$(BINDGEN_TARGET)
 
+# Auto variable zero-initialization requires an additional special option with
+# clang that is going to be removed sometime in the future (likely in
+# clang-18), so make sure to pass this option only if clang supports it
+# (libclang major version < 16).
+#
+# https://github.com/llvm/llvm-project/issues/44842
+# https://github.com/llvm/llvm-project/blob/llvmorg-16.0.0-rc2/clang/docs/ReleaseNotes.rst#deprecated-compiler-flags
+ifdef CONFIG_INIT_STACK_ALL_ZERO
+libclang_maj_ver=$(shell $(BINDGEN) $(srctree)/scripts/rust_is_available_bindgen_libclang.h 2>&1 | sed -ne 's/.*clang version \([0-9]*\).*/\1/p')
+ifeq ($(shell expr $(libclang_maj_ver) \< 16), 1)
+bindgen_extra_c_flags += -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
+endif
+endif
+
 bindgen_c_flags = $(filter-out $(bindgen_skip_c_flags), $(c_flags)) \
 	$(bindgen_extra_c_flags)
 endif
@@ -283,7 +297,7 @@ quiet_cmd_bindgen = BINDGEN $@
 		$(bindgen_target_cflags) $(bindgen_target_extra)
 
 $(obj)/bindings/bindings_generated.rs: private bindgen_target_flags = \
-    $(shell grep -v '^\#\|^$$' $(srctree)/$(src)/bindgen_parameters)
+    $(shell grep -v '^#\|^$$' $(srctree)/$(src)/bindgen_parameters)
 $(obj)/bindings/bindings_generated.rs: $(src)/bindings/bindings_helper.h \
     $(src)/bindgen_parameters FORCE
 	$(call if_changed_dep,bindgen)

rust/kernel/print.rs

@@ -18,7 +18,11 @@
 
 // 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 {
+unsafe extern "C" 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()) };

rust/kernel/str.rs

@@ -408,7 +408,7 @@ fn new() -> Self {
     /// If `pos` is less than `end`, then the region between `pos` (inclusive) and `end`
     /// (exclusive) must be valid for writes for the lifetime of the returned [`RawFormatter`].
     pub(crate) unsafe fn from_ptrs(pos: *mut u8, end: *mut u8) -> Self {
-        // INVARIANT: The safety requierments guarantee the type invariants.
+        // INVARIANT: The safety requirements guarantee the type invariants.
         Self {
             beg: pos as _,
             pos: pos as _,

scripts/generate_rust_analyzer.py

@@ -104,7 +104,10 @@ def generate_crates(srctree, objtree, sysroot_src):
             name = path.name.replace(".rs", "")
 
             # Skip those that are not crate roots.
-            if f"{name}.o" not in open(path.parent / "Makefile").read():
+            try:
+                if f"{name}.o" not in open(path.parent / "Makefile").read():
+                    continue
+            except FileNotFoundError:
                 continue
 
             logging.info("Adding %s", name)

scripts/is_rust_module.sh

@@ -13,4 +13,4 @@ set -e
 #
 # In the future, checking for the `.comment` section may be another
 # option, see https://github.com/rust-lang/rust/pull/97550.
-${NM} "$*" | grep -qE '^[0-9a-fA-F]+ r _R[^[:space:]]+16___IS_RUST_MODULE[^[:space:]]*$'
+${NM} "$*" | grep -qE '^[0-9a-fA-F]+ [Rr] _R[^[:space:]]+16___IS_RUST_MODULE[^[:space:]]*$'