rust: warn about `bindgen` versions 0.66.0 and 0.66.1

`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]
Link: https://lore.kernel.org/r/20240709160615.998336-11-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

3 files changed, 38 insertions, 3 deletions

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 })