kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 125 insertions, 0 deletions

diff --git a/lib/tests/glob_kunit.c b/lib/tests/glob_kunit.c
new file mode 100644
index 000000000..362b1eda8
--- /dev/null
+++ b/lib/tests/glob_kunit.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: MIT OR GPL-2.0
+/*
+ * Test cases for glob functions.
+ */
+
+#include <kunit/test.h>
+#include <linux/glob.h>
+#include <linux/module.h>
+
+/**
+ * struct glob_test_case - Test case for glob matching.
+ * @pat: Pattern to match.
+ * @str: String to match against.
+ * @expected: Expected glob_match result, true if matched.
+ */
+struct glob_test_case {
+	const char *pat;
+	const char *str;
+	bool expected;
+};
+
+static const struct glob_test_case glob_test_cases[] = {
+	/* Some basic tests */
+	{ .pat = "a", .str = "a", .expected = true },
+	{ .pat = "a", .str = "b", .expected = false },
+	{ .pat = "a", .str = "aa", .expected = false },
+	{ .pat = "a", .str = "", .expected = false },
+	{ .pat = "", .str = "", .expected = true },
+	{ .pat = "", .str = "a", .expected = false },
+	/* Simple character class tests */
+	{ .pat = "[a]", .str = "a", .expected = true },
+	{ .pat = "[a]", .str = "b", .expected = false },
+	{ .pat = "[!a]", .str = "a", .expected = false },
+	{ .pat = "[!a]", .str = "b", .expected = true },
+	{ .pat = "[ab]", .str = "a", .expected = true },
+	{ .pat = "[ab]", .str = "b", .expected = true },
+	{ .pat = "[ab]", .str = "c", .expected = false },
+	{ .pat = "[!ab]", .str = "c", .expected = true },
+	{ .pat = "[a-c]", .str = "b", .expected = true },
+	{ .pat = "[a-c]", .str = "d", .expected = false },
+	/* Corner cases in character class parsing */
+	{ .pat = "[a-c-e-g]", .str = "-", .expected = true },
+	{ .pat = "[a-c-e-g]", .str = "d", .expected = false },
+	{ .pat = "[a-c-e-g]", .str = "f", .expected = true },
+	{ .pat = "[]a-ceg-ik[]", .str = "a", .expected = true },
+	{ .pat = "[]a-ceg-ik[]", .str = "]", .expected = true },
+	{ .pat = "[]a-ceg-ik[]", .str = "[", .expected = true },
+	{ .pat = "[]a-ceg-ik[]", .str = "h", .expected = true },
+	{ .pat = "[]a-ceg-ik[]", .str = "f", .expected = false },
+	{ .pat = "[!]a-ceg-ik[]", .str = "h", .expected = false },
+	{ .pat = "[!]a-ceg-ik[]", .str = "]", .expected = false },
+	{ .pat = "[!]a-ceg-ik[]", .str = "f", .expected = true },
+	/* Simple wild cards */
+	{ .pat = "?", .str = "a", .expected = true },
+	{ .pat = "?", .str = "aa", .expected = false },
+	{ .pat = "??", .str = "a", .expected = false },
+	{ .pat = "?x?", .str = "axb", .expected = true },
+	{ .pat = "?x?", .str = "abx", .expected = false },
+	{ .pat = "?x?", .str = "xab", .expected = false },
+	/* Asterisk wild cards (backtracking) */
+	{ .pat = "*??", .str = "a", .expected = false },
+	{ .pat = "*??", .str = "ab", .expected = true },
+	{ .pat = "*??", .str = "abc", .expected = true },
+	{ .pat = "*??", .str = "abcd", .expected = true },
+	{ .pat = "??*", .str = "a", .expected = false },
+	{ .pat = "??*", .str = "ab", .expected = true },
+	{ .pat = "??*", .str = "abc", .expected = true },
+	{ .pat = "??*", .str = "abcd", .expected = true },
+	{ .pat = "?*?", .str = "a", .expected = false },
+	{ .pat = "?*?", .str = "ab", .expected = true },
+	{ .pat = "?*?", .str = "abc", .expected = true },
+	{ .pat = "?*?", .str = "abcd", .expected = true },
+	{ .pat = "*b", .str = "b", .expected = true },
+	{ .pat = "*b", .str = "ab", .expected = true },
+	{ .pat = "*b", .str = "ba", .expected = false },
+	{ .pat = "*b", .str = "bb", .expected = true },
+	{ .pat = "*b", .str = "abb", .expected = true },
+	{ .pat = "*b", .str = "bab", .expected = true },
+	{ .pat = "*bc", .str = "abbc", .expected = true },
+	{ .pat = "*bc", .str = "bc", .expected = true },
+	{ .pat = "*bc", .str = "bbc", .expected = true },
+	{ .pat = "*bc", .str = "bcbc", .expected = true },
+	/* Multiple asterisks (complex backtracking) */
+	{ .pat = "*ac*", .str = "abacadaeafag", .expected = true },
+	{ .pat = "*ac*ae*ag*", .str = "abacadaeafag", .expected = true },
+	{ .pat = "*a*b*[bc]*[ef]*g*", .str = "abacadaeafag", .expected = true },
+	{ .pat = "*a*b*[ef]*[cd]*g*", .str = "abacadaeafag", .expected = false },
+	{ .pat = "*abcd*", .str = "abcabcabcabcdefg", .expected = true },
+	{ .pat = "*ab*cd*", .str = "abcabcabcabcdefg", .expected = true },
+	{ .pat = "*abcd*abcdef*", .str = "abcabcdabcdeabcdefg", .expected = true },
+	{ .pat = "*abcd*", .str = "abcabcabcabcefg", .expected = false },
+	{ .pat = "*ab*cd*", .str = "abcabcabcabcefg", .expected = false },
+};
+
+static void glob_case_to_desc(const struct glob_test_case *t, char *desc)
+{
+	snprintf(desc, KUNIT_PARAM_DESC_SIZE, "pat:\"%s\" str:\"%s\"", t->pat, t->str);
+}
+
+KUNIT_ARRAY_PARAM(glob, glob_test_cases, glob_case_to_desc);
+
+static void glob_test_match(struct kunit *test)
+{
+	const struct glob_test_case *params = test->param_value;
+
+	KUNIT_EXPECT_EQ_MSG(test,
+			    glob_match(params->pat, params->str),
+			    params->expected,
+			    "Pattern: \"%s\", String: \"%s\", Expected: %d",
+			    params->pat, params->str, params->expected);
+}
+
+static struct kunit_case glob_kunit_test_cases[] = {
+	KUNIT_CASE_PARAM(glob_test_match, glob_gen_params),
+	{}
+};
+
+static struct kunit_suite glob_test_suite = {
+	.name = "glob",
+	.test_cases = glob_kunit_test_cases,
+};
+
+kunit_test_suite(glob_test_suite);
+MODULE_DESCRIPTION("Test cases for glob functions");
+MODULE_LICENSE("Dual MIT/GPL");