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>

2 files changed, 300 insertions, 0 deletions

diff --git a/fs/unicode/tests/.kunitconfig b/fs/unicode/tests/.kunitconfig
new file mode 100644
index 000000000..62dd5c171
--- /dev/null
+++ b/fs/unicode/tests/.kunitconfig
@@ -0,0 +1,3 @@
+CONFIG_KUNIT=y
+CONFIG_UNICODE=y
+CONFIG_UNICODE_NORMALIZATION_KUNIT_TEST=y
diff --git a/fs/unicode/tests/utf8_kunit.c b/fs/unicode/tests/utf8_kunit.c
new file mode 100644
index 000000000..5063e8138
--- /dev/null
+++ b/fs/unicode/tests/utf8_kunit.c
@@ -0,0 +1,297 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KUnit tests for utf-8 support.
+ *
+ * Copyright 2017 Collabora Ltd.
+ */
+
+#include <linux/unicode.h>
+#include <kunit/test.h>
+
+#include "../utf8n.h"
+
+static const struct {
+	/* UTF-8 strings in this vector _must_ be NULL-terminated. */
+	unsigned char str[10];
+	unsigned char dec[10];
+} nfdi_test_data[] = {
+	/* Trivial sequence */
+	{
+		/* "ABba" decomposes to itself */
+		.str = "aBba",
+		.dec = "aBba",
+	},
+	/* Simple equivalent sequences */
+	{
+               /* 'VULGAR FRACTION ONE QUARTER' cannot decompose to
+                  'NUMBER 1' + 'FRACTION SLASH' + 'NUMBER 4' on
+                  canonical decomposition */
+               .str = {0xc2, 0xbc, 0x00},
+	       .dec = {0xc2, 0xbc, 0x00},
+	},
+	{
+		/* 'LATIN SMALL LETTER A WITH DIAERESIS' decomposes to
+		   'LETTER A' + 'COMBINING DIAERESIS' */
+		.str = {0xc3, 0xa4, 0x00},
+		.dec = {0x61, 0xcc, 0x88, 0x00},
+	},
+	{
+		/* 'LATIN SMALL LETTER LJ' can't decompose to
+		   'LETTER L' + 'LETTER J' on canonical decomposition */
+		.str = {0xC7, 0x89, 0x00},
+		.dec = {0xC7, 0x89, 0x00},
+	},
+	{
+		/* GREEK ANO TELEIA decomposes to MIDDLE DOT */
+		.str = {0xCE, 0x87, 0x00},
+		.dec = {0xC2, 0xB7, 0x00}
+	},
+	/* Canonical ordering */
+	{
+		/* A + 'COMBINING ACUTE ACCENT' + 'COMBINING OGONEK' decomposes
+		   to A + 'COMBINING OGONEK' + 'COMBINING ACUTE ACCENT' */
+		.str = {0x41, 0xcc, 0x81, 0xcc, 0xa8, 0x0},
+		.dec = {0x41, 0xcc, 0xa8, 0xcc, 0x81, 0x0},
+	},
+	{
+		/* 'LATIN SMALL LETTER A WITH DIAERESIS' + 'COMBINING OGONEK'
+		   decomposes to
+		   'LETTER A' + 'COMBINING OGONEK' + 'COMBINING DIAERESIS' */
+		.str = {0xc3, 0xa4, 0xCC, 0xA8, 0x00},
+
+		.dec = {0x61, 0xCC, 0xA8, 0xcc, 0x88, 0x00},
+	},
+
+};
+
+static const struct {
+	/* UTF-8 strings in this vector _must_ be NULL-terminated. */
+	unsigned char str[30];
+	unsigned char ncf[30];
+} nfdicf_test_data[] = {
+	/* Trivial sequences */
+	{
+		/* "ABba" folds to lowercase */
+		.str = {0x41, 0x42, 0x62, 0x61, 0x00},
+		.ncf = {0x61, 0x62, 0x62, 0x61, 0x00},
+	},
+	{
+		/* All ASCII folds to lower-case */
+		.str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0.1",
+		.ncf = "abcdefghijklmnopqrstuvwxyz0.1",
+	},
+	{
+		/* LATIN SMALL LETTER SHARP S folds to
+		   LATIN SMALL LETTER S + LATIN SMALL LETTER S */
+		.str = {0xc3, 0x9f, 0x00},
+		.ncf = {0x73, 0x73, 0x00},
+	},
+	{
+		/* LATIN CAPITAL LETTER A WITH RING ABOVE folds to
+		   LATIN SMALL LETTER A + COMBINING RING ABOVE */
+		.str = {0xC3, 0x85, 0x00},
+		.ncf = {0x61, 0xcc, 0x8a, 0x00},
+	},
+	/* Introduced by UTF-8.0.0. */
+	/* Cherokee letters are interesting test-cases because they fold
+	   to upper-case.  Before 8.0.0, Cherokee lowercase were
+	   undefined, thus, the folding from LC is not stable between
+	   7.0.0 -> 8.0.0, but it is from UC. */
+	{
+		/* CHEROKEE SMALL LETTER A folds to CHEROKEE LETTER A */
+		.str = {0xea, 0xad, 0xb0, 0x00},
+		.ncf = {0xe1, 0x8e, 0xa0, 0x00},
+	},
+	{
+		/* CHEROKEE SMALL LETTER YE folds to CHEROKEE LETTER YE */
+		.str = {0xe1, 0x8f, 0xb8, 0x00},
+		.ncf = {0xe1, 0x8f, 0xb0, 0x00},
+	},
+	{
+		/* OLD HUNGARIAN CAPITAL LETTER AMB folds to
+		   OLD HUNGARIAN SMALL LETTER AMB */
+		.str = {0xf0, 0x90, 0xb2, 0x83, 0x00},
+		.ncf = {0xf0, 0x90, 0xb3, 0x83, 0x00},
+	},
+	/* Introduced by UTF-9.0.0. */
+	{
+		/* OSAGE CAPITAL LETTER CHA folds to
+		   OSAGE SMALL LETTER CHA */
+		.str = {0xf0, 0x90, 0x92, 0xb5, 0x00},
+		.ncf = {0xf0, 0x90, 0x93, 0x9d, 0x00},
+	},
+	{
+		/* LATIN CAPITAL LETTER SMALL CAPITAL I folds to
+		   LATIN LETTER SMALL CAPITAL I */
+		.str = {0xea, 0x9e, 0xae, 0x00},
+		.ncf = {0xc9, 0xaa, 0x00},
+	},
+	/* Introduced by UTF-11.0.0. */
+	{
+		/* GEORGIAN SMALL LETTER AN folds to GEORGIAN MTAVRULI
+		   CAPITAL LETTER AN */
+		.str = {0xe1, 0xb2, 0x90, 0x00},
+		.ncf = {0xe1, 0x83, 0x90, 0x00},
+	}
+};
+
+static ssize_t utf8len(const struct unicode_map *um, enum utf8_normalization n,
+		const char *s)
+{
+	return utf8nlen(um, n, s, (size_t)-1);
+}
+
+static int utf8cursor(struct utf8cursor *u8c, const struct unicode_map *um,
+		enum utf8_normalization n, const char *s)
+{
+	return utf8ncursor(u8c, um, n, s, (unsigned int)-1);
+}
+
+static void check_utf8_nfdi(struct kunit *test)
+{
+	int i;
+	struct utf8cursor u8c;
+	struct unicode_map *um = test->priv;
+
+	for (i = 0; i < ARRAY_SIZE(nfdi_test_data); i++) {
+		int len = strlen(nfdi_test_data[i].str);
+		int nlen = strlen(nfdi_test_data[i].dec);
+		int j = 0;
+		unsigned char c;
+		int ret;
+
+		KUNIT_EXPECT_EQ(test, utf8len(um, UTF8_NFDI, nfdi_test_data[i].str), nlen);
+		KUNIT_EXPECT_EQ(test, utf8nlen(um, UTF8_NFDI, nfdi_test_data[i].str, len),
+				nlen);
+
+
+		ret = utf8cursor(&u8c, um, UTF8_NFDI, nfdi_test_data[i].str);
+		KUNIT_EXPECT_TRUE_MSG(test, ret >= 0, "Can't create cursor\n");
+
+		while ((c = utf8byte(&u8c)) > 0) {
+			KUNIT_EXPECT_EQ_MSG(test, c, nfdi_test_data[i].dec[j],
+					    "Unexpected byte 0x%x should be 0x%x\n",
+					    c, nfdi_test_data[i].dec[j]);
+			j++;
+		}
+
+		KUNIT_EXPECT_EQ(test, j, nlen);
+	}
+}
+
+static void check_utf8_nfdicf(struct kunit *test)
+{
+	int i;
+	struct utf8cursor u8c;
+	struct unicode_map *um = test->priv;
+
+	for (i = 0; i < ARRAY_SIZE(nfdicf_test_data); i++) {
+		int len = strlen(nfdicf_test_data[i].str);
+		int nlen = strlen(nfdicf_test_data[i].ncf);
+		int j = 0;
+		int ret;
+		unsigned char c;
+
+		KUNIT_EXPECT_EQ(test, utf8len(um, UTF8_NFDICF, nfdicf_test_data[i].str),
+				nlen);
+		KUNIT_EXPECT_EQ(test, utf8nlen(um, UTF8_NFDICF, nfdicf_test_data[i].str, len),
+				nlen);
+
+		ret = utf8cursor(&u8c, um, UTF8_NFDICF, nfdicf_test_data[i].str);
+		KUNIT_EXPECT_TRUE_MSG(test, ret >= 0, "Can't create cursor\n");
+
+		while ((c = utf8byte(&u8c)) > 0) {
+			KUNIT_EXPECT_EQ_MSG(test, c, nfdicf_test_data[i].ncf[j],
+					    "Unexpected byte 0x%x should be 0x%x\n",
+					    c, nfdicf_test_data[i].ncf[j]);
+			j++;
+		}
+
+		KUNIT_EXPECT_EQ(test, j, nlen);
+	}
+}
+
+static void check_utf8_comparisons(struct kunit *test)
+{
+	int i;
+	struct unicode_map *um = test->priv;
+
+	for (i = 0; i < ARRAY_SIZE(nfdi_test_data); i++) {
+		const struct qstr s1 = {.name = nfdi_test_data[i].str,
+					.len = sizeof(nfdi_test_data[i].str)};
+		const struct qstr s2 = {.name = nfdi_test_data[i].dec,
+					.len = sizeof(nfdi_test_data[i].dec)};
+
+		/* strncmp returns 0 when strings are equal */
+		KUNIT_EXPECT_TRUE_MSG(test, utf8_strncmp(um, &s1, &s2) == 0,
+				    "%s %s comparison mismatch\n", s1.name, s2.name);
+	}
+
+	for (i = 0; i < ARRAY_SIZE(nfdicf_test_data); i++) {
+		const struct qstr s1 = {.name = nfdicf_test_data[i].str,
+					.len = sizeof(nfdicf_test_data[i].str)};
+		const struct qstr s2 = {.name = nfdicf_test_data[i].ncf,
+					.len = sizeof(nfdicf_test_data[i].ncf)};
+
+		/* strncasecmp returns 0 when strings are equal */
+		KUNIT_EXPECT_TRUE_MSG(test, utf8_strncasecmp(um, &s1, &s2) == 0,
+				    "%s %s comparison mismatch\n", s1.name, s2.name);
+	}
+}
+
+static void check_supported_versions(struct kunit *test)
+{
+	struct unicode_map *um = test->priv;
+	/* Unicode 7.0.0 should be supported. */
+	KUNIT_EXPECT_TRUE(test, utf8version_is_supported(um, UNICODE_AGE(7, 0, 0)));
+
+	/* Unicode 9.0.0 should be supported. */
+	KUNIT_EXPECT_TRUE(test, utf8version_is_supported(um, UNICODE_AGE(9, 0, 0)));
+
+	/* Unicode 1x.0.0 (the latest version) should be supported. */
+	KUNIT_EXPECT_TRUE(test, utf8version_is_supported(um, UTF8_LATEST));
+
+	/* Next versions don't exist. */
+	KUNIT_EXPECT_FALSE(test, utf8version_is_supported(um, UNICODE_AGE(13, 0, 0)));
+	KUNIT_EXPECT_FALSE(test, utf8version_is_supported(um, UNICODE_AGE(0, 0, 0)));
+	KUNIT_EXPECT_FALSE(test, utf8version_is_supported(um, UNICODE_AGE(-1, -1, -1)));
+}
+
+static struct kunit_case unicode_normalization_test_cases[] = {
+	KUNIT_CASE(check_supported_versions),
+	KUNIT_CASE(check_utf8_comparisons),
+	KUNIT_CASE(check_utf8_nfdicf),
+	KUNIT_CASE(check_utf8_nfdi),
+	{}
+};
+
+static int init_test_ucd(struct kunit *test)
+{
+	struct unicode_map *um = utf8_load(UTF8_LATEST);
+
+	test->priv = um;
+
+	KUNIT_EXPECT_EQ_MSG(test, IS_ERR(um), 0,
+			    "%s: Unable to load utf8 table.\n", __func__);
+
+	return 0;
+}
+
+static void exit_test_ucd(struct kunit *test)
+{
+	utf8_unload(test->priv);
+}
+
+static struct kunit_suite unicode_normalization_test_suite = {
+	.name = "unicode_normalization",
+	.test_cases = unicode_normalization_test_cases,
+	.init = init_test_ucd,
+	.exit = exit_test_ucd,
+};
+
+kunit_test_suite(unicode_normalization_test_suite);
+
+
+MODULE_AUTHOR("Gabriel Krisman Bertazi <krisman@collabora.co.uk>");
+MODULE_DESCRIPTION("KUnit tests for utf-8 support.");
+MODULE_LICENSE("GPL");