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, 146 insertions, 0 deletions

diff --git a/fs/ntfs/collate.c b/fs/ntfs/collate.c
new file mode 100644
index 000000000..77e340389
--- /dev/null
+++ b/fs/ntfs/collate.c
@@ -0,0 +1,146 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * NTFS kernel collation handling.
+ *
+ * Copyright (c) 2004 Anton Altaparmakov
+ *
+ * Part of this file is based on code from the NTFS-3G.
+ * and is copyrighted by the respective authors below:
+ * Copyright (c) 2004 Anton Altaparmakov
+ * Copyright (c) 2005 Yura Pakhuchiy
+ */
+
+#include "collate.h"
+#include "debug.h"
+#include "ntfs.h"
+
+#include <linux/sort.h>
+
+static int ntfs_collate_binary(struct ntfs_volume *vol,
+		const void *data1, const u32 data1_len,
+		const void *data2, const u32 data2_len)
+{
+	int rc;
+
+	rc = memcmp(data1, data2, min(data1_len, data2_len));
+	if (!rc && (data1_len != data2_len)) {
+		if (data1_len < data2_len)
+			rc = -1;
+		else
+			rc = 1;
+	}
+	return rc;
+}
+
+static int ntfs_collate_ntofs_ulong(struct ntfs_volume *vol,
+		const void *data1, const u32 data1_len,
+		const void *data2, const u32 data2_len)
+{
+	int rc;
+	u32 d1 = le32_to_cpup(data1), d2 = le32_to_cpup(data2);
+
+	if (data1_len != data2_len || data1_len != 4)
+		return -EINVAL;
+
+	if (d1 < d2)
+		rc = -1;
+	else {
+		if (d1 == d2)
+			rc = 0;
+		else
+			rc = 1;
+	}
+	return rc;
+}
+
+/*
+ * ntfs_collate_ntofs_ulongs - Which of two le32 arrays should be listed first
+ * @vol: ntfs volume
+ * @data1: first ulong array to collate
+ * @data1_len: length in bytes of @data1
+ * @data2: second ulong array to collate
+ * @data2_len: length in bytes of @data2
+ *
+ * Returns: -1, 0 or 1 depending of how the arrays compare
+ */
+static int ntfs_collate_ntofs_ulongs(struct ntfs_volume *vol,
+		const void *data1, const u32 data1_len,
+		const void *data2, const u32 data2_len)
+{
+	int len;
+	const __le32 *p1 = data1, *p2 = data2;
+	u32 d1, d2;
+
+	if (data1_len != data2_len || data1_len & 3) {
+		ntfs_error(vol->sb, "data1_len or data2_len not valid\n");
+		return -1;
+	}
+
+	len = data1_len;
+	do {
+		d1 = le32_to_cpup(p1);
+		p1++;
+		d2 = le32_to_cpup(p2);
+		p2++;
+	} while (d1 == d2 && (len -= 4) > 0);
+	return cmp_int(d1, d2);
+}
+
+/*
+ * ntfs_collate_file_name - Which of two filenames should be listed first
+ * @vol: ntfs volume
+ * @data1: first filename to collate
+ * @data1_len: length in bytes of @data1(unused)
+ * @data2: second filename to collate
+ * @data2_len: length in bytes of @data2(unused)
+ */
+static int ntfs_collate_file_name(struct ntfs_volume *vol,
+		const void *data1, const u32 data1_len,
+		const void *data2, const u32 data2_len)
+{
+	int rc;
+
+	rc = ntfs_file_compare_values(data1, data2, -EINVAL,
+			IGNORE_CASE, vol->upcase, vol->upcase_len);
+	if (!rc)
+		rc = ntfs_file_compare_values(data1, data2,
+			-EINVAL, CASE_SENSITIVE, vol->upcase, vol->upcase_len);
+	return rc;
+}
+
+/*
+ * ntfs_collate - collate two data items using a specified collation rule
+ * @vol:	ntfs volume to which the data items belong
+ * @cr:		collation rule to use when comparing the items
+ * @data1:	first data item to collate
+ * @data1_len:	length in bytes of @data1
+ * @data2:	second data item to collate
+ * @data2_len:	length in bytes of @data2
+ *
+ * Collate the two data items @data1 and @data2 using the collation rule @cr
+ * and return -1, 0, ir 1 if @data1 is found, respectively, to collate before,
+ * to match, or to collate after @data2. return -EINVAL if an error occurred.
+ */
+int ntfs_collate(struct ntfs_volume *vol, __le32 cr,
+		const void *data1, const u32 data1_len,
+		const void *data2, const u32 data2_len)
+{
+	switch (le32_to_cpu(cr)) {
+	case le32_to_cpu(COLLATION_BINARY):
+		return ntfs_collate_binary(vol, data1, data1_len,
+					   data2, data2_len);
+	case le32_to_cpu(COLLATION_FILE_NAME):
+		return ntfs_collate_file_name(vol, data1, data1_len,
+					      data2, data2_len);
+	case le32_to_cpu(COLLATION_NTOFS_ULONG):
+		return ntfs_collate_ntofs_ulong(vol, data1, data1_len,
+						data2, data2_len);
+	case le32_to_cpu(COLLATION_NTOFS_ULONGS):
+		return ntfs_collate_ntofs_ulongs(vol, data1, data1_len,
+						 data2, data2_len);
+	default:
+		ntfs_error(vol->sb, "Unknown collation rule 0x%x",
+			   le32_to_cpu(cr));
+		return -EINVAL;
+	}
+}