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, 99 insertions, 0 deletions

diff --git a/include/scsi/scsi_common.h b/include/scsi/scsi_common.h
new file mode 100644
index 000000000..00c8a16d3
--- /dev/null
+++ b/include/scsi/scsi_common.h
@@ -0,0 +1,99 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Functions used by both the SCSI initiator code and the SCSI target code.
+ */
+
+#ifndef _SCSI_COMMON_H_
+#define _SCSI_COMMON_H_
+
+#include <linux/types.h>
+#include <uapi/linux/pr.h>
+#include <scsi/scsi_proto.h>
+
+/* From the standard INQUIRY data description in SPC-6. */
+#define INQUIRY_VENDOR_OFFSET	8
+#define INQUIRY_VENDOR_LEN	8
+#define INQUIRY_MODEL_OFFSET	16
+#define INQUIRY_MODEL_LEN	16
+#define INQUIRY_REVISION_OFFSET	32
+#define INQUIRY_REVISION_LEN	4
+
+enum scsi_pr_type {
+	SCSI_PR_WRITE_EXCLUSIVE			= 0x01,
+	SCSI_PR_EXCLUSIVE_ACCESS		= 0x03,
+	SCSI_PR_WRITE_EXCLUSIVE_REG_ONLY	= 0x05,
+	SCSI_PR_EXCLUSIVE_ACCESS_REG_ONLY	= 0x06,
+	SCSI_PR_WRITE_EXCLUSIVE_ALL_REGS	= 0x07,
+	SCSI_PR_EXCLUSIVE_ACCESS_ALL_REGS	= 0x08,
+};
+
+enum scsi_pr_type block_pr_type_to_scsi(enum pr_type type);
+enum pr_type scsi_pr_type_to_block(enum scsi_pr_type type);
+
+static inline unsigned
+scsi_varlen_cdb_length(const void *hdr)
+{
+	return ((struct scsi_varlen_cdb_hdr *)hdr)->additional_cdb_length + 8;
+}
+
+extern const unsigned char scsi_command_size_tbl[8];
+#define COMMAND_SIZE(opcode) scsi_command_size_tbl[((opcode) >> 5) & 7]
+
+static inline unsigned
+scsi_command_size(const unsigned char *cmnd)
+{
+	return (cmnd[0] == VARIABLE_LENGTH_CMD) ?
+		scsi_varlen_cdb_length(cmnd) : COMMAND_SIZE(cmnd[0]);
+}
+
+static inline unsigned char
+scsi_command_control(const unsigned char *cmnd)
+{
+	return (cmnd[0] == VARIABLE_LENGTH_CMD) ?
+		cmnd[1] : cmnd[COMMAND_SIZE(cmnd[0]) - 1];
+}
+
+/* Returns a human-readable name for the device */
+extern const char *scsi_device_type(unsigned type);
+
+extern void int_to_scsilun(u64, struct scsi_lun *);
+extern u64 scsilun_to_int(struct scsi_lun *);
+
+/*
+ * This is a slightly modified SCSI sense "descriptor" format header.
+ * The addition is to allow the 0x70 and 0x71 response codes. The idea
+ * is to place the salient data from either "fixed" or "descriptor" sense
+ * format into one structure to ease application processing.
+ *
+ * The original sense buffer should be kept around for those cases
+ * in which more information is required (e.g. the LBA of a MEDIUM ERROR).
+ */
+struct scsi_sense_hdr {		/* See SPC-3 section 4.5 */
+	u8 response_code;	/* permit: 0x0, 0x70, 0x71, 0x72, 0x73 */
+	u8 sense_key;
+	u8 asc;
+	u8 ascq;
+	u8 byte4;
+	u8 byte5;
+	u8 byte6;
+	u8 additional_length;	/* always 0 for fixed sense format */
+};
+
+static inline bool scsi_sense_valid(const struct scsi_sense_hdr *sshdr)
+{
+	if (!sshdr)
+		return false;
+
+	return (sshdr->response_code & 0x70) == 0x70;
+}
+
+extern bool scsi_normalize_sense(const u8 *sense_buffer, int sb_len,
+				 struct scsi_sense_hdr *sshdr);
+
+extern void scsi_build_sense_buffer(int desc, u8 *buf, u8 key, u8 asc, u8 ascq);
+int scsi_set_sense_information(u8 *buf, int buf_len, u64 info);
+int scsi_set_sense_field_pointer(u8 *buf, int buf_len, u16 fp, u8 bp, bool cd);
+extern const u8 * scsi_sense_desc_find(const u8 * sense_buffer, int sb_len,
+				       int desc_type);
+
+#endif /* _SCSI_COMMON_H_ */