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, 55 insertions, 0 deletions

diff --git a/include/scsi/scsi_ioctl.h b/include/scsi/scsi_ioctl.h
new file mode 100644
index 000000000..a207c07da
--- /dev/null
+++ b/include/scsi/scsi_ioctl.h
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _SCSI_IOCTL_H
+#define _SCSI_IOCTL_H 
+
+#define SCSI_IOCTL_SEND_COMMAND 1
+#define SCSI_IOCTL_TEST_UNIT_READY 2
+#define SCSI_IOCTL_BENCHMARK_COMMAND 3
+#define SCSI_IOCTL_SYNC 4			/* Request synchronous parameters */
+#define SCSI_IOCTL_START_UNIT 5
+#define SCSI_IOCTL_STOP_UNIT 6
+/* The door lock/unlock constants are compatible with Sun constants for
+   the cdrom */
+#define SCSI_IOCTL_DOORLOCK 0x5380		/* lock the eject mechanism */
+#define SCSI_IOCTL_DOORUNLOCK 0x5381		/* unlock the mechanism	  */
+
+#define	SCSI_REMOVAL_PREVENT	1
+#define	SCSI_REMOVAL_ALLOW	0
+
+#ifdef __KERNEL__
+
+struct gendisk;
+struct scsi_device;
+struct sg_io_hdr;
+
+/*
+ * Structures used for scsi_ioctl et al.
+ */
+
+typedef struct scsi_ioctl_command {
+	unsigned int inlen;
+	unsigned int outlen;
+	unsigned char data[];
+} Scsi_Ioctl_Command;
+
+typedef struct scsi_idlun {
+	__u32 dev_id;
+	__u32 host_unique_id;
+} Scsi_Idlun;
+
+/* Fibre Channel WWN, port_id struct */
+typedef struct scsi_fctargaddress {
+	__u32 host_port_id;
+	unsigned char host_wwn[8]; // include NULL term.
+} Scsi_FCTargAddress;
+
+int scsi_ioctl_block_when_processing_errors(struct scsi_device *sdev,
+		int cmd, bool ndelay);
+int scsi_ioctl(struct scsi_device *sdev, bool open_for_write, int cmd,
+		void __user *arg);
+int get_sg_io_hdr(struct sg_io_hdr *hdr, const void __user *argp);
+int put_sg_io_hdr(const struct sg_io_hdr *hdr, void __user *argp);
+bool scsi_cmd_allowed(unsigned char *cmd, bool open_for_write);
+
+#endif /* __KERNEL__ */
+#endif /* _SCSI_IOCTL_H */