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, 59 insertions, 0 deletions

diff --git a/include/scsi/scsi_eh.h b/include/scsi/scsi_eh.h
new file mode 100644
index 000000000..15679be90
--- /dev/null
+++ b/include/scsi/scsi_eh.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _SCSI_SCSI_EH_H
+#define _SCSI_SCSI_EH_H
+
+#include <linux/scatterlist.h>
+
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_common.h>
+struct scsi_device;
+struct Scsi_Host;
+
+extern void scsi_eh_finish_cmd(struct scsi_cmnd *scmd,
+			       struct list_head *done_q);
+extern void scsi_eh_flush_done_q(struct list_head *done_q);
+extern void scsi_report_bus_reset(struct Scsi_Host *, int);
+extern void scsi_report_device_reset(struct Scsi_Host *, int, int);
+extern int scsi_block_when_processing_errors(struct scsi_device *);
+extern bool scsi_command_normalize_sense(const struct scsi_cmnd *cmd,
+					 struct scsi_sense_hdr *sshdr);
+extern enum scsi_disposition scsi_check_sense(struct scsi_cmnd *);
+
+static inline bool scsi_sense_is_deferred(const struct scsi_sense_hdr *sshdr)
+{
+	return ((sshdr->response_code >= 0x70) && (sshdr->response_code & 1));
+}
+
+extern bool scsi_get_sense_info_fld(const u8 *sense_buffer, int sb_len,
+				    u64 *info_out);
+
+extern int scsi_ioctl_reset(struct scsi_device *, int __user *);
+
+struct scsi_eh_save {
+	/* saved state */
+	int result;
+	unsigned int resid_len;
+	int eh_eflags;
+	enum dma_data_direction data_direction;
+	unsigned underflow;
+	unsigned char cmd_len;
+	unsigned char prot_op;
+	unsigned char cmnd[32];
+	struct scsi_data_buffer sdb;
+	struct scatterlist sense_sgl;
+
+	/* struct request fields */
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+	struct bio_crypt_ctx *rq_crypt_ctx;
+	struct blk_crypto_keyslot *rq_crypt_keyslot;
+#endif
+};
+
+extern void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd,
+		struct scsi_eh_save *ses, unsigned char *cmnd,
+		int cmnd_size, unsigned sense_bytes);
+
+extern void scsi_eh_restore_cmnd(struct scsi_cmnd* scmd,
+		struct scsi_eh_save *ses);
+
+#endif /* _SCSI_SCSI_EH_H */