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, 220 insertions, 0 deletions

diff --git a/include/trace/events/target.h b/include/trace/events/target.h
new file mode 100644
index 000000000..7e2e20ba2
--- /dev/null
+++ b/include/trace/events/target.h
@@ -0,0 +1,220 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM target
+
+#if !defined(_TRACE_TARGET_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_TARGET_H
+
+#include <linux/tracepoint.h>
+#include <linux/trace_seq.h>
+#include <scsi/scsi_proto.h>
+#include <scsi/scsi_tcq.h>
+#include <target/target_core_base.h>
+
+/* cribbed verbatim from <trace/event/scsi.h> */
+#define scsi_opcode_name(opcode)	{ opcode, #opcode }
+#define show_opcode_name(val)					\
+	__print_symbolic(val,					\
+		scsi_opcode_name(TEST_UNIT_READY),		\
+		scsi_opcode_name(REZERO_UNIT),			\
+		scsi_opcode_name(REQUEST_SENSE),		\
+		scsi_opcode_name(FORMAT_UNIT),			\
+		scsi_opcode_name(READ_BLOCK_LIMITS),		\
+		scsi_opcode_name(REASSIGN_BLOCKS),		\
+		scsi_opcode_name(INITIALIZE_ELEMENT_STATUS),	\
+		scsi_opcode_name(READ_6),			\
+		scsi_opcode_name(WRITE_6),			\
+		scsi_opcode_name(SEEK_6),			\
+		scsi_opcode_name(READ_REVERSE),			\
+		scsi_opcode_name(WRITE_FILEMARKS),		\
+		scsi_opcode_name(SPACE),			\
+		scsi_opcode_name(INQUIRY),			\
+		scsi_opcode_name(RECOVER_BUFFERED_DATA),	\
+		scsi_opcode_name(MODE_SELECT),			\
+		scsi_opcode_name(RESERVE_6),			\
+		scsi_opcode_name(RELEASE_6),			\
+		scsi_opcode_name(COPY),				\
+		scsi_opcode_name(ERASE),			\
+		scsi_opcode_name(MODE_SENSE),			\
+		scsi_opcode_name(START_STOP),			\
+		scsi_opcode_name(RECEIVE_DIAGNOSTIC),		\
+		scsi_opcode_name(SEND_DIAGNOSTIC),		\
+		scsi_opcode_name(ALLOW_MEDIUM_REMOVAL),		\
+		scsi_opcode_name(SET_WINDOW),			\
+		scsi_opcode_name(READ_CAPACITY),		\
+		scsi_opcode_name(READ_10),			\
+		scsi_opcode_name(WRITE_10),			\
+		scsi_opcode_name(SEEK_10),			\
+		scsi_opcode_name(POSITION_TO_ELEMENT),		\
+		scsi_opcode_name(WRITE_VERIFY),			\
+		scsi_opcode_name(VERIFY),			\
+		scsi_opcode_name(SEARCH_HIGH),			\
+		scsi_opcode_name(SEARCH_EQUAL),			\
+		scsi_opcode_name(SEARCH_LOW),			\
+		scsi_opcode_name(SET_LIMITS),			\
+		scsi_opcode_name(PRE_FETCH),			\
+		scsi_opcode_name(READ_POSITION),		\
+		scsi_opcode_name(SYNCHRONIZE_CACHE),		\
+		scsi_opcode_name(LOCK_UNLOCK_CACHE),		\
+		scsi_opcode_name(READ_DEFECT_DATA),		\
+		scsi_opcode_name(MEDIUM_SCAN),			\
+		scsi_opcode_name(COMPARE),			\
+		scsi_opcode_name(COPY_VERIFY),			\
+		scsi_opcode_name(WRITE_BUFFER),			\
+		scsi_opcode_name(READ_BUFFER),			\
+		scsi_opcode_name(UPDATE_BLOCK),			\
+		scsi_opcode_name(READ_LONG),			\
+		scsi_opcode_name(WRITE_LONG),			\
+		scsi_opcode_name(CHANGE_DEFINITION),		\
+		scsi_opcode_name(WRITE_SAME),			\
+		scsi_opcode_name(UNMAP),			\
+		scsi_opcode_name(READ_TOC),			\
+		scsi_opcode_name(LOG_SELECT),			\
+		scsi_opcode_name(LOG_SENSE),			\
+		scsi_opcode_name(XDWRITEREAD_10),		\
+		scsi_opcode_name(MODE_SELECT_10),		\
+		scsi_opcode_name(RESERVE_10),			\
+		scsi_opcode_name(RELEASE_10),			\
+		scsi_opcode_name(MODE_SENSE_10),		\
+		scsi_opcode_name(PERSISTENT_RESERVE_IN),	\
+		scsi_opcode_name(PERSISTENT_RESERVE_OUT),	\
+		scsi_opcode_name(VARIABLE_LENGTH_CMD),		\
+		scsi_opcode_name(REPORT_LUNS),			\
+		scsi_opcode_name(MAINTENANCE_IN),		\
+		scsi_opcode_name(MAINTENANCE_OUT),		\
+		scsi_opcode_name(MOVE_MEDIUM),			\
+		scsi_opcode_name(EXCHANGE_MEDIUM),		\
+		scsi_opcode_name(READ_12),			\
+		scsi_opcode_name(WRITE_12),			\
+		scsi_opcode_name(WRITE_VERIFY_12),		\
+		scsi_opcode_name(SEARCH_HIGH_12),		\
+		scsi_opcode_name(SEARCH_EQUAL_12),		\
+		scsi_opcode_name(SEARCH_LOW_12),		\
+		scsi_opcode_name(READ_ELEMENT_STATUS),		\
+		scsi_opcode_name(SEND_VOLUME_TAG),		\
+		scsi_opcode_name(WRITE_LONG_2),			\
+		scsi_opcode_name(READ_16),			\
+		scsi_opcode_name(WRITE_16),			\
+		scsi_opcode_name(VERIFY_16),			\
+		scsi_opcode_name(WRITE_SAME_16),		\
+		scsi_opcode_name(SERVICE_ACTION_IN_16),		\
+		scsi_opcode_name(SAI_READ_CAPACITY_16),		\
+		scsi_opcode_name(SAI_GET_LBA_STATUS),		\
+		scsi_opcode_name(MI_REPORT_TARGET_PGS),		\
+		scsi_opcode_name(MO_SET_TARGET_PGS),		\
+		scsi_opcode_name(READ_32),			\
+		scsi_opcode_name(WRITE_32),			\
+		scsi_opcode_name(WRITE_SAME_32),		\
+		scsi_opcode_name(ATA_16),			\
+		scsi_opcode_name(ATA_12))
+
+#define show_task_attribute_name(val)				\
+	__print_symbolic(val,					\
+		{ TCM_SIMPLE_TAG,	"SIMPLE"	},	\
+		{ TCM_HEAD_TAG,		"HEAD"		},	\
+		{ TCM_ORDERED_TAG,	"ORDERED"	},	\
+		{ TCM_ACA_TAG,		"ACA"		} )
+
+#define show_scsi_status_name(val)				\
+	__print_symbolic(val,					\
+		{ SAM_STAT_GOOD,	"GOOD" },		\
+		{ SAM_STAT_CHECK_CONDITION, "CHECK CONDITION" }, \
+		{ SAM_STAT_CONDITION_MET, "CONDITION MET" },	\
+		{ SAM_STAT_BUSY,	"BUSY" },		\
+		{ SAM_STAT_INTERMEDIATE, "INTERMEDIATE" },	\
+		{ SAM_STAT_INTERMEDIATE_CONDITION_MET, "INTERMEDIATE CONDITION MET" }, \
+		{ SAM_STAT_RESERVATION_CONFLICT, "RESERVATION CONFLICT" }, \
+		{ SAM_STAT_COMMAND_TERMINATED, "COMMAND TERMINATED" }, \
+		{ SAM_STAT_TASK_SET_FULL, "TASK SET FULL" },	\
+		{ SAM_STAT_ACA_ACTIVE, "ACA ACTIVE" },		\
+		{ SAM_STAT_TASK_ABORTED, "TASK ABORTED" } )
+
+TRACE_EVENT(target_sequencer_start,
+
+	TP_PROTO(struct se_cmd *cmd),
+
+	TP_ARGS(cmd),
+
+	TP_STRUCT__entry(
+		__field( unsigned int,	unpacked_lun	)
+		__field( unsigned long long,	tag	)
+		__field( unsigned int,	opcode		)
+		__field( unsigned int,	data_length	)
+		__field( unsigned int,	task_attribute  )
+		__field( unsigned char,	control		)
+		__array( unsigned char,	cdb, TCM_MAX_COMMAND_SIZE	)
+		__string( initiator,	cmd->se_sess->se_node_acl->initiatorname	)
+	),
+
+	TP_fast_assign(
+		__entry->unpacked_lun	= cmd->orig_fe_lun;
+		__entry->tag		= cmd->tag;
+		__entry->opcode		= cmd->t_task_cdb[0];
+		__entry->data_length	= cmd->data_length;
+		__entry->task_attribute	= cmd->sam_task_attr;
+		__entry->control	= scsi_command_control(cmd->t_task_cdb);
+		memcpy(__entry->cdb, cmd->t_task_cdb, TCM_MAX_COMMAND_SIZE);
+		__assign_str(initiator);
+	),
+
+	TP_printk("%s -> LUN %03u tag %#llx %s data_length %6u  CDB %s  (TA:%s C:%02x)",
+		  __get_str(initiator), __entry->unpacked_lun,
+		  __entry->tag, show_opcode_name(__entry->opcode),
+		  __entry->data_length, __print_hex(__entry->cdb, 16),
+		  show_task_attribute_name(__entry->task_attribute),
+		  __entry->control
+	)
+);
+
+TRACE_EVENT(target_cmd_complete,
+
+	TP_PROTO(struct se_cmd *cmd),
+
+	TP_ARGS(cmd),
+
+	TP_STRUCT__entry(
+		__field( unsigned int,	unpacked_lun	)
+		__field( unsigned long long,	tag	)
+		__field( unsigned int,	opcode		)
+		__field( unsigned int,	data_length	)
+		__field( unsigned int,	task_attribute  )
+		__field( unsigned char,	control		)
+		__field( unsigned char,	scsi_status	)
+		__field( unsigned char,	sense_length	)
+		__array( unsigned char,	cdb, TCM_MAX_COMMAND_SIZE	)
+		__array( unsigned char,	sense_data, 18	)
+		__string(initiator,	cmd->se_sess->se_node_acl->initiatorname)
+	),
+
+	TP_fast_assign(
+		__entry->unpacked_lun	= cmd->orig_fe_lun;
+		__entry->tag		= cmd->tag;
+		__entry->opcode		= cmd->t_task_cdb[0];
+		__entry->data_length	= cmd->data_length;
+		__entry->task_attribute	= cmd->sam_task_attr;
+		__entry->control	= scsi_command_control(cmd->t_task_cdb);
+		__entry->scsi_status	= cmd->scsi_status;
+		__entry->sense_length	= cmd->scsi_status == SAM_STAT_CHECK_CONDITION ?
+			min(18, ((u8 *) cmd->sense_buffer)[SPC_ADD_SENSE_LEN_OFFSET] + 8) : 0;
+		memcpy(__entry->cdb, cmd->t_task_cdb, TCM_MAX_COMMAND_SIZE);
+		memcpy(__entry->sense_data, cmd->sense_buffer, __entry->sense_length);
+		__assign_str(initiator);
+	),
+
+	TP_printk("%s <- LUN %03u tag %#llx status %s (sense len %d%s%s)  %s data_length %6u  CDB %s  (TA:%s C:%02x)",
+		  __get_str(initiator), __entry->unpacked_lun,
+		  __entry->tag,
+		  show_scsi_status_name(__entry->scsi_status),
+		  __entry->sense_length, __entry->sense_length ? " / " : "",
+		  __print_hex(__entry->sense_data, __entry->sense_length),
+		  show_opcode_name(__entry->opcode),
+		  __entry->data_length, __print_hex(__entry->cdb, 16),
+		  show_task_attribute_name(__entry->task_attribute),
+		  __entry->control
+	)
+);
+
+#endif /*  _TRACE_TARGET_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>