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, 589 insertions, 0 deletions

diff --git a/drivers/acpi/acpica/psloop.c b/drivers/acpi/acpica/psloop.c
new file mode 100644
index 000000000..24a57f971
--- /dev/null
+++ b/drivers/acpi/acpica/psloop.c
@@ -0,0 +1,589 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/******************************************************************************
+ *
+ * Module Name: psloop - Main AML parse loop
+ *
+ * Copyright (C) 2000 - 2026, Intel Corp.
+ *
+ *****************************************************************************/
+
+/*
+ * Parse the AML and build an operation tree as most interpreters, (such as
+ * Perl) do. Parsing is done by hand rather than with a YACC generated parser
+ * to tightly constrain stack and dynamic memory usage. Parsing is kept
+ * flexible and the code fairly compact by parsing based on a list of AML
+ * opcode templates in aml_op_info[].
+ */
+
+#include <acpi/acpi.h>
+#include "accommon.h"
+#include "acinterp.h"
+#include "acparser.h"
+#include "acdispat.h"
+#include "amlcode.h"
+#include "acconvert.h"
+#include "acnamesp.h"
+
+#define _COMPONENT          ACPI_PARSER
+ACPI_MODULE_NAME("psloop")
+
+/* Local prototypes */
+static acpi_status
+acpi_ps_get_arguments(struct acpi_walk_state *walk_state,
+		      u8 * aml_op_start, union acpi_parse_object *op);
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ps_get_arguments
+ *
+ * PARAMETERS:  walk_state          - Current state
+ *              aml_op_start        - Op start in AML
+ *              op                  - Current Op
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Get arguments for passed Op.
+ *
+ ******************************************************************************/
+
+static acpi_status
+acpi_ps_get_arguments(struct acpi_walk_state *walk_state,
+		      u8 * aml_op_start, union acpi_parse_object *op)
+{
+	acpi_status status = AE_OK;
+	union acpi_parse_object *arg = NULL;
+
+	ACPI_FUNCTION_TRACE_PTR(ps_get_arguments, walk_state);
+
+	ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
+			  "Get arguments for opcode [%s]\n",
+			  op->common.aml_op_name));
+
+	switch (op->common.aml_opcode) {
+	case AML_BYTE_OP:	/* AML_BYTEDATA_ARG */
+	case AML_WORD_OP:	/* AML_WORDDATA_ARG */
+	case AML_DWORD_OP:	/* AML_DWORDATA_ARG */
+	case AML_QWORD_OP:	/* AML_QWORDATA_ARG */
+	case AML_STRING_OP:	/* AML_ASCIICHARLIST_ARG */
+
+		/* Fill in constant or string argument directly */
+
+		acpi_ps_get_next_simple_arg(&(walk_state->parser_state),
+					    GET_CURRENT_ARG_TYPE(walk_state->
+								 arg_types),
+					    op);
+		break;
+
+	case AML_INT_NAMEPATH_OP:	/* AML_NAMESTRING_ARG */
+
+		status = acpi_ps_get_next_namepath(walk_state,
+						   &(walk_state->parser_state),
+						   op,
+						   ACPI_POSSIBLE_METHOD_CALL);
+		if (ACPI_FAILURE(status)) {
+			return_ACPI_STATUS(status);
+		}
+
+		walk_state->arg_types = 0;
+		break;
+
+	default:
+		/*
+		 * Op is not a constant or string, append each argument to the Op
+		 */
+		while (GET_CURRENT_ARG_TYPE(walk_state->arg_types) &&
+		       !walk_state->arg_count) {
+			walk_state->aml = walk_state->parser_state.aml;
+
+			switch (op->common.aml_opcode) {
+			case AML_METHOD_OP:
+			case AML_BUFFER_OP:
+			case AML_PACKAGE_OP:
+			case AML_VARIABLE_PACKAGE_OP:
+			case AML_WHILE_OP:
+
+				break;
+
+			default:
+
+				ASL_CV_CAPTURE_COMMENTS(walk_state);
+				break;
+			}
+
+			status =
+			    acpi_ps_get_next_arg(walk_state,
+						 &(walk_state->parser_state),
+						 GET_CURRENT_ARG_TYPE
+						 (walk_state->arg_types), &arg);
+			if (ACPI_FAILURE(status)) {
+				return_ACPI_STATUS(status);
+			}
+
+			if (arg) {
+				acpi_ps_append_arg(op, arg);
+			}
+
+			INCREMENT_ARG_LIST(walk_state->arg_types);
+		}
+
+		ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
+				  "Final argument count: %8.8X pass %u\n",
+				  walk_state->arg_count,
+				  walk_state->pass_number));
+
+		/* Special processing for certain opcodes */
+
+		switch (op->common.aml_opcode) {
+		case AML_METHOD_OP:
+			/*
+			 * Skip parsing of control method because we don't have enough
+			 * info in the first pass to parse it correctly.
+			 *
+			 * Save the length and address of the body
+			 */
+			op->named.data = walk_state->parser_state.aml;
+			op->named.length = (u32)
+			    (walk_state->parser_state.pkg_end -
+			     walk_state->parser_state.aml);
+
+			/* Skip body of method */
+
+			walk_state->parser_state.aml =
+			    walk_state->parser_state.pkg_end;
+			walk_state->arg_count = 0;
+			break;
+
+		case AML_BUFFER_OP:
+		case AML_PACKAGE_OP:
+		case AML_VARIABLE_PACKAGE_OP:
+
+			if ((op->common.parent) &&
+			    (op->common.parent->common.aml_opcode ==
+			     AML_NAME_OP)
+			    && (walk_state->pass_number <=
+				ACPI_IMODE_LOAD_PASS2)) {
+				ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
+						  "Setup Package/Buffer: Pass %u, AML Ptr: %p\n",
+						  walk_state->pass_number,
+						  aml_op_start));
+
+				/*
+				 * Skip parsing of Buffers and Packages because we don't have
+				 * enough info in the first pass to parse them correctly.
+				 */
+				op->named.data = aml_op_start;
+				op->named.length = (u32)
+				    (walk_state->parser_state.pkg_end -
+				     aml_op_start);
+
+				/* Skip body */
+
+				walk_state->parser_state.aml =
+				    walk_state->parser_state.pkg_end;
+				walk_state->arg_count = 0;
+			}
+			break;
+
+		case AML_WHILE_OP:
+
+			if (walk_state->control_state) {
+				walk_state->control_state->control.package_end =
+				    walk_state->parser_state.pkg_end;
+			}
+			break;
+
+		default:
+
+			/* No action for all other opcodes */
+
+			break;
+		}
+
+		break;
+	}
+
+	return_ACPI_STATUS(AE_OK);
+}
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ps_parse_loop
+ *
+ * PARAMETERS:  walk_state          - Current state
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Parse AML (pointed to by the current parser state) and return
+ *              a tree of ops.
+ *
+ ******************************************************************************/
+
+acpi_status acpi_ps_parse_loop(struct acpi_walk_state *walk_state)
+{
+	acpi_status status = AE_OK;
+	union acpi_parse_object *op = NULL;	/* current op */
+	struct acpi_parse_state *parser_state;
+	u8 *aml_op_start = NULL;
+	u8 opcode_length;
+
+	ACPI_FUNCTION_TRACE_PTR(ps_parse_loop, walk_state);
+
+	if (walk_state->descending_callback == NULL) {
+		return_ACPI_STATUS(AE_BAD_PARAMETER);
+	}
+
+	parser_state = &walk_state->parser_state;
+	walk_state->arg_types = 0;
+
+#ifndef ACPI_CONSTANT_EVAL_ONLY
+
+	if (walk_state->walk_type & ACPI_WALK_METHOD_RESTART) {
+
+		/* We are restarting a preempted control method */
+
+		if (acpi_ps_has_completed_scope(parser_state)) {
+			/*
+			 * We must check if a predicate to an IF or WHILE statement
+			 * was just completed
+			 */
+			if ((parser_state->scope->parse_scope.op) &&
+			    ((parser_state->scope->parse_scope.op->common.
+			      aml_opcode == AML_IF_OP)
+			     || (parser_state->scope->parse_scope.op->common.
+				 aml_opcode == AML_WHILE_OP))
+			    && (walk_state->control_state)
+			    && (walk_state->control_state->common.state ==
+				ACPI_CONTROL_PREDICATE_EXECUTING)) {
+				/*
+				 * A predicate was just completed, get the value of the
+				 * predicate and branch based on that value
+				 */
+				walk_state->op = NULL;
+				status =
+				    acpi_ds_get_predicate_value(walk_state,
+								ACPI_TO_POINTER
+								(TRUE));
+				if (ACPI_FAILURE(status)
+				    && !ACPI_CNTL_EXCEPTION(status)) {
+					if (status == AE_AML_NO_RETURN_VALUE) {
+						ACPI_EXCEPTION((AE_INFO, status,
+								"Invoked method did not return a value"));
+					}
+
+					ACPI_EXCEPTION((AE_INFO, status,
+							"GetPredicate Failed"));
+					return_ACPI_STATUS(status);
+				}
+
+				status =
+				    acpi_ps_next_parse_state(walk_state, op,
+							     status);
+			}
+
+			acpi_ps_pop_scope(parser_state, &op,
+					  &walk_state->arg_types,
+					  &walk_state->arg_count);
+			ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
+					  "Popped scope, Op=%p\n", op));
+		} else if (walk_state->prev_op) {
+
+			/* We were in the middle of an op */
+
+			op = walk_state->prev_op;
+			walk_state->arg_types = walk_state->prev_arg_types;
+		}
+	}
+#endif
+
+	/* Iterative parsing loop, while there is more AML to process: */
+
+	while ((parser_state->aml < parser_state->aml_end) || (op)) {
+		ASL_CV_CAPTURE_COMMENTS(walk_state);
+
+		aml_op_start = parser_state->aml;
+		if (!op) {
+			status =
+			    acpi_ps_create_op(walk_state, aml_op_start, &op);
+			if (ACPI_FAILURE(status)) {
+				/*
+				 * ACPI_PARSE_MODULE_LEVEL means that we are loading a table by
+				 * executing it as a control method. However, if we encounter
+				 * an error while loading the table, we need to keep trying to
+				 * load the table rather than aborting the table load. Set the
+				 * status to AE_OK to proceed with the table load.
+				 */
+				if ((walk_state->
+				     parse_flags & ACPI_PARSE_MODULE_LEVEL)
+				    && ((status == AE_ALREADY_EXISTS)
+					|| (status == AE_NOT_FOUND))) {
+					status = AE_OK;
+				}
+				if (status == AE_CTRL_PARSE_CONTINUE) {
+					continue;
+				}
+
+				if (status == AE_CTRL_PARSE_PENDING) {
+					status = AE_OK;
+				}
+
+				if (status == AE_CTRL_TERMINATE) {
+					return_ACPI_STATUS(status);
+				}
+
+				status =
+				    acpi_ps_complete_op(walk_state, &op,
+							status);
+				if (ACPI_FAILURE(status)) {
+					return_ACPI_STATUS(status);
+				}
+				if (acpi_ns_opens_scope
+				    (acpi_ps_get_opcode_info
+				     (walk_state->opcode)->object_type)) {
+					/*
+					 * If the scope/device op fails to parse, skip the body of
+					 * the scope op because the parse failure indicates that
+					 * the device may not exist.
+					 */
+					ACPI_INFO(("Skipping parse of AML opcode: %s (0x%4.4X)", acpi_ps_get_opcode_name(walk_state->opcode), walk_state->opcode));
+
+					/*
+					 * Determine the opcode length before skipping the opcode.
+					 * An opcode can be 1 byte or 2 bytes in length.
+					 */
+					opcode_length = 1;
+					if ((walk_state->opcode & 0xFF00) ==
+					    AML_EXTENDED_OPCODE) {
+						opcode_length = 2;
+					}
+					walk_state->parser_state.aml =
+					    walk_state->aml + opcode_length;
+
+					walk_state->parser_state.aml =
+					    acpi_ps_get_next_package_end
+					    (&walk_state->parser_state);
+					if ((walk_state->parser_state.aml >
+					     walk_state->parser_state.aml_end)
+					    || (walk_state->parser_state.aml <
+						walk_state->aml)) {
+						return_ACPI_STATUS
+						    (AE_AML_PACKAGE_LIMIT);
+					}
+					walk_state->aml =
+					    walk_state->parser_state.aml;
+				}
+
+				continue;
+			}
+
+			acpi_ex_start_trace_opcode(op, walk_state);
+		}
+
+		/*
+		 * Start arg_count at zero because we don't know if there are
+		 * any args yet
+		 */
+		walk_state->arg_count = 0;
+
+		switch (op->common.aml_opcode) {
+		case AML_BYTE_OP:
+		case AML_WORD_OP:
+		case AML_DWORD_OP:
+		case AML_QWORD_OP:
+
+			break;
+
+		default:
+
+			ASL_CV_CAPTURE_COMMENTS(walk_state);
+			break;
+		}
+
+		/* Are there any arguments that must be processed? */
+
+		if (walk_state->arg_types) {
+
+			/* Get arguments */
+
+			status =
+			    acpi_ps_get_arguments(walk_state, aml_op_start, op);
+			if (ACPI_FAILURE(status)) {
+				status =
+				    acpi_ps_complete_op(walk_state, &op,
+							status);
+				if (ACPI_FAILURE(status)) {
+					return_ACPI_STATUS(status);
+				}
+				if ((walk_state->control_state) &&
+				    ((walk_state->control_state->control.
+				      opcode == AML_IF_OP)
+				     || (walk_state->control_state->control.
+					 opcode == AML_WHILE_OP))) {
+					/*
+					 * If the if/while op fails to parse, we will skip parsing
+					 * the body of the op.
+					 */
+					parser_state->aml =
+					    walk_state->control_state->control.
+					    aml_predicate_start + 1;
+					parser_state->aml =
+					    acpi_ps_get_next_package_end
+					    (parser_state);
+					if ((parser_state->aml >
+					     parser_state->aml_end)
+					    || (parser_state->aml <
+						walk_state->control_state->
+						control.aml_predicate_start)) {
+						return_ACPI_STATUS
+						    (AE_AML_PACKAGE_LIMIT);
+					}
+					walk_state->aml = parser_state->aml;
+
+					ACPI_ERROR((AE_INFO,
+						    "Skipping While/If block"));
+					if ((walk_state->aml <
+					     parser_state->aml_end)
+					    && (*walk_state->aml ==
+						AML_ELSE_OP)) {
+						ACPI_ERROR((AE_INFO,
+							    "Skipping Else block"));
+						walk_state->parser_state.aml =
+						    walk_state->aml + 1;
+						walk_state->parser_state.aml =
+						    acpi_ps_get_next_package_end
+						    (parser_state);
+						if ((walk_state->parser_state.
+						     aml >
+						     walk_state->parser_state.
+						     aml_end)
+						    || (walk_state->
+							parser_state.aml <
+							walk_state->aml)) {
+							return_ACPI_STATUS
+							    (AE_AML_PACKAGE_LIMIT);
+						}
+						walk_state->aml =
+						    parser_state->aml;
+					}
+					ACPI_FREE(acpi_ut_pop_generic_state
+						  (&walk_state->control_state));
+				}
+				op = NULL;
+				continue;
+			}
+		}
+
+		/* Check for arguments that need to be processed */
+
+		ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
+				  "Parseloop: argument count: %8.8X\n",
+				  walk_state->arg_count));
+
+		if (walk_state->arg_count) {
+			/*
+			 * There are arguments (complex ones), push Op and
+			 * prepare for argument
+			 */
+			status = acpi_ps_push_scope(parser_state, op,
+						    walk_state->arg_types,
+						    walk_state->arg_count);
+			if (ACPI_FAILURE(status)) {
+				status =
+				    acpi_ps_complete_op(walk_state, &op,
+							status);
+				if (ACPI_FAILURE(status)) {
+					return_ACPI_STATUS(status);
+				}
+
+				continue;
+			}
+
+			op = NULL;
+			continue;
+		}
+
+		/*
+		 * All arguments have been processed -- Op is complete,
+		 * prepare for next
+		 */
+		walk_state->op_info =
+		    acpi_ps_get_opcode_info(op->common.aml_opcode);
+		if (walk_state->op_info->flags & AML_NAMED) {
+			if (op->common.aml_opcode == AML_REGION_OP ||
+			    op->common.aml_opcode == AML_DATA_REGION_OP) {
+				/*
+				 * Skip parsing of control method or opregion body,
+				 * because we don't have enough info in the first pass
+				 * to parse them correctly.
+				 *
+				 * Completed parsing an op_region declaration, we now
+				 * know the length.
+				 */
+				op->named.length =
+				    (u32) (parser_state->aml - op->named.data);
+			}
+		}
+
+		if (walk_state->op_info->flags & AML_CREATE) {
+			/*
+			 * Backup to beginning of create_XXXfield declaration (1 for
+			 * Opcode)
+			 *
+			 * body_length is unknown until we parse the body
+			 */
+			op->named.length =
+			    (u32) (parser_state->aml - op->named.data);
+		}
+
+		if (op->common.aml_opcode == AML_BANK_FIELD_OP) {
+			/*
+			 * Backup to beginning of bank_field declaration
+			 *
+			 * body_length is unknown until we parse the body
+			 */
+			op->named.length =
+			    (u32) (parser_state->aml - op->named.data);
+		}
+
+		/* This op complete, notify the dispatcher */
+
+		if (walk_state->ascending_callback != NULL) {
+			walk_state->op = op;
+			walk_state->opcode = op->common.aml_opcode;
+
+			status = walk_state->ascending_callback(walk_state);
+			status =
+			    acpi_ps_next_parse_state(walk_state, op, status);
+			if (status == AE_CTRL_PENDING) {
+				status = AE_OK;
+			} else
+			    if ((walk_state->
+				 parse_flags & ACPI_PARSE_MODULE_LEVEL)
+				&& (ACPI_AML_EXCEPTION(status)
+				    || status == AE_ALREADY_EXISTS
+				    || status == AE_NOT_FOUND)) {
+				/*
+				 * ACPI_PARSE_MODULE_LEVEL flag means that we
+				 * are currently loading a table by executing
+				 * it as a control method. However, if we
+				 * encounter an error while loading the table,
+				 * we need to keep trying to load the table
+				 * rather than aborting the table load (setting
+				 * the status to AE_OK continues the table
+				 * load). If we get a failure at this point, it
+				 * means that the dispatcher got an error while
+				 * trying to execute the Op.
+				 */
+				status = AE_OK;
+			}
+		}
+
+		status = acpi_ps_complete_op(walk_state, &op, status);
+		if (ACPI_FAILURE(status)) {
+			return_ACPI_STATUS(status);
+		}
+
+	}			/* while parser_state->Aml */
+
+	status = acpi_ps_complete_final_op(walk_state, op, status);
+	return_ACPI_STATUS(status);
+}