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, 357 insertions, 0 deletions

diff --git a/drivers/acpi/acpica/utalloc.c b/drivers/acpi/acpica/utalloc.c
new file mode 100644
index 000000000..da12b6fec
--- /dev/null
+++ b/drivers/acpi/acpica/utalloc.c
@@ -0,0 +1,357 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/******************************************************************************
+ *
+ * Module Name: utalloc - local memory allocation routines
+ *
+ * Copyright (C) 2000 - 2026, Intel Corp.
+ *
+ *****************************************************************************/
+
+#include <acpi/acpi.h>
+#include "accommon.h"
+#include "acdebug.h"
+
+#define _COMPONENT          ACPI_UTILITIES
+ACPI_MODULE_NAME("utalloc")
+
+#if !defined (USE_NATIVE_ALLOCATE_ZEROED)
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_os_allocate_zeroed
+ *
+ * PARAMETERS:  size                - Size of the allocation
+ *
+ * RETURN:      Address of the allocated memory on success, NULL on failure.
+ *
+ * DESCRIPTION: Subsystem equivalent of calloc. Allocate and zero memory.
+ *              This is the default implementation. Can be overridden via the
+ *              USE_NATIVE_ALLOCATE_ZEROED flag.
+ *
+ ******************************************************************************/
+void *acpi_os_allocate_zeroed(acpi_size size)
+{
+	void *allocation;
+
+	ACPI_FUNCTION_ENTRY();
+
+	allocation = acpi_os_allocate(size);
+	if (allocation) {
+
+		/* Clear the memory block */
+
+		memset(allocation, 0, size);
+	}
+
+	return (allocation);
+}
+
+#endif				/* !USE_NATIVE_ALLOCATE_ZEROED */
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ut_create_caches
+ *
+ * PARAMETERS:  None
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Create all local caches
+ *
+ ******************************************************************************/
+
+acpi_status acpi_ut_create_caches(void)
+{
+	acpi_status status;
+
+	/* Object Caches, for frequently used objects */
+
+	status =
+	    acpi_os_create_cache("Acpi-Namespace",
+				 sizeof(struct acpi_namespace_node),
+				 ACPI_MAX_NAMESPACE_CACHE_DEPTH,
+				 &acpi_gbl_namespace_cache);
+	if (ACPI_FAILURE(status)) {
+		return (status);
+	}
+
+	status =
+	    acpi_os_create_cache("Acpi-State", sizeof(union acpi_generic_state),
+				 ACPI_MAX_STATE_CACHE_DEPTH,
+				 &acpi_gbl_state_cache);
+	if (ACPI_FAILURE(status)) {
+		return (status);
+	}
+
+	status =
+	    acpi_os_create_cache("Acpi-Parse",
+				 sizeof(struct acpi_parse_obj_common),
+				 ACPI_MAX_PARSE_CACHE_DEPTH,
+				 &acpi_gbl_ps_node_cache);
+	if (ACPI_FAILURE(status)) {
+		return (status);
+	}
+
+	status =
+	    acpi_os_create_cache("Acpi-ParseExt",
+				 sizeof(struct acpi_parse_obj_named),
+				 ACPI_MAX_EXTPARSE_CACHE_DEPTH,
+				 &acpi_gbl_ps_node_ext_cache);
+	if (ACPI_FAILURE(status)) {
+		return (status);
+	}
+
+	status =
+	    acpi_os_create_cache("Acpi-Operand",
+				 sizeof(union acpi_operand_object),
+				 ACPI_MAX_OBJECT_CACHE_DEPTH,
+				 &acpi_gbl_operand_cache);
+	if (ACPI_FAILURE(status)) {
+		return (status);
+	}
+#ifdef ACPI_ASL_COMPILER
+	/*
+	 * For use with the ASL-/ASL+ option. This cache keeps track of regular
+	 * 0xA9 0x01 comments.
+	 */
+	status =
+	    acpi_os_create_cache("Acpi-Comment",
+				 sizeof(struct acpi_comment_node),
+				 ACPI_MAX_COMMENT_CACHE_DEPTH,
+				 &acpi_gbl_reg_comment_cache);
+	if (ACPI_FAILURE(status)) {
+		return (status);
+	}
+
+	/*
+	 * This cache keeps track of the starting addresses of where the comments
+	 * lie. This helps prevent duplication of comments.
+	 */
+	status =
+	    acpi_os_create_cache("Acpi-Comment-Addr",
+				 sizeof(struct acpi_comment_addr_node),
+				 ACPI_MAX_COMMENT_CACHE_DEPTH,
+				 &acpi_gbl_comment_addr_cache);
+	if (ACPI_FAILURE(status)) {
+		return (status);
+	}
+
+	/*
+	 * This cache will be used for nodes that represent files.
+	 */
+	status =
+	    acpi_os_create_cache("Acpi-File", sizeof(struct acpi_file_node),
+				 ACPI_MAX_COMMENT_CACHE_DEPTH,
+				 &acpi_gbl_file_cache);
+	if (ACPI_FAILURE(status)) {
+		return (status);
+	}
+#endif
+
+#ifdef ACPI_DBG_TRACK_ALLOCATIONS
+
+	/* Memory allocation lists */
+
+	status = acpi_ut_create_list("Acpi-Global", 0, &acpi_gbl_global_list);
+	if (ACPI_FAILURE(status)) {
+		return (status);
+	}
+
+	status =
+	    acpi_ut_create_list("Acpi-Namespace",
+				sizeof(struct acpi_namespace_node),
+				&acpi_gbl_ns_node_list);
+	if (ACPI_FAILURE(status)) {
+		return (status);
+	}
+#endif
+
+	return (AE_OK);
+}
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ut_delete_caches
+ *
+ * PARAMETERS:  None
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Purge and delete all local caches
+ *
+ ******************************************************************************/
+
+acpi_status acpi_ut_delete_caches(void)
+{
+#ifdef ACPI_DBG_TRACK_ALLOCATIONS
+	char buffer[7];
+
+	if (acpi_gbl_display_final_mem_stats) {
+		strcpy(buffer, "MEMORY");
+		(void)acpi_db_display_statistics(buffer);
+	}
+#endif
+
+	(void)acpi_os_delete_cache(acpi_gbl_namespace_cache);
+	acpi_gbl_namespace_cache = NULL;
+
+	(void)acpi_os_delete_cache(acpi_gbl_state_cache);
+	acpi_gbl_state_cache = NULL;
+
+	(void)acpi_os_delete_cache(acpi_gbl_operand_cache);
+	acpi_gbl_operand_cache = NULL;
+
+	(void)acpi_os_delete_cache(acpi_gbl_ps_node_cache);
+	acpi_gbl_ps_node_cache = NULL;
+
+	(void)acpi_os_delete_cache(acpi_gbl_ps_node_ext_cache);
+	acpi_gbl_ps_node_ext_cache = NULL;
+
+#ifdef ACPI_ASL_COMPILER
+	(void)acpi_os_delete_cache(acpi_gbl_reg_comment_cache);
+	acpi_gbl_reg_comment_cache = NULL;
+
+	(void)acpi_os_delete_cache(acpi_gbl_comment_addr_cache);
+	acpi_gbl_comment_addr_cache = NULL;
+
+	(void)acpi_os_delete_cache(acpi_gbl_file_cache);
+	acpi_gbl_file_cache = NULL;
+#endif
+
+#ifdef ACPI_DBG_TRACK_ALLOCATIONS
+
+	/* Debug only - display leftover memory allocation, if any */
+
+	acpi_ut_dump_allocations(ACPI_UINT32_MAX, NULL);
+
+	/* Free memory lists */
+
+	acpi_os_free(acpi_gbl_global_list);
+	acpi_gbl_global_list = NULL;
+
+	acpi_os_free(acpi_gbl_ns_node_list);
+	acpi_gbl_ns_node_list = NULL;
+#endif
+
+	return (AE_OK);
+}
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ut_validate_buffer
+ *
+ * PARAMETERS:  buffer              - Buffer descriptor to be validated
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Perform parameter validation checks on an struct acpi_buffer
+ *
+ ******************************************************************************/
+
+acpi_status acpi_ut_validate_buffer(struct acpi_buffer *buffer)
+{
+
+	/* Obviously, the structure pointer must be valid */
+
+	if (!buffer) {
+		return (AE_BAD_PARAMETER);
+	}
+
+	/* Special semantics for the length */
+
+	if ((buffer->length == ACPI_NO_BUFFER) ||
+	    (buffer->length == ACPI_ALLOCATE_BUFFER) ||
+	    (buffer->length == ACPI_ALLOCATE_LOCAL_BUFFER)) {
+		return (AE_OK);
+	}
+
+	/* Length is valid, the buffer pointer must be also */
+
+	if (!buffer->pointer) {
+		return (AE_BAD_PARAMETER);
+	}
+
+	return (AE_OK);
+}
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ut_initialize_buffer
+ *
+ * PARAMETERS:  buffer              - Buffer to be validated
+ *              required_length     - Length needed
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Validate that the buffer is of the required length or
+ *              allocate a new buffer. Returned buffer is always zeroed.
+ *
+ ******************************************************************************/
+
+acpi_status
+acpi_ut_initialize_buffer(struct acpi_buffer *buffer, acpi_size required_length)
+{
+	acpi_size input_buffer_length;
+
+	/* Parameter validation */
+
+	if (!buffer || !required_length) {
+		return (AE_BAD_PARAMETER);
+	}
+
+	/*
+	 * Buffer->Length is used as both an input and output parameter. Get the
+	 * input actual length and set the output required buffer length.
+	 */
+	input_buffer_length = buffer->length;
+	buffer->length = required_length;
+
+	/*
+	 * The input buffer length contains the actual buffer length, or the type
+	 * of buffer to be allocated by this routine.
+	 */
+	switch (input_buffer_length) {
+	case ACPI_NO_BUFFER:
+
+		/* Return the exception (and the required buffer length) */
+
+		return (AE_BUFFER_OVERFLOW);
+
+	case ACPI_ALLOCATE_BUFFER:
+		/*
+		 * Allocate a new buffer. We directectly call acpi_os_allocate here to
+		 * purposefully bypass the (optionally enabled) internal allocation
+		 * tracking mechanism since we only want to track internal
+		 * allocations. Note: The caller should use acpi_os_free to free this
+		 * buffer created via ACPI_ALLOCATE_BUFFER.
+		 */
+		buffer->pointer = acpi_os_allocate(required_length);
+		break;
+
+	case ACPI_ALLOCATE_LOCAL_BUFFER:
+
+		/* Allocate a new buffer with local interface to allow tracking */
+
+		buffer->pointer = ACPI_ALLOCATE(required_length);
+		break;
+
+	default:
+
+		/* Existing buffer: Validate the size of the buffer */
+
+		if (input_buffer_length < required_length) {
+			return (AE_BUFFER_OVERFLOW);
+		}
+		break;
+	}
+
+	/* Validate allocation from above or input buffer pointer */
+
+	if (!buffer->pointer) {
+		return (AE_NO_MEMORY);
+	}
+
+	/* Have a valid buffer, clear it */
+
+	memset(buffer->pointer, 0, required_length);
+	return (AE_OK);
+}