ACPICA: Use original data_table_region pointer for accesses

ACPICA commit d9eb82bd7515989f0b29d79deeeb758db4d6529c

Currently the pointer to the table is cast to acpi_physical_address and
later cast back to a pointer to be dereferenced. Whether or not this is
supported is implementation-defined.

On CHERI, and thus Arm's experimental Morello prototype architecture,
pointers are represented as capabilities, which are unforgeable bounded
pointers, providing always-on fine-grained spatial memory safety. This
means that any pointer cast to a plain integer will lose all its
associated metadata, and when cast back to a pointer it will give a
null-derived pointer (one that has the same metadata as null but an
address equal to the integer) that will trap on any dereference. As a
result, this is an implementation where acpi_physical_address cannot be
used as a hack to store real pointers.

Thus, add a new field to struct acpi_object_region to store the pointer for
table regions, and propagate it to acpi_ex_data_table_space_handler via the
region context, to use a more portable implementation that supports
CHERI.

Link: https://github.com/acpica/acpica/commit/d9eb82bd
Signed-off-by: Bob Moore <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/acpi/acpica/acevents.h

···
 			     void *handler_context, void **region_context);
 
 acpi_status
+acpi_ev_data_table_region_setup(acpi_handle handle,
+				u32 function,
+				void *handler_context, void **region_context);
+
+acpi_status
 acpi_ev_default_region_setup(acpi_handle handle,
 			     u32 function,
 			     void *handler_context, void **region_context);

drivers/acpi/acpica/acobject.h

···
 	union acpi_operand_object *next;
 	acpi_physical_address address;
 	u32 length;
+	void *pointer;		/* Only for data table regions */
 };
 
 struct acpi_object_method {

drivers/acpi/acpica/dsopcode.c

···
 
 	obj_desc->region.address = ACPI_PTR_TO_PHYSADDR(table);
 	obj_desc->region.length = table->length;
+	obj_desc->region.pointer = table;
 
 	ACPI_DEBUG_PRINT((ACPI_DB_EXEC, "RgnObj %p Addr %8.8X%8.8X Len %X\n",
 			  obj_desc,

drivers/acpi/acpica/evhandler.c

···
 		case ACPI_ADR_SPACE_DATA_TABLE:
 
 			handler = acpi_ex_data_table_space_handler;
-			setup = NULL;
+			setup = acpi_ev_data_table_region_setup;
 			break;
 
 		default:

drivers/acpi/acpica/evrgnini.c

···
 
 /*******************************************************************************
  *
+ * FUNCTION:    acpi_ev_data_table_region_setup
+ *
+ * PARAMETERS:  handle              - Region we are interested in
+ *              function            - Start or stop
+ *              handler_context     - Address space handler context
+ *              region_context      - Region specific context
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Setup a data_table_region
+ *
+ * MUTEX:       Assumes namespace is not locked
+ *
+ ******************************************************************************/
+
+acpi_status
+acpi_ev_data_table_region_setup(acpi_handle handle,
+				u32 function,
+				void *handler_context, void **region_context)
+{
+	union acpi_operand_object *region_desc =
+	    (union acpi_operand_object *)handle;
+	struct acpi_data_table_space_context *local_region_context;
+
+	ACPI_FUNCTION_TRACE(ev_data_table_region_setup);
+
+	if (function == ACPI_REGION_DEACTIVATE) {
+		if (*region_context) {
+			ACPI_FREE(*region_context);
+			*region_context = NULL;
+		}
+		return_ACPI_STATUS(AE_OK);
+	}
+
+	/* Create a new context */
+
+	local_region_context =
+	    ACPI_ALLOCATE_ZEROED(sizeof(struct acpi_data_table_space_context));
+	if (!(local_region_context)) {
+		return_ACPI_STATUS(AE_NO_MEMORY);
+	}
+
+	/* Save the data table pointer for use in the handler */
+
+	local_region_context->pointer = region_desc->region.pointer;
+
+	*region_context = local_region_context;
+	return_ACPI_STATUS(AE_OK);
+}
+
+/*******************************************************************************
+ *
  * FUNCTION:    acpi_ev_default_region_setup
  *
  * PARAMETERS:  handle              - Region we are interested in

drivers/acpi/acpica/excreate.c

···
 	obj_desc->region.space_id = space_id;
 	obj_desc->region.address = 0;
 	obj_desc->region.length = 0;
+	obj_desc->region.pointer = NULL;
 	obj_desc->region.node = node;
 	obj_desc->region.handler = NULL;
 	obj_desc->common.flags &=

drivers/acpi/acpica/exregion.c

···
 				 u64 *value,
 				 void *handler_context, void *region_context)
 {
+	struct acpi_data_table_space_context *mapping;
+	char *pointer;
+
 	ACPI_FUNCTION_TRACE(ex_data_table_space_handler);
+
+	mapping = (struct acpi_data_table_space_context *) region_context;
+	pointer = ACPI_CAST_PTR(char, mapping->pointer) +
+	    (address - ACPI_PTR_TO_PHYSADDR(mapping->pointer));
 
 	/*
 	 * Perform the memory read or write. The bit_width was already
···
 	switch (function) {
 	case ACPI_READ:
 
-		memcpy(ACPI_CAST_PTR(char, value),
-		       ACPI_PHYSADDR_TO_PTR(address), ACPI_DIV_8(bit_width));
+		memcpy(ACPI_CAST_PTR(char, value), pointer,
+		       ACPI_DIV_8(bit_width));
 		break;
 
 	case ACPI_WRITE:
 
-		memcpy(ACPI_PHYSADDR_TO_PTR(address),
-		       ACPI_CAST_PTR(char, value), ACPI_DIV_8(bit_width));
+		memcpy(pointer, ACPI_CAST_PTR(char, value),
+		       ACPI_DIV_8(bit_width));
 		break;
 
 	default:

include/acpi/actypes.h

···
 	struct acpi_mem_mapping *first_mm;
 };
 
+struct acpi_data_table_space_context {
+	void *pointer;
+};
+
 /*
  * struct acpi_memory_list is used only if the ACPICA local cache is enabled
  */