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 <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 52 insertions, 0 deletions

diff --git a/drivers/acpi/acpica/evrgnini.c b/drivers/acpi/acpica/evrgnini.c
index 984c172453bf..d28dee929e61 100644
--- a/drivers/acpi/acpica/evrgnini.c
+++ b/drivers/acpi/acpica/evrgnini.c
@@ -408,6 +408,58 @@ acpi_ev_cmos_region_setup(acpi_handle handle,
 
 /*******************************************************************************
  *
+ * 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