ACPICA: actbl2: Replace 1-element arrays with flexible arrays

ACPICA commit 44f1af0664599e87bebc3a1260692baa27b2f264

Similar to "Replace one-element array with flexible-array", replace the
1-element array with a proper flexible array member as defined by C99.

This allows the code to operate without tripping compile-time and run-
time bounds checkers (e.g. via __builtin_object_size(), -fsanitize=bounds,
and/or -fstrict-flex-arrays=3).

The sizeof() uses with struct acpi_nfit_flush_address and struct
acpi_nfit_smbios have been adjusted to drop the open-coded subtraction
of the trailing single element. The result is no binary differences in
.text nor .data sections.

Link: https://github.com/acpica/acpica/commit/44f1af06
Signed-off-by: Bob Moore <robert.moore@intel.com>
Co-developed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/nfit/core.c

@@ -894,7 +894,7 @@ static size_t sizeof_flush(struct acpi_nfit_flush_address *flush)
 {
 	if (flush->header.length < sizeof(*flush))
 		return 0;
-	return sizeof(*flush) + sizeof(u64) * (flush->hint_count - 1);
+	return struct_size(flush, hint_address, flush->hint_count);
 }
 
 static bool add_flush(struct acpi_nfit_desc *acpi_desc,
@@ -3477,7 +3477,7 @@ static __init int nfit_init(void)
 	BUILD_BUG_ON(sizeof(struct acpi_nfit_system_address) != 64);
 	BUILD_BUG_ON(sizeof(struct acpi_nfit_memory_map) != 48);
 	BUILD_BUG_ON(sizeof(struct acpi_nfit_interleave) != 20);
-	BUILD_BUG_ON(sizeof(struct acpi_nfit_smbios) != 9);
+	BUILD_BUG_ON(sizeof(struct acpi_nfit_smbios) != 8);
 	BUILD_BUG_ON(sizeof(struct acpi_nfit_control_region) != 80);
 	BUILD_BUG_ON(sizeof(struct acpi_nfit_data_region) != 40);
 	BUILD_BUG_ON(sizeof(struct acpi_nfit_capabilities) != 16);

include/acpi/actbl2.h

@@ -397,7 +397,7 @@ struct acpi_iort_node {
 	u32 identifier;
 	u32 mapping_count;
 	u32 mapping_offset;
-	char node_data[1];
+	char node_data[];
 };
 
 /* Values for subtable Type above */
@@ -453,14 +453,14 @@ struct acpi_iort_memory_access {
  */
 struct acpi_iort_its_group {
 	u32 its_count;
-	u32 identifiers[1];	/* GIC ITS identifier array */
+	u32 identifiers[];	/* GIC ITS identifier array */
 };
 
 struct acpi_iort_named_component {
 	u32 node_flags;
 	u64 memory_properties;	/* Memory access properties */
 	u8 memory_address_limit;	/* Memory address size limit */
-	char device_name[1];	/* Path of namespace object */
+	char device_name[];	/* Path of namespace object */
 };
 
 /* Masks for Flags field above */
@@ -474,7 +474,7 @@ struct acpi_iort_root_complex {
 	u32 pci_segment_number;
 	u8 memory_address_limit;	/* Memory address size limit */
 	u16 pasid_capabilities;	/* PASID Capabilities */
-	u8 reserved[1];		/* Reserved, must be zero */
+	u8 reserved[];		/* Reserved, must be zero */
 };
 
 /* Masks for ats_attribute field above */
@@ -496,7 +496,7 @@ struct acpi_iort_smmu {
 	u32 context_interrupt_offset;
 	u32 pmu_interrupt_count;
 	u32 pmu_interrupt_offset;
-	u64 interrupts[1];	/* Interrupt array */
+	u64 interrupts[];	/* Interrupt array */
 };
 
 /* Values for Model field above */
@@ -975,7 +975,7 @@ struct acpi_madt_local_sapic {
 	u8 reserved[3];		/* Reserved, must be zero */
 	u32 lapic_flags;
 	u32 uid;		/* Numeric UID - ACPI 3.0 */
-	char uid_string[1];	/* String UID  - ACPI 3.0 */
+	char uid_string[];	/* String UID  - ACPI 3.0 */
 };
 
 /* 8: Platform Interrupt Source */
@@ -1708,7 +1708,7 @@ struct acpi_nfit_interleave {
 struct acpi_nfit_smbios {
 	struct acpi_nfit_header header;
 	u32 reserved;		/* Reserved, must be zero */
-	u8 data[1];		/* Variable length */
+	u8 data[];		/* Variable length */
 };
 
 /* 4: NVDIMM Control Region Structure */
@@ -1765,7 +1765,7 @@ struct acpi_nfit_flush_address {
 	u32 device_handle;
 	u16 hint_count;
 	u8 reserved[6];		/* Reserved, must be zero */
-	u64 hint_address[1];	/* Variable length */
+	u64 hint_address[];	/* Variable length */
 };
 
 /* 7: Platform Capabilities Structure */

tools/testing/nvdimm/test/nfit.c

@@ -1878,14 +1878,14 @@ static size_t sizeof_spa(struct acpi_nfit_system_address *spa)
 static int nfit_test0_alloc(struct nfit_test *t)
 {
 	struct acpi_nfit_system_address *spa = NULL;
+	struct acpi_nfit_flush_address *flush;
 	size_t nfit_size = sizeof_spa(spa) * NUM_SPA
 			+ sizeof(struct acpi_nfit_memory_map) * NUM_MEM
 			+ sizeof(struct acpi_nfit_control_region) * NUM_DCR
 			+ offsetof(struct acpi_nfit_control_region,
 					window_size) * NUM_DCR
 			+ sizeof(struct acpi_nfit_data_region) * NUM_BDW
-			+ (sizeof(struct acpi_nfit_flush_address)
-					+ sizeof(u64) * NUM_HINTS) * NUM_DCR
+			+ struct_size(flush, hint_address, NUM_HINTS) * NUM_DCR
 			+ sizeof(struct acpi_nfit_capabilities);
 	int i;