acpi: arm: virt: build_dsdt: use acpi_table_begin()/acpi_table_end() instead of build_header()

it replaces error-prone pointer arithmetic for build_header() API,
with 2 calls to start and finish table creation,
which hides offsets magic from API user.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-Id: <20210924122802.1455362-28-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/arm/virt-acpi-build.c

@@ -729,10 +729,11 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
     MachineState *ms = MACHINE(vms);
     const MemMapEntry *memmap = vms->memmap;
     const int *irqmap = vms->irqmap;
+    AcpiTable table = { .sig = "DSDT", .rev = 2, .oem_id = vms->oem_id,
+                        .oem_table_id = vms->oem_table_id };
 
+    acpi_table_begin(&table, table_data);
     dsdt = init_aml_allocator();
-    /* Reserve space for header */
-    acpi_data_push(dsdt->buf, sizeof(AcpiTableHeader));
 
     /* When booting the VM with UEFI, UEFI takes ownership of the RTC hardware.
      * While UEFI can use libfdt to disable the RTC device node in the DTB that
@@ -779,12 +780,10 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
 
     aml_append(dsdt, scope);
 
-    /* copy AML table into ACPI tables blob and patch header there */
+    /* copy AML table into ACPI tables blob */
     g_array_append_vals(table_data, dsdt->buf->data, dsdt->buf->len);
-    build_header(linker, table_data,
-        (void *)(table_data->data + table_data->len - dsdt->buf->len),
-                 "DSDT", dsdt->buf->len, 2, vms->oem_id,
-                 vms->oem_table_id);
+
+    acpi_table_end(linker, &table);
     free_aml_allocator();
 }