block: initial VHDX driver support framework - supports open and probe

This is the initial block driver framework for VHDX image support
(i.e. Hyper-V image file formats), that supports opening VHDX files, and
parsing the headers.

This commit does not yet enable:
    - reading
    - writing
    - updating the header
    - differencing files (images with parents)
    - log replay / dirty logs (only clean images)

This is based on Microsoft's VHDX specification:
    "VHDX Format Specification v0.95", published 4/12/2012
    https://www.microsoft.com/en-us/download/details.aspx?id=29681

Signed-off-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/Makefile.objs

@@ -2,6 +2,7 @@ block-obj-y += raw.o cow.o qcow.o vdi.o vmdk.o cloop.o dmg.o bochs.o vpc.o vvfat
 block-obj-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o qcow2-cache.o
 block-obj-y += qed.o qed-gencb.o qed-l2-cache.o qed-table.o qed-cluster.o
 block-obj-y += qed-check.o
+block-obj-y += vhdx.o
 block-obj-y += parallels.o blkdebug.o blkverify.o
 block-obj-$(CONFIG_WIN32) += raw-win32.o win32-aio.o
 block-obj-$(CONFIG_POSIX) += raw-posix.o

block/vhdx.h

@@ -308,4 +308,18 @@ typedef struct QEMU_PACKED VHDXParentLocatorEntry {
 
 /* ----- END VHDX SPECIFICATION STRUCTURES ---- */
 
+
+uint32_t vhdx_checksum_calc(uint32_t crc, uint8_t *buf, size_t size,
+                            int crc_offset);
+
+bool vhdx_checksum_is_valid(uint8_t *buf, size_t size, int crc_offset);
+
+
+static void leguid_to_cpus(MSGUID *guid)
+{
+    le32_to_cpus(&guid->data1);
+    le16_to_cpus(&guid->data2);
+    le16_to_cpus(&guid->data3);
+}
+
 #endif