Add cimfs differ and snapshotter

Details about CimFs project are discussed in #8346

Signed-off-by: Amit Barve <ambarve@microsoft.com>

vendor/github.com/Microsoft/hcsshim/internal/vhdx/doc.go

@@ -0,0 +1,3 @@
+// vhdx package adds the utility methods necessary to deal with the vhdx that are used as the scratch
+// space for the containers and the uvm.
+package vhdx

vendor/github.com/Microsoft/hcsshim/internal/vhdx/info.go

@@ -0,0 +1,233 @@
+//go:build windows
+
+package vhdx
+
+import (
+	"bytes"
+	"context"
+	"encoding/binary"
+	"fmt"
+	"os"
+	"syscall"
+	"unsafe"
+
+	"github.com/Microsoft/go-winio/pkg/guid"
+	"github.com/Microsoft/go-winio/vhd"
+	"github.com/Microsoft/hcsshim/internal/log"
+	"github.com/Microsoft/hcsshim/internal/oc"
+	"github.com/sirupsen/logrus"
+	"go.opencensus.io/trace"
+	"golang.org/x/sys/windows"
+)
+
+const _IOCTL_DISK_GET_DRIVE_LAYOUT_EX = 0x00070050
+
+var partitionBasicDataGUID = guid.GUID{
+	Data1: 0xebd0a0a2,
+	Data2: 0xb9e5,
+	Data3: 0x4433,
+	Data4: [8]byte{0x87, 0xc0, 0x68, 0xb6, 0xb7, 0x26, 0x99, 0xc7},
+}
+
+const (
+	partitionStyleMBR uint32 = iota
+	partitionStyleGPT
+	partitionStyleRaw
+)
+
+// type partitionInformationMBR struct {
+// 	PartitionType       uint8
+// 	BootIndicator       uint8
+// 	RecognizedPartition uint8
+// 	HiddenSectors       uint32
+// 	PartitionId         guid.GUID
+// }
+
+type partitionInformationGPT struct {
+	PartitionType guid.GUID
+	PartitionId   guid.GUID
+	Attributes    uint64
+	Name          [72]byte // wide char
+}
+
+type partitionInformationEx struct {
+	PartitionStyle     uint32
+	StartingOffset     int64
+	PartitionLength    int64
+	PartitionNumber    uint32
+	RewritePartition   uint8
+	IsServicePartition uint8
+	_                  uint16
+	// A union of partitionInformationMBR and partitionInformationGPT
+	// since partitionInformationGPT is largest with 112 bytes
+	GptMbrUnion [112]byte
+}
+
+type driveLayoutInformationGPT struct {
+	DiskID               guid.GUID
+	StartingUsableOffset int64
+	UsableLength         int64
+	MaxPartitionCount    uint32
+}
+
+// type driveLayoutInformationMBR struct {
+// 	Signature uint32
+// 	Checksum  uint32
+// }
+
+type driveLayoutInformationEx struct {
+	PartitionStyle uint32
+	PartitionCount uint32
+	// A union of driveLayoutInformationGPT and driveLayoutInformationMBR
+	// since driveLayoutInformationGPT is largest with 40 bytes
+	GptMbrUnion    [40]byte
+	PartitionEntry [1]partitionInformationEx
+}
+
+// Takes the physical path of a disk and retrieves the drive layout information of that disk.  Returns the
+// driveLayoutInformationEx struct and a slice of partitionInfomrationEx struct containing one element for
+// each partition found on the vhdx. Note: some of the members like (GptMbrUnion) of these structs are raw
+// byte arrays and it is the responsibility of the calling function to properly parse them.
+func getDriveLayout(ctx context.Context, drivePhysicalPath string) (driveLayoutInformationEx, []partitionInformationEx, error) {
+	var (
+		outBytes uint32
+		err      error
+		volume   *os.File
+	)
+
+	layoutData := struct {
+		info driveLayoutInformationEx
+		// driveLayoutInformationEx has a flexible array member at the end. The data returned
+		// by IOCTL_DISK_GET_DRIVE_LAYOUT_EX usually has driveLayoutInformationEx.PartitionCount
+		// number of elements in this array. For all practical purposes we don't expect to have
+		// more than 64 partitions in a container/uvm vhdx.
+		partitions [63]partitionInformationEx
+	}{}
+
+	volume, err = os.OpenFile(drivePhysicalPath, os.O_RDONLY, 0)
+	if err != nil {
+		return layoutData.info, layoutData.partitions[:0], fmt.Errorf("failed to open drive: %w", err)
+	}
+	defer volume.Close()
+
+	err = windows.DeviceIoControl(windows.Handle(volume.Fd()),
+		_IOCTL_DISK_GET_DRIVE_LAYOUT_EX,
+		nil,
+		0,
+		(*byte)(unsafe.Pointer(&layoutData)),
+		uint32(unsafe.Sizeof(layoutData)),
+		&outBytes,
+		nil)
+	if err != nil {
+		return layoutData.info, layoutData.partitions[:0], fmt.Errorf("IOCTL to get disk layout failed: %w", err)
+	}
+
+	if layoutData.info.PartitionCount == 0 {
+		return layoutData.info, []partitionInformationEx{}, nil
+	} else {
+		// parse the retrieved data into driveLayoutInformationEx and partitionInformationEx
+		partitions := make([]partitionInformationEx, layoutData.info.PartitionCount)
+		partitions[0] = layoutData.info.PartitionEntry[0]
+		copy(partitions[1:], layoutData.partitions[:layoutData.info.PartitionCount-1])
+		return layoutData.info, partitions, nil
+	}
+}
+
+// Scratch VHDs are formatted with GPT style and have 1 MSFT_RESERVED
+// partition and 1 BASIC_DATA partition.  This struct contains the
+// partitionID of this BASIC_DATA partition and the DiskID of this
+// scratch vhdx.
+type ScratchVhdxPartitionInfo struct {
+	DiskID      guid.GUID
+	PartitionID guid.GUID
+}
+
+// Returns the VhdxInfo of a GPT vhdx at path vhdxPath.
+func GetScratchVhdPartitionInfo(ctx context.Context, vhdxPath string) (_ ScratchVhdxPartitionInfo, err error) {
+	var (
+		diskHandle       syscall.Handle
+		driveLayout      driveLayoutInformationEx
+		partitions       []partitionInformationEx
+		gptDriveLayout   driveLayoutInformationGPT
+		gptPartitionInfo partitionInformationGPT
+		volumePath       string
+	)
+
+	title := "hcsshim::GetScratchVhdPartitionInfo"
+	ctx, span := trace.StartSpan(ctx, title)
+	defer span.End()
+	defer func() { oc.SetSpanStatus(span, err) }()
+	span.AddAttributes(
+		trace.StringAttribute("path", vhdxPath))
+
+	diskHandle, err = vhd.OpenVirtualDisk(vhdxPath, vhd.VirtualDiskAccessNone, vhd.OpenVirtualDiskFlagNone)
+	if err != nil {
+		return ScratchVhdxPartitionInfo{}, fmt.Errorf("get scratch vhd info failed: %w", err)
+	}
+	defer func() {
+		if closeErr := syscall.CloseHandle(diskHandle); closeErr != nil {
+			log.G(ctx).WithFields(logrus.Fields{
+				"disk path": vhdxPath,
+				"error":     closeErr,
+			}).Warn("failed to close vhd handle")
+		}
+	}()
+
+	err = vhd.AttachVirtualDisk(diskHandle, vhd.AttachVirtualDiskFlagNone, &vhd.AttachVirtualDiskParameters{Version: 2})
+	if err != nil {
+		return ScratchVhdxPartitionInfo{}, fmt.Errorf("get scratch vhd info failed: %w", err)
+	}
+
+	defer func() {
+		if detachErr := vhd.DetachVirtualDisk(diskHandle); detachErr != nil {
+			log.G(ctx).WithFields(logrus.Fields{
+				"disk path": vhdxPath,
+				"error":     detachErr,
+			}).Warn("failed to detach vhd")
+		}
+	}()
+
+	volumePath, err = vhd.GetVirtualDiskPhysicalPath(diskHandle)
+	if err != nil {
+		return ScratchVhdxPartitionInfo{}, fmt.Errorf("get vhd physical path: %w", err)
+	}
+
+	driveLayout, partitions, err = getDriveLayout(ctx, volumePath)
+	if err != nil {
+		return ScratchVhdxPartitionInfo{}, err
+	}
+
+	if driveLayout.PartitionStyle != partitionStyleGPT {
+		return ScratchVhdxPartitionInfo{}, fmt.Errorf("drive Layout:Expected partition style GPT(%d) found %d", partitionStyleGPT, driveLayout.PartitionStyle)
+	}
+
+	if driveLayout.PartitionCount != 2 || len(partitions) != 2 {
+		return ScratchVhdxPartitionInfo{}, fmt.Errorf("expected exactly 2 partitions. Got %d partitions and partition count of %d", len(partitions), driveLayout.PartitionCount)
+	}
+
+	if partitions[1].PartitionStyle != partitionStyleGPT {
+		return ScratchVhdxPartitionInfo{}, fmt.Errorf("partition Info:Expected partition style GPT(%d) found %d", partitionStyleGPT, partitions[1].PartitionStyle)
+	}
+
+	bufReader := bytes.NewBuffer(driveLayout.GptMbrUnion[:])
+	if err := binary.Read(bufReader, binary.LittleEndian, &gptDriveLayout); err != nil {
+		return ScratchVhdxPartitionInfo{}, fmt.Errorf("failed to parse drive GPT layout: %w", err)
+	}
+
+	bufReader = bytes.NewBuffer(partitions[1].GptMbrUnion[:])
+	if err := binary.Read(bufReader, binary.LittleEndian, &gptPartitionInfo); err != nil {
+		return ScratchVhdxPartitionInfo{}, fmt.Errorf("failed to parse GPT partition info: %w", err)
+	}
+
+	if gptPartitionInfo.PartitionType != partitionBasicDataGUID {
+		return ScratchVhdxPartitionInfo{}, fmt.Errorf("expected partition type to have %s GUID found %s instead", partitionBasicDataGUID, gptPartitionInfo.PartitionType)
+	}
+
+	log.G(ctx).WithFields(logrus.Fields{
+		"Disk ID":          gptDriveLayout.DiskID,
+		"GPT Partition ID": gptPartitionInfo.PartitionId,
+	}).Debug("Scratch VHD partition info")
+
+	return ScratchVhdxPartitionInfo{DiskID: gptDriveLayout.DiskID, PartitionID: gptPartitionInfo.PartitionId}, nil
+
+}