feat: wcow: add support for bind and cache mounts

Currently, mounts are not supported for WCOW builds,
see #5678. This commit introduces support for
bind and cache mounts. The remaining two require
a little more work and consultation with the platform
teams for enlightment.

WIP Checklist:

- [x] Support for bind mounts
- [x] Support for cache mounts
- [x] add frontend/dockerfile integration tests
- [ ] add client integration tests
- [ ] add documentatio
- [ ] add note and plan on the missing feature(s)
	i.e. secret mounts (that need tmpfs)
- [ ] spec out / second attempt for SSH mount

Fixes #5603
Addresses part of #5678

Signed-off-by: Anthony Nandaa <[email protected]>

client/client_test.go

@@ -1561,15 +1561,22 @@ func testLocalSymlinkEscape(t *testing.T, sb integration.Sandbox) {
 }
 
 func testRelativeWorkDir(t *testing.T, sb integration.Sandbox) {
-	requiresLinux(t)
 	c, err := New(sb.Context(), sb.Address())
 	require.NoError(t, err)
 	defer c.Close()
 
-	pwd := llb.Image("docker.io/library/busybox:latest").
+	imgName := integration.UnixOrWindows(
+		"docker.io/library/busybox:latest",
+		"mcr.microsoft.com/windows/nanoserver:ltsc2022",
+	)
+	cmdStr := integration.UnixOrWindows(
+		`sh -c "pwd > /out/pwd"`,
+		`cmd /C "cd > /out/pwd"`,
+	)
+	pwd := llb.Image(imgName).
 		Dir("test1").
 		Dir("test2").
-		Run(llb.Shlex(`sh -c "pwd > /out/pwd"`)).
+		Run(llb.Shlex(cmdStr)).
 		AddMount("/out", llb.Scratch())
 
 	def, err := pwd.Marshal(sb.Context())
@@ -1589,7 +1596,11 @@ func testRelativeWorkDir(t *testing.T, sb integration.Sandbox) {
 
 	dt, err := os.ReadFile(filepath.Join(destDir, "pwd"))
 	require.NoError(t, err)
-	require.Equal(t, []byte("/test1/test2\n"), dt)
+	pathStr := integration.UnixOrWindows(
+		"/test1/test2\n",
+		"C:\\test1\\test2\r\n",
+	)
+	require.Equal(t, []byte(pathStr), dt)
 }
 
 // TODO: remove this test once `client.SolveOpt.LocalDirs`, now marked as deprecated, is removed.
@@ -7480,7 +7491,7 @@ func testMergeOp(t *testing.T, sb integration.Sandbox) {
 		File(llb.Mkfile("bar/D", 0644, []byte("D"))).
 		File(llb.Mkfile("bar/E", 0755, nil)).
 		File(llb.Mkfile("qaz", 0644, nil)),
-	// /foo from stateE is not here because it is deleted in stateB, which is part of a submerge of mergeD
+		// /foo from stateE is not here because it is deleted in stateB, which is part of a submerge of mergeD
 	)
 }
 

executor/oci/spec.go

@@ -2,6 +2,7 @@ package oci
 
 import (
 	"context"
+	"github.com/moby/buildkit/util/system"
 	"os"
 	"path"
 	"path/filepath"
@@ -201,8 +202,8 @@ func GenerateSpec(ctx context.Context, meta executor.Meta, mounts []executor.Mou
 				return nil, nil, err
 			}
 			s.Mounts = append(s.Mounts, specs.Mount{
-				Destination: m.Dest,
-				Type:        mount.Type,
+				Destination: system.GetAbsolutePath(m.Dest),
+				Type:        getMountType(mount.Type),
 				Source:      mount.Source,
 				Options:     mount.Options,
 			})
@@ -243,6 +244,10 @@ type submounts struct {
 
 func (s *submounts) subMount(m mount.Mount, subPath string) (mount.Mount, error) {
 	if path.Join("/", subPath) == "/" {
+		// for Windows, the mounting by HCS doesn't go through
+		// WCIFS, hence we have to give the direct path of the
+		// mount, which is in the /Files subdirectory.
+		m.Source = getCompleteSourcePath(m.Source)
 		return m, nil
 	}
 	if s.m == nil {

executor/oci/spec_unix.go

@@ -0,0 +1,13 @@
+//go:build !windows
+
+package oci
+
+// no effect for non-Windows
+func getMountType(mType string) string {
+	return mType
+}
+
+// no effect for non-Windows
+func getCompleteSourcePath(p string) string {
+	return p
+}

executor/oci/spec_windows.go

@@ -110,3 +110,16 @@ func sub(m mount.Mount, subPath string) (mount.Mount, func() error, error) {
 	m.Source = src
 	return m, func() error { return nil }, nil
 }
+
+func getMountType(_ string) string {
+	// HCS shim doesn't expect a named type
+	// for the mount.
+	return ""
+}
+
+// For Windows, the mounting by HCS doesn't go through
+// WCIFS, hence we have to give the direct path of the
+// mount, which is in the /Files subdirectory.
+func getCompleteSourcePath(p string) string {
+	return filepath.Join(p, "Files")
+}

frontend/dockerfile/dockerfile2llb/convert_runmount.go

@@ -2,6 +2,7 @@ package dockerfile2llb
 
 import (
 	"context"
+	"github.com/moby/buildkit/util/system"
 	"os"
 	"path"
 	"path/filepath"
@@ -118,7 +119,7 @@ func dispatchRunMounts(d *dispatchState, c *instructions.RunCommand, sources []*
 			mountOpts = append(mountOpts, llb.AsPersistentCacheDir(opt.cacheIDNamespace+"/"+mount.CacheID, sharing))
 		}
 		target := mount.Target
-		if !filepath.IsAbs(filepath.Clean(mount.Target)) {
+		if !system.IsAbsolutePath(filepath.Clean(mount.Target)) {
 			dir, err := d.state.GetDir(context.TODO())
 			if err != nil {
 				return nil, err