@@ -14,6 +14,7 @@ import (

 	"strings"

 	"sync"

+	"github.com/containerd/containerd/platforms"

 	"github.com/docker/docker/api/server/httputils"

 	"github.com/docker/docker/api/types"

 	"github.com/docker/docker/api/types/backend"

@@ -72,11 +73,16 @@ func newImageBuildOptions(ctx context.Context, r *http.Request) (*types.ImageBui

 	options.RemoteContext = r.FormValue("remote")

 	if versions.GreaterThanOrEqualTo(version, "1.32") {

 		apiPlatform := r.FormValue("platform")

-		p := system.ParsePlatform(apiPlatform)

-		if err := system.ValidatePlatform(p); err != nil {

-			return nil, errdefs.InvalidParameter(errors.Errorf("invalid platform: %s", err))

+		if apiPlatform != "" {

+			sp, err := platforms.Parse(apiPlatform)

+			if err != nil {

+				return nil, err

+			}

+			if err := system.ValidatePlatform(sp); err != nil {

+				return nil, err

+			}

+			options.Platform = &sp

 		}

-		options.Platform = p.OS

 	}

 	if r.Form.Get("shmsize") != "" {

@@ -8,6 +8,7 @@ import (

 	"github.com/docker/docker/api/types/filters"

 	"github.com/docker/docker/api/types/image"

 	"github.com/docker/docker/api/types/registry"

+	specs "github.com/opencontainers/image-spec/specs-go/v1"

 )

 // Backend is all the methods that need to be implemented

@@ -34,7 +35,7 @@ type importExportBackend interface {

 }

 type registryBackend interface {

-	PullImage(ctx context.Context, image, tag, platform string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error

+	PullImage(ctx context.Context, image, tag string, platform *specs.Platform, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error

 	PushImage(ctx context.Context, image, tag string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error

 	SearchRegistryForImages(ctx context.Context, filtersArgs string, term string, limit int, authConfig *types.AuthConfig, metaHeaders map[string][]string) (*registry.SearchResults, error)

 }

@@ -4,11 +4,11 @@ import (

 	"context"

 	"encoding/base64"

 	"encoding/json"

-	"fmt"

 	"net/http"

 	"strconv"

 	"strings"

+	"github.com/containerd/containerd/platforms"

 	"github.com/docker/docker/api/server/httputils"

 	"github.com/docker/docker/api/types"

 	"github.com/docker/docker/api/types/filters"

@@ -36,7 +36,7 @@ func (s *imageRouter) postImagesCreate(ctx context.Context, w http.ResponseWrite

 		message  = r.Form.Get("message")

 		err      error

 		output   = ioutils.NewWriteFlusher(w)

-		platform = &specs.Platform{}

+		platform *specs.Platform

 	)

 	defer output.Close()

@@ -45,9 +45,15 @@ func (s *imageRouter) postImagesCreate(ctx context.Context, w http.ResponseWrite

 	version := httputils.VersionFromContext(ctx)

 	if versions.GreaterThanOrEqualTo(version, "1.32") {

 		apiPlatform := r.FormValue("platform")

-		platform = system.ParsePlatform(apiPlatform)

-		if err = system.ValidatePlatform(platform); err != nil {

-			err = fmt.Errorf("invalid platform: %s", err)

+		if apiPlatform != "" {

+			sp, err := platforms.Parse(apiPlatform)

+			if err != nil {

+				return err

+			}

+			if err := system.ValidatePlatform(sp); err != nil {

+				return err

+			}

+			platform = &sp

 		}

 	}

@@ -70,13 +76,17 @@ func (s *imageRouter) postImagesCreate(ctx context.Context, w http.ResponseWrite

 					authConfig = &types.AuthConfig{}

 				}

 			}

-			err = s.backend.PullImage(ctx, image, tag, platform.OS, metaHeaders, authConfig, output)

+			err = s.backend.PullImage(ctx, image, tag, platform, metaHeaders, authConfig, output)

 		} else { //import

 			src := r.Form.Get("fromSrc")

 			// 'err' MUST NOT be defined within this block, we need any error

 			// generated from the download to be available to the output

 			// stream processing below

-			err = s.backend.ImportImage(src, repo, platform.OS, tag, message, r.Body, output, r.Form["changes"])

+			os := ""

+			if platform != nil {

+				os = platform.OS

+			}

+			err = s.backend.ImportImage(src, repo, os, tag, message, r.Body, output, r.Form["changes"])

 		}

 	}

 	if err != nil {

@@ -5,6 +5,7 @@ import (

 	"github.com/docker/docker/api/types"

 	"github.com/docker/docker/pkg/streamformatter"

+	specs "github.com/opencontainers/image-spec/specs-go/v1"

 )

 // PullOption defines different modes for accessing images

@@ -40,5 +41,5 @@ type GetImageAndLayerOptions struct {

 	PullOption PullOption

 	AuthConfig map[string]types.AuthConfig

 	Output     io.Writer

-	OS         string

+	Platform   *specs.Platform

 }

@@ -8,6 +8,7 @@ import (

 	"github.com/docker/docker/api/types/container"

 	"github.com/docker/docker/api/types/filters"

 	"github.com/docker/go-units"

+	specs "github.com/opencontainers/image-spec/specs-go/v1"

 )

 // CheckpointCreateOptions holds parameters to create a checkpoint from a container

@@ -180,7 +181,7 @@ type ImageBuildOptions struct {

 	ExtraHosts  []string // List of extra hosts

 	Target      string

 	SessionID   string

-	Platform    string

+	Platform    *specs.Platform

 	// Version specifies the version of the unerlying builder to use

 	Version BuilderVersion

 	// BuildID is an optional identifier that can be passed together with the

@@ -113,7 +113,7 @@ func (is *imageSource) resolveLocal(refStr string) ([]byte, error) {

 	return img.RawJSON(), nil

 }

-func (is *imageSource) ResolveImageConfig(ctx context.Context, ref string) (digest.Digest, []byte, error) {

+func (is *imageSource) ResolveImageConfig(ctx context.Context, ref string, platform *ocispec.Platform) (digest.Digest, []byte, error) {

 	if preferLocal {

 		dt, err := is.resolveLocal(ref)

 		if err == nil {

@@ -126,7 +126,7 @@ func (is *imageSource) ResolveImageConfig(ctx context.Context, ref string) (dige

 		dt   []byte

 	}

 	res, err := is.g.Do(ctx, ref, func(ctx context.Context) (interface{}, error) {

-		dgst, dt, err := imageutil.Config(ctx, ref, is.getResolver(ctx), is.ContentStore, "")

+		dgst, dt, err := imageutil.Config(ctx, ref, is.getResolver(ctx), is.ContentStore, platform)

 		if err != nil {

 			return nil, err

 		}

@@ -145,10 +145,16 @@ func (is *imageSource) Resolve(ctx context.Context, id source.Identifier) (sourc

 		return nil, errors.Errorf("invalid image identifier %v", id)

 	}

+	platform := platforms.DefaultSpec()

+	if imageIdentifier.Platform != nil {

+		platform = *imageIdentifier.Platform

+	}

+

 	p := &puller{

 		src:      imageIdentifier,

 		is:       is,

 		resolver: is.getResolver(ctx),

+		platform: platform,

 	}

 	return p, nil

 }

@@ -163,17 +169,20 @@ type puller struct {

 	resolveErr       error

 	resolver         remotes.Resolver

 	config           []byte

+	platform         ocispec.Platform

 }

-func (p *puller) mainManifestKey(dgst digest.Digest) (digest.Digest, error) {

+func (p *puller) mainManifestKey(dgst digest.Digest, platform ocispec.Platform) (digest.Digest, error) {

 	dt, err := json.Marshal(struct {

-		Digest digest.Digest

-		OS     string

-		Arch   string

+		Digest  digest.Digest

+		OS      string

+		Arch    string

+		Variant string `json:",omitempty"`

 	}{

-		Digest: p.desc.Digest,

-		OS:     runtime.GOOS,

-		Arch:   runtime.GOARCH,

+		Digest:  p.desc.Digest,

+		OS:      platform.OS,

+		Arch:    platform.Architecture,

+		Variant: platform.Variant,

 	})

 	if err != nil {

 		return "", err

@@ -248,7 +257,7 @@ func (p *puller) resolve(ctx context.Context) error {

 				return

 			}

-			_, dt, err := p.is.ResolveImageConfig(ctx, ref.String())

+			_, dt, err := p.is.ResolveImageConfig(ctx, ref.String(), &p.platform)

 			if err != nil {

 				p.resolveErr = err

 				resolveProgressDone(err)

@@ -266,7 +275,7 @@ func (p *puller) CacheKey(ctx context.Context, index int) (string, bool, error)

 	p.resolveLocal()

 	if p.desc.Digest != "" && index == 0 {

-		dgst, err := p.mainManifestKey(p.desc.Digest)

+		dgst, err := p.mainManifestKey(p.desc.Digest, p.platform)

 		if err != nil {

 			return "", false, err

 		}

@@ -282,7 +291,7 @@ func (p *puller) CacheKey(ctx context.Context, index int) (string, bool, error)

 	}

 	if p.desc.Digest != "" && index == 0 {

-		dgst, err := p.mainManifestKey(p.desc.Digest)

+		dgst, err := p.mainManifestKey(p.desc.Digest, p.platform)

 		if err != nil {

 			return "", false, err

 		}

@@ -9,6 +9,7 @@ import (

 	"time"

 	"github.com/containerd/containerd/content"

+	"github.com/containerd/containerd/platforms"

 	"github.com/docker/docker/api/types"

 	"github.com/docker/docker/api/types/backend"

 	"github.com/docker/docker/builder"

@@ -208,6 +209,10 @@ func (b *Builder) Build(ctx context.Context, opt backend.BuildConfig) (*builder.

 		frontendAttrs["no-cache"] = ""

 	}

+	if opt.Options.Platform != nil {

+		frontendAttrs["platform"] = platforms.Format(*opt.Options.Platform)

+	}

+

 	exporterAttrs := map[string]string{}

 	if len(opt.Options.Tags) > 0 {

@@ -10,6 +10,7 @@ import (

 	"time"

 	"github.com/containerd/containerd/content"

+	"github.com/containerd/containerd/platforms"

 	"github.com/containerd/containerd/rootfs"

 	"github.com/docker/docker/distribution"

 	distmetadata "github.com/docker/docker/distribution/metadata"

@@ -122,6 +123,12 @@ func (w *Worker) Labels() map[string]string {

 	return w.Opt.Labels

 }

+// Platforms returns one or more platforms supported by the image.

+func (w *Worker) Platforms() []ocispec.Platform {

+	// does not handle lcow

+	return []ocispec.Platform{platforms.DefaultSpec()}

+}

+

 // LoadRef loads a reference by ID

 func (w *Worker) LoadRef(id string) (cache.ImmutableRef, error) {

 	return w.CacheManager.Get(context.TODO(), id)

@@ -129,26 +136,27 @@ func (w *Worker) LoadRef(id string) (cache.ImmutableRef, error) {

 // ResolveOp converts a LLB vertex into a LLB operation

 func (w *Worker) ResolveOp(v solver.Vertex, s frontend.FrontendLLBBridge) (solver.Op, error) {

-	switch op := v.Sys().(type) {

-	case *pb.Op_Source:

-		return ops.NewSourceOp(v, op, w.SourceManager, w)

-	case *pb.Op_Exec:

-		return ops.NewExecOp(v, op, w.CacheManager, w.MetadataStore, w.Executor, w)

-	case *pb.Op_Build:

-		return ops.NewBuildOp(v, op, s, w)

-	default:

-		return nil, errors.Errorf("could not resolve %v", v)

+	if baseOp, ok := v.Sys().(*pb.Op); ok {

+		switch op := baseOp.Op.(type) {

+		case *pb.Op_Source:

+			return ops.NewSourceOp(v, op, baseOp.Platform, w.SourceManager, w)

+		case *pb.Op_Exec:

+			return ops.NewExecOp(v, op, w.CacheManager, w.MetadataStore, w.Executor, w)

+		case *pb.Op_Build:

+			return ops.NewBuildOp(v, op, s, w)

+		}

 	}

+	return nil, errors.Errorf("could not resolve %v", v)

 }

 // ResolveImageConfig returns image config for an image

-func (w *Worker) ResolveImageConfig(ctx context.Context, ref string) (digest.Digest, []byte, error) {

+func (w *Worker) ResolveImageConfig(ctx context.Context, ref string, platform *ocispec.Platform) (digest.Digest, []byte, error) {

 	// ImageSource is typically source/containerimage

 	resolveImageConfig, ok := w.ImageSource.(resolveImageConfig)

 	if !ok {

 		return "", nil, errors.Errorf("worker %q does not implement ResolveImageConfig", w.ID())

 	}

-	return resolveImageConfig.ResolveImageConfig(ctx, ref)

+	return resolveImageConfig.ResolveImageConfig(ctx, ref, platform)

 }

 // Exec executes a process directly on a worker

@@ -319,5 +327,5 @@ func oneOffProgress(ctx context.Context, id string) func(err error) error {

 }

 type resolveImageConfig interface {

-	ResolveImageConfig(ctx context.Context, ref string) (digest.Digest, []byte, error)

+	ResolveImageConfig(ctx context.Context, ref string, platform *ocispec.Platform) (digest.Digest, []byte, error)

 }

@@ -104,13 +104,6 @@ func (bm *BuildManager) Build(ctx context.Context, config backend.BuildConfig) (

 		source = src

 	}

-	os := ""

-	apiPlatform := system.ParsePlatform(config.Options.Platform)

-	if apiPlatform.OS != "" {

-		os = apiPlatform.OS

-	}

-	config.Options.Platform = os

-

 	builderOptions := builderOptions{

 		Options:        config.Options,

 		ProgressWriter: config.ProgressWriter,

@@ -24,6 +24,7 @@ import (

 	"github.com/docker/docker/pkg/streamformatter"

 	"github.com/docker/docker/pkg/system"

 	"github.com/docker/docker/pkg/urlutil"

+	specs "github.com/opencontainers/image-spec/specs-go/v1"

 	"github.com/pkg/errors"

 )

@@ -72,7 +73,7 @@ type copier struct {

 	source      builder.Source

 	pathCache   pathCache

 	download    sourceDownloader

-	platform    string

+	platform    *specs.Platform

 	// for cleanup. TODO: having copier.cleanup() is error prone and hard to

 	// follow. Code calling performCopy should manage the lifecycle of its params.

 	// Copier should take override source as input, not imageMount.

@@ -95,8 +96,14 @@ func (o *copier) createCopyInstruction(args []string, cmdName string) (copyInstr

 	last := len(args) - 1

 	// Work in platform-specific filepath semantics

-	inst.dest = fromSlash(args[last], o.platform)

-	separator := string(separator(o.platform))

+	// TODO: This OS switch for paths is NOT correct and should not be supported.

+	// Maintained for backwards compatibility

+	pathOS := runtime.GOOS

+	if o.platform != nil {

+		pathOS = o.platform.OS

+	}

+	inst.dest = fromSlash(args[last], pathOS)

+	separator := string(separator(pathOS))

 	infos, err := o.getCopyInfosForSourcePaths(args[0:last], inst.dest)

 	if err != nil {

 		return inst, errors.Wrapf(err, "%s failed", cmdName)

@@ -14,6 +14,7 @@ import (

 	"sort"

 	"strings"

+	"github.com/containerd/containerd/platforms"

 	"github.com/docker/docker/api"

 	"github.com/docker/docker/api/types/container"

 	"github.com/docker/docker/api/types/strslice"

@@ -27,6 +28,7 @@ import (

 	"github.com/moby/buildkit/frontend/dockerfile/instructions"

 	"github.com/moby/buildkit/frontend/dockerfile/parser"

 	"github.com/moby/buildkit/frontend/dockerfile/shell"

+	specs "github.com/opencontainers/image-spec/specs-go/v1"

 	"github.com/pkg/errors"

 )

@@ -102,7 +104,7 @@ func dispatchAdd(d dispatchRequest, c *instructions.AddCommand) error {

 	copyInstruction.chownStr = c.Chown

 	copyInstruction.allowLocalDecompression = true

-	return d.builder.performCopy(d.state, copyInstruction)

+	return d.builder.performCopy(d, copyInstruction)

 }

 // COPY foo /path

@@ -126,7 +128,7 @@ func dispatchCopy(d dispatchRequest, c *instructions.CopyCommand) error {

 	}

 	copyInstruction.chownStr = c.Chown

-	return d.builder.performCopy(d.state, copyInstruction)

+	return d.builder.performCopy(d, copyInstruction)

 }

 func (d *dispatchRequest) getImageMount(imageRefOrID string) (*imageMount, error) {

@@ -144,17 +146,32 @@ func (d *dispatchRequest) getImageMount(imageRefOrID string) (*imageMount, error

 		imageRefOrID = stage.Image

 		localOnly = true

 	}

-	return d.builder.imageSources.Get(imageRefOrID, localOnly, d.state.operatingSystem)

+	return d.builder.imageSources.Get(imageRefOrID, localOnly, d.builder.options.Platform)

 }

 // FROM [--platform=platform] imagename[:tag | @digest] [AS build-stage-name]

 //

 func initializeStage(d dispatchRequest, cmd *instructions.Stage) error {

 	d.builder.imageProber.Reset()

-	if err := system.ValidatePlatform(&cmd.Platform); err != nil {

-		return err

+

+	var platform *specs.Platform

+	if v := cmd.Platform; v != "" {

+		v, err := d.getExpandedString(d.shlex, v)

+		if err != nil {

+			return errors.Wrapf(err, "failed to process arguments for platform %s", v)

+		}

+

+		p, err := platforms.Parse(v)

+		if err != nil {

+			return errors.Wrapf(err, "failed to parse platform %s", v)

+		}

+		if err := system.ValidatePlatform(p); err != nil {

+			return err

+		}

+		platform = &p

 	}

-	image, err := d.getFromImage(d.shlex, cmd.BaseName, cmd.Platform.OS)

+

+	image, err := d.getFromImage(d.shlex, cmd.BaseName, platform)

 	if err != nil {

 		return err

 	}

@@ -200,82 +217,72 @@ func dispatchTriggeredOnBuild(d dispatchRequest, triggers []string) error {

 	return nil

 }

-func (d *dispatchRequest) getExpandedImageName(shlex *shell.Lex, name string) (string, error) {

+func (d *dispatchRequest) getExpandedString(shlex *shell.Lex, str string) (string, error) {

 	substitutionArgs := []string{}

 	for key, value := range d.state.buildArgs.GetAllMeta() {

 		substitutionArgs = append(substitutionArgs, key+"="+value)

 	}

-	name, err := shlex.ProcessWord(name, substitutionArgs)

+	name, err := shlex.ProcessWord(str, substitutionArgs)

 	if err != nil {

 		return "", err

 	}

 	return name, nil

 }

-// getOsFromFlagsAndStage calculates the operating system if we need to pull an image.

-// stagePlatform contains the value supplied by optional `--platform=` on

-// a current FROM statement. b.builder.options.Platform contains the operating

-// system part of the optional flag passed in the API call (or CLI flag

-// through `docker build --platform=...`). Precedence is for an explicit

-// platform indication in the FROM statement.

-func (d *dispatchRequest) getOsFromFlagsAndStage(stageOS string) string {

-	switch {

-	case stageOS != "":

-		return stageOS

-	case d.builder.options.Platform != "":

-		// Note this is API "platform", but by this point, as the daemon is not

-		// multi-arch aware yet, it is guaranteed to only hold the OS part here.

-		return d.builder.options.Platform

-	default:

-		return runtime.GOOS

-	}

-}

-

-func (d *dispatchRequest) getImageOrStage(name string, stageOS string) (builder.Image, error) {

+func (d *dispatchRequest) getImageOrStage(name string, platform *specs.Platform) (builder.Image, error) {

 	var localOnly bool

 	if im, ok := d.stages.getByName(name); ok {

 		name = im.Image

 		localOnly = true

 	}

-	os := d.getOsFromFlagsAndStage(stageOS)

+	if platform == nil {

+		platform = d.builder.options.Platform

+	}

 	// Windows cannot support a container with no base image unless it is LCOW.

 	if name == api.NoBaseImageSpecifier {

+		p := platforms.DefaultSpec()

+		if platform != nil {

+			p = *platform

+		}

 		imageImage := &image.Image{}

-		imageImage.OS = runtime.GOOS

+		imageImage.OS = p.OS

+

+		// old windows scratch handling

+		// TODO: scratch should not have an os. It should be nil image.

+		// Windows supports scratch. What is not supported is running containers

+		// from it.

 		if runtime.GOOS == "windows" {

-			switch os {

-			case "windows", "":

-				return nil, errors.New("Windows does not support FROM scratch")

-			case "linux":

+			if platform == nil || platform.OS == "linux" {

 				if !system.LCOWSupported() {

 					return nil, errors.New("Linux containers are not supported on this system")

 				}

 				imageImage.OS = "linux"

-			default:

-				return nil, errors.Errorf("operating system %q is not supported", os)

+			} else if platform.OS == "windows" {

+				return nil, errors.New("Windows does not support FROM scratch")

+			} else {

+				return nil, errors.Errorf("platform %s is not supported", platforms.Format(p))

 			}

 		}

 		return builder.Image(imageImage), nil

 	}

-	imageMount, err := d.builder.imageSources.Get(name, localOnly, os)

+	imageMount, err := d.builder.imageSources.Get(name, localOnly, platform)

 	if err != nil {

 		return nil, err

 	}

 	return imageMount.Image(), nil

 }

-func (d *dispatchRequest) getFromImage(shlex *shell.Lex, name string, stageOS string) (builder.Image, error) {

-	name, err := d.getExpandedImageName(shlex, name)

+func (d *dispatchRequest) getFromImage(shlex *shell.Lex, name string, platform *specs.Platform) (builder.Image, error) {

+	name, err := d.getExpandedString(shlex, name)

 	if err != nil {

 		return nil, err

 	}

-	return d.getImageOrStage(name, stageOS)

+	return d.getImageOrStage(name, platform)

 }

 func dispatchOnbuild(d dispatchRequest, c *instructions.OnbuildCommand) error {

-

 	d.state.runConfig.OnBuild = append(d.state.runConfig.OnBuild, c.Expression)

 	return d.builder.commit(d.state, "ONBUILD "+c.Expression)

 }

@@ -6,6 +6,7 @@ import (

 	"runtime"

 	"testing"

+	"github.com/containerd/containerd/platforms"

 	"github.com/docker/docker/api/types"

 	"github.com/docker/docker/api/types/backend"

 	"github.com/docker/docker/api/types/container"

@@ -22,15 +23,17 @@ import (

 func newBuilderWithMockBackend() *Builder {

 	mockBackend := &MockBackend{}

+	defaultPlatform := platforms.DefaultSpec()

+	opts := &types.ImageBuildOptions{Platform: &defaultPlatform}

 	ctx := context.Background()

 	b := &Builder{

-		options:       &types.ImageBuildOptions{Platform: runtime.GOOS},

+		options:       opts,

 		docker:        mockBackend,

 		Stdout:        new(bytes.Buffer),

 		clientCtx:     ctx,

 		disableCommit: true,

 		imageSources: newImageSources(ctx, builderOptions{

-			Options: &types.ImageBuildOptions{Platform: runtime.GOOS},

+			Options: opts,

 			Backend: mockBackend,

 		}),

 		imageProber:      newImageProber(mockBackend, nil, false),

@@ -7,11 +7,12 @@ import (

 	"github.com/docker/docker/api/types/backend"

 	"github.com/docker/docker/builder"

 	dockerimage "github.com/docker/docker/image"

+	specs "github.com/opencontainers/image-spec/specs-go/v1"

 	"github.com/pkg/errors"

 	"github.com/sirupsen/logrus"

 )

-type getAndMountFunc func(string, bool, string) (builder.Image, builder.ROLayer, error)

+type getAndMountFunc func(string, bool, *specs.Platform) (builder.Image, builder.ROLayer, error)

 // imageSources mounts images and provides a cache for mounted images. It tracks

 // all images so they can be unmounted at the end of the build.

@@ -22,7 +23,7 @@ type imageSources struct {

 }

 func newImageSources(ctx context.Context, options builderOptions) *imageSources {

-	getAndMount := func(idOrRef string, localOnly bool, osForPull string) (builder.Image, builder.ROLayer, error) {

+	getAndMount := func(idOrRef string, localOnly bool, platform *specs.Platform) (builder.Image, builder.ROLayer, error) {

 		pullOption := backend.PullOptionNoPull

 		if !localOnly {

 			if options.Options.PullParent {

@@ -35,7 +36,7 @@ func newImageSources(ctx context.Context, options builderOptions) *imageSources

 			PullOption: pullOption,

 			AuthConfig: options.Options.AuthConfigs,

 			Output:     options.ProgressWriter.Output,

-			OS:         osForPull,

+			Platform:   platform,

 		})

 	}

@@ -45,12 +46,12 @@ func newImageSources(ctx context.Context, options builderOptions) *imageSources

 	}

 }

-func (m *imageSources) Get(idOrRef string, localOnly bool, osForPull string) (*imageMount, error) {

+func (m *imageSources) Get(idOrRef string, localOnly bool, platform *specs.Platform) (*imageMount, error) {

 	if im, ok := m.byImageID[idOrRef]; ok {

 		return im, nil

 	}

-	image, layer, err := m.getImage(idOrRef, localOnly, osForPull)

+	image, layer, err := m.getImage(idOrRef, localOnly, platform)

 	if err != nil {

 		return nil, err

 	}

@@ -150,7 +150,8 @@ func (b *Builder) exportImage(state *dispatchState, layer builder.RWLayer, paren

 	return nil

 }

-func (b *Builder) performCopy(state *dispatchState, inst copyInstruction) error {

+func (b *Builder) performCopy(req dispatchRequest, inst copyInstruction) error {

+	state := req.state

 	srcHash := getSourceHashFromInfos(inst.infos)

 	var chownComment string

@@ -168,7 +169,7 @@ func (b *Builder) performCopy(state *dispatchState, inst copyInstruction) error

 		return err

 	}

-	imageMount, err := b.imageSources.Get(state.imageID, true, state.operatingSystem)

+	imageMount, err := b.imageSources.Get(state.imageID, true, req.builder.options.Platform)

 	if err != nil {

 		return errors.Wrapf(err, "failed to get destination image %q", state.imageID)

 	}

@@ -456,7 +457,7 @@ func hostConfigFromOptions(options *types.ImageBuildOptions) *container.HostConf

 	// is too small for builder scenarios where many users are

 	// using RUN statements to install large amounts of data.

 	// Use 127GB as that's the default size of a VHD in Hyper-V.

-	if runtime.GOOS == "windows" && options.Platform == "windows" {

+	if runtime.GOOS == "windows" && options.Platform != nil && options.Platform.OS == "windows" {

 		hc.StorageOpt = make(map[string]string)

 		hc.StorageOpt["size"] = "127GB"

 	}

@@ -8,8 +8,8 @@ import (

 	"net/http"

 	"net/url"

 	"strconv"

-	"strings"

+	"github.com/containerd/containerd/platforms"

 	"github.com/docker/docker/api/types"

 	"github.com/docker/docker/api/types/container"

 )

@@ -30,11 +30,11 @@ func (cli *Client) ImageBuild(ctx context.Context, buildContext io.Reader, optio

 	}

 	headers.Add("X-Registry-Config", base64.URLEncoding.EncodeToString(buf))

-	if options.Platform != "" {

+	if options.Platform != nil {

 		if err := cli.NewVersionError("1.32", "platform"); err != nil {

 			return types.ImageBuildResponse{}, err

 		}

-		query.Set("platform", options.Platform)

+		query.Set("platform", platforms.Format(*options.Platform))

 	}

 	headers.Set("Content-Type", "application/x-tar")

@@ -130,8 +130,8 @@ func (cli *Client) imageBuildOptionsToQuery(options types.ImageBuildOptions) (ur

 	if options.SessionID != "" {

 		query.Set("session", options.SessionID)

 	}

-	if options.Platform != "" {

-		query.Set("platform", strings.ToLower(options.Platform))

+	if options.Platform != nil {

+		query.Set("platform", platforms.Format(*options.Platform))

 	}

 	if options.BuildID != "" {

 		query.Set("buildid", options.BuildID)

@@ -23,6 +23,7 @@ import (

 	"github.com/docker/libnetwork/cluster"

 	networktypes "github.com/docker/libnetwork/types"

 	"github.com/docker/swarmkit/agent/exec"

+	specs "github.com/opencontainers/image-spec/specs-go/v1"

 )

 // Backend defines the executor component for a swarm agent.

@@ -69,7 +70,7 @@ type VolumeBackend interface {

 // ImageBackend is used by an executor to perform image operations

 type ImageBackend interface {

-	PullImage(ctx context.Context, image, tag, platform string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error

+	PullImage(ctx context.Context, image, tag string, platform *specs.Platform, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error

 	GetRepository(context.Context, reference.Named, *types.AuthConfig) (distribution.Repository, bool, error)

 	LookupImage(name string) (*types.ImageInspect, error)

 }

@@ -8,7 +8,6 @@ import (

 	"fmt"

 	"io"

 	"os"

-	"runtime"

 	"strings"

 	"syscall"

 	"time"

@@ -97,8 +96,7 @@ func (c *containerAdapter) pullImage(ctx context.Context) error {

 	go func() {

 		// TODO @jhowardmsft LCOW Support: This will need revisiting as

 		// the stack is built up to include LCOW support for swarm.

-		platform := runtime.GOOS

-		err := c.imageBackend.PullImage(ctx, c.container.image(), "", platform, metaHeaders, authConfig, pw)

+		err := c.imageBackend.PullImage(ctx, c.container.image(), "", nil, metaHeaders, authConfig, pw)

 		pw.CloseWithError(err)

 	}()

@@ -3,6 +3,7 @@ package images // import "github.com/docker/docker/daemon/images"

 import (

 	"context"

 	"io"

+	"runtime"

 	"github.com/docker/distribution/reference"

 	"github.com/docker/docker/api/types"

@@ -14,6 +15,7 @@ import (

 	"github.com/docker/docker/pkg/stringid"

 	"github.com/docker/docker/pkg/system"

 	"github.com/docker/docker/registry"

+	specs "github.com/opencontainers/image-spec/specs-go/v1"

 	"github.com/pkg/errors"

 )

@@ -137,7 +139,7 @@ func newROLayerForImage(img *image.Image, layerStore layer.Store) (builder.ROLay

 }

 // TODO: could this use the regular daemon PullImage ?

-func (i *ImageService) pullForBuilder(ctx context.Context, name string, authConfigs map[string]types.AuthConfig, output io.Writer, os string) (*image.Image, error) {

+func (i *ImageService) pullForBuilder(ctx context.Context, name string, authConfigs map[string]types.AuthConfig, output io.Writer, platform *specs.Platform) (*image.Image, error) {

 	ref, err := reference.ParseNormalizedNamed(name)

 	if err != nil {

 		return nil, err

@@ -156,7 +158,7 @@ func (i *ImageService) pullForBuilder(ctx context.Context, name string, authConf

 		pullRegistryAuth = &resolvedConfig

 	}

-	if err := i.pullImageWithReference(ctx, ref, os, nil, pullRegistryAuth, output); err != nil {

+	if err := i.pullImageWithReference(ctx, ref, platform, nil, pullRegistryAuth, output); err != nil {

 		return nil, err

 	}

 	return i.GetImage(name)

@@ -166,11 +168,15 @@ func (i *ImageService) pullForBuilder(ctx context.Context, name string, authConf

 // Every call to GetImageAndReleasableLayer MUST call releasableLayer.Release() to prevent

 // leaking of layers.

 func (i *ImageService) GetImageAndReleasableLayer(ctx context.Context, refOrID string, opts backend.GetImageAndLayerOptions) (builder.Image, builder.ROLayer, error) {

-	if refOrID == "" {

-		if !system.IsOSSupported(opts.OS) {

+	if refOrID == "" { // ie FROM scratch

+		os := runtime.GOOS

+		if opts.Platform != nil {

+			os = opts.Platform.OS

+		}

+		if !system.IsOSSupported(os) {

 			return nil, nil, system.ErrNotSupportedOperatingSystem

 		}

-		layer, err := newROLayerForImage(nil, i.layerStores[opts.OS])

+		layer, err := newROLayerForImage(nil, i.layerStores[os])

 		return nil, layer, err

 	}

@@ -189,7 +195,7 @@ func (i *ImageService) GetImageAndReleasableLayer(ctx context.Context, refOrID s

 		}

 	}

-	image, err := i.pullForBuilder(ctx, refOrID, opts.AuthConfig, opts.Output, opts.OS)

+	image, err := i.pullForBuilder(ctx, refOrID, opts.AuthConfig, opts.Output, opts.Platform)

 	if err != nil {

 		return nil, nil, err

 	}

@@ -3,7 +3,6 @@ package images // import "github.com/docker/docker/daemon/images"

 import (

 	"context"

 	"io"

-	"runtime"

 	"strings"

 	"time"

@@ -16,11 +15,12 @@ import (

 	"github.com/docker/docker/pkg/progress"

 	"github.com/docker/docker/registry"

 	"github.com/opencontainers/go-digest"

+	specs "github.com/opencontainers/image-spec/specs-go/v1"

 )

 // PullImage initiates a pull operation. image is the repository name to pull, and

 // tag may be either empty, or indicate a specific tag to pull.

-func (i *ImageService) PullImage(ctx context.Context, image, tag, os string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error {

+func (i *ImageService) PullImage(ctx context.Context, image, tag string, platform *specs.Platform, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error {

 	start := time.Now()

 	// Special case: "pull -a" may send an image name with a

 	// trailing :. This is ugly, but let's not break API

@@ -46,12 +46,12 @@ func (i *ImageService) PullImage(ctx context.Context, image, tag, os string, met

 		}

 	}

-	err = i.pullImageWithReference(ctx, ref, os, metaHeaders, authConfig, outStream)

+	err = i.pullImageWithReference(ctx, ref, platform, metaHeaders, authConfig, outStream)

 	imageActions.WithValues("pull").UpdateSince(start)

 	return err

 }

-func (i *ImageService) pullImageWithReference(ctx context.Context, ref reference.Named, os string, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error {

+func (i *ImageService) pullImageWithReference(ctx context.Context, ref reference.Named, platform *specs.Platform, metaHeaders map[string][]string, authConfig *types.AuthConfig, outStream io.Writer) error {

 	// Include a buffer so that slow client connections don't affect

 	// transfer performance.

 	progressChan := make(chan progress.Progress, 100)

@@ -65,11 +65,6 @@ func (i *ImageService) pullImageWithReference(ctx context.Context, ref reference

 		close(writesDone)

 	}()

-	// Default to the host OS platform in case it hasn't been populated with an explicit value.

-	if os == "" {

-		os = runtime.GOOS

-	}

-

 	imagePullConfig := &distribution.ImagePullConfig{

 		Config: distribution.Config{

 			MetaHeaders:      metaHeaders,

@@ -83,7 +78,7 @@ func (i *ImageService) pullImageWithReference(ctx context.Context, ref reference

 		},

 		DownloadManager: i.downloadManager,

 		Schema2Types:    distribution.ImageTypes,

-		OS:              os,

+		Platform:        platform,

 	}

 	err := distribution.Pull(ctx, ref, imagePullConfig)

@@ -60,9 +60,8 @@ type ImagePullConfig struct {

 	// Schema2Types is the valid schema2 configuration types allowed

 	// by the pull operation.

 	Schema2Types []string

-	// OS is the requested operating system of the image being pulled to ensure it can be validated

-	// when the host OS supports multiple image operating systems.

-	OS string

+	// Platform is the requested platform of the image being pulled

+	Platform *specs.Platform

 }

 // ImagePushConfig stores push configuration.

@@ -171,7 +170,7 @@ func (s *imageConfigStore) PlatformFromConfig(c []byte) (*specs.Platform, error)

 	if !system.IsOSSupported(os) {

 		return nil, system.ErrNotSupportedOperatingSystem

 	}

-	return &specs.Platform{OS: os, OSVersion: unmarshalledConfig.OSVersion}, nil