feat(cross-platform-builds): basic support of --platform=OS/ARCH[/VARIANT] parameter for buildah builder

Signed-off-by: Timofey Kirillov <timofey.kirillov@flant.com>

Author: distorhead

cmd/werf/common/common.go

@@ -1434,7 +1434,7 @@ func SetupPlatform(cmdData *CmdData, cmd *cobra.Command) {
 		}
 	}
 
-	cmd.Flags().StringVarP(cmdData.Platform, "platform", "", defaultValue, "Enable platform emulation when building images with werf. The only supported option for now is linux/amd64.")
+	cmd.Flags().StringVarP(cmdData.Platform, "platform", "", defaultValue, "Enable platform emulation when building images with werf, format: OS/ARCH[/VARIANT].")
 }
 
 func GetContext() context.Context {

cmd/werf/common/container_backend.go

@@ -117,12 +117,15 @@ func InitProcessContainerBackend(ctx context.Context, cmdData *CmdData) (contain
 				Isolation:     buildahIsolation,
 				StorageDriver: storageDriver,
 			},
+			NativeModeOpts: buildah.NativeModeOpts{
+				Platform: *cmdData.Platform,
+			},
 		})
 		if err != nil {
 			return nil, ctx, fmt.Errorf("unable to get buildah client: %w", err)
 		}
 
-		return wrapContainerBackend(container_backend.NewBuildahBackend(b, filepath.Join(werf.GetServiceDir(), "tmp", "buildah"))), ctx, nil
+		return wrapContainerBackend(container_backend.NewBuildahBackend(b, container_backend.BuildahBackendOptions{TmpDir: filepath.Join(werf.GetServiceDir(), "tmp", "buildah")})), ctx, nil
 	}
 
 	newCtx, err := InitProcessDocker(ctx, cmdData)

pkg/buildah/common.go

@@ -123,7 +123,9 @@ type CommonBuildahOpts struct {
 	Insecure      bool
 }
 
-type NativeModeOpts struct{}
+type NativeModeOpts struct {
+	Platform string
+}
 
 type DockerWithFuseModeOpts struct{}
 

pkg/buildah/native_linux.go

@@ -17,6 +17,7 @@ import (
 	"github.com/containers/buildah/define"
 	"github.com/containers/buildah/docker"
 	"github.com/containers/buildah/imagebuildah"
+	"github.com/containers/buildah/pkg/parse"
 	"github.com/containers/common/libimage"
 	"github.com/containers/image/v5/manifest"
 	imgstor "github.com/containers/image/v5/storage"
@@ -62,6 +63,8 @@ type NativeBuildah struct {
 	Runtime                   libimage.Runtime
 	DefaultSystemContext      imgtypes.SystemContext
 	DefaultCommonBuildOptions define.CommonBuildOptions
+
+	platforms []struct{ OS, Arch, Variant string }
 }
 
 func NewNativeBuildah(commonOpts CommonBuildahOpts, opts NativeModeOpts) (*NativeBuildah, error) {
@@ -95,6 +98,21 @@ func NewNativeBuildah(commonOpts CommonBuildahOpts, opts NativeModeOpts) (*Nativ
 		DockerDaemonInsecureSkipTLSVerify: b.Insecure,
 	}
 
+	if opts.Platform != "" {
+		os, arch, variant, err := parse.Platform(opts.Platform)
+		if err != nil {
+			return nil, fmt.Errorf("unable to parse platform %q: %w", opts.Platform, err)
+		}
+
+		b.DefaultSystemContext.OSChoice = os
+		b.DefaultSystemContext.ArchitectureChoice = arch
+		b.DefaultSystemContext.VariantChoice = variant
+
+		b.platforms = []struct{ OS, Arch, Variant string }{
+			{os, arch, variant},
+		}
+	}
+
 	b.DefaultCommonBuildOptions = define.CommonBuildOptions{
 		ShmSize: DefaultShmSize,
 	}
@@ -177,6 +195,7 @@ func (b *NativeBuildah) BuildFromDockerfile(ctx context.Context, dockerfile []by
 		Target:              opts.Target,
 		MaxPullPushRetries:  MaxPullPushRetries,
 		PullPushRetryDelay:  PullPushRetryDelay,
+		Platforms:           b.platforms,
 	}
 
 	errLog := &bytes.Buffer{}
@@ -287,10 +306,36 @@ func (b *NativeBuildah) Pull(ctx context.Context, ref string, opts PullOpts) err
 		PullPolicy:          define.PullIfNewer,
 	}
 
-	if _, err := buildah.Pull(ctx, ref, pullOpts); err != nil {
+	imageID, err := buildah.Pull(ctx, ref, pullOpts)
+	if err != nil {
 		return fmt.Errorf("error pulling image %q: %w", ref, err)
 	}
 
+	imageInspect, err := b.Inspect(ctx, imageID)
+	if err != nil {
+		return fmt.Errorf("unable to inspect pulled image %q: %w", imageID, err)
+	}
+
+	platformMismatch := false
+	if b.DefaultSystemContext.OSChoice != "" && b.DefaultSystemContext.OSChoice != imageInspect.OCIv1.OS {
+		platformMismatch = true
+	}
+	if b.DefaultSystemContext.ArchitectureChoice != "" && b.DefaultSystemContext.ArchitectureChoice != imageInspect.OCIv1.Architecture {
+		platformMismatch = true
+	}
+	if b.DefaultSystemContext.VariantChoice != "" && b.DefaultSystemContext.VariantChoice != imageInspect.OCIv1.Variant {
+		platformMismatch = true
+	}
+
+	if platformMismatch {
+		imagePlatform := fmt.Sprintf("%s/%s/%s", imageInspect.OCIv1.OS, imageInspect.OCIv1.Architecture, imageInspect.OCIv1.Variant)
+		expectedPlatform := fmt.Sprintf("%s/%s", b.DefaultSystemContext.OSChoice, b.DefaultSystemContext.ArchitectureChoice)
+		if b.DefaultSystemContext.VariantChoice != "" {
+			expectedPlatform = fmt.Sprintf("%s/%s", expectedPlatform, b.DefaultSystemContext.VariantChoice)
+		}
+		return fmt.Errorf("image platform mismatch: image uses %s, expecting %s platform", imagePlatform, expectedPlatform)
+	}
+
 	return nil
 }
 

pkg/container_backend/buildah_backend.go

@@ -25,16 +25,16 @@ import (
 )
 
 type BuildahBackend struct {
-	TmpDir  string
 	buildah buildah.Buildah
+	BuildahBackendOptions
 }
 
-type BuildahImage struct {
-	Image LegacyImageInterface
+type BuildahBackendOptions struct {
+	TmpDir string
 }
 
-func NewBuildahBackend(buildah buildah.Buildah, tmpDir string) *BuildahBackend {
-	return &BuildahBackend{buildah: buildah, TmpDir: tmpDir}
+func NewBuildahBackend(buildah buildah.Buildah, opts BuildahBackendOptions) *BuildahBackend {
+	return &BuildahBackend{buildah: buildah, BuildahBackendOptions: opts}
 }
 
 func (runtime *BuildahBackend) HasStapelBuildSupport() bool {