runtime: share initdata setup code

Move setup code such that it can be used by other hypervisors.

Signed-off-by: Saul Paredes <saulparedes@microsoft.com>

src/runtime/virtcontainers/hypervisor.go

@@ -7,10 +7,14 @@ package virtcontainers
 
 import (
 	"bufio"
+	"bytes"
+	"compress/gzip"
 	"context"
+	"encoding/binary"
 	"fmt"
 	"math"
 	"os"
+	"path/filepath"
 	"runtime"
 	"strings"
 
@@ -1184,3 +1188,94 @@ func KernelParamFields(s string) []string {
 
 	return params
 }
+
+// prepareInitdataMount prepares the on-disk initdata image for a VM/sandbox.
+//
+// It reads the initdata payload from config.Initdata, creates a working directory
+// at /run/kata-containers/shared/initdata/<id>, builds the image file
+// (data.img) via prepareInitdataImage, and sets config.InitdataImage to the
+// resulting absolute path.
+func prepareInitdataMount(logger *logrus.Entry, id string, config *HypervisorConfig) error {
+	if len(config.Initdata) == 0 {
+		logger.Info("No initdata provided. Skip prepare initdata device")
+		return nil
+	}
+
+	logger.Info("Start to prepare initdata")
+	initdataWorkdir := filepath.Join("/run/kata-containers/shared/initdata", id)
+	initdataImagePath := filepath.Join(initdataWorkdir, "data.img")
+
+	if err := os.MkdirAll(initdataWorkdir, 0o755); err != nil {
+		logger.WithField("initdata", "create initdata image path").WithError(err).Error("mkdir failed")
+		return err
+	}
+
+	if err := prepareInitdataImage(config.Initdata, initdataImagePath); err != nil {
+		logger.WithField("initdata", "prepare initdata image").WithError(err).Error("prepare failed")
+		return err
+	}
+
+	config.InitdataImage = initdataImagePath
+	return nil
+}
+
+// prepareInitdataImage will create an image with a very simple layout
+//
+// There will be multiple sectors. The first 8 bytes are Magic number "initdata".
+// Then a "length" field of 8 bytes follows (unsigned int64).
+// Finally the gzipped initdata toml. The image will be padded to an
+// integer multiple of the sector size for alignment.
+//
+// offset 0                                8                    16
+// 0	  'i' 'n' 'i' 't' 'd' 'a' 't' 'a'  | gzip length in le  |
+// 16	  gzip(initdata toml) ...
+// (end of the last sector)  '\0' paddings
+func prepareInitdataImage(initdata string, imagePath string) error {
+	SectorSize := 512
+	var buf bytes.Buffer
+	gzipper := gzip.NewWriter(&buf)
+	defer gzipper.Close()
+
+	gzipper.Write([]byte(initdata))
+	err := gzipper.Close()
+	if err != nil {
+		return fmt.Errorf("failed to compress initdata: %v", err)
+	}
+
+	compressedInitdata := buf.Bytes()
+
+	compressedInitdataLength := len(compressedInitdata)
+	lengthBuffer := make([]byte, 8)
+	binary.LittleEndian.PutUint64(lengthBuffer, uint64(compressedInitdataLength))
+
+	paddingLength := (compressedInitdataLength+16+SectorSize-1)/SectorSize*SectorSize - (compressedInitdataLength + 16)
+	paddingBuffer := make([]byte, paddingLength)
+
+	file, err := os.OpenFile(imagePath, os.O_CREATE|os.O_RDWR, 0640)
+	if err != nil {
+		return fmt.Errorf("failed to create initdata image: %v", err)
+	}
+	defer file.Close()
+
+	_, err = file.Write([]byte("initdata"))
+	if err != nil {
+		return fmt.Errorf("failed to write magic number to initdata image: %v", err)
+	}
+
+	_, err = file.Write(lengthBuffer)
+	if err != nil {
+		return fmt.Errorf("failed to write data length to initdata image: %v", err)
+	}
+
+	_, err = file.Write([]byte(compressedInitdata))
+	if err != nil {
+		return fmt.Errorf("failed to write compressed initdata to initdata image: %v", err)
+	}
+
+	_, err = file.Write(paddingBuffer)
+	if err != nil {
+		return fmt.Errorf("failed to write compressed initdata to initdata image: %v", err)
+	}
+
+	return nil
+}

src/runtime/virtcontainers/qemu.go

@@ -9,10 +9,7 @@ package virtcontainers
 
 import (
 	"bufio"
-	"bytes"
-	"compress/gzip"
 	"context"
-	"encoding/binary"
 	"encoding/hex"
 	"encoding/json"
 	"fmt"
@@ -544,94 +541,6 @@ func (q *qemu) createVirtiofsDaemon(sharedPath string) (VirtiofsDaemon, error) {
 	}, nil
 }
 
-// prepareInitdataImage will create an image with a very simple layout
-//
-// There will be multiple sectors. The first 8 bytes are Magic number "initdata".
-// Then a "length" field of 8 bytes follows (unsigned int64).
-// Finally the gzipped initdata toml. The image will be padded to an
-// integer multiple of the sector size for alignment.
-//
-// offset 0                                8                    16
-// 0	  'i' 'n' 'i' 't' 'd' 'a' 't' 'a'  | gzip length in le  |
-// 16	  gzip(initdata toml) ...
-// (end of the last sector)  '\0' paddings
-func prepareInitdataImage(initdata string, imagePath string) error {
-	SectorSize := 512
-	var buf bytes.Buffer
-	gzipper := gzip.NewWriter(&buf)
-	defer gzipper.Close()
-
-	gzipper.Write([]byte(initdata))
-	err := gzipper.Close()
-	if err != nil {
-		return fmt.Errorf("failed to compress initdata: %v", err)
-	}
-
-	compressedInitdata := buf.Bytes()
-
-	compressedInitdataLength := len(compressedInitdata)
-	lengthBuffer := make([]byte, 8)
-	binary.LittleEndian.PutUint64(lengthBuffer, uint64(compressedInitdataLength))
-
-	paddingLength := (compressedInitdataLength+16+SectorSize-1)/SectorSize*SectorSize - (compressedInitdataLength + 16)
-	paddingBuffer := make([]byte, paddingLength)
-
-	file, err := os.OpenFile(imagePath, os.O_CREATE|os.O_RDWR, 0640)
-	if err != nil {
-		return fmt.Errorf("failed to create initdata image: %v", err)
-	}
-	defer file.Close()
-
-	_, err = file.Write([]byte("initdata"))
-	if err != nil {
-		return fmt.Errorf("failed to write magic number to initdata image: %v", err)
-	}
-
-	_, err = file.Write(lengthBuffer)
-	if err != nil {
-		return fmt.Errorf("failed to write data length to initdata image: %v", err)
-	}
-
-	_, err = file.Write([]byte(compressedInitdata))
-	if err != nil {
-		return fmt.Errorf("failed to write compressed initdata to initdata image: %v", err)
-	}
-
-	_, err = file.Write(paddingBuffer)
-	if err != nil {
-		return fmt.Errorf("failed to write compressed initdata to initdata image: %v", err)
-	}
-
-	return nil
-}
-
-func (q *qemu) prepareInitdataMount(config *HypervisorConfig) error {
-	if len(config.Initdata) == 0 {
-		q.Logger().Info("No initdata provided. Skip prepare initdata device")
-		return nil
-	}
-
-	q.Logger().Info("Start to prepare initdata")
-	initdataWorkdir := filepath.Join("/run/kata-containers/shared/initdata", q.id)
-	initdataImagePath := filepath.Join(initdataWorkdir, "data.img")
-
-	err := os.MkdirAll(initdataWorkdir, 0755)
-	if err != nil {
-		q.Logger().WithField("initdata", "create initdata image path").WithError(err)
-		return err
-	}
-
-	err = prepareInitdataImage(config.Initdata, initdataImagePath)
-	if err != nil {
-		q.Logger().WithField("initdata", "prepare initdata image").WithError(err)
-		return err
-	}
-
-	config.InitdataImage = initdataImagePath
-
-	return nil
-}
-
 // CreateVM is the Hypervisor VM creation implementation for govmmQemu.
 // This function is complex and there's not much to be done about it, unfortunately.
 //
@@ -647,7 +556,7 @@ func (q *qemu) CreateVM(ctx context.Context, id string, network Network, hypervi
 		return err
 	}
 
-	if err := q.prepareInitdataMount(hypervisorConfig); err != nil {
+	if err := prepareInitdataMount(q.Logger(), q.id, hypervisorConfig); err != nil {
 		return err
 	}