Merge pull request #141 from tri-adam/fix-padding-v1

Fix Inconsistent Alignment Accounting for Data Objects (v1)
sylabs · Sep 9, 2021 · 26f00a3 · 26f00a3
2 parents 9af8c2f + b8aa7fd
commit 26f00a3
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Showing 2 changed files with 11 additions and 5 deletions.
diff --git a/pkg/sif/create.go b/pkg/sif/create.go
@@ -197,7 +197,6 @@ func writeDescriptors(fimg *FileImage) error {
 			return fmt.Errorf("binary writing descrtable to buf: %s", err)
 		}
 	}
-	fimg.Header.Descrlen = int64(binary.Size(fimg.DescrArr))
 
 	return nil
 }
@@ -225,6 +224,7 @@ func writeHeader(fimg *FileImage) error {
 func CreateContainer(cinfo CreateInfo) (fimg *FileImage, err error) {
 	fimg = &FileImage{}
 	fimg.DescrArr = make([]Descriptor, DescrNumEntries)
+	descrLen := int64(binary.Size(fimg.DescrArr))
 
 	// Prepare a fresh global header
 	copy(fimg.Header.Launch[:], cinfo.Launchstr)
@@ -237,7 +237,8 @@ func CreateContainer(cinfo CreateInfo) (fimg *FileImage, err error) {
 	fimg.Header.Dfree = DescrNumEntries
 	fimg.Header.Dtotal = DescrNumEntries
 	fimg.Header.Descroff = DescrStartOffset
-	fimg.Header.Dataoff = DataStartOffset
+	fimg.Header.Descrlen = descrLen
+	fimg.Header.Dataoff = DescrStartOffset + descrLen
 
 	// Create container file
 	fimg.Fp, err = os.OpenFile(cinfo.Pathname, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0o755)
@@ -251,8 +252,8 @@ func CreateContainer(cinfo CreateInfo) (fimg *FileImage, err error) {
 	}()
 
 	// set file pointer to start of data section */
-	if _, err = fimg.Fp.Seek(DataStartOffset, 0); err != nil {
-		return nil, fmt.Errorf("setting file offset pointer to DataStartOffset: %s", err)
+	if _, err = fimg.Fp.Seek(fimg.Header.Dataoff, 0); err != nil {
+		return nil, fmt.Errorf("setting file offset pointer to Dataoff: %s", err)
 	}
 
 	for _, v := range cinfo.InputDescr {

diff --git a/pkg/sif/sif.go b/pkg/sif/sif.go
@@ -122,9 +122,14 @@ const (
 	DescrNameLen      = 128                // descriptor name (string identifier)
 	DescrMaxPrivLen   = 384                // size reserved for descriptor specific data
 	DescrStartOffset  = 4096               // where descriptors start after global header
-	DataStartOffset   = 32768              // where data object start after descriptors
 )
 
+// DataStartOffset indicates where data object start after descriptors.
+//
+// Deprecated: this value may not be accurate for all images. Use (Header).Dataoff from the image
+// instead.
+const DataStartOffset = 32768
+
 // Datatype represents the different SIF data object types stored in the image.
 type Datatype int32