feat: add ext4 filesystem detection logic

This simply detects the ext filesystem superblock.

Signed-off-by: Andrey Smirnov <[email protected]>

blockdevice/filesystem/ext4/doc.go

@@ -0,0 +1,6 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+// Package ext4 provides functions for working with the ext filesystems.
+package ext4

blockdevice/filesystem/ext4/superblock.go

@@ -0,0 +1,51 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package ext4
+
+import (
+	"unsafe"
+)
+
+const (
+	// Magic is the ext magic signature.
+	Magic = 0xef53
+)
+
+// SuperBlock represents the ext filesystem super block.
+//
+// See https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout#The_Super_Block for the reference.
+type SuperBlock struct {
+	_     [0x38]uint8
+	Magic [2]uint8
+	_     [0x3e]uint8
+	Label [0x10]uint8
+	_     [0x378]uint8
+}
+
+// Is implements the SuperBlocker interface.
+func (sb *SuperBlock) Is() bool {
+	return sb.Magic[1] == Magic>>8 && sb.Magic[0] == Magic&0xff
+}
+
+// Offset implements the SuperBlocker interface.
+func (sb *SuperBlock) Offset() int64 {
+	return 0x400
+}
+
+// Type implements the SuperBlocker interface.
+func (sb *SuperBlock) Type() string {
+	return "ext4"
+}
+
+// Encrypted implements the SuperBlocker interface.
+func (sb *SuperBlock) Encrypted() bool {
+	return false
+}
+
+func init() {
+	if unsafe.Sizeof(SuperBlock{}) != 0x400 {
+		panic("ext4: SuperBlock size is not 0x400")
+	}
+}

blockdevice/filesystem/fs.go

@@ -13,6 +13,7 @@ import (
 
 	"github.com/siderolabs/go-retry/retry"
 
+	"github.com/siderolabs/go-blockdevice/blockdevice/filesystem/ext4"
 	"github.com/siderolabs/go-blockdevice/blockdevice/filesystem/iso9660"
 	"github.com/siderolabs/go-blockdevice/blockdevice/filesystem/luks"
 	"github.com/siderolabs/go-blockdevice/blockdevice/filesystem/msdos"
@@ -67,6 +68,7 @@ func Probe(path string) (SuperBlocker, error) { //nolint:ireturn
 		&msdos.SuperBlock{},
 		&xfs.SuperBlock{},
 		&luks.SuperBlock{},
+		&ext4.SuperBlock{},
 	}
 
 	for _, sb := range superblocks {

blockdevice/probe/probe.go

@@ -12,6 +12,7 @@ import (
 
 	"github.com/siderolabs/go-blockdevice/blockdevice"
 	"github.com/siderolabs/go-blockdevice/blockdevice/filesystem"
+	"github.com/siderolabs/go-blockdevice/blockdevice/filesystem/ext4"
 	"github.com/siderolabs/go-blockdevice/blockdevice/filesystem/iso9660"
 	"github.com/siderolabs/go-blockdevice/blockdevice/filesystem/msdos"
 	"github.com/siderolabs/go-blockdevice/blockdevice/filesystem/vfat"
@@ -73,6 +74,11 @@ func WithFileSystemLabel(label string) SelectOption {
 				if bytes.Equal(trimmed, []byte(label)) {
 					return true, nil
 				}
+			case *ext4.SuperBlock:
+				trimmed := bytes.Trim(sb.Label[:], " \x00")
+				if bytes.Equal(trimmed, []byte(label)) {
+					return true, nil
+				}
 			}
 		}
 

blockdevice/probe/probe_test.go

@@ -56,11 +56,16 @@ func (suite *ProbeSuite) addPartition(name string, size uint64, fatBits int) *gp
 	return partition
 }
 
-func (suite *ProbeSuite) setSystemLabel(name string, fatBits int) {
+func (suite *ProbeSuite) setSystemLabelVFAT(name string, fatBits int) {
 	cmd := exec.Command("mkfs.vfat", "-F", strconv.Itoa(fatBits), "-n", name, suite.LoopbackDevice.Name())
 	suite.Require().NoError(cmd.Run())
 }
 
+func (suite *ProbeSuite) setSystemLabelEXT4(name string) {
+	cmd := exec.Command("mkfs.ext4", "-L", name, suite.LoopbackDevice.Name())
+	suite.Require().NoError(cmd.Run())
+}
+
 func (suite *ProbeSuite) TestDevForPartitionLabel() {
 	part12 := suite.addPartition("devpart12", 1024*1024, 12)
 	part32 := suite.addPartition("devpart32", 1024*1024*256, 32)
@@ -103,7 +108,7 @@ func (suite *ProbeSuite) TestGetDevWithPartitionName() {
 func (suite *ProbeSuite) testGetDevWithFileSystemLabel(fatBits int) {
 	label := fmt.Sprintf("LABELSYS%d", fatBits)
 
-	suite.setSystemLabel(label, fatBits)
+	suite.setSystemLabelVFAT(label, fatBits)
 
 	dev, err := probe.GetDevWithFileSystemLabel(label)
 	suite.Require().NoError(err)
@@ -129,8 +134,8 @@ func (suite *ProbeSuite) TestProbeByPartitionLabel() {
 	suite.Require().Equal(suite.LoopbackDevice.Name(), probed[0].Device().Name())
 }
 
-func (suite *ProbeSuite) TestProbeByFilesystemLabelBlockdevice() {
-	suite.setSystemLabel("FSLBABELBD", 32)
+func (suite *ProbeSuite) TestProbeByFilesystemLabelBlockdeviceVFAT() {
+	suite.setSystemLabelVFAT("FSLBABELBD", 32)
 
 	probed, err := probe.All(probe.WithFileSystemLabel("FSLBABELBD"))
 	suite.Require().NoError(err)
@@ -140,6 +145,17 @@ func (suite *ProbeSuite) TestProbeByFilesystemLabelBlockdevice() {
 	suite.Require().Equal(suite.LoopbackDevice.Name(), probed[0].Path)
 }
 
+func (suite *ProbeSuite) TestProbeByFilesystemLabelBlockdeviceEXT4() {
+	suite.setSystemLabelEXT4("EXTBD")
+
+	probed, err := probe.All(probe.WithFileSystemLabel("EXTBD"))
+	suite.Require().NoError(err)
+	suite.Require().Equal(1, len(probed))
+
+	suite.Require().Equal(suite.LoopbackDevice.Name(), probed[0].Device().Name())
+	suite.Require().Equal(suite.LoopbackDevice.Name(), probed[0].Path)
+}
+
 func (suite *ProbeSuite) TestProbeByFilesystemLabelPartition() {
 	suite.addPartition("FOO", 1024*1024*256, 16)
 	suite.addPartition("FSLABELPART", 1024*1024*2, 12)