diff --git a/metropolis/pkg/efivarfs/devicepath.go b/metropolis/pkg/efivarfs/devicepath.go
new file mode 100644
index 0000000..1606fd6
--- /dev/null
+++ b/metropolis/pkg/efivarfs/devicepath.go
@@ -0,0 +1,323 @@
+package efivarfs
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"math"
+	"strings"
+
+	"github.com/google/uuid"
+
+	"source.monogon.dev/metropolis/pkg/msguid"
+)
+
+// DevicePath represents a path consisting of one or more elements to an
+// entity implementing an EFI protocol. It's very broadly used inside EFI
+// for representing all sorts of abstract paths. In the context of this
+// package it is used to represent paths to EFI loaders.
+// See https://uefi.org/specs/UEFI/2.10/10_Protocols_Device_Path_Protocol.html
+// for more information.
+type DevicePath []DevicePathElem
+
+// DevicePathElem is a common interface for all UEFI device path elements.
+type DevicePathElem interface {
+	typ() uint8
+	subType() uint8
+	data() ([]byte, error)
+}
+
+type pathElemUnmarshalFunc func([]byte) (DevicePathElem, error)
+
+// PartitionMBR matches a drive or partition formatted with legacy MBR
+// (Master Boot Record).
+type PartitionMBR struct {
+	// DiskSignature contains a 4-byte signature identifying the drive, located
+	// just after the 440 bytes of boot sector loading code.
+	// Note that since MBR does not have per-partition signatures, this is
+	// combined with PartitionNumber to select a partition.
+	DiskSignature [4]byte
+}
+
+func (p PartitionMBR) partitionSignature() (sig [16]byte) {
+	copy(sig[:4], p.DiskSignature[:])
+	return
+}
+
+func (p PartitionMBR) partitionFormat() uint8 {
+	return 0x01
+}
+
+func (p PartitionMBR) signatureType() uint8 {
+	return 0x01
+}
+
+// PartitionGPT matches a partition on a drive formatted with GPT.
+type PartitionGPT struct {
+	// UUID of the partition to be matched. Conversion into mixed-endian format
+	// is taken care of, a standard big-endian UUID can be put in here.
+	PartitionUUID uuid.UUID
+}
+
+func (p PartitionGPT) partitionSignature() [16]byte {
+	return msguid.From(p.PartitionUUID)
+}
+
+func (p PartitionGPT) partitionFormat() uint8 {
+	return 0x02
+}
+
+func (p PartitionGPT) signatureType() uint8 {
+	return 0x02
+}
+
+// PartitionUnknown is being used to represent unknown partitioning schemas or
+// combinations of PartitionFormat/SignatureType. It contains raw uninterpreted
+// data.
+type PartitionUnknown struct {
+	PartitionSignature [16]byte
+	PartitionFormat    uint8
+	SignatureType      uint8
+}
+
+func (p PartitionUnknown) partitionSignature() [16]byte {
+	return p.PartitionSignature
+}
+
+func (p PartitionUnknown) partitionFormat() uint8 {
+	return p.PartitionFormat
+}
+
+func (p PartitionUnknown) signatureType() uint8 {
+	return p.SignatureType
+}
+
+type PartitionMatch interface {
+	partitionSignature() [16]byte
+	partitionFormat() uint8
+	signatureType() uint8
+}
+
+// HardDrivePath matches whole drives or partitions on GPT/MBR formatted
+// drives.
+type HardDrivePath struct {
+	// Partition number, starting at 1. If zero or unset, the whole drive is
+	// selected.
+	PartitionNumber uint32
+	// Block address at which the partition starts. Not used for matching
+	// partitions in EDK2.
+	PartitionStartBlock uint64
+	// Number of blocks occupied by the partition starting from the
+	// PartitionStartBlock. Not used for matching partitions in EDK2.
+	PartitionSizeBlocks uint64
+	// PartitionMatch is used to match drive or partition signatures.
+	// Use PartitionMBR and PartitionGPT types here.
+	PartitionMatch PartitionMatch
+}
+
+func (h *HardDrivePath) typ() uint8 {
+	return 4
+}
+
+func (h *HardDrivePath) subType() uint8 {
+	return 1
+}
+
+func (h *HardDrivePath) data() ([]byte, error) {
+	out := make([]byte, 38)
+	le := binary.LittleEndian
+	le.PutUint32(out[0:4], h.PartitionNumber)
+	le.PutUint64(out[4:12], h.PartitionStartBlock)
+	le.PutUint64(out[12:20], h.PartitionSizeBlocks)
+	if h.PartitionMatch == nil {
+		return nil, errors.New("PartitionMatch needs to be set")
+	}
+	sig := h.PartitionMatch.partitionSignature()
+	copy(out[20:36], sig[:])
+	out[36] = h.PartitionMatch.partitionFormat()
+	out[37] = h.PartitionMatch.signatureType()
+	return out, nil
+}
+
+func unmarshalHardDrivePath(data []byte) (DevicePathElem, error) {
+	var h HardDrivePath
+	if len(data) != 38 {
+		return nil, fmt.Errorf("invalid HardDrivePath element, expected 38 bytes, got %d", len(data))
+	}
+	le := binary.LittleEndian
+	h.PartitionNumber = le.Uint32(data[0:4])
+	h.PartitionStartBlock = le.Uint64(data[4:12])
+	h.PartitionSizeBlocks = le.Uint64(data[12:20])
+	partitionFormat := data[36]
+	signatureType := data[37]
+	var rawSig [16]byte
+	copy(rawSig[:], data[20:36])
+	switch {
+	case partitionFormat == 1 && signatureType == 1:
+		// MBR
+		var mbr PartitionMBR
+		copy(mbr.DiskSignature[:], rawSig[:4])
+		h.PartitionMatch = mbr
+	case partitionFormat == 2 && signatureType == 2:
+		// GPT
+		h.PartitionMatch = PartitionGPT{
+			PartitionUUID: msguid.To(rawSig),
+		}
+	default:
+		// Unknown
+		h.PartitionMatch = PartitionUnknown{
+			PartitionSignature: rawSig,
+			PartitionFormat:    partitionFormat,
+			SignatureType:      signatureType,
+		}
+	}
+	return &h, nil
+}
+
+// FilePath contains a backslash-separated path or part of a path to a file on
+// a filesystem.
+type FilePath string
+
+func (f FilePath) typ() uint8 {
+	return 4
+}
+
+func (f FilePath) subType() uint8 {
+	return 4
+}
+
+func (f FilePath) data() ([]byte, error) {
+	if strings.IndexByte(string(f), 0x00) != -1 {
+		return nil, fmt.Errorf("contains invalid null bytes")
+	}
+	withBackslashes := bytes.ReplaceAll([]byte(f), []byte(`/`), []byte(`\`))
+	out, err := Encoding.NewEncoder().Bytes(withBackslashes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to encode FilePath to UTF-16: %w", err)
+	}
+	return append(out, 0x00, 0x00), nil
+}
+
+func unmarshalFilePath(data []byte) (DevicePathElem, error) {
+	if len(data) < 2 {
+		return nil, fmt.Errorf("FilePath must be at least 2 bytes because of UTF-16 null terminator")
+	}
+	out, err := Encoding.NewDecoder().Bytes(data)
+	if err != nil {
+		return nil, fmt.Errorf("error decoding FilePath UTF-16 string: %w", err)
+	}
+	nullIdx := bytes.IndexByte(out, 0x00)
+	if nullIdx != len(out)-1 {
+		return nil, fmt.Errorf("FilePath not properly null-terminated")
+	}
+	withoutBackslashes := strings.Replace(string(out[:len(out)-1]), `\`, `/`, -1)
+	return FilePath(withoutBackslashes), nil
+}
+
+// Map key contains type and subtype
+var pathElementUnmarshalMap = map[[2]byte]pathElemUnmarshalFunc{
+	{4, 1}: unmarshalHardDrivePath,
+	{4, 4}: unmarshalFilePath,
+}
+
+// UnknownPath is a generic structure for all types of path elements not
+// understood by this library. The UEFI-specified set of path element
+// types is vast and mostly unused, this generic type allows for parsing as
+// well as pass-through of not-understood path elements.
+type UnknownPath struct {
+	TypeVal    uint8
+	SubTypeVal uint8
+	DataVal    []byte
+}
+
+func (u UnknownPath) typ() uint8 {
+	return u.TypeVal
+}
+
+func (u UnknownPath) subType() uint8 {
+	return u.SubTypeVal
+}
+
+func (u UnknownPath) data() ([]byte, error) {
+	return u.DataVal, nil
+}
+
+// Marshal encodes the device path in binary form.
+func (d DevicePath) Marshal() ([]byte, error) {
+	var buf []byte
+	for _, p := range d {
+		buf = append(buf, p.typ(), p.subType())
+		elemBuf, err := p.data()
+		if err != nil {
+			return nil, fmt.Errorf("failed marshaling path element: %w", err)
+		}
+		// 4 is size of header which is included in length field
+		if len(elemBuf)+4 > math.MaxUint16 {
+			return nil, fmt.Errorf("path element payload over maximum size")
+		}
+		buf = append16(buf, uint16(len(elemBuf)+4))
+		buf = append(buf, elemBuf...)
+	}
+	// End of device path (Type 0x7f, SubType 0xFF)
+	buf = append(buf, 0x7f, 0xff, 0x04, 0x00)
+	return buf, nil
+}
+
+// UnmarshalDevicePath parses a binary device path.
+func UnmarshalDevicePath(data []byte) (DevicePath, error) {
+	rest := data
+	var p DevicePath
+	for {
+		if len(rest) < 4 {
+			if len(rest) != 0 {
+				return nil, fmt.Errorf("dangling bytes at the end of device path: %x", rest)
+			}
+			break
+		}
+		t := rest[0]
+		subT := rest[1]
+		dataLen := binary.LittleEndian.Uint16(rest[2:4])
+		if int(dataLen) > len(rest) {
+			return nil, fmt.Errorf("path element larger than rest of buffer: %d > %d", dataLen, len(rest))
+		}
+		if dataLen < 4 {
+			return nil, fmt.Errorf("path element must be at least 4 bytes (header), length indicates %d", dataLen)
+		}
+		elemData := rest[4:dataLen]
+		rest = rest[dataLen:]
+
+		unmarshal, ok := pathElementUnmarshalMap[[2]byte{t, subT}]
+		if !ok {
+			p = append(p, &UnknownPath{
+				TypeVal:    t,
+				SubTypeVal: subT,
+				DataVal:    elemData,
+			})
+			continue
+		}
+		elem, err := unmarshal(elemData)
+		if err != nil {
+			return nil, fmt.Errorf("failed decoding path element %d: %w", len(p), err)
+		}
+		p = append(p, elem)
+	}
+	var endOfPathIdx int
+	for i, e := range p {
+		if e.typ() == 0x7f && e.subType() == 0xff {
+			endOfPathIdx = i
+			break
+		}
+	}
+	switch {
+	case len(p) == 0:
+		return nil, errors.New("empty DevicePath without End Of Path element")
+	case endOfPathIdx == -1:
+		return nil, fmt.Errorf("got DevicePath with %d elements, but without End Of Path element", len(p))
+	case endOfPathIdx != len(p)-1:
+		return nil, fmt.Errorf("got DevicePath with %d elements with End Of Path element at %d (wanted as last element)", len(p), endOfPathIdx)
+	}
+	p = p[:len(p)-1]
+
+	return p, nil
+}