support cgroup2

* only shim v2 runc v2 ("io.containerd.runc.v2") is supported
* only PID metrics is implemented. Others should be implemented in separate PRs.
* lots of code duplication in v1 metrics and v2 metrics. Dedupe should be separate PR.

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

vendor/github.com/cilium/ebpf/abi.go

@@ -0,0 +1,203 @@
+package ebpf
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"syscall"
+
+	"github.com/cilium/ebpf/internal"
+	"github.com/pkg/errors"
+)
+
+// MapABI are the attributes of a Map which are available across all supported kernels.
+type MapABI struct {
+	Type       MapType
+	KeySize    uint32
+	ValueSize  uint32
+	MaxEntries uint32
+	Flags      uint32
+}
+
+func newMapABIFromSpec(spec *MapSpec) *MapABI {
+	return &MapABI{
+		spec.Type,
+		spec.KeySize,
+		spec.ValueSize,
+		spec.MaxEntries,
+		spec.Flags,
+	}
+}
+
+func newMapABIFromFd(fd *bpfFD) (string, *MapABI, error) {
+	info, err := bpfGetMapInfoByFD(fd)
+	if err != nil {
+		if errors.Cause(err) == syscall.EINVAL {
+			abi, err := newMapABIFromProc(fd)
+			return "", abi, err
+		}
+		return "", nil, err
+	}
+
+	return "", &MapABI{
+		MapType(info.mapType),
+		info.keySize,
+		info.valueSize,
+		info.maxEntries,
+		info.flags,
+	}, nil
+}
+
+func newMapABIFromProc(fd *bpfFD) (*MapABI, error) {
+	var abi MapABI
+	err := scanFdInfo(fd, map[string]interface{}{
+		"map_type":    &abi.Type,
+		"key_size":    &abi.KeySize,
+		"value_size":  &abi.ValueSize,
+		"max_entries": &abi.MaxEntries,
+		"map_flags":   &abi.Flags,
+	})
+	if err != nil {
+		return nil, err
+	}
+	return &abi, nil
+}
+
+// Equal returns true if two ABIs have the same values.
+func (abi *MapABI) Equal(other *MapABI) bool {
+	switch {
+	case abi.Type != other.Type:
+		return false
+	case abi.KeySize != other.KeySize:
+		return false
+	case abi.ValueSize != other.ValueSize:
+		return false
+	case abi.MaxEntries != other.MaxEntries:
+		return false
+	case abi.Flags != other.Flags:
+		return false
+	default:
+		return true
+	}
+}
+
+// ProgramABI are the attributes of a Program which are available across all supported kernels.
+type ProgramABI struct {
+	Type ProgramType
+}
+
+func newProgramABIFromSpec(spec *ProgramSpec) *ProgramABI {
+	return &ProgramABI{
+		spec.Type,
+	}
+}
+
+func newProgramABIFromFd(fd *bpfFD) (string, *ProgramABI, error) {
+	info, err := bpfGetProgInfoByFD(fd)
+	if err != nil {
+		if errors.Cause(err) == syscall.EINVAL {
+			return newProgramABIFromProc(fd)
+		}
+
+		return "", nil, err
+	}
+
+	var name string
+	if bpfName := convertCString(info.name[:]); bpfName != "" {
+		name = bpfName
+	} else {
+		name = convertCString(info.tag[:])
+	}
+
+	return name, &ProgramABI{
+		Type: ProgramType(info.progType),
+	}, nil
+}
+
+func newProgramABIFromProc(fd *bpfFD) (string, *ProgramABI, error) {
+	var (
+		abi  ProgramABI
+		name string
+	)
+
+	err := scanFdInfo(fd, map[string]interface{}{
+		"prog_type": &abi.Type,
+		"prog_tag":  &name,
+	})
+	if errors.Cause(err) == errMissingFields {
+		return "", nil, &internal.UnsupportedFeatureError{
+			Name:           "reading ABI from /proc/self/fdinfo",
+			MinimumVersion: internal.Version{4, 11, 0},
+		}
+	}
+	if err != nil {
+		return "", nil, err
+	}
+
+	return name, &abi, nil
+}
+
+func scanFdInfo(fd *bpfFD, fields map[string]interface{}) error {
+	raw, err := fd.value()
+	if err != nil {
+		return err
+	}
+
+	fh, err := os.Open(fmt.Sprintf("/proc/self/fdinfo/%d", raw))
+	if err != nil {
+		return err
+	}
+	defer fh.Close()
+
+	return errors.Wrap(scanFdInfoReader(fh, fields), fh.Name())
+}
+
+var errMissingFields = errors.New("missing fields")
+
+func scanFdInfoReader(r io.Reader, fields map[string]interface{}) error {
+	var (
+		scanner = bufio.NewScanner(r)
+		scanned int
+	)
+
+	for scanner.Scan() {
+		parts := bytes.SplitN(scanner.Bytes(), []byte("\t"), 2)
+		if len(parts) != 2 {
+			continue
+		}
+
+		name := bytes.TrimSuffix(parts[0], []byte(":"))
+		field, ok := fields[string(name)]
+		if !ok {
+			continue
+		}
+
+		if n, err := fmt.Fscanln(bytes.NewReader(parts[1]), field); err != nil || n != 1 {
+			return errors.Wrapf(err, "can't parse field %s", name)
+		}
+
+		scanned++
+	}
+
+	if err := scanner.Err(); err != nil {
+		return err
+	}
+
+	if scanned != len(fields) {
+		return errMissingFields
+	}
+
+	return nil
+}
+
+// Equal returns true if two ABIs have the same values.
+func (abi *ProgramABI) Equal(other *ProgramABI) bool {
+	switch {
+	case abi.Type != other.Type:
+		return false
+	default:
+		return true
+	}
+}