package btf
import (
"encoding/binary"
"errors"
"fmt"
"math"
"reflect"
"strconv"
"strings"
"github.com/cilium/ebpf/asm"
)
// Code in this file is derived from libbpf, which is available under a BSD
// 2-Clause license.
// COREFixup is the result of computing a CO-RE relocation for a target.
type COREFixup struct {
kind coreKind
local uint32
target uint32
// True if there is no valid fixup. The instruction is replaced with an
// invalid dummy.
poison bool
// True if the validation of the local value should be skipped. Used by
// some kinds of bitfield relocations.
skipLocalValidation bool
}
func (f *COREFixup) equal(other COREFixup) bool {
return f.local == other.local && f.target == other.target
}
func (f *COREFixup) String() string {
if f.poison {
return fmt.Sprintf("%s=poison", f.kind)
}
return fmt.Sprintf("%s=%d->%d", f.kind, f.local, f.target)
}
func (f *COREFixup) Apply(ins *asm.Instruction) error {
if f.poison {
const badRelo = 0xbad2310
*ins = asm.BuiltinFunc(badRelo).Call()
return nil
}
switch class := ins.OpCode.Class(); class {
case asm.LdXClass, asm.StClass, asm.StXClass:
if want := int16(f.local); !f.skipLocalValidation && want != ins.Offset {
return fmt.Errorf("invalid offset %d, expected %d", ins.Offset, f.local)
}
if f.target > math.MaxInt16 {
return fmt.Errorf("offset %d exceeds MaxInt16", f.target)
}
ins.Offset = int16(f.target)
case asm.LdClass:
if !ins.IsConstantLoad(asm.DWord) {
return fmt.Errorf("not a dword-sized immediate load")
}
if want := int64(f.local); !f.skipLocalValidation && want != ins.Constant {
return fmt.Errorf("invalid immediate %d, expected %d (fixup: %v)", ins.Constant, want, f)
}
ins.Constant = int64(f.target)
case asm.ALUClass:
if ins.OpCode.ALUOp() == asm.Swap {
return fmt.Errorf("relocation against swap")
}
fallthrough
case asm.ALU64Class:
if src := ins.OpCode.Source(); src != asm.ImmSource {
return fmt.Errorf("invalid source %s", src)
}
if want := int64(f.local); !f.skipLocalValidation && want != ins.Constant {
return fmt.Errorf("invalid immediate %d, expected %d (fixup: %v, kind: %v, ins: %v)", ins.Constant, want, f, f.kind, ins)
}
if f.target > math.MaxInt32 {
return fmt.Errorf("immediate %d exceeds MaxInt32", f.target)
}
ins.Constant = int64(f.target)
default:
return fmt.Errorf("invalid class %s", class)
}
return nil
}
func (f COREFixup) isNonExistant() bool {
return f.kind.checksForExistence() && f.target == 0
}
// coreKind is the type of CO-RE relocation as specified in BPF source code.
type coreKind uint32
const (
reloFieldByteOffset coreKind = iota /* field byte offset */
reloFieldByteSize /* field size in bytes */
reloFieldExists /* field existence in target kernel */
reloFieldSigned /* field signedness (0 - unsigned, 1 - signed) */
reloFieldLShiftU64 /* bitfield-specific left bitshift */
reloFieldRShiftU64 /* bitfield-specific right bitshift */
reloTypeIDLocal /* type ID in local BPF object */
reloTypeIDTarget /* type ID in target kernel */
reloTypeExists /* type existence in target kernel */
reloTypeSize /* type size in bytes */
reloEnumvalExists /* enum value existence in target kernel */
reloEnumvalValue /* enum value integer value */
)
func (k coreKind) checksForExistence() bool {
return k == reloEnumvalExists || k == reloTypeExists || k == reloFieldExists
}
func (k coreKind) String() string {
switch k {
case reloFieldByteOffset:
return "byte_off"
case reloFieldByteSize:
return "byte_sz"
case reloFieldExists:
return "field_exists"
case reloFieldSigned:
return "signed"
case reloFieldLShiftU64:
return "lshift_u64"
case reloFieldRShiftU64:
return "rshift_u64"
case reloTypeIDLocal:
return "local_type_id"
case reloTypeIDTarget:
return "target_type_id"
case reloTypeExists:
return "type_exists"
case reloTypeSize:
return "type_size"
case reloEnumvalExists:
return "enumval_exists"
case reloEnumvalValue:
return "enumval_value"
default:
return "unknown"
}
}
// CORERelocate calculates changes needed to adjust eBPF instructions for differences
// in types.
//
// Returns a list of fixups which can be applied to instructions to make them
// match the target type(s).
//
// Fixups are returned in the order of relos, e.g. fixup[i] is the solution
// for relos[i].
func CORERelocate(relos []*CORERelocation, target *Spec, bo binary.ByteOrder) ([]COREFixup, error) {
if target == nil {
var err error
target, _, err = kernelSpec()
if err != nil {
return nil, fmt.Errorf("load kernel spec: %w", err)
}
}
if bo != target.byteOrder {
return nil, fmt.Errorf("can't relocate %s against %s", bo, target.byteOrder)
}
type reloGroup struct {
relos []*CORERelocation
// Position of each relocation in relos.
indices []int
}
// Split relocations into per Type lists.
relosByType := make(map[Type]*reloGroup)
result := make([]COREFixup, len(relos))
for i, relo := range relos {
if relo.kind == reloTypeIDLocal {
// Filtering out reloTypeIDLocal here makes our lives a lot easier
// down the line, since it doesn't have a target at all.
if len(relo.accessor) > 1 || relo.accessor[0] != 0 {
return nil, fmt.Errorf("%s: unexpected accessor %v", relo.kind, relo.accessor)
}
result[i] = COREFixup{
kind: relo.kind,
local: uint32(relo.id),
// NB: Using relo.id as the target here is incorrect, since
// it doesn't match the BTF we generate on the fly. This isn't
// too bad for now since there are no uses of the local type ID
// in the kernel, yet.
target: uint32(relo.id),
}
continue
}
group, ok := relosByType[relo.typ]
if !ok {
group = &reloGroup{}
relosByType[relo.typ] = group
}
group.relos = append(group.relos, relo)
group.indices = append(group.indices, i)
}
for localType, group := range relosByType {
localTypeName := localType.TypeName()
if localTypeName == "" {
return nil, fmt.Errorf("relocate unnamed or anonymous type %s: %w", localType, ErrNotSupported)
}
targets := target.namedTypes[newEssentialName(localTypeName)]
fixups, err := coreCalculateFixups(group.relos, target, targets, bo)
if err != nil {
return nil, fmt.Errorf("relocate %s: %w", localType, err)
}
for j, index := range group.indices {
result[index] = fixups[j]
}
}
return result, nil
}
var errAmbiguousRelocation = errors.New("ambiguous relocation")
var errImpossibleRelocation = errors.New("impossible relocation")
var errIncompatibleTypes = errors.New("incompatible types")
// coreCalculateFixups finds the target type that best matches all relocations.
//
// All relos must target the same type.
//
// The best target is determined by scoring: the less poisoning we have to do
// the better the target is.
func coreCalculateFixups(relos []*CORERelocation, targetSpec *Spec, targets []Type, bo binary.ByteOrder) ([]COREFixup, error) {
bestScore := len(relos)
var bestFixups []COREFixup
for _, target := range targets {
targetID, err := targetSpec.TypeID(target)
if err != nil {
return nil, fmt.Errorf("target type ID: %w", err)
}
score := 0 // lower is better
fixups := make([]COREFixup, 0, len(relos))
for _, relo := range relos {
fixup, err := coreCalculateFixup(relo, target, targetID, bo)
if err != nil {
return nil, fmt.Errorf("target %s: %s: %w", target, relo.kind, err)
}
if fixup.poison || fixup.isNonExistant() {
score++
}
fixups = append(fixups, fixup)
}
if score > bestScore {
// We have a better target already, ignore this one.
continue
}
if score < bestScore {
// This is the best target yet, use it.
bestScore = score
bestFixups = fixups
continue
}
// Some other target has the same score as the current one. Make sure
// the fixups agree with each other.
for i, fixup := range bestFixups {
if !fixup.equal(fixups[i]) {
return nil, fmt.Errorf("%s: multiple types match: %w", fixup.kind, errAmbiguousRelocation)
}
}
}
if bestFixups == nil {
// Nothing at all matched, probably because there are no suitable
// targets at all.
//
// Poison everything except checksForExistence.
bestFixups = make([]COREFixup, len(relos))
for i, relo := range relos {
if relo.kind.checksForExistence() {
bestFixups[i] = COREFixup{kind: relo.kind, local: 1, target: 0}
} else {
bestFixups[i] = COREFixup{kind: relo.kind, poison: true}
}
}
}
return bestFixups, nil
}
var errNoSignedness = errors.New("no signedness")
// coreCalculateFixup calculates the fixup for a single local type, target type
// and relocation.
func coreCalculateFixup(relo *CORERelocation, target Type, targetID TypeID, bo binary.ByteOrder) (COREFixup, error) {
fixup := func(local, target uint32) (COREFixup, error) {
return COREFixup{kind: relo.kind, local: local, target: target}, nil
}
fixupWithoutValidation := func(local, target uint32) (COREFixup, error) {
return COREFixup{kind: relo.kind, local: local, target: target, skipLocalValidation: true}, nil
}
poison := func() (COREFixup, error) {
if relo.kind.checksForExistence() {
return fixup(1, 0)
}
return COREFixup{kind: relo.kind, poison: true}, nil
}
zero := COREFixup{}
local := relo.typ
switch relo.kind {
case reloTypeIDTarget, reloTypeSize, reloTypeExists:
if len(relo.accessor) > 1 || relo.accessor[0] != 0 {
return zero, fmt.Errorf("unexpected accessor %v", relo.accessor)
}
err := coreAreTypesCompatible(local, target)
if errors.Is(err, errIncompatibleTypes) {
return poison()
}
if err != nil {
return zero, err
}
switch relo.kind {
case reloTypeExists:
return fixup(1, 1)
case reloTypeIDTarget:
return fixup(uint32(relo.id), uint32(targetID))
case reloTypeSize:
localSize, err := Sizeof(local)
if err != nil {
return zero, err
}
targetSize, err := Sizeof(target)
if err != nil {
return zero, err
}
return fixup(uint32(localSize), uint32(targetSize))
}
case reloEnumvalValue, reloEnumvalExists:
localValue, targetValue, err := coreFindEnumValue(local, relo.accessor, target)
if errors.Is(err, errImpossibleRelocation) {
return poison()
}
if err != nil {
return zero, err
}
switch relo.kind {
case reloEnumvalExists:
return fixup(1, 1)
case reloEnumvalValue:
return fixup(uint32(localValue.Value), uint32(targetValue.Value))
}
case reloFieldByteOffset, reloFieldByteSize, reloFieldExists, reloFieldLShiftU64, reloFieldRShiftU64, reloFieldSigned:
if _, ok := as[*Fwd](target); ok {
// We can't relocate fields using a forward declaration, so
// skip it. If a non-forward declaration is present in the BTF
// we'll find it in one of the other iterations.
return poison()
}
localField, targetField, err := coreFindField(local, relo.accessor, target)
if errors.Is(err, errImpossibleRelocation) {
return poison()
}
if err != nil {
return zero, err
}
maybeSkipValidation := func(f COREFixup, err error) (COREFixup, error) {
f.skipLocalValidation = localField.bitfieldSize > 0
return f, err
}
switch relo.kind {
case reloFieldExists:
return fixup(1, 1)
case reloFieldByteOffset:
return maybeSkipValidation(fixup(localField.offset, targetField.offset))
case reloFieldByteSize:
localSize, err := Sizeof(localField.Type)
if err != nil {
return zero, err
}
targetSize, err := Sizeof(targetField.Type)
if err != nil {
return zero, err
}
return maybeSkipValidation(fixup(uint32(localSize), uint32(targetSize)))
case reloFieldLShiftU64:
var target uint32
if bo == binary.LittleEndian {
targetSize, err := targetField.sizeBits()
if err != nil {
return zero, err
}
target = uint32(64 - targetField.bitfieldOffset - targetSize)
} else {
loadWidth, err := Sizeof(targetField.Type)
if err != nil {
return zero, err
}
target = uint32(64 - Bits(loadWidth*8) + targetField.bitfieldOffset)
}
return fixupWithoutValidation(0, target)
case reloFieldRShiftU64:
targetSize, err := targetField.sizeBits()
if err != nil {
return zero, err
}
return fixupWithoutValidation(0, uint32(64-targetSize))
case reloFieldSigned:
switch local := UnderlyingType(localField.Type).(type) {
case *Enum:
target, ok := as[*Enum](targetField.Type)
if !ok {
return zero, fmt.Errorf("target isn't *Enum but %T", targetField.Type)
}
return fixup(boolToUint32(local.Signed), boolToUint32(target.Signed))
case *Int:
target, ok := as[*Int](targetField.Type)
if !ok {
return zero, fmt.Errorf("target isn't *Int but %T", targetField.Type)
}
return fixup(
uint32(local.Encoding&Signed),
uint32(target.Encoding&Signed),
)
default:
return zero, fmt.Errorf("type %T: %w", local, errNoSignedness)
}
}
}
return zero, ErrNotSupported
}
func boolToUint32(val bool) uint32 {
if val {
return 1
}
return 0
}
/* coreAccessor contains a path through a struct. It contains at least one index.
*
* The interpretation depends on the kind of the relocation. The following is
* taken from struct bpf_core_relo in libbpf_internal.h:
*
* - for field-based relocations, string encodes an accessed field using
* a sequence of field and array indices, separated by colon (:). It's
* conceptually very close to LLVM's getelementptr ([0]) instruction's
* arguments for identifying offset to a field.
* - for type-based relocations, strings is expected to be just "0";
* - for enum value-based relocations, string contains an index of enum
* value within its enum type;
*
* Example to provide a better feel.
*
* struct sample {
* int a;
* struct {
* int b[10];
* };
* };
*
* struct sample s = ...;
* int x = &s->a; // encoded as "0:0" (a is field #0)
* int y = &s->b[5]; // encoded as "0:1:0:5" (anon struct is field #1,
* // b is field #0 inside anon struct, accessing elem #5)
* int z = &s[10]->b; // encoded as "10:1" (ptr is used as an array)
*/
type coreAccessor []int
func parseCOREAccessor(accessor string) (coreAccessor, error) {
if accessor == "" {
return nil, fmt.Errorf("empty accessor")
}
parts := strings.Split(accessor, ":")
result := make(coreAccessor, 0, len(parts))
for _, part := range parts {
// 31 bits to avoid overflowing int on 32 bit platforms.
index, err := strconv.ParseUint(part, 10, 31)
if err != nil {
return nil, fmt.Errorf("accessor index %q: %s", part, err)
}
result = append(result, int(index))
}
return result, nil
}
func (ca coreAccessor) String() string {
strs := make([]string, 0, len(ca))
for _, i := range ca {
strs = append(strs, strconv.Itoa(i))
}
return strings.Join(strs, ":")
}
func (ca coreAccessor) enumValue(t Type) (*EnumValue, error) {
e, ok := as[*Enum](t)
if !ok {
return nil, fmt.Errorf("not an enum: %s", t)
}
if len(ca) > 1 {
return nil, fmt.Errorf("invalid accessor %s for enum", ca)
}
i := ca[0]
if i >= len(e.Values) {
return nil, fmt.Errorf("invalid index %d for %s", i, e)
}
return &e.Values[i], nil
}
// coreField represents the position of a "child" of a composite type from the
// start of that type.
//
// /- start of composite
// | offset * 8 | bitfieldOffset | bitfieldSize | ... |
// \- start of field end of field -/
type coreField struct {
Type Type
// The position of the field from the start of the composite type in bytes.
offset uint32
// The offset of the bitfield in bits from the start of the field.
bitfieldOffset Bits
// The size of the bitfield in bits.
//
// Zero if the field is not a bitfield.
bitfieldSize Bits
}
func (cf *coreField) adjustOffsetToNthElement(n int) error {
if n == 0 {
return nil
}
size, err := Sizeof(cf.Type)
if err != nil {
return err
}
cf.offset += uint32(n) * uint32(size)
return nil
}
func (cf *coreField) adjustOffsetBits(offset Bits) error {
align, err := alignof(cf.Type)
if err != nil {
return err
}
// We can compute the load offset by:
// 1) converting the bit offset to bytes with a flooring division.
// 2) dividing and multiplying that offset by the alignment, yielding the
// load size aligned offset.
offsetBytes := uint32(offset/8) / uint32(align) * uint32(align)
// The number of bits remaining is the bit offset less the number of bits
// we can "skip" with the aligned offset.
cf.bitfieldOffset = offset - Bits(offsetBytes*8)
// We know that cf.offset is aligned at to at least align since we get it
// from the compiler via BTF. Adding an aligned offsetBytes preserves the
// alignment.
cf.offset += offsetBytes
return nil
}
func (cf *coreField) sizeBits() (Bits, error) {
if cf.bitfieldSize > 0 {
return cf.bitfieldSize, nil
}
// Someone is trying to access a non-bitfield via a bit shift relocation.
// This happens when a field changes from a bitfield to a regular field
// between kernel versions. Synthesise the size to make the shifts work.
size, err := Sizeof(cf.Type)
if err != nil {
return 0, err
}
return Bits(size * 8), nil
}
// coreFindField descends into the local type using the accessor and tries to
// find an equivalent field in target at each step.
//
// Returns the field and the offset of the field from the start of
// target in bits.
func coreFindField(localT Type, localAcc coreAccessor, targetT Type) (coreField, coreField, error) {
local := coreField{Type: localT}
target := coreField{Type: targetT}
if err := coreAreMembersCompatible(local.Type, target.Type); err != nil {
return coreField{}, coreField{}, fmt.Errorf("fields: %w", err)
}
// The first index is used to offset a pointer of the base type like
// when accessing an array.
if err := local.adjustOffsetToNthElement(localAcc[0]); err != nil {
return coreField{}, coreField{}, err
}
if err := target.adjustOffsetToNthElement(localAcc[0]); err != nil {
return coreField{}, coreField{}, err
}
var localMaybeFlex, targetMaybeFlex bool
for i, acc := range localAcc[1:] {
switch localType := UnderlyingType(local.Type).(type) {
case composite:
// For composite types acc is used to find the field in the local type,
// and then we try to find a field in target with the same name.
localMembers := localType.members()
if acc >= len(localMembers) {
return coreField{}, coreField{}, fmt.Errorf("invalid accessor %d for %s", acc, localType)
}
localMember := localMembers[acc]
if localMember.Name == "" {
localMemberType, ok := as[composite](localMember.Type)
if !ok {
return coreField{}, coreField{}, fmt.Errorf("unnamed field with type %s: %s", localMember.Type, ErrNotSupported)
}
// This is an anonymous struct or union, ignore it.
local = coreField{
Type: localMemberType,
offset: local.offset + localMember.Offset.Bytes(),
}
localMaybeFlex = false
continue
}
targetType, ok := as[composite](target.Type)
if !ok {
return coreField{}, coreField{}, fmt.Errorf("target not composite: %w", errImpossibleRelocation)
}
targetMember, last, err := coreFindMember(targetType, localMember.Name)
if err != nil {
return coreField{}, coreField{}, err
}
local = coreField{
Type: localMember.Type,
offset: local.offset,
bitfieldSize: localMember.BitfieldSize,
}
localMaybeFlex = acc == len(localMembers)-1
target = coreField{
Type: targetMember.Type,
offset: target.offset,
bitfieldSize: targetMember.BitfieldSize,
}
targetMaybeFlex = last
if local.bitfieldSize == 0 && target.bitfieldSize == 0 {
local.offset += localMember.Offset.Bytes()
target.offset += targetMember.Offset.Bytes()
break
}
// Either of the members is a bitfield. Make sure we're at the
// end of the accessor.
if next := i + 1; next < len(localAcc[1:]) {
return coreField{}, coreField{}, fmt.Errorf("can't descend into bitfield")
}
if err := local.adjustOffsetBits(localMember.Offset); err != nil {
return coreField{}, coreField{}, err
}
if err := target.adjustOffsetBits(targetMember.Offset); err != nil {
return coreField{}, coreField{}, err
}
case *Array:
// For arrays, acc is the index in the target.
targetType, ok := as[*Array](target.Type)
if !ok {
return coreField{}, coreField{}, fmt.Errorf("target not array: %w", errImpossibleRelocation)
}
if localType.Nelems == 0 && !localMaybeFlex {
return coreField{}, coreField{}, fmt.Errorf("local type has invalid flexible array")
}
if targetType.Nelems == 0 && !targetMaybeFlex {
return coreField{}, coreField{}, fmt.Errorf("target type has invalid flexible array")
}
if localType.Nelems > 0 && acc >= int(localType.Nelems) {
return coreField{}, coreField{}, fmt.Errorf("invalid access of %s at index %d", localType, acc)
}
if targetType.Nelems > 0 && acc >= int(targetType.Nelems) {
return coreField{}, coreField{}, fmt.Errorf("out of bounds access of target: %w", errImpossibleRelocation)
}
local = coreField{
Type: localType.Type,
offset: local.offset,
}
localMaybeFlex = false
if err := local.adjustOffsetToNthElement(acc); err != nil {
return coreField{}, coreField{}, err
}
target = coreField{
Type: targetType.Type,
offset: target.offset,
}
targetMaybeFlex = false
if err := target.adjustOffsetToNthElement(acc); err != nil {
return coreField{}, coreField{}, err
}
default:
return coreField{}, coreField{}, fmt.Errorf("relocate field of %T: %w", localType, ErrNotSupported)
}
if err := coreAreMembersCompatible(local.Type, target.Type); err != nil {
return coreField{}, coreField{}, err
}
}
return local, target, nil
}
// coreFindMember finds a member in a composite type while handling anonymous
// structs and unions.
func coreFindMember(typ composite, name string) (Member, bool, error) {
if name == "" {
return Member{}, false, errors.New("can't search for anonymous member")
}
type offsetTarget struct {
composite
offset Bits
}
targets := []offsetTarget{{typ, 0}}
visited := make(map[composite]bool)
for i := 0; i < len(targets); i++ {
target := targets[i]
// Only visit targets once to prevent infinite recursion.
if visited[target] {
continue
}
if len(visited) >= maxTypeDepth {
// This check is different than libbpf, which restricts the entire
// path to BPF_CORE_SPEC_MAX_LEN items.
return Member{}, false, fmt.Errorf("type is nested too deep")
}
visited[target] = true
members := target.members()
for j, member := range members {
if member.Name == name {
// NB: This is safe because member is a copy.
member.Offset += target.offset
return member, j == len(members)-1, nil
}
// The names don't match, but this member could be an anonymous struct
// or union.
if member.Name != "" {
continue
}
comp, ok := as[composite](member.Type)
if !ok {
return Member{}, false, fmt.Errorf("anonymous non-composite type %T not allowed", member.Type)
}
targets = append(targets, offsetTarget{comp, target.offset + member.Offset})
}
}
return Member{}, false, fmt.Errorf("no matching member: %w", errImpossibleRelocation)
}
// coreFindEnumValue follows localAcc to find the equivalent enum value in target.
func coreFindEnumValue(local Type, localAcc coreAccessor, target Type) (localValue, targetValue *EnumValue, _ error) {
localValue, err := localAcc.enumValue(local)
if err != nil {
return nil, nil, err
}
targetEnum, ok := as[*Enum](target)
if !ok {
return nil, nil, errImpossibleRelocation
}
localName := newEssentialName(localValue.Name)
for i, targetValue := range targetEnum.Values {
if newEssentialName(targetValue.Name) != localName {
continue
}
return localValue, &targetEnum.Values[i], nil
}
return nil, nil, errImpossibleRelocation
}
// CheckTypeCompatibility checks local and target types for Compatibility according to CO-RE rules.
//
// Only layout compatibility is checked, ignoring names of the root type.
func CheckTypeCompatibility(localType Type, targetType Type) error {
return coreAreTypesCompatible(localType, targetType)
}
/* The comment below is from bpf_core_types_are_compat in libbpf.c:
*
* Check local and target types for compatibility. This check is used for
* type-based CO-RE relocations and follow slightly different rules than
* field-based relocations. This function assumes that root types were already
* checked for name match. Beyond that initial root-level name check, names
* are completely ignored. Compatibility rules are as follows:
* - any two STRUCTs/UNIONs/FWDs/ENUMs/INTs are considered compatible, but
* kind should match for local and target types (i.e., STRUCT is not
* compatible with UNION);
* - for ENUMs, the size is ignored;
* - for INT, size and signedness are ignored;
* - for ARRAY, dimensionality is ignored, element types are checked for
* compatibility recursively;
* - CONST/VOLATILE/RESTRICT modifiers are ignored;
* - TYPEDEFs/PTRs are compatible if types they pointing to are compatible;
* - FUNC_PROTOs are compatible if they have compatible signature: same
* number of input args and compatible return and argument types.
* These rules are not set in stone and probably will be adjusted as we get
* more experience with using BPF CO-RE relocations.
*
* Returns errIncompatibleTypes if types are not compatible.
*/
func coreAreTypesCompatible(localType Type, targetType Type) error {
var (
localTs, targetTs typeDeque
l, t = &localType, &targetType
depth = 0
)
for ; l != nil && t != nil; l, t = localTs.Shift(), targetTs.Shift() {
if depth >= maxTypeDepth {
return errors.New("types are nested too deep")
}
localType = UnderlyingType(*l)
targetType = UnderlyingType(*t)
if reflect.TypeOf(localType) != reflect.TypeOf(targetType) {
return fmt.Errorf("type mismatch: %w", errIncompatibleTypes)
}
switch lv := (localType).(type) {
case *Void, *Struct, *Union, *Enum, *Fwd, *Int:
// Nothing to do here
case *Pointer, *Array:
depth++
walkType(localType, localTs.Push)
walkType(targetType, targetTs.Push)
case *FuncProto:
tv := targetType.(*FuncProto)
if len(lv.Params) != len(tv.Params) {
return fmt.Errorf("function param mismatch: %w", errIncompatibleTypes)
}
depth++
walkType(localType, localTs.Push)
walkType(targetType, targetTs.Push)
default:
return fmt.Errorf("unsupported type %T", localType)
}
}
if l != nil {
return fmt.Errorf("dangling local type %T", *l)
}
if t != nil {
return fmt.Errorf("dangling target type %T", *t)
}
return nil
}
/* coreAreMembersCompatible checks two types for field-based relocation compatibility.
*
* The comment below is from bpf_core_fields_are_compat in libbpf.c:
*
* Check two types for compatibility for the purpose of field access
* relocation. const/volatile/restrict and typedefs are skipped to ensure we
* are relocating semantically compatible entities:
* - any two STRUCTs/UNIONs are compatible and can be mixed;
* - any two FWDs are compatible, if their names match (modulo flavor suffix);
* - any two PTRs are always compatible;
* - for ENUMs, names should be the same (ignoring flavor suffix) or at
* least one of enums should be anonymous;
* - for ENUMs, check sizes, names are ignored;
* - for INT, size and signedness are ignored;
* - any two FLOATs are always compatible;
* - for ARRAY, dimensionality is ignored, element types are checked for
* compatibility recursively;
* [ NB: coreAreMembersCompatible doesn't recurse, this check is done
* by coreFindField. ]
* - everything else shouldn't be ever a target of relocation.
* These rules are not set in stone and probably will be adjusted as we get
* more experience with using BPF CO-RE relocations.
*
* Returns errImpossibleRelocation if the members are not compatible.
*/
func coreAreMembersCompatible(localType Type, targetType Type) error {
localType = UnderlyingType(localType)
targetType = UnderlyingType(targetType)
doNamesMatch := func(a, b string) error {
if a == "" || b == "" {
// allow anonymous and named type to match
return nil
}
if newEssentialName(a) == newEssentialName(b) {
return nil
}
return fmt.Errorf("names don't match: %w", errImpossibleRelocation)
}
_, lok := localType.(composite)
_, tok := targetType.(composite)
if lok && tok {
return nil
}
if reflect.TypeOf(localType) != reflect.TypeOf(targetType) {
return fmt.Errorf("type mismatch: %w", errImpossibleRelocation)
}
switch lv := localType.(type) {
case *Array, *Pointer, *Float, *Int:
return nil
case *Enum:
tv := targetType.(*Enum)
return doNamesMatch(lv.Name, tv.Name)
case *Fwd:
tv := targetType.(*Fwd)
return doNamesMatch(lv.Name, tv.Name)
default:
return fmt.Errorf("type %s: %w", localType, ErrNotSupported)
}
}
Codebase Browser
kubernetes