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package btf
import (
"errors"
"math"
"github.com/cilium/ebpf/internal"
"github.com/cilium/ebpf/internal/sys"
"github.com/cilium/ebpf/internal/unix"
)
// haveBTF attempts to load a BTF blob containing an Int. It should pass on any
// kernel that supports BPF_BTF_LOAD.
var haveBTF = internal.NewFeatureTest("BTF", func() error {
// 0-length anonymous integer
err := probeBTF(&Int{})
if errors.Is(err, unix.EINVAL) || errors.Is(err, unix.EPERM) {
return internal.ErrNotSupported
}
return err
}, "4.18")
// haveMapBTF attempts to load a minimal BTF blob containing a Var. It is
// used as a proxy for .bss, .data and .rodata map support, which generally
// come with a Var and Datasec. These were introduced in Linux 5.2.
var haveMapBTF = internal.NewFeatureTest("Map BTF (Var/Datasec)", func() error {
if err := haveBTF(); err != nil {
return err
}
v := &Var{
Name: "a",
Type: &Pointer{(*Void)(nil)},
}
err := probeBTF(v)
if errors.Is(err, unix.EINVAL) || errors.Is(err, unix.EPERM) {
// Treat both EINVAL and EPERM as not supported: creating the map may still
// succeed without Btf* attrs.
return internal.ErrNotSupported
}
return err
}, "5.2")
// haveProgBTF attempts to load a BTF blob containing a Func and FuncProto. It
// is used as a proxy for ext_info (func_info) support, which depends on
// Func(Proto) by definition.
var haveProgBTF = internal.NewFeatureTest("Program BTF (func/line_info)", func() error {
if err := haveBTF(); err != nil {
return err
}
fn := &Func{
Name: "a",
Type: &FuncProto{Return: (*Void)(nil)},
}
err := probeBTF(fn)
if errors.Is(err, unix.EINVAL) || errors.Is(err, unix.EPERM) {
return internal.ErrNotSupported
}
return err
}, "5.0")
var haveFuncLinkage = internal.NewFeatureTest("BTF func linkage", func() error {
if err := haveProgBTF(); err != nil {
return err
}
fn := &Func{
Name: "a",
Type: &FuncProto{Return: (*Void)(nil)},
Linkage: GlobalFunc,
}
err := probeBTF(fn)
if errors.Is(err, unix.EINVAL) {
return internal.ErrNotSupported
}
return err
}, "5.6")
var haveDeclTags = internal.NewFeatureTest("BTF decl tags", func() error {
if err := haveBTF(); err != nil {
return err
}
t := &Typedef{
Name: "a",
Type: &Int{},
Tags: []string{"a"},
}
err := probeBTF(t)
if errors.Is(err, unix.EINVAL) {
return internal.ErrNotSupported
}
return err
}, "5.16")
var haveTypeTags = internal.NewFeatureTest("BTF type tags", func() error {
if err := haveBTF(); err != nil {
return err
}
t := &TypeTag{
Type: &Int{},
Value: "a",
}
err := probeBTF(t)
if errors.Is(err, unix.EINVAL) {
return internal.ErrNotSupported
}
return err
}, "5.17")
var haveEnum64 = internal.NewFeatureTest("ENUM64", func() error {
if err := haveBTF(); err != nil {
return err
}
enum := &Enum{
Size: 8,
Values: []EnumValue{
{"TEST", math.MaxUint32 + 1},
},
}
err := probeBTF(enum)
if errors.Is(err, unix.EINVAL) {
return internal.ErrNotSupported
}
return err
}, "6.0")
func probeBTF(typ Type) error {
b, err := NewBuilder([]Type{typ})
if err != nil {
return err
}
buf, err := b.Marshal(nil, nil)
if err != nil {
return err
}
fd, err := sys.BtfLoad(&sys.BtfLoadAttr{
Btf: sys.NewSlicePointer(buf),
BtfSize: uint32(len(buf)),
})
if err == nil {
fd.Close()
}
return err
}
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