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package linux
import (
"errors"
"fmt"
"io"
_ "unsafe"
"github.com/cilium/ebpf/internal"
)
type auxvPairReader interface {
Close() error
ReadAuxvPair() (uint64, uint64, error)
}
// See https://elixir.bootlin.com/linux/v6.5.5/source/include/uapi/linux/auxvec.h
const (
_AT_NULL = 0 // End of vector
_AT_SYSINFO_EHDR = 33 // Offset to vDSO blob in process image
)
//go:linkname runtime_getAuxv runtime.getAuxv
func runtime_getAuxv() []uintptr
type auxvRuntimeReader struct {
data []uintptr
index int
}
func (r *auxvRuntimeReader) Close() error {
return nil
}
func (r *auxvRuntimeReader) ReadAuxvPair() (uint64, uint64, error) {
if r.index >= len(r.data)+2 {
return 0, 0, io.EOF
}
// we manually add the (_AT_NULL, _AT_NULL) pair at the end
// that is not provided by the go runtime
var tag, value uintptr
if r.index+1 < len(r.data) {
tag, value = r.data[r.index], r.data[r.index+1]
} else {
tag, value = _AT_NULL, _AT_NULL
}
r.index += 2
return uint64(tag), uint64(value), nil
}
func newAuxvRuntimeReader() (auxvPairReader, error) {
if !internal.OnLinux {
return nil, fmt.Errorf("read auxv from runtime: %w", internal.ErrNotSupportedOnOS)
}
data := runtime_getAuxv()
if len(data)%2 != 0 {
return nil, errors.New("malformed auxv passed from runtime")
}
return &auxvRuntimeReader{
data: data,
index: 0,
}, nil
}
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