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package linux
import (
"encoding/binary"
"errors"
"fmt"
"os"
"testing"
"unsafe"
"github.com/cilium/ebpf/internal"
"github.com/cilium/ebpf/internal/unix"
)
type auxvFileReader struct {
file *os.File
order binary.ByteOrder
uintptrIs32bits bool
}
func (r *auxvFileReader) Close() error {
return r.file.Close()
}
type auxvPair32 struct {
Tag, Value uint32
}
type auxvPair64 struct {
Tag, Value uint64
}
func (r *auxvFileReader) ReadAuxvPair() (tag, value uint64, _ error) {
if r.uintptrIs32bits {
var aux auxvPair32
if err := binary.Read(r.file, r.order, &aux); err != nil {
return 0, 0, fmt.Errorf("reading auxv entry: %w", err)
}
return uint64(aux.Tag), uint64(aux.Value), nil
}
var aux auxvPair64
if err := binary.Read(r.file, r.order, &aux); err != nil {
return 0, 0, fmt.Errorf("reading auxv entry: %w", err)
}
return aux.Tag, aux.Value, nil
}
func newAuxFileReader(path string, order binary.ByteOrder, uintptrIs32bits bool) (auxvPairReader, error) {
// Read data from the auxiliary vector, which is normally passed directly
// to the process. Go does not expose that data before go 1.21, so we must read it from procfs.
// https://man7.org/linux/man-pages/man3/getauxval.3.html
av, err := os.Open(path)
if errors.Is(err, unix.EACCES) {
return nil, fmt.Errorf("opening auxv: %w (process may not be dumpable due to file capabilities)", err)
}
if err != nil {
return nil, fmt.Errorf("opening auxv: %w", err)
}
return &auxvFileReader{
file: av,
order: order,
uintptrIs32bits: uintptrIs32bits,
}, nil
}
func newDefaultAuxvFileReader() (auxvPairReader, error) {
const uintptrIs32bits = unsafe.Sizeof((uintptr)(0)) == 4
return newAuxFileReader("/proc/self/auxv", internal.NativeEndian, uintptrIs32bits)
}
func TestAuxvBothSourcesEqual(t *testing.T) {
runtimeBased, err := newAuxvRuntimeReader()
skipIfNotSupportedOnOS(t, err)
if err != nil {
t.Fatal(err)
}
fileBased, err := newDefaultAuxvFileReader()
if err != nil {
t.Fatal(err)
}
for {
runtimeTag, runtimeValue, err := runtimeBased.ReadAuxvPair()
if err != nil {
t.Fatal(err)
}
fileTag, fileValue, err := fileBased.ReadAuxvPair()
if err != nil {
t.Fatal(err)
}
if runtimeTag != fileTag {
t.Errorf("mismatching tags: runtime=%v, file=%v", runtimeTag, fileTag)
}
if runtimeValue != fileValue {
t.Errorf("mismatching values: runtime=%v, file=%v", runtimeValue, fileValue)
}
if runtimeTag == _AT_NULL {
break
}
}
}
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