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package internal
import (
"errors"
"fmt"
"os"
"path/filepath"
"runtime"
"unsafe"
"github.com/cilium/ebpf/internal/sys"
"github.com/cilium/ebpf/internal/unix"
)
func Pin(currentPath, newPath string, fd *sys.FD) error {
const bpfFSType = 0xcafe4a11
if newPath == "" {
return errors.New("given pinning path cannot be empty")
}
if currentPath == newPath {
return nil
}
var statfs unix.Statfs_t
if err := unix.Statfs(filepath.Dir(newPath), &statfs); err != nil {
return err
}
fsType := int64(statfs.Type)
if unsafe.Sizeof(statfs.Type) == 4 {
// We're on a 32 bit arch, where statfs.Type is int32. bpfFSType is a
// negative number when interpreted as int32 so we need to cast via
// uint32 to avoid sign extension.
fsType = int64(uint32(statfs.Type))
}
if fsType != bpfFSType {
return fmt.Errorf("%s is not on a bpf filesystem", newPath)
}
defer runtime.KeepAlive(fd)
if currentPath == "" {
return sys.ObjPin(&sys.ObjPinAttr{
Pathname: sys.NewStringPointer(newPath),
BpfFd: fd.Uint(),
})
}
// Renameat2 is used instead of os.Rename to disallow the new path replacing
// an existing path.
err := unix.Renameat2(unix.AT_FDCWD, currentPath, unix.AT_FDCWD, newPath, unix.RENAME_NOREPLACE)
if err == nil {
// Object is now moved to the new pinning path.
return nil
}
if !os.IsNotExist(err) {
return fmt.Errorf("unable to move pinned object to new path %v: %w", newPath, err)
}
// Internal state not in sync with the file system so let's fix it.
return sys.ObjPin(&sys.ObjPinAttr{
Pathname: sys.NewStringPointer(newPath),
BpfFd: fd.Uint(),
})
}
func Unpin(pinnedPath string) error {
if pinnedPath == "" {
return nil
}
err := os.Remove(pinnedPath)
if err == nil || os.IsNotExist(err) {
return nil
}
return err
}
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