RtlAbsoluteToSelfRelativeSD - NtDoc

Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers 
#ifndef _NTRTL_H

NTSYSAPI
NTSTATUS
NTAPI
RtlAbsoluteToSelfRelativeSD(
    _In_ PSECURITY_DESCRIPTOR AbsoluteSecurityDescriptor,
    _Out_writes_bytes_to_opt_(*BufferLength, *BufferLength) PSECURITY_DESCRIPTOR SelfRelativeSecurityDescriptor,
    _Inout_ PULONG BufferLength
    );

#endif

View code on GitHub

This function is documented in Windows Driver Kit.

Edit description on GitHub