NtQueryBootEntryOrder - NtDoc

#ifndef _NTEXAPI_H
#if (PHNT_MODE != PHNT_MODE_KERNEL)

/**
 * The NtQueryBootEntryOrder routine retrieves the current boot entry order.
 *
 * \param Ids A pointer to a buffer that receives the identifiers of the boot entries in the current boot order.
 * \param Count A pointer to a variable that specifies the number of entries in the buffer. On return, it contains the number of entries returned.
 * \return NTSTATUS Successful or errant status.
 */
NTSYSCALLAPI
NTSTATUS
NTAPI
NtQueryBootEntryOrder(
    _Out_writes_opt_(*Count) PULONG Ids,
    _Inout_ PULONG Count
    );

#endif
#endif
View code on GitHub

#ifndef _NTZWAPI_H

NTSYSCALLAPI
NTSTATUS
NTAPI
ZwQueryBootEntryOrder(
    _Out_writes_opt_(*Count) PULONG Ids,
    _Inout_ PULONG Count
    );

#endif
View code on GitHub