NtAllocateVirtualMemory - NtDoc

Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers 
#ifndef _NTMMAPI_H
// Virtual memory
#if (PHNT_MODE != PHNT_MODE_KERNEL)

_Must_inspect_result_
_When_(return == 0, __drv_allocatesMem(mem))
NTSYSCALLAPI
NTSTATUS
NTAPI
NtAllocateVirtualMemory(
    _In_ HANDLE ProcessHandle,
    _Inout_ _At_(*BaseAddress, _Readable_bytes_(*RegionSize) _Writable_bytes_(*RegionSize) _Post_readable_byte_size_(*RegionSize)) PVOID *BaseAddress,
    _In_ ULONG_PTR ZeroBits,
    _Inout_ PSIZE_T RegionSize,
    _In_ ULONG AllocationType,
    _In_ ULONG Protect
    );

#endif
#endif

View code on GitHub
#ifndef _NTZWAPI_H

NTSYSCALLAPI
NTSTATUS
NTAPI
ZwAllocateVirtualMemory(
    _In_ HANDLE ProcessHandle,
    _Inout_ _At_(*BaseAddress, _Readable_bytes_(*RegionSize) _Writable_bytes_(*RegionSize) _Post_readable_byte_size_(*RegionSize)) PVOID *BaseAddress,
    _In_ ULONG_PTR ZeroBits,
    _Inout_ PSIZE_T RegionSize,
    _In_ ULONG AllocationType,
    _In_ ULONG Protect
    );

#endif

View code on GitHub

This function is documented in Windows Driver Kit here and here.

ProcessHandle

Handle to Process Object opened with PROCESS_VM_OPERATION access.

*BaseAddress

If not zero, system tries to allocate virtual memory block on this virtual address. If BaseAddress is zero, system use first free virtual location.

AllocationType

Can be MEM_RESERVE or MEM_COMMIT.

Protect

One or combination of PAGE_*** attributes.

Documented by

See also

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