BL3Lua/Helper.hpp

#pragma once
#include <windows.h>

/*
A safer replacement for the obsolete IsBadReadPtr() and IsBadWritePtr() WinAPI functions
on top of VirtualQuery() which respects Windows guard pages. It does not use SEH
and is designed to be compatible with the above-mentioned functions.
The calls to the IsBadReadPtr() and IsBadWritePtr() can be replaced with the calls to
the IsBadMemPtr() as follows:
- IsBadReadPtr(...)  => IsBadMemPtr(FALSE, ...)
- IsBadWritePtr(...) => IsBadMemPtr(TRUE, ...)
*/
BOOL IsBadMemPtr(/*BOOL write, */void* ptr, size_t size)
{
	MEMORY_BASIC_INFORMATION mbi;
	BOOL ok;
	DWORD mask;
	BYTE* p = (BYTE*)ptr;
	BYTE* maxp = p + size;
	BYTE* regend = NULL;

	if (size == 0)
	{
		return FALSE;
	}

	if (p == NULL)
	{
		return TRUE;
	}

	/*if (write == FALSE)
	{
		mask = PAGE_READONLY | PAGE_READWRITE | PAGE_WRITECOPY | PAGE_EXECUTE_READ | PAGE_EXECUTE_READWRITE | PAGE_EXECUTE_WRITECOPY;
	}
	else
	{*/
	mask = PAGE_READWRITE | PAGE_WRITECOPY | PAGE_EXECUTE_READWRITE | PAGE_EXECUTE_WRITECOPY;
	/*}*/

	do
	{
		if (p == ptr || p == regend)
		{
			if (VirtualQuery((LPCVOID)p, &mbi, sizeof(mbi)) == 0)
			{
				return TRUE;
			}
			else
			{
				regend = ((BYTE*)mbi.BaseAddress + mbi.RegionSize);
			}
		}

		ok = (mbi.Protect & mask) != 0;

		if (mbi.Protect & (PAGE_GUARD | PAGE_NOACCESS))
		{
			ok = FALSE;
		}

		if (!ok)
		{
			return TRUE;
		}

		if (maxp <= regend) /* the whole address range is inside the current memory region */
		{
			return FALSE;
		}
		else if (maxp > regend) /* this region is a part of (or overlaps with) the address range we are checking */
		{
			p = regend; /* lets move to the next memory region */
		}
	} while (p < maxp);

	return FALSE;
}