/// <summary>
/// Reserves a region of memory within the virtual address space of a specified process.
/// </summary>
/// <param name="processHandle">The handle to a process.</param>
/// <param name="allocAddress">The rough address of where the allocation should take place.</param>
/// <param name="size">The size of the region of memory to allocate, in bytes.</param>
/// <param name="protectionFlags">The memory protection for the region of pages to be allocated.</param>
/// <param name="allocationFlags">The type of memory allocation.</param>
/// <returns>The base address of the allocated region</returns>
public static UInt64 Allocate(
IntPtr processHandle,
UInt64 allocAddress,
Int32 size,
MemoryProtectionFlags protectionFlags = MemoryProtectionFlags.ExecuteReadWrite,
MemoryAllocationFlags allocationFlags = MemoryAllocationFlags.Commit | MemoryAllocationFlags.Reserve)
{
if (allocAddress != 0)
{
/* A specific address has been given. We will modify it to support the following constraints:
* - Aligned by 0x10000 / 65536
* - Pointing to an unallocated region of memory
* - Within +/- 2GB (using 1GB for safety) of address space of the originally specified address, such as to always be in range of a far jump instruction
* Note: A retry count has been put in place because VirtualAllocEx with an allocAddress specified may be invalid by the time we request the allocation.
*/
UInt64 result = 0;
Int32 retryCount = 0;
// Request all chunks of unallocated memory. These will be very large in a 64-bit process.
IEnumerable <MemoryBasicInformation64> freeMemory = Memory.QueryUnallocatedMemory(
processHandle,
allocAddress.Subtract(Int32.MaxValue >> 1, wrapAround: false),
allocAddress.Add(Int32.MaxValue >> 1, wrapAround: false));
// Convert to normalized regions
IEnumerable <NormalizedRegion> regions = freeMemory.Select(x => new NormalizedRegion(x.BaseAddress.ToUInt64(), x.RegionSize.ToInt32()));
// Chunk the large regions into smaller regions based on the allocation size (minimum size is the alloc alignment to prevent creating too many chunks)
List <NormalizedRegion> subRegions = new List <NormalizedRegion>();
foreach (NormalizedRegion region in regions)
{
region.BaseAddress = region.BaseAddress.Subtract(region.BaseAddress.Mod(Memory.AllocAlignment), wrapAround: false);
IEnumerable <NormalizedRegion> chunkedRegions = region.ChunkNormalizedRegion(Math.Max(size, Memory.AllocAlignment)).Take(128).Where(x => x.RegionSize >= size);
subRegions.AddRange(chunkedRegions);
}
do
{
// Sample a random chunk and attempt to allocate the memory
result = subRegions.ElementAt(StaticRandom.Next(0, subRegions.Count())).BaseAddress;
result = NativeMethods.VirtualAllocEx(processHandle, result.ToIntPtr(), size, allocationFlags, protectionFlags).ToUInt64();
if (result != 0 || retryCount >= Memory.AllocateRetryCount)
{
break;
}
retryCount++;
}while (result == 0);
return(result);
}
else
{
// Allocate a memory page
return(NativeMethods.VirtualAllocEx(processHandle, allocAddress.ToIntPtr(), size, allocationFlags, protectionFlags).ToUInt64());
}
}
