Created
May 5, 2021 14:30
-
-
Save stevemk14ebr/ae240f47510198657028fab8018ec4f0 to your computer and use it in GitHub Desktop.
VirtualAlloc2 Bounded Allocation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| // Alloc2Test.cpp : This file contains the 'main' function. Program execution begins and ends there. | |
| // | |
| #include <iostream> | |
| #include <Windows.h> | |
| #include <string> | |
| #include <assert.h> | |
| static inline char* AlignUpwards(const char* stack, size_t align) { | |
| assert(align > 0 && (align & (align - 1)) == 0); /* Power of 2 */ | |
| assert(stack != 0); | |
| auto addr = reinterpret_cast<uintptr_t>(stack); | |
| if (addr % align != 0) | |
| addr += align - addr % align; | |
| assert(addr >= reinterpret_cast<uintptr_t>(stack)); | |
| return reinterpret_cast<char*>(addr); | |
| } | |
| static inline char* AlignDownwards(const char* stack, size_t align) { | |
| assert(align > 0 && (align & (align - 1)) == 0); /* Power of 2 */ | |
| assert(stack != 0); | |
| auto addr = reinterpret_cast<uintptr_t>(stack); | |
| addr -= addr % align; | |
| assert(addr <= reinterpret_cast<uintptr_t>(stack)); | |
| return reinterpret_cast<char*>(addr); | |
| } | |
| // based on: https://stackoverflow.com/questions/54223343/virtualalloc2-with-memextendedparameteraddressrequirements-always-produces-error | |
| uint64_t boundAlloc(uint64_t min, uint64_t max, uint64_t size) | |
| { | |
| MEM_ADDRESS_REQUIREMENTS addressReqs = { 0 }; | |
| MEM_EXTENDED_PARAMETER param = { 0 }; | |
| addressReqs.Alignment = 0; // any alignment | |
| addressReqs.LowestStartingAddress = (PVOID)min; // PAGE_SIZE aligned | |
| addressReqs.HighestEndingAddress = (PVOID)(max - 1); // PAGE_SIZE aligned, exclusive so -1 | |
| param.Type = MemExtendedParameterAddressRequirements; | |
| param.Pointer = &addressReqs; | |
| auto pVirtualAlloc2 = (decltype(&::VirtualAlloc2))GetProcAddress(LoadLibrary(L"kernelbase.dll"), "VirtualAlloc2"); | |
| return (uint64_t)pVirtualAlloc2( | |
| GetCurrentProcess(), (PVOID)0, | |
| size, | |
| MEM_RESERVE | MEM_COMMIT, | |
| PAGE_READWRITE, | |
| ¶m, 1); | |
| } | |
| int main() | |
| { | |
| auto calc_2gb_below = [](uint64_t address) -> uint64_t | |
| { | |
| return (address > (uint64_t)0x7ff80000) ? address - 0x7ff80000 : 0x80000; | |
| }; | |
| auto calc2gb_above = [](uint64_t address) -> uint64_t | |
| { | |
| return (address < (uint64_t)0xffffffff80000000) ? address + 0x7ff80000 : (uint64_t)0xfffffffffff80000; | |
| }; | |
| uint64_t randAddr = (uint64_t)new char[64]; | |
| uint64_t max = (uint64_t)AlignDownwards((char*)calc2gb_above(randAddr), 0x10000); | |
| uint64_t min = (uint64_t)AlignDownwards((char*)calc_2gb_below(randAddr), 0x10000); | |
| printf("Pivot %I64X +-2GB_Range: [%I64X, %I64X)\n", randAddr, min, max); | |
| uint64_t alloc = boundAlloc(min, max, 0x10000); | |
| printf("Alloc %I64X\n", alloc); | |
| } |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment