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Enhancement to VM::INTERRUPT_SHADOW #701

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Merged
NotRequiem merged 3 commits into from
May 24, 2026
+21 −18
Merged

Enhancement to VM::INTERRUPT_SHADOW #701

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9f56763
Enhancement to VM::INTERRUPT_SHADOW
wiisus May 23, 2026
a8cdebe
Fixed wrong scoring logic
wiisus May 23, 2026
715fbf3
Apply suggestions from code review
NotRequiem May 24, 2026
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39 changes: 21 additions & 18 deletions src/vmaware.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -10729,6 +10729,9 @@ struct VM {
* @implements VM::INTERRUPT_SHADOW
*/
[[nodiscard]] static bool interrupt_shadow() {
if (util::hyper_x() == HYPERV_ARTIFACT_VM) {
return false;
}
volatile ULONG_PTR trap_ip = 0;

#if (x86_32) && !(CLANG || GCC)
Expand Down Expand Up @@ -10760,7 +10763,7 @@ struct VM {
EXCEPTION_CONTINUE_EXECUTION
) : EXCEPTION_CONTINUE_SEARCH) {}

// hypervisor is detected if the trap fired at any IP differing from the expected baremetal target
// hypervisor is detected if the trap fired at any IP differing from the expected baremetal target
// OR if the single step exception never fired at all (trap_ip == 0)
return (trap_ip == 0 || trap_ip != baremetal_target_ip);

Expand All @@ -10775,30 +10778,30 @@ struct VM {
void* funcs[ARRAYSIZE(names)] = {};
util::get_function_address(ntdll, names, funcs, ARRAYSIZE(names));

const auto nt_alloc = reinterpret_cast<NTSTATUS(__stdcall*)(HANDLE, PVOID*, ULONG_PTR, PSIZE_T, ULONG, ULONG)>(funcs[0]);
const auto nt_alloc = reinterpret_cast<NTSTATUS(__stdcall*)(HANDLE, PVOID*, ULONG_PTR, PSIZE_T, ULONG, ULONG)>(funcs[0]);
const auto nt_protect = reinterpret_cast<NTSTATUS(__stdcall*)(HANDLE, PVOID*, PSIZE_T, ULONG, PULONG)>(funcs[1]);
const auto nt_flush = reinterpret_cast<NTSTATUS(__stdcall*)(HANDLE, PVOID, SIZE_T)>(funcs[2]);
const auto nt_free = reinterpret_cast<NTSTATUS(__stdcall*)(HANDLE, PVOID*, PSIZE_T, ULONG)>(funcs[3]);
const auto nt_flush = reinterpret_cast<NTSTATUS(__stdcall*)(HANDLE, PVOID, SIZE_T)>(funcs[2]);
const auto nt_free = reinterpret_cast<NTSTATUS(__stdcall*)(HANDLE, PVOID*, PSIZE_T, ULONG)>(funcs[3]);

if (!nt_alloc || !nt_protect || !nt_flush || !nt_free) return false;

// these opcodes are byte-for-byte identical for both x86_32 and x86_64 architectures
// 0x53 maps to push ebx in 32-bit and push rbx in 64-bit
static constexpr u8 blockstep_opcodes[] = {
0x53, // 0: push rbx/ebx (preserve non-volatile register)
0x31, 0xC0, // 1: xor eax, eax
0x8C, 0xD0, // 3: mov ax, ss
0x9C, // 5: pushfq/pushfd
0x53, // 0: push rbx/ebx (preserve non-volatile register)
0x31, 0xC0, // 1: xor eax, eax
0x8C, 0xD0, // 3: mov ax, ss
0x9C, // 5: pushfq/pushfd
0x81, 0x0C, 0x24, 0x00, 0x01, 0x00, 0x00, // 6: or dword ptr [rsp/esp], 0x100
0x9D, // 13: popfq/popfd
0x8E, 0xD0, // 14: mov ss, ax <- shadow starts here
0x0F, 0xA2, // 16: cpuid <- buggy hypervisor traps here
0x5B, // 18: pop rbx/ebx <- baremetal traps here
0x90, // 19: nop
0x9C, // 20: pushfq/pushfd
0x9D, // 13: popfq/popfd
0x8E, 0xD0, // 14: mov ss, ax <- shadow starts here
0x0F, 0xA2, // 16: cpuid <- buggy hypervisor traps here
0x5B, // 18: pop rbx/ebx <- baremetal traps here
0x90, // 19: nop
0x9C, // 20: pushfq/pushfd
0x81, 0x24, 0x24, 0xFF, 0xFE, 0xFF, 0xFF, // 21: and dword ptr [rsp/esp], 0xFFFFFEFF
0x9D, // 28: popfq/popfd
0xC3 // 29: ret
0x9D, // 28: popfq/popfd
0xC3 // 29: ret
};

const HANDLE current_process = reinterpret_cast<HANDLE>(-1LL);
Expand Down Expand Up @@ -10830,7 +10833,7 @@ struct VM {
trap_ip = GetExceptionInformation()->ContextRecord->Eip,
#endif
GetExceptionInformation()->ContextRecord->EFlags &= ~0x100, // to avoid infinite looping
EXCEPTION_CONTINUE_EXECUTION
EXCEPTION_CONTINUE_EXECUTION
) : EXCEPTION_CONTINUE_SEARCH) {}
}

Expand All @@ -10839,7 +10842,7 @@ struct VM {

// hypervisor is detected if execution trapped at any offset other than expected baremetal
// OR if the single step exception never fired at all (trap_ip == 0)
return NT_SUCCESS(st) && (trap_ip == 0 || trap_ip != baremetal_target_ip);
return NT_SUCCESS(st) && (trap_ip == 0 || trap_ip != baremetal_target_ip);
#else
return false;
#endif
Expand Down
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