Function LoadActiveCode

runtime/interception/tests/interception_win_test.cpp:295–343

template<class T>
static void LoadActiveCode(
    const T &code,
    uptr *entry_point,
    FunctionPrefixKind prefix_kind = FunctionPrefixNone) {
  if (ActiveCode == nullptr) {
    ActiveCode = AllocateCode2GBAway((u8*)&InterceptorFunction);
    ASSERT_NE(ActiveCode, nullptr) << "failed to allocate RWX memory 2GB away";
  }

  size_t position = 0;

  // Add padding to avoid memory violation when scanning the prefix.
  for (int i = 0; i < 16; ++i)
    ActiveCode[position++] = 0xC3;  // Instruction 'ret'.

  // Add function padding.
  size_t padding = 0;
  if (prefix_kind == FunctionPrefixPadding)
    padding = 16;
  else if (prefix_kind == FunctionPrefixDetour ||
           prefix_kind == FunctionPrefixHotPatch)
    padding = FIRST_32_SECOND_64(5, 6);
  // Insert |padding| instructions 'nop'.
  for (size_t i = 0; i < padding; ++i)
    ActiveCode[position++] = 0x90;

  // Keep track of the entry point.
  *entry_point = (uptr)&ActiveCode[position];

  // Add the detour instruction (i.e. mov edi, edi)
  if (prefix_kind == FunctionPrefixDetour) {
#if SANITIZER_WINDOWS64
    // Note that "mov edi,edi" is NOP in 32-bit only, in 64-bit it clears
    // higher bits of RDI.
    // Use 66,90H as NOP for Windows64.
    ActiveCode[position++] = 0x66;
    ActiveCode[position++] = 0x90;
#else
    // mov edi,edi.
    ActiveCode[position++] = 0x8B;
    ActiveCode[position++] = 0xFF;
#endif

  }

  // Copy the function body.
  for (size_t i = 0; i < sizeof(T); ++i)
    ActiveCode[position++] = code[i];
}

int InterceptorFunctionCalled;
IdentityFunction InterceptedRealFunction;