}
static bool DistanceIsWithin2Gig(uptr from, uptr target) {
+#if SANITIZER_WINDOWS64
if (from < target)
return target - from <= (uptr)0x7FFFFFFFU;
else
return from - target <= (uptr)0x80000000U;
+#else
+ // In a 32-bit address space, the address calculation will wrap, so this check
+ // is unnecessary.
+ return true;
+#endif
}
static uptr GetMmapGranularity() {
// A buffer holding the dynamically generated code under test.
u8* ActiveCode;
-size_t ActiveCodeLength = 4096;
+const size_t ActiveCodeLength = 4096;
+
+int InterceptorFunction(int x);
+
+/// Allocate code memory more than 2GB away from Base.
+u8 *AllocateCode2GBAway(u8 *Base) {
+ // Find a 64K aligned location after Base plus 2GB.
+ size_t TwoGB = 0x80000000;
+ size_t AllocGranularity = 0x10000;
+ Base = (u8 *)((((uptr)Base + TwoGB + AllocGranularity)) & ~(AllocGranularity - 1));
+
+ // Check if that location is free, and if not, loop over regions until we find
+ // one that is.
+ MEMORY_BASIC_INFORMATION mbi = {};
+ while (sizeof(mbi) == VirtualQuery(Base, &mbi, sizeof(mbi))) {
+ if (mbi.State & MEM_FREE) break;
+ Base += mbi.RegionSize;
+ }
+
+ // Allocate one RWX page at the free location.
+ return (u8 *)::VirtualAlloc(Base, ActiveCodeLength, MEM_COMMIT | MEM_RESERVE,
+ PAGE_EXECUTE_READWRITE);
+}
template<class T>
static void LoadActiveCode(
uptr *entry_point,
FunctionPrefixKind prefix_kind = FunctionPrefixNone) {
if (ActiveCode == nullptr) {
- ActiveCode =
- (u8*)::VirtualAlloc(nullptr, ActiveCodeLength,
- MEM_COMMIT | MEM_RESERVE,
- PAGE_EXECUTE_READWRITE);
- ASSERT_NE(ActiveCode, nullptr);
+ ActiveCode = AllocateCode2GBAway((u8*)&InterceptorFunction);
+ ASSERT_NE(ActiveCode, nullptr) << "failed to allocate RWX memory 2GB away";
}
size_t position = 0;