[interception] Check for export table's size before referring to its …

…elements.

This fix a bug, when calling InternalGetProcAddress() for an executable that
doesn't export any symbol. So the table is empty.
If we don't check for this condition, the program fails with Error 0xc0000142.

Also, I add a regression test for Windows.

Differential Revision: https://reviews.llvm.org/D28502

llvm-svn: 293521

compiler-rt/lib/interception/interception_win.cc

@@ -878,6 +878,8 @@ uptr InternalGetProcAddress(void *module, const char *func_name) {
 
   IMAGE_DATA_DIRECTORY *export_directory =
       &headers->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT];
+  if (export_directory->Size == 0)
+    return 0;
   RVAPtr<IMAGE_EXPORT_DIRECTORY> exports(module,
                                          export_directory->VirtualAddress);
   RVAPtr<DWORD> functions(module, exports->AddressOfFunctions);

compiler-rt/lib/interception/tests/interception_win_test.cc

@@ -613,6 +613,13 @@ TEST(Interception, PatchableFunctionPadding) {
   EXPECT_FALSE(TestFunctionPatching(kUnpatchableCode6, override, prefix));
 }
 
+TEST(Interception, EmptyExportTable) {
+  // We try to get a pointer to a function from an executable that doesn't
+  // export any symbol (empty export table).
+  uptr FunPtr = InternalGetProcAddress((void *)GetModuleHandleA(0), "example");
+  EXPECT_EQ(0U, FunPtr);
+}
+
 }  // namespace __interception
 
 #endif  // SANITIZER_WINDOWS