Revert "ubsan: Implement memory permission validation for vtables."

This reverts r247484 and two follow-up commits.
Breaks ppc and x86_64 sanitizer bots.

llvm-svn: 247921

compiler-rt/lib/ubsan/ubsan_type_hash_itanium.cc

@@ -17,7 +17,6 @@
 #include "ubsan_type_hash.h"
 
 #include "sanitizer_common/sanitizer_common.h"
-#include "sanitizer_common/sanitizer_procmaps.h"
 
 // The following are intended to be binary compatible with the definitions
 // given in the Itanium ABI. We make no attempt to be ODR-compatible with
@@ -192,45 +191,7 @@ struct VtablePrefix {
   /// The type_info object describing the most-derived class type.
   std::type_info *TypeInfo;
 };
-
-#if SANITIZER_LINUX && !defined(__powerpc64__)
-bool isValidVptr(void *Vtable) {
-  // Validate the memory permissions of the vtable pointer and the first
-  // function pointer in the vtable. They should be r-- or r-x and r-x
-  // respectively. Only enabled for Linux; this hasn't been tested on FreeBSD,
-  // and vtables are writable on Mac (PR24782) so this won't work there.
-  uptr FirstFunctionPtr = *reinterpret_cast<uptr *>(Vtable);
-  bool ValidVtable = false, ValidFirstFunctionPtr = false;
-  MemoryMappingLayout Layout(/*cache_enabled=*/true);
-  uptr Start, End, Prot;
-  while (Layout.Next(&Start, &End, 0, 0, 0, &Prot)) {
-    if (Start <= ((uptr)Vtable) && ((uptr)Vtable) <= End &&
-        (Prot == MemoryMappingLayout::kProtectionRead ||
-         Prot == (MemoryMappingLayout::kProtectionRead |
-                  MemoryMappingLayout::kProtectionExecute)))
-      ValidVtable = true;
-    if (Start <= FirstFunctionPtr && FirstFunctionPtr <= End &&
-        Prot == (MemoryMappingLayout::kProtectionRead |
-                 MemoryMappingLayout::kProtectionExecute))
-      ValidFirstFunctionPtr = true;
-    if (ValidVtable && ValidFirstFunctionPtr)
-      return true;
-  }
-  return false;
-}
-#else  // !SANITIZER_LINUX || __powerpc64__
-bool isValidVptr(void *Vtable) {
-  return true;
-}
-#endif
-
 VtablePrefix *getVtablePrefix(void *Vtable) {
-  if (!IsAccessibleMemoryRange((uptr)Vtable, sizeof(void *)))
-    return 0;
-
-  if (!isValidVptr(Vtable))
-    return 0;
-
   VtablePrefix *Vptr = reinterpret_cast<VtablePrefix*>(Vtable);
   if (!Vptr)
     return 0;

compiler-rt/test/ubsan/TestCases/TypeCheck/vptr-bad-perms.cpp

@@ -1,33 +0,0 @@
-// RUN: %clangxx -frtti -fsanitize=vptr -fno-sanitize-recover=vptr -g %s -O3 -o %t
-// RUN: not %run %t 2>&1 | FileCheck %s
-
-// Tests that we consider vtable pointers in writable memory to be invalid.
-
-// REQUIRES: vptr-validation
-
-#include <string.h>
-
-struct A {
-  virtual void f();
-};
-
-void A::f() {}
-
-struct B {
-  virtual void f();
-};
-
-void B::f() {}
-
-int main() {
-  // Create a fake vtable for A in writable memory and copy A's vtable into it.
-  void *fake_vtable[3];
-  A a;
-  void ***vtp = (void ***)&a;
-  memcpy(fake_vtable, *vtp - 2, sizeof(void *) * 3);
-  *vtp = fake_vtable + 2;
-
-  // A's vtable is invalid because it lives in writable memory.
-  // CHECK: invalid vptr
-  reinterpret_cast<B*>(&a)->f();
-}

compiler-rt/test/ubsan/lit.common.cfg

@@ -77,7 +77,3 @@ if config.host_os == 'Windows':
 # because the test hangs or fails on one configuration and not the other.
 if config.target_arch.startswith('arm') == False:
   config.available_features.add('stable-runtime')
-
-if config.host_os == 'Linux' and config.target_arch != 'powerpc64' and \
-   config.target_arch != 'powerpc64le':
-  config.available_features.add('vptr-validation')