pcc created this revision.
Under the Microsoft ABI, it is possible for an object not to have
a virtual table pointer of its own if all of its virtual functions
were introduced by virtual bases. In that case, we need to load the
vtable pointer from one of the virtual bases and perform the type
check using its type.
https://reviews.llvm.org/D41036
Files:
clang/lib/CodeGen/CGCXXABI.h
clang/lib/CodeGen/CGClass.cpp
clang/lib/CodeGen/CGExprCXX.cpp
clang/lib/CodeGen/ItaniumCXXABI.cpp
clang/lib/CodeGen/MicrosoftCXXABI.cpp
clang/test/CodeGenCXX/cfi-ms-vbase-derived-cast.cpp
clang/test/CodeGenCXX/cfi-ms-vbase-nvcall.cpp
Index: clang/test/CodeGenCXX/cfi-ms-vbase-nvcall.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/cfi-ms-vbase-nvcall.cpp
@@ -0,0 +1,27 @@
+// RUN: %clang_cc1 -flto -flto-unit -emit-llvm -o - -triple=x86_64-pc-win32 %s -fsanitize=cfi-nvcall -fsanitize-trap=cfi-nvcall | FileCheck %s
+
+struct foo {
+ virtual ~foo() {}
+ virtual void f() = 0;
+};
+
+template <typename T>
+struct bar : virtual public foo {
+ void f() {}
+};
+
+struct baz : public bar<baz> {
+ virtual ~baz() {}
+ void g() {}
+};
+
+void f(baz *z) {
+ // CHECK: define{{.*}}@"\01?f@@YAXPEAUbaz@@@Z"
+ // Load z, vbtable, vbase offset and vtable.
+ // CHECK: load
+ // CHECK: load
+ // CHECK: load
+ // CHECK: load
+ // CHECK: @llvm.type.test{{.*}}!"?AUfoo@@"
+ z->g();
+}
Index: clang/test/CodeGenCXX/cfi-ms-vbase-derived-cast.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/cfi-ms-vbase-derived-cast.cpp
@@ -0,0 +1,29 @@
+// RUN: %clang_cc1 -flto -flto-unit -emit-llvm -o - -triple=x86_64-pc-win32 %s -fsanitize=cfi-derived-cast -fsanitize-trap=cfi-derived-cast | FileCheck %s
+
+struct foo {
+ virtual ~foo() {}
+ virtual void f() = 0;
+};
+
+template <typename T>
+struct bar : virtual public foo {
+ void f() {
+ // CHECK: define{{.*}}@"\01?f@?$bar@Ubaz@@@@UEAAXXZ"
+ // Load "this", vbtable, vbase offset and vtable.
+ // CHECK: load
+ // CHECK: load
+ // CHECK: load
+ // CHECK: load
+ // CHECK: @llvm.type.test{{.*}}!"?AUfoo@@"
+ static_cast<T&>(*this);
+ }
+};
+
+struct baz : public bar<baz> {
+ virtual ~baz() {}
+};
+
+int main() {
+ baz *z = new baz;
+ z->f();
+}
Index: clang/lib/CodeGen/MicrosoftCXXABI.cpp
===================================================================
--- clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -578,7 +578,7 @@
return GetVBaseOffsetFromVBPtr(CGF, Base, VBPOffset, VBTOffset, VBPtr);
}
- std::pair<Address, llvm::Value *>
+ std::tuple<Address, llvm::Value *, const CXXRecordDecl *>
performBaseAdjustment(CodeGenFunction &CGF, Address Value,
QualType SrcRecordTy);
@@ -745,6 +745,10 @@
llvm::GlobalVariable *getThrowInfo(QualType T) override;
+ std::pair<llvm::Value *, const CXXRecordDecl *>
+ LoadVTablePtr(CodeGenFunction &CGF, Address This,
+ const CXXRecordDecl *RD) override;
+
private:
typedef std::pair<const CXXRecordDecl *, CharUnits> VFTableIdTy;
typedef llvm::DenseMap<VFTableIdTy, llvm::GlobalVariable *> VTablesMapTy;
@@ -926,7 +930,7 @@
/// We need to perform a generic polymorphic operation (like a typeid
/// or a cast), which requires an object with a vfptr. Adjust the
/// address to point to an object with a vfptr.
-std::pair<Address, llvm::Value *>
+std::tuple<Address, llvm::Value *, const CXXRecordDecl *>
MicrosoftCXXABI::performBaseAdjustment(CodeGenFunction &CGF, Address Value,
QualType SrcRecordTy) {
Value = CGF.Builder.CreateBitCast(Value, CGF.Int8PtrTy);
@@ -937,7 +941,8 @@
// covers non-virtual base subobjects: a class with its own virtual
// functions would be a candidate to be a primary base.
if (Context.getASTRecordLayout(SrcDecl).hasExtendableVFPtr())
- return std::make_pair(Value, llvm::ConstantInt::get(CGF.Int32Ty, 0));
+ return std::make_tuple(Value, llvm::ConstantInt::get(CGF.Int32Ty, 0),
+ SrcDecl);
// Okay, one of the vbases must have a vfptr, or else this isn't
// actually a polymorphic class.
@@ -956,7 +961,7 @@
llvm::Value *Ptr = CGF.Builder.CreateInBoundsGEP(Value.getPointer(), Offset);
CharUnits VBaseAlign =
CGF.CGM.getVBaseAlignment(Value.getAlignment(), SrcDecl, PolymorphicBase);
- return std::make_pair(Address(Ptr, VBaseAlign), Offset);
+ return std::make_tuple(Address(Ptr, VBaseAlign), Offset, PolymorphicBase);
}
bool MicrosoftCXXABI::shouldTypeidBeNullChecked(bool IsDeref,
@@ -987,7 +992,7 @@
QualType SrcRecordTy,
Address ThisPtr,
llvm::Type *StdTypeInfoPtrTy) {
- std::tie(ThisPtr, std::ignore) =
+ std::tie(ThisPtr, std::ignore, std::ignore) =
performBaseAdjustment(CGF, ThisPtr, SrcRecordTy);
auto Typeid = emitRTtypeidCall(CGF, ThisPtr.getPointer()).getInstruction();
return CGF.Builder.CreateBitCast(Typeid, StdTypeInfoPtrTy);
@@ -1011,7 +1016,8 @@
CGF.CGM.GetAddrOfRTTIDescriptor(DestRecordTy.getUnqualifiedType());
llvm::Value *Offset;
- std::tie(This, Offset) = performBaseAdjustment(CGF, This, SrcRecordTy);
+ std::tie(This, Offset, std::ignore) =
+ performBaseAdjustment(CGF, This, SrcRecordTy);
llvm::Value *ThisPtr = This.getPointer();
Offset = CGF.Builder.CreateTrunc(Offset, CGF.Int32Ty);
@@ -1037,7 +1043,8 @@
MicrosoftCXXABI::EmitDynamicCastToVoid(CodeGenFunction &CGF, Address Value,
QualType SrcRecordTy,
QualType DestTy) {
- std::tie(Value, std::ignore) = performBaseAdjustment(CGF, Value, SrcRecordTy);
+ std::tie(Value, std::ignore, std::ignore) =
+ performBaseAdjustment(CGF, Value, SrcRecordTy);
// PVOID __RTCastToVoid(
// PVOID inptr)
@@ -4244,3 +4251,11 @@
};
CGF.EmitNoreturnRuntimeCallOrInvoke(getThrowFn(), Args);
}
+
+std::pair<llvm::Value *, const CXXRecordDecl *>
+MicrosoftCXXABI::LoadVTablePtr(CodeGenFunction &CGF, Address This,
+ const CXXRecordDecl *RD) {
+ std::tie(This, std::ignore, RD) =
+ performBaseAdjustment(CGF, This, QualType(RD->getTypeForDecl(), 0));
+ return {CGF.GetVTablePtr(This, CGM.Int8PtrTy, RD), RD};
+}
Index: clang/lib/CodeGen/ItaniumCXXABI.cpp
===================================================================
--- clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -389,6 +389,10 @@
void emitCXXStructor(const CXXMethodDecl *MD, StructorType Type) override;
+ std::pair<llvm::Value *, const CXXRecordDecl *>
+ LoadVTablePtr(CodeGenFunction &CGF, Address This,
+ const CXXRecordDecl *RD) override;
+
private:
bool hasAnyUnusedVirtualInlineFunction(const CXXRecordDecl *RD) const {
const auto &VtableLayout =
@@ -4041,3 +4045,9 @@
}
return CGF.EmitNounwindRuntimeCall(CGF.CGM.getTerminateFn());
}
+
+std::pair<llvm::Value *, const CXXRecordDecl *>
+ItaniumCXXABI::LoadVTablePtr(CodeGenFunction &CGF, Address This,
+ const CXXRecordDecl *RD) {
+ return {CGF.GetVTablePtr(This, CGM.Int8PtrTy, RD), RD};
+}
Index: clang/lib/CodeGen/CGExprCXX.cpp
===================================================================
--- clang/lib/CodeGen/CGExprCXX.cpp
+++ clang/lib/CodeGen/CGExprCXX.cpp
@@ -368,9 +368,11 @@
} else {
if (SanOpts.has(SanitizerKind::CFINVCall) &&
MD->getParent()->isDynamicClass()) {
- llvm::Value *VTable = GetVTablePtr(This, Int8PtrTy, MD->getParent());
- EmitVTablePtrCheckForCall(MD->getParent(), VTable, CFITCK_NVCall,
- CE->getLocStart());
+ llvm::Value *VTable;
+ const CXXRecordDecl *RD;
+ std::tie(VTable, RD) =
+ CGM.getCXXABI().LoadVTablePtr(*this, This, MD->getParent());
+ EmitVTablePtrCheckForCall(RD, VTable, CFITCK_NVCall, CE->getLocStart());
}
if (getLangOpts().AppleKext && MD->isVirtual() && HasQualifier)
Index: clang/lib/CodeGen/CGClass.cpp
===================================================================
--- clang/lib/CodeGen/CGClass.cpp
+++ clang/lib/CodeGen/CGClass.cpp
@@ -2627,8 +2627,9 @@
EmitBlock(CheckBlock);
}
- llvm::Value *VTable =
- GetVTablePtr(Address(Derived, getPointerAlign()), Int8PtrTy, ClassDecl);
+ llvm::Value *VTable;
+ std::tie(VTable, ClassDecl) = CGM.getCXXABI().LoadVTablePtr(
+ *this, Address(Derived, getPointerAlign()), ClassDecl);
EmitVTablePtrCheck(ClassDecl, VTable, TCK, Loc);
Index: clang/lib/CodeGen/CGCXXABI.h
===================================================================
--- clang/lib/CodeGen/CGCXXABI.h
+++ clang/lib/CodeGen/CGCXXABI.h
@@ -582,6 +582,13 @@
/// Emit a single constructor/destructor with the given type from a C++
/// constructor Decl.
virtual void emitCXXStructor(const CXXMethodDecl *MD, StructorType Type) = 0;
+
+ /// Load a vtable from This, an object of polymorphic type RD, or from one of
+ /// its virtual bases if it does not have its own vtable. Returns the vtable
+ /// and the class from which the vtable was loaded.
+ virtual std::pair<llvm::Value *, const CXXRecordDecl *>
+ LoadVTablePtr(CodeGenFunction &CGF, Address This,
+ const CXXRecordDecl *RD) = 0;
};
// Create an instance of a C++ ABI class:
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