[Clang] Implement labelled type filtering for overflow/truncation sanitizers w/ SSCLs

clang/docs/ReleaseNotes.rst

@@ -635,6 +635,14 @@ Sanitizers
   This new flag should allow those projects to enable integer sanitizers with
   less noise.
 
+- Arithmetic overflow sanitizers ``-fsanitize=signed-integer-overflow`` and
+  ``-fsanitize=unsigned-integer-overflow`` as well as the implicit integer
+  truncation sanitizers ``-fsanitize=implicit-signed-integer-truncation`` and
+  ``-fsanitize=implicit-unsigned-integer-truncation`` now properly support the
+  "type" prefix within `Sanitizer Special Case Lists (SSCL)
+  <https://clang.llvm.org/docs/SanitizerSpecialCaseList.html>`_. See that link
+  for examples.
+
 Python Binding Changes
 ----------------------
 - Fixed an issue that led to crashes when calling ``Type.get_exception_specification_kind``.

clang/docs/SanitizerSpecialCaseList.rst

@@ -15,8 +15,9 @@ file at compile-time.
 Goal and usage
 ==============
 
-Users of sanitizer tools, such as :doc:`AddressSanitizer`, :doc:`ThreadSanitizer`
-or :doc:`MemorySanitizer` may want to disable or alter some checks for
+Users of sanitizer tools, such as :doc:`AddressSanitizer`,
+:doc:`ThreadSanitizer`, :doc:`MemorySanitizer` or :doc:
+`UndefinedBehaviorSanitizer` may want to disable or alter some checks for
 certain source-level entities to:
 
 * speedup hot function, which is known to be correct;
@@ -48,6 +49,58 @@ Example
   $ clang -fsanitize=address -fsanitize-ignorelist=ignorelist.txt foo.c ; ./a.out
   # No error report here.
 
+Usage with UndefinedBehaviorSanitizer
+=====================================
+
+The arithmetic overflow sanitizers ``unsigned-integer-overflow`` and
+``signed-integer-overflow`` as well as the implicit integer truncation
+sanitizers ``implicit-signed-integer-truncation`` and
+``implicit-unsigned-integer-truncation`` support the ability to adjust
+instrumentation based on type.
+
+.. code-block:: bash
+
+  $ cat foo.c
+  void foo() {
+    int a = 2147483647; // INT_MAX
+    ++a;                // Normally, an overflow with -fsanitize=signed-integer-overflow
+  }
+  $ cat ignorelist.txt
+  [signed-integer-overflow]
+  type:int
+  $ clang -fsanitize=signed-integer-overflow -fsanitize-ignorelist=ignorelist.txt foo.c ; ./a.out
+  # no signed-integer-overflow error
+
+Supplying ``ignorelist.txt`` with ``-fsanitize-ignorelist=ignorelist.txt``
+disables overflow sanitizer instrumentation for arithmetic operations
+containing values of type ``int``, for example. Custom types may be used.
+
+The following SCL categories are supported: ``=no_sanitize`` and ``=sanitize``.
+The ``no_sanitize`` category is the default for any entry within an ignorelist
+and specifies that the query, if matched, will have its sanitizer
+instrumentation ignored. Conversely, ``sanitize`` causes its queries, if
+matched, to be left out of the ignorelist -- essentially ensuring sanitizer
+instrumentation remains for those types. This is useful for whitelisting
+specific types.
+
+With this, one may disable instrumentation for all types and specifically allow
+instrumentation for one or many types.
+
+.. code-block:: bash
+
+  $ cat ignorelist.txt
+  [implicit-signed-integer-truncation]
+  type:*=no_sanitize
+  type:T=sanitize
+  $ cat foo.c
+  typedef char T;
+  typedef char U;
+  void foo(int toobig) {
+    T a = toobig;    // instrumented
+    U b = toobig;    // not instrumented
+    char c = toobig; // also not instrumented
+  }
+
 Format
 ======
 

clang/include/clang/AST/ASTContext.h

@@ -830,6 +830,9 @@ class ASTContext : public RefCountedBase<ASTContext> {
 
   const NoSanitizeList &getNoSanitizeList() const { return *NoSanitizeL; }
 
+  bool isTypeIgnoredBySanitizer(const SanitizerMask &Mask,
+                                const QualType &Ty) const;
+
   const XRayFunctionFilter &getXRayFilter() const {
     return *XRayFilter;
   }

clang/lib/AST/ASTContext.cpp

@@ -831,6 +831,28 @@ ASTContext::getCanonicalTemplateTemplateParmDecl(
   return CanonTTP;
 }
 
+/// Check if a type can have its sanitizer instrumentation elided.
+/// Determine this by its presence in a SCL alongside its specified categories.
+/// For example:
+/// ignorelist.txt>
+/// [{unsigned-integer-overflow,signed-integer-overflow}]
+/// type:*=no_sanitize
+/// type:size_t=sanitize
+/// <ignorelist.txt
+/// Supplying the above ignorelist.txt will disable overflow sanitizer
+/// instrumentation for all types except "size_t".
+bool ASTContext::isTypeIgnoredBySanitizer(const SanitizerMask &Mask,
+                                          const QualType &Ty) const {
+  bool sanitizeType =
+      NoSanitizeL->containsType(Mask, Ty.getAsString(), "sanitize");
+
+  bool noSanitizeType =
+      NoSanitizeL->containsType(Mask, Ty.getAsString(), "no_sanitize") ||
+      NoSanitizeL->containsType(Mask, Ty.getAsString());
+
+  return noSanitizeType && !sanitizeType;
+}
+
 TargetCXXABI::Kind ASTContext::getCXXABIKind() const {
   auto Kind = getTargetInfo().getCXXABI().getKind();
   return getLangOpts().CXXABI.value_or(Kind);

clang/lib/CodeGen/CGExprScalar.cpp

@@ -197,6 +197,18 @@ static bool CanElideOverflowCheck(const ASTContext &Ctx, const BinOpInfo &Op) {
   if (!Op.mayHaveIntegerOverflow())
     return true;
 
+  if (Op.Ty->isSignedIntegerType() &&
+      Ctx.isTypeIgnoredBySanitizer(SanitizerKind::SignedIntegerOverflow,
+                                   Op.Ty)) {
+    return true;
+  }
+
+  if (Op.Ty->isUnsignedIntegerType() &&
+      Ctx.isTypeIgnoredBySanitizer(SanitizerKind::UnsignedIntegerOverflow,
+                                   Op.Ty)) {
+    return true;
+  }
+
   const UnaryOperator *UO = dyn_cast<UnaryOperator>(Op.E);
 
   if (UO && UO->getOpcode() == UO_Minus &&
@@ -1121,6 +1133,10 @@ void ScalarExprEmitter::EmitIntegerTruncationCheck(Value *Src, QualType SrcType,
   if (!CGF.SanOpts.has(Check.second.second))
     return;
 
+  // Does some SSCL ignore this type?
+  if (CGF.getContext().isTypeIgnoredBySanitizer(Check.second.second, DstType))
+    return;
+
   llvm::Constant *StaticArgs[] = {
       CGF.EmitCheckSourceLocation(Loc), CGF.EmitCheckTypeDescriptor(SrcType),
       CGF.EmitCheckTypeDescriptor(DstType),
@@ -1231,6 +1247,15 @@ void ScalarExprEmitter::EmitIntegerSignChangeCheck(Value *Src, QualType SrcType,
     // Because here sign change check is interchangeable with truncation check.
     return;
   }
+  // Does an SSCL have an entry for the DstType under its respective sanitizer
+  // section?
+  if (DstSigned && CGF.getContext().isTypeIgnoredBySanitizer(
+                       SanitizerKind::ImplicitSignedIntegerTruncation, DstType))
+    return;
+  if (!DstSigned &&
+      CGF.getContext().isTypeIgnoredBySanitizer(
+          SanitizerKind::ImplicitUnsignedIntegerTruncation, DstType))
+    return;
   // That's it. We can't rule out any more cases with the data we have.
 
   CodeGenFunction::SanitizerScope SanScope(&CGF);
@@ -2780,10 +2805,11 @@ llvm::Value *ScalarExprEmitter::EmitIncDecConsiderOverflowBehavior(
       return Builder.CreateNSWAdd(InVal, Amount, Name);
     [[fallthrough]];
   case LangOptions::SOB_Trapping:
-    if (!E->canOverflow())
+    BinOpInfo Info = createBinOpInfoFromIncDec(
+        E, InVal, IsInc, E->getFPFeaturesInEffect(CGF.getLangOpts()));
+    if (!E->canOverflow() || CanElideOverflowCheck(CGF.getContext(), Info))
       return Builder.CreateNSWAdd(InVal, Amount, Name);
-    return EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(
-        E, InVal, IsInc, E->getFPFeaturesInEffect(CGF.getLangOpts())));
+    return EmitOverflowCheckedBinOp(Info);
   }
   llvm_unreachable("Unknown SignedOverflowBehaviorTy");
 }
@@ -2986,7 +3012,9 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
       value = EmitIncDecConsiderOverflowBehavior(E, value, isInc);
     } else if (E->canOverflow() && type->isUnsignedIntegerType() &&
                CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow) &&
-               !excludeOverflowPattern) {
+               !excludeOverflowPattern &&
+               !CGF.getContext().isTypeIgnoredBySanitizer(
+                   SanitizerKind::UnsignedIntegerOverflow, E->getType())) {
       value = EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(
           E, value, isInc, E->getFPFeaturesInEffect(CGF.getLangOpts())));
     } else {

clang/test/CodeGen/ubsan-type-ignorelist.test

@@ -0,0 +1,105 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+
+// Verify ubsan doesn't emit checks for ignorelisted types
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -fsanitize=signed-integer-overflow,unsigned-integer-overflow -fsanitize-ignorelist=%t/int.ignorelist -emit-llvm %t/test.cpp -o - | FileCheck %s --check-prefix=INT
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -fsanitize=signed-integer-overflow,unsigned-integer-overflow -fsanitize-ignorelist=%t/nosection.ignorelist -emit-llvm %t/test.cpp -o - | FileCheck %s --check-prefix=INT
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -fsanitize=signed-integer-overflow,unsigned-integer-overflow -fsanitize-ignorelist=%t/nosan-same-as-no-category.ignorelist -emit-llvm %t/test.cpp -o - | FileCheck %s --check-prefix=INT
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -fsanitize=signed-integer-overflow,unsigned-integer-overflow -fsanitize-ignorelist=%t/myty.ignorelist -emit-llvm %t/test.cpp -o - | FileCheck %s --check-prefix=MYTY
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -fsanitize=implicit-signed-integer-truncation,implicit-unsigned-integer-truncation -fsanitize-ignorelist=%t/trunc.ignorelist -emit-llvm %t/test.cpp -o - | FileCheck %s --check-prefix=TRUNC
+
+// Verify ubsan vptr does not check down-casts on ignorelisted types.
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -fsanitize=vptr -fsanitize-recover=vptr -emit-llvm %t/test.cpp -o - | FileCheck %s --check-prefix=VPTR
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -fsanitize=vptr -fsanitize-recover=vptr -fsanitize-ignorelist=%t/vptr.ignorelist -emit-llvm %t/test.cpp -o - | FileCheck %s --check-prefix=VPTR-TYPE
+
+
+//--- int.ignorelist
+[{unsigned-integer-overflow,signed-integer-overflow}]
+type:int
+
+//--- nosection.ignorelist
+type:int
+
+//--- nosan-same-as-no-category.ignorelist
+type:int=no_sanitize
+
+//--- myty.ignorelist
+[{unsigned-integer-overflow,signed-integer-overflow}]
+type:*
+type:myty=sanitize
+
+//--- trunc.ignorelist
+[{implicit-signed-integer-truncation,implicit-unsigned-integer-truncation}]
+type:char
+type:unsigned char
+
+
+//--- vptr.ignorelist
+type:_ZTI3Foo
+
+//--- test.cpp
+class Bar {
+public:
+  virtual ~Bar() {}
+};
+class Foo : public Bar {};
+
+Bar bar;
+
+// VPTR: @_Z7checkmev
+// VPTR-TYPE: @_Z7checkmev
+void checkme() {
+// VPTR: call void @__ubsan_handle_dynamic_type_cache_miss({{.*}} (ptr @bar to
+// VPTR-TYPE-NOT: @__ubsan_handle_dynamic_type_cache_miss
+  Foo* foo = static_cast<Foo*>(&bar); // down-casting
+// VPTR: ret void
+// VPTR-TYPE: ret void
+  return;
+}
+
+// INT-LABEL: ignore_int
+void ignore_int(int A, int B, unsigned C, unsigned D, long E) {
+// INT: llvm.uadd.with.overflow.i32
+  (void)(C+D);
+// INT-NOT: llvm.sadd.with.overflow.i32
+  (void)(A+B);
+// INT: llvm.sadd.with.overflow.i64
+  (void)(++E);
+}
+
+
+typedef unsigned long myty;
+typedef myty derivative;
+// INT-LABEL: ignore_all_except_myty
+// MYTY-LABEL: ignore_all_except_myty
+void ignore_all_except_myty(myty A, myty B, int C, unsigned D, derivative E) {
+// MYTY-NOT: llvm.sadd.with.overflow.i32
+  (void)(++C);
+
+// MYTY-NOT: llvm.uadd.with.overflow.i32
+  (void)(D+D);
+
+// MYTY-NOT: llvm.umul.with.overflow.i64
+  (void)(E*2);
+
+// MYTY: llvm.uadd.with.overflow.i64
+  (void)(A+B);
+}
+
+// INT-LABEL: truncation
+// MYTY-LABEL: truncation
+// TRUNC-LABEL: truncation
+void truncation(char A, int B, unsigned char C, short D) {
+// TRUNC-NOT: %handler.implicit_conversion
+  A = B;
+// TRUNC-NOT: %handler.implicit_conversion
+  A = C;
+// TRUNC-NOT: %handler.implicit_conversion
+  C = B;
+
+// TRUNC: %handler.implicit_conversion
+  D = B;
+
+  (void)A;
+  (void)D;
+}