[CFI] Add CFI-icall pointer type generalization

Summary:
This change allows generalizing pointers in type signatures used for
cfi-icall by enabling the -fsanitize-cfi-icall-generalize-pointers flag.
This works by 1) emitting an additional generalized type signature
metadata node for functions and 2) llvm.type.test()ing for the
generalized type for translation units with the flag specified.

This flag is incompatible with -fsanitize-cfi-cross-dso because it would
require emitting twice as many type hashes which would increase artifact
size.

Reviewers: pcc, eugenis

Reviewed By: pcc

Subscribers: kcc

Differential Revision: https://reviews.llvm.org/D39358

llvm-svn: 317044

clang/docs/ClangCommandLineReference.rst

@@ -740,6 +740,10 @@ Path to blacklist file for sanitizers
 
 Enable control flow integrity (CFI) checks for cross-DSO calls.
 
+.. option:: -fsanitize-cfi-icall-generalize-pointers
+
+Generalize pointers in function type signatures used for Control Flow Integrity (CFI) indirect call checking
+
 .. option:: -fsanitize-coverage=<arg1>,<arg2>..., -fno-sanitize-coverage=<arg1>,<arg2>...
 
 Specify the type of coverage instrumentation for Sanitizers

clang/docs/ControlFlowIntegrity.rst

@@ -215,6 +215,23 @@ shared library boundaries are handled as if the callee was not compiled with
 
 This scheme is currently only supported on the x86 and x86_64 architectures.
 
+``-fsanitize-cfi-icall-generalize-pointers``
+--------------------------------------------
+
+Mismatched pointer types are a common cause of cfi-icall check failures.
+Translation units compiled with the ``-fsanitize-cfi-icall-generalize-pointers``
+flag relax pointer type checking for call sites in that translation unit,
+applied across all functions compiled with ``-fsanitize=cfi-icall``.
+
+Specifically, pointers in return and argument types are treated as equivalent as
+long as the qualifiers for the type they point to match. For example, ``char*``
+``char**`, and ``int*`` are considered equivalent types. However, ``char*`` and
+``const char*`` are considered separate types.
+
+``-fsanitize-cfi-icall-generalize-pointers`` is not compatible with
+``-fsanitize-cfi-cross-dso``.
+
+
 ``-fsanitize=cfi-icall`` and ``-fsanitize=function``
 ----------------------------------------------------
 

clang/docs/UsersManual.rst

@@ -1147,6 +1147,11 @@ are listed below.
    the behavior of sanitizers in the ``cfi`` group to allow checking
    of cross-DSO virtual and indirect calls.
 
+.. option:: -fsanitize-cfi-icall-generalize-pointers
+
+   Generalize pointers in return and argument types in function type signatures
+   checked by Control Flow Integrity indirect call checking. See
+   :doc:`ControlFlowIntegrity` for more details.
 
 .. option:: -fstrict-vtable-pointers
 

clang/include/clang/Driver/Options.td

@@ -914,6 +914,9 @@ def fno_sanitize_cfi_cross_dso : Flag<["-"], "fno-sanitize-cfi-cross-dso">,
                                  Flags<[CoreOption, DriverOption]>,
                                  Group<f_clang_Group>,
                                  HelpText<"Disable control flow integrity (CFI) checks for cross-DSO calls.">;
+def fsanitize_cfi_icall_generalize_pointers : Flag<["-"], "fsanitize-cfi-icall-generalize-pointers">,
+                                              Group<f_clang_Group>,
+                                              HelpText<"Generalize pointers in CFI indirect call type signature checks">;
 def fsanitize_stats : Flag<["-"], "fsanitize-stats">,
                               Group<f_clang_Group>,
                               HelpText<"Enable sanitizer statistics gathering.">;

clang/include/clang/Driver/SanitizerArgs.h

@@ -32,6 +32,7 @@ class SanitizerArgs {
   int MsanTrackOrigins = 0;
   bool MsanUseAfterDtor = false;
   bool CfiCrossDso = false;
+  bool CfiICallGeneralizePointers = false;
   int AsanFieldPadding = 0;
   bool SharedRuntime = false;
   bool AsanUseAfterScope = true;

clang/include/clang/Frontend/CodeGenOptions.def

@@ -154,6 +154,8 @@ CODEGENOPT(SanitizeMemoryUseAfterDtor, 1, 0) ///< Enable use-after-delete detect
 CODEGENOPT(SanitizeCfiCrossDso, 1, 0) ///< Enable cross-dso support in CFI.
 CODEGENOPT(SanitizeMinimalRuntime, 1, 0) ///< Use "_minimal" sanitizer runtime for
                                          ///< diagnostics.
+CODEGENOPT(SanitizeCfiICallGeneralizePointers, 1, 0) ///< Generalize pointer types in
+                                                     ///< CFI icall function signatures
 CODEGENOPT(SanitizeCoverageType, 2, 0) ///< Type of sanitizer coverage
                                        ///< instrumentation.
 CODEGENOPT(SanitizeCoverageIndirectCalls, 1, 0) ///< Enable sanitizer coverage

clang/lib/CodeGen/CGExpr.cpp

@@ -4475,7 +4475,12 @@ RValue CodeGenFunction::EmitCall(QualType CalleeType, const CGCallee &OrigCallee
     SanitizerScope SanScope(this);
     EmitSanitizerStatReport(llvm::SanStat_CFI_ICall);
 
-    llvm::Metadata *MD = CGM.CreateMetadataIdentifierForType(QualType(FnType, 0));
+    llvm::Metadata *MD;
+    if (CGM.getCodeGenOpts().SanitizeCfiICallGeneralizePointers)
+      MD = CGM.CreateMetadataIdentifierGeneralized(QualType(FnType, 0));
+    else
+      MD = CGM.CreateMetadataIdentifierForType(QualType(FnType, 0));
+
     llvm::Value *TypeId = llvm::MetadataAsValue::get(getLLVMContext(), MD);
 
     llvm::Value *CalleePtr = Callee.getFunctionPointer();

clang/lib/CodeGen/CodeGenModule.cpp

@@ -1152,6 +1152,7 @@ void CodeGenModule::CreateFunctionTypeMetadata(const FunctionDecl *FD,
 
   llvm::Metadata *MD = CreateMetadataIdentifierForType(FD->getType());
   F->addTypeMetadata(0, MD);
+  F->addTypeMetadata(0, CreateMetadataIdentifierGeneralized(FD->getType()));
 
   // Emit a hash-based bit set entry for cross-DSO calls.
   if (CodeGenOpts.SanitizeCfiCrossDso)
@@ -4543,6 +4544,60 @@ llvm::Metadata *CodeGenModule::CreateMetadataIdentifierForType(QualType T) {
   return InternalId;
 }
 
+// Generalize pointer types to a void pointer with the qualifiers of the
+// originally pointed-to type, e.g. 'const char *' and 'char * const *'
+// generalize to 'const void *' while 'char *' and 'const char **' generalize to
+// 'void *'.
+static QualType GeneralizeType(ASTContext &Ctx, QualType Ty) {
+  if (!Ty->isPointerType())
+    return Ty;
+
+  return Ctx.getPointerType(
+      QualType(Ctx.VoidTy).withCVRQualifiers(
+          Ty->getPointeeType().getCVRQualifiers()));
+}
+
+// Apply type generalization to a FunctionType's return and argument types
+static QualType GeneralizeFunctionType(ASTContext &Ctx, QualType Ty) {
+  if (auto *FnType = Ty->getAs<FunctionProtoType>()) {
+    SmallVector<QualType, 8> GeneralizedParams;
+    for (auto &Param : FnType->param_types())
+      GeneralizedParams.push_back(GeneralizeType(Ctx, Param));
+
+    return Ctx.getFunctionType(
+        GeneralizeType(Ctx, FnType->getReturnType()),
+        GeneralizedParams, FnType->getExtProtoInfo());
+  }
+
+  if (auto *FnType = Ty->getAs<FunctionNoProtoType>())
+    return Ctx.getFunctionNoProtoType(
+        GeneralizeType(Ctx, FnType->getReturnType()));
+
+  llvm_unreachable("Encountered unknown FunctionType");
+}
+
+llvm::Metadata *CodeGenModule::CreateMetadataIdentifierGeneralized(QualType T) {
+  T = GeneralizeFunctionType(getContext(), T);
+
+  llvm::Metadata *&InternalId = GeneralizedMetadataIdMap[T.getCanonicalType()];
+  if (InternalId)
+    return InternalId;
+
+  if (isExternallyVisible(T->getLinkage())) {
+    std::string OutName;
+    llvm::raw_string_ostream Out(OutName);
+    getCXXABI().getMangleContext().mangleTypeName(T, Out);
+    Out << ".generalized";
+
+    InternalId = llvm::MDString::get(getLLVMContext(), Out.str());
+  } else {
+    InternalId = llvm::MDNode::getDistinct(getLLVMContext(),
+                                           llvm::ArrayRef<llvm::Metadata *>());
+  }
+
+  return InternalId;
+}
+
 /// Returns whether this module needs the "all-vtables" type identifier.
 bool CodeGenModule::NeedAllVtablesTypeId() const {
   // Returns true if at least one of vtable-based CFI checkers is enabled and

clang/lib/CodeGen/CodeGenModule.h

@@ -497,7 +497,9 @@ class CodeGenModule : public CodeGenTypeCache {
   /// Mapping from canonical types to their metadata identifiers. We need to
   /// maintain this mapping because identifiers may be formed from distinct
   /// MDNodes.
-  llvm::DenseMap<QualType, llvm::Metadata *> MetadataIdMap;
+  typedef llvm::DenseMap<QualType, llvm::Metadata *> MetadataTypeMap;
+  MetadataTypeMap MetadataIdMap;
+  MetadataTypeMap GeneralizedMetadataIdMap;
 
 public:
   CodeGenModule(ASTContext &C, const HeaderSearchOptions &headersearchopts,
@@ -1209,6 +1211,11 @@ class CodeGenModule : public CodeGenTypeCache {
   /// internal identifiers).
   llvm::Metadata *CreateMetadataIdentifierForType(QualType T);
 
+  /// Create a metadata identifier for the generalization of the given type.
+  /// This may either be an MDString (for external identifiers) or a distinct
+  /// unnamed MDNode (for internal identifiers).
+  llvm::Metadata *CreateMetadataIdentifierGeneralized(QualType T);
+
   /// Create and attach type metadata to the given function.
   void CreateFunctionTypeMetadata(const FunctionDecl *FD, llvm::Function *F);
 

clang/lib/Driver/SanitizerArgs.cpp

@@ -520,6 +520,13 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
     // Without PIE, external function address may resolve to a PLT record, which
     // can not be verified by the target module.
     NeedPIE |= CfiCrossDso;
+    CfiICallGeneralizePointers =
+        Args.hasArg(options::OPT_fsanitize_cfi_icall_generalize_pointers);
+
+    if (CfiCrossDso && CfiICallGeneralizePointers)
+      D.Diag(diag::err_drv_argument_not_allowed_with)
+          << "-fsanitize-cfi-cross-dso"
+          << "-fsanitize-cfi-icall-generalize-pointers";
   }
 
   Stats = Args.hasFlag(options::OPT_fsanitize_stats,
@@ -807,6 +814,9 @@ void SanitizerArgs::addArgs(const ToolChain &TC, const llvm::opt::ArgList &Args,
   if (CfiCrossDso)
     CmdArgs.push_back("-fsanitize-cfi-cross-dso");
 
+  if (CfiICallGeneralizePointers)
+    CmdArgs.push_back("-fsanitize-cfi-icall-generalize-pointers");
+
   if (Stats)
     CmdArgs.push_back("-fsanitize-stats");
 

clang/lib/Frontend/CompilerInvocation.cpp

@@ -839,6 +839,8 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
                    false);
   Opts.SanitizeMinimalRuntime = Args.hasArg(OPT_fsanitize_minimal_runtime);
   Opts.SanitizeCfiCrossDso = Args.hasArg(OPT_fsanitize_cfi_cross_dso);
+  Opts.SanitizeCfiICallGeneralizePointers =
+      Args.hasArg(OPT_fsanitize_cfi_icall_generalize_pointers);
   Opts.SanitizeStats = Args.hasArg(OPT_fsanitize_stats);
   if (Arg *A = Args.getLastArg(OPT_fsanitize_address_use_after_scope,
                                OPT_fno_sanitize_address_use_after_scope)) {

clang/test/CodeGen/cfi-icall-cross-dso.c

@@ -46,7 +46,7 @@ void caller(void (*f)()) {
 // Check that we emit both string and hash based type entries for static void g(),
 // and don't emit them for the declaration of h().
 
-// CHECK: define internal void @g({{.*}} !type [[TVOID:![0-9]+]] !type [[TVOID_ID:![0-9]+]]
+// CHECK: define internal void @g({{.*}} !type [[TVOID:![0-9]+]] !type [[TVOID_GENERALIZED:![0-9]+]] !type [[TVOID_ID:![0-9]+]]
 static void g(void) {}
 
 // CHECK: declare void @h({{[^!]*$}}
@@ -60,9 +60,9 @@ Fn h1() {
   return &h;
 }
 
-// CHECK: define void @bar({{.*}} !type [[TNOPROTO:![0-9]+]] !type [[TNOPROTO_ID:![0-9]+]]
+// CHECK: define void @bar({{.*}} !type [[TNOPROTO:![0-9]+]] !type [[TNOPROTO_GENERALIZED:![0-9]+]] !type [[TNOPROTO_ID:![0-9]+]]
 // ITANIUM: define available_externally void @foo({{[^!]*$}}
-// MS: define linkonce_odr void @foo({{.*}} !type [[TNOPROTO]] !type [[TNOPROTO_ID]]
+// MS: define linkonce_odr void @foo({{.*}} !type [[TNOPROTO]] !type [[TNOPROTO_GENERALIZED:![0-9]+]] !type [[TNOPROTO_ID]]
 inline void foo() {}
 void bar() { foo(); }
 
@@ -71,11 +71,15 @@ void bar() { foo(); }
 // Check that the type entries are correct.
 
 // ITANIUM: [[TVOID]] = !{i64 0, !"_ZTSFvvE"}
+// ITANIUM: [[TVOID_GENERALIZED]] = !{i64 0, !"_ZTSFvvE.generalized"}
 // ITANIUM: [[TVOID_ID]] = !{i64 0, i64 9080559750644022485}
 // ITANIUM: [[TNOPROTO]] = !{i64 0, !"_ZTSFvE"}
+// ITANIUM: [[TNOPROTO_GENERALIZED]] = !{i64 0, !"_ZTSFvE.generalized"}
 // ITANIUM: [[TNOPROTO_ID]] = !{i64 0, i64 6588678392271548388}
 
 // MS: [[TVOID]] = !{i64 0, !"?6AXXZ"}
+// MS: [[TVOID_GENERALIZED]] = !{i64 0, !"?6AXXZ.generalized"}
 // MS: [[TVOID_ID]] = !{i64 0, i64 5113650790573562461}
 // MS: [[TNOPROTO]] = !{i64 0, !"?6AX@Z"}
+// MS: [[TNOPROTO_GENERALIZED]] = !{i64 0, !"?6AX@Z.generalized"}
 // MS: [[TNOPROTO_ID]] = !{i64 0, i64 4195979634929632483}

clang/test/CodeGen/cfi-icall-generalize.c

@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -fsanitize=cfi-icall -fsanitize-trap=cfi-icall -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=UNGENERALIZED %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -fsanitize=cfi-icall -fsanitize-trap=cfi-icall -fsanitize-cfi-icall-generalize-pointers -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=GENERALIZED %s
+
+// Test that const char* is generalized to const void* and that const char** is
+// generalized to void*
+
+// CHECK: define i32** @f({{.*}} !type [[TYPE:![0-9]+]] !type [[TYPE_GENERALIZED:![0-9]+]]
+int** f(const char *a, const char **b) {
+  return (int**)0;
+}
+
+void g(int** (*fp)(const char *, const char **)) {
+  // UNGENERALIZED: call i1 @llvm.type.test(i8* {{.*}}, metadata !"_ZTSFPPiPKcPS2_E")
+  // GENERALIZED: call i1 @llvm.type.test(i8* {{.*}}, metadata !"_ZTSFPvPKvS_E.generalized")
+  fp(0, 0);
+}
+
+// CHECK: [[TYPE]] = !{i64 0, !"_ZTSFPPiPKcPS2_E"}
+// CHECK: [[TYPE_GENERALIZED]] = !{i64 0, !"_ZTSFPvPKvS_E.generalized"}

clang/test/CodeGen/cfi-icall.c

@@ -3,22 +3,26 @@
 
 // Tests that we assign appropriate identifiers to unprototyped functions.
 
-// CHECK: define void @f({{.*}} !type [[TVOID:![0-9]+]]
+// CHECK: define void @f({{.*}} !type [[TVOID:![0-9]+]] !type [[TVOID_GENERALIZED:![0-9]+]]
 void f() {
 }
 
 void xf();
 
-// CHECK: define void @g({{.*}} !type [[TINT:![0-9]+]]
+// CHECK: define void @g({{.*}} !type [[TINT:![0-9]+]] !type [[TINT_GENERALIZED:![0-9]+]]
 void g(int b) {
   void (*fp)() = b ? f : xf;
   // ITANIUM: call i1 @llvm.type.test(i8* {{.*}}, metadata !"_ZTSFvE")
   fp();
 }
 
-// CHECK: declare !type [[TVOID:![0-9]+]] void @xf({{.*}}
+// CHECK: declare !type [[TVOID]] !type [[TVOID_GENERALIZED]] void @xf({{.*}}
 
 // ITANIUM-DAG: [[TVOID]] = !{i64 0, !"_ZTSFvE"}
+// ITANIUM-DAG: [[TVOID_GENERALIZED]] = !{i64 0, !"_ZTSFvE.generalized"}
 // ITANIUM-DAG: [[TINT]] = !{i64 0, !"_ZTSFviE"}
+// ITANIUM-DAG: [[TINT_GENERALIZED]] = !{i64 0, !"_ZTSFviE.generalized"}
 // MS-DAG: [[TVOID]] = !{i64 0, !"?6AX@Z"}
+// MS-DAG: [[TVOID_GENERALIZED]] = !{i64 0, !"?6AX@Z.generalized"}
 // MS-DAG: [[TINT]] = !{i64 0, !"?6AXH@Z"}
+// MS-DAG: [[TINT_GENERALIZED]] = !{i64 0, !"?6AXH@Z.generalized"}

clang/test/CodeGenCXX/cfi-icall.cpp

@@ -8,19 +8,22 @@ namespace {
 
 struct S {};
 
-void f(S *s) {
+void f(S s) {
 }
 
 }
 
 void g() {
-  void (*fp)(S *) = f;
-  // CHECK: call i1 @llvm.type.test(i8* {{.*}}, metadata [[VOIDS:![0-9]+]])
-  fp(0);
+  struct S s;
+  void (*fp)(S) = f;
+  // CHECK: call i1 @llvm.type.test(i8* {{.*}}, metadata [[VOIDS1:![0-9]+]])
+  fp(s);
 }
 
-// ITANIUM: define internal void @_ZN12_GLOBAL__N_11fEPNS_1SE({{.*}} !type [[TS:![0-9]+]]
-// MS: define internal void @"\01?f@?A@@YAXPEAUS@?A@@@Z"({{.*}} !type [[TS:![0-9]+]]
+// ITANIUM: define internal void @_ZN12_GLOBAL__N_11fENS_1SE({{.*}} !type [[TS1:![0-9]+]] !type [[TS2:![0-9]+]]
+// MS: define internal void @"\01?f@?A@@YAXUS@?A@@@Z"({{.*}} !type [[TS1:![0-9]+]] !type [[TS2:![0-9]+]]
 
-// CHECK: [[VOIDS]] = distinct !{}
-// CHECK: [[TS]] = !{i64 0, [[VOIDS]]}
+// CHECK: [[VOIDS1]] = distinct !{}
+// CHECK: [[TS1]] = !{i64 0, [[VOIDS1]]}
+// CHECK: [[TS2]] = !{i64 0, [[VOIDS2:![0-9]+]]}
+// CHECK: [[VOIDS2]] = distinct !{}

clang/test/Driver/fsanitize.c

@@ -480,6 +480,14 @@
 // CHECK-CFI-NO-CROSS-DSO: -emit-llvm-bc
 // CHECK-CFI-NO-CROSS-DSO-NOT: -fsanitize-cfi-cross-dso
 
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi-icall -fsanitize-cfi-icall-generalize-pointers -fvisibility=hidden -flto -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-GENERALIZE-POINTERS
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi-icall -fvisibility=hidden -flto -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-NO-CFI-GENERALIZE-POINTERS
+// CHECK-CFI-GENERALIZE-POINTERS: -fsanitize-cfi-icall-generalize-pointers
+// CHECK-NO-CFI-GENERALIZE-POINTERS-NOT: -fsanitize-cfi-icall-generalize-pointers
+
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi-icall -fsanitize-cfi-icall-generalize-pointers -fsanitize-cfi-cross-dso -fvisibility=hidden -flto -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-GENERALIZE-AND-CROSS-DSO
+// CHECK-CFI-GENERALIZE-AND-CROSS-DSO: error: invalid argument '-fsanitize-cfi-cross-dso' not allowed with '-fsanitize-cfi-icall-generalize-pointers'
+
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi -fsanitize-stats -flto -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-STATS
 // CHECK-CFI-STATS: -fsanitize-stats