Added Control Flow Protection Flag

Cf-protection is a target independent flag that instructs the back-end to instrument control flow mechanisms like: Branch, Return, etc.
For example in X86 this flag will be used to instrument Indirect Branch Tracking instructions.

Differential Revision: https://reviews.llvm.org/D40478

Change-Id: I5126e766c0e6b84118cae0ee8a20fe78cc373dea

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@322063 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/DiagnosticCommonKinds.td

@@ -203,6 +203,8 @@ def err_target_unsupported_execute_only : Error<
   "execute only is not supported for the %0 sub-architecture">;
 def err_opt_not_valid_with_opt : Error<
   "option '%0' cannot be specified with '%1'">;
+def err_opt_not_valid_without_opt : Error<
+  "option '%0' cannot be specified without '%1'">;
 
 // Source manager
 def err_cannot_open_file : Error<"cannot open file '%0': %1">, DefaultFatal;

include/clang/Basic/TargetInfo.h

@@ -1051,6 +1051,18 @@ public:
     return false;
   }
 
+  /// Check if the target supports CFProtection branch.
+  virtual bool
+  checkCFProtectionBranchSupported(DiagnosticsEngine &Diags) const {
+    return false;
+  }
+
+  /// Check if the target supports CFProtection branch.
+  virtual bool
+  checkCFProtectionReturnSupported(DiagnosticsEngine &Diags) const {
+    return false;
+  }
+
   /// \brief Whether target allows to overalign ABI-specified preferred alignment
   virtual bool allowsLargerPreferedTypeAlignment() const { return true; }
 

include/clang/Driver/Options.td

@@ -1042,6 +1042,11 @@ def finstrument_functions_after_inlining : Flag<["-"], "finstrument-functions-af
   HelpText<"Like -finstrument-functions, but insert the calls after inlining">;
 def finstrument_function_entry_bare : Flag<["-"], "finstrument-function-entry-bare">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Instrument function entry only, after inlining, without arguments to the instrumentation call">;
+def fcf_protection_EQ : Joined<["-"], "fcf-protection=">, Flags<[CoreOption, CC1Option]>, Group<f_Group>,
+  HelpText<"Instrument control-flow architecture protection. Options: return, branch, full, none.">, Values<"return,branch,full,none">;
+def fcf_protection : Flag<["-"], "fcf-protection">, Group<f_Group>, Flags<[CoreOption, CC1Option]>,
+  Alias<fcf_protection_EQ>, AliasArgs<["full"]>,
+  HelpText<"Enable cf-protection in 'full' mode">;
 
 def fxray_instrument : Flag<["-"], "fxray-instrument">, Group<f_Group>,
   Flags<[CC1Option]>,

include/clang/Frontend/CodeGenOptions.def

@@ -80,7 +80,10 @@ CODEGENOPT(InstrumentFunctionsAfterInlining , 1, 0) ///< Set when
                           ///< -finstrument-functions-after-inlining is enabled.
 CODEGENOPT(InstrumentFunctionEntryBare , 1, 0) ///< Set when
                                ///< -finstrument-function-entry-bare is enabled.
-
+CODEGENOPT(CFProtectionReturn , 1, 0) ///< if -fcf-protection is
+                                      ///< set to full or return.
+CODEGENOPT(CFProtectionBranch , 1, 0) ///< if -fcf-protection is
+                                      ///< set to full or branch.
 CODEGENOPT(XRayInstrumentFunctions , 1, 0) ///< Set when -fxray-instrument is
                                            ///< enabled.
 CODEGENOPT(StackSizeSection  , 1, 0) ///< Set when -fstack-size-section is enabled.

lib/Basic/Targets/X86.cpp

@@ -101,6 +101,26 @@ bool X86TargetInfo::setFPMath(StringRef Name) {
   return false;
 }
 
+bool X86TargetInfo::checkCFProtectionReturnSupported(
+    DiagnosticsEngine &Diags) const {
+  if (HasSHSTK)
+    return true;
+
+  Diags.Report(diag::err_opt_not_valid_without_opt) << "cf-protection=return"
+                                                    << "-mshstk";
+  return false;
+}
+
+bool X86TargetInfo::checkCFProtectionBranchSupported(
+    DiagnosticsEngine &Diags) const {
+  if (HasIBT)
+    return true;
+
+  Diags.Report(diag::err_opt_not_valid_without_opt) << "cf-protection=branch"
+                                                    << "-mibt";
+  return false;
+}
+
 bool X86TargetInfo::initFeatureMap(
     llvm::StringMap<bool> &Features, DiagnosticsEngine &Diags, StringRef CPU,
     const std::vector<std::string> &FeaturesVec) const {

lib/Basic/Targets/X86.h

@@ -158,6 +158,12 @@ public:
 
   bool validateInputSize(StringRef Constraint, unsigned Size) const override;
 
+  virtual bool
+  checkCFProtectionReturnSupported(DiagnosticsEngine &Diags) const override;
+
+  virtual bool
+  checkCFProtectionBranchSupported(DiagnosticsEngine &Diags) const override;
+
   virtual bool validateOperandSize(StringRef Constraint, unsigned Size) const;
 
   std::string convertConstraint(const char *&Constraint) const override;

lib/CodeGen/CodeGenFunction.cpp

@@ -887,7 +887,8 @@ void CodeGenFunction::StartFunction(GlobalDecl GD,
   }
 
   // Apply xray attributes to the function (as a string, for now)
-  if (D && ShouldXRayInstrumentFunction()) {
+  bool InstrumentXray = ShouldXRayInstrumentFunction();
+  if (D && InstrumentXray) {
     if (const auto *XRayAttr = D->getAttr<XRayInstrumentAttr>()) {
       if (XRayAttr->alwaysXRayInstrument())
         Fn->addFnAttr("function-instrument", "xray-always");

lib/CodeGen/CodeGenModule.cpp

@@ -502,6 +502,20 @@ void CodeGenModule::Release() {
     getModule().addModuleFlag(llvm::Module::Override, "Cross-DSO CFI", 1);
   }
 
+  if (CodeGenOpts.CFProtectionReturn &&
+      Target.checkCFProtectionReturnSupported(getDiags())) {
+    // Indicate that we want to instrument return control flow protection.
+    getModule().addModuleFlag(llvm::Module::Override, "cf-protection-return",
+                              1);
+  }
+
+  if (CodeGenOpts.CFProtectionBranch &&
+      Target.checkCFProtectionBranchSupported(getDiags())) {
+    // Indicate that we want to instrument branch control flow protection.
+    getModule().addModuleFlag(llvm::Module::Override, "cf-protection-branch",
+                              1);
+  }
+
   if (LangOpts.CUDAIsDevice && getTriple().isNVPTX()) {
     // Indicate whether __nvvm_reflect should be configured to flush denormal
     // floating point values to 0.  (This corresponds to its "__CUDA_FTZ"

lib/Driver/ToolChains/Clang.cpp

@@ -4008,6 +4008,11 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   // Forward -cl options to -cc1
   RenderOpenCLOptions(Args, CmdArgs);
 
+  if (Arg *A = Args.getLastArg(options::OPT_fcf_protection_EQ)) {
+    CmdArgs.push_back(
+        Args.MakeArgString(Twine("-fcf-protection=") + A->getValue()));
+  }
+
   // Forward -f options with positive and negative forms; we translate
   // these by hand.
   if (Arg *A = getLastProfileSampleUseArg(Args)) {

lib/Frontend/CompilerInvocation.cpp

@@ -798,6 +798,21 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.CallFEntry = Args.hasArg(OPT_mfentry);
   Opts.EmitOpenCLArgMetadata = Args.hasArg(OPT_cl_kernel_arg_info);
 
+  if (const Arg *A = Args.getLastArg(OPT_fcf_protection_EQ)) {
+    StringRef Name = A->getValue();
+    if (Name == "full") {
+      Opts.CFProtectionReturn = 1;
+      Opts.CFProtectionBranch = 1;
+    } else if (Name == "return")
+      Opts.CFProtectionReturn = 1;
+    else if (Name == "branch")
+      Opts.CFProtectionBranch = 1;
+    else if (Name != "none") {
+      Diags.Report(diag::err_drv_invalid_value) << A->getAsString(Args) << Name;
+      Success = false;
+    }
+  }
+
   if (const Arg *A = Args.getLastArg(OPT_compress_debug_sections,
                                      OPT_compress_debug_sections_EQ)) {
     if (A->getOption().getID() == OPT_compress_debug_sections) {

test/CodeGen/x86-cf-protection.c

@@ -0,0 +1,6 @@
+// RUN: not %clang_cc1 -fsyntax-only -S -emit-llvm -triple i386-unknown-unknown -fcf-protection=return %s 2>&1 | FileCheck %s --check-prefix=RETURN
+// RUN: not %clang_cc1 -fsyntax-only -S -emit-llvm -triple i386-unknown-unknown -fcf-protection=branch %s 2>&1 | FileCheck %s --check-prefix=BRANCH
+
+// RETURN: error: option 'cf-protection=return' cannot be specified without '-mshstk'
+// BRANCH: error: option 'cf-protection=branch' cannot be specified without '-mibt'
+void foo() {}

test/Driver/clang_f_opts.c

@@ -503,3 +503,17 @@
 // CHECK-WINDOWS-ISO10646: "-fwchar-type=int"
 // CHECK-WINDOWS-ISO10646: "-fsigned-wchar"
 
+// RUN: %clang -### -S -fcf-protection %s 2>&1 | FileCheck -check-prefix=CHECK-CF-PROTECTION-FULL %s
+// RUN: %clang -### -S %s 2>&1 | FileCheck -check-prefix=CHECK-NO-CF-PROTECTION-FULL %s
+// RUN: %clang -### -S -fcf-protection=full %s 2>&1 | FileCheck -check-prefix=CHECK-CF-PROTECTION-FULL %s
+// RUN: %clang -### -S %s 2>&1 | FileCheck -check-prefix=CHECK-NO-CF-PROTECTION-FULL %s
+// CHECK-CF-PROTECTION-FULL: -fcf-protection=full
+// CHECK-NO-CF-PROTECTION-FULL-NOT: -fcf-protection=full
+// RUN: %clang -### -S -fcf-protection=return %s 2>&1 | FileCheck -check-prefix=CHECK-CF-PROTECTION-RETURN %s
+// RUN: %clang -### -S %s 2>&1 | FileCheck -check-prefix=CHECK-NO-CF-PROTECTION-RETURN %s
+// CHECK-CF-PROTECTION-RETURN: -fcf-protection=return
+// CHECK-NO-CF-PROTECTION-RETURN-NOT: -fcf-protection=return
+// RUN: %clang -### -S -fcf-protection=branch %s 2>&1 | FileCheck -check-prefix=CHECK-CF-PROTECTION-BRANCH %s
+// RUN: %clang -### -S %s 2>&1 | FileCheck -check-prefix=CHECK-NO-CF-PROTECTION-BRANCH %s
+// CHECK-CF-PROTECTION-BRANCH: -fcf-protection=branch
+// CHECK-NO-CF-PROTECTION-BRANCH-NOT: -fcf-protection=branch