Implement Control Flow Integrity for virtual calls.

This patch introduces the -fsanitize=cfi-vptr flag, which enables a control
flow integrity scheme that checks that virtual calls take place using a vptr of
the correct dynamic type. More details in the new docs/ControlFlowIntegrity.rst
file.

It also introduces the -fsanitize=cfi flag, which is currently a synonym for
-fsanitize=cfi-vptr, but will eventually cover all CFI checks implemented
in Clang.

Differential Revision: http://reviews.llvm.org/D7424

llvm-svn: 230055

1 files changed, 9 insertions, 4 deletions

diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 0424c4b2653..61aaa9751be 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -17,6 +17,7 @@
 #include "clang/Driver/DriverDiagnostic.h"
 #include "clang/Driver/Job.h"
 #include "clang/Driver/Options.h"
+#include "clang/Driver/SanitizerArgs.h"
 #include "clang/Driver/Tool.h"
 #include "clang/Driver/ToolChain.h"
 #include "llvm/ADT/ArrayRef.h"
@@ -1269,7 +1270,7 @@ void Driver::BuildActions(const ToolChain &TC, DerivedArgList &Args,
         continue;
 
       // Otherwise construct the appropriate action.
-      Current = ConstructPhaseAction(Args, Phase, std::move(Current));
+      Current = ConstructPhaseAction(TC, Args, Phase, std::move(Current));
       if (Current->getType() == types::TY_Nothing)
         break;
     }
@@ -1295,7 +1296,8 @@ void Driver::BuildActions(const ToolChain &TC, DerivedArgList &Args,
 }
 
 std::unique_ptr<Action>
-Driver::ConstructPhaseAction(const ArgList &Args, phases::ID Phase,
+Driver::ConstructPhaseAction(const ToolChain &TC, const ArgList &Args,
+                             phases::ID Phase,
                              std::unique_ptr<Action> Input) const {
   llvm::PrettyStackTraceString CrashInfo("Constructing phase actions");
   // Build the appropriate action.
@@ -1354,7 +1356,7 @@ Driver::ConstructPhaseAction(const ArgList &Args, phases::ID Phase,
                                                types::TY_LLVM_BC);
   }
   case phases::Backend: {
-    if (IsUsingLTO(Args)) {
+    if (IsUsingLTO(TC, Args)) {
       types::ID Output =
         Args.hasArg(options::OPT_S) ? types::TY_LTO_IR : types::TY_LTO_BC;
       return llvm::make_unique<BackendJobAction>(std::move(Input), Output);
@@ -1375,7 +1377,10 @@ Driver::ConstructPhaseAction(const ArgList &Args, phases::ID Phase,
   llvm_unreachable("invalid phase in ConstructPhaseAction");
 }
 
-bool Driver::IsUsingLTO(const ArgList &Args) const {
+bool Driver::IsUsingLTO(const ToolChain &TC, const ArgList &Args) const {
+  if (TC.getSanitizerArgs().needsLTO())
+    return true;
+
   if (Args.hasFlag(options::OPT_flto, options::OPT_fno_lto, false))
     return true;