Initial checkin for stack protectors. Here's what it does:

* The prologue is modified to read the __stack_chk_guard global and insert it
  onto the stack.

* The epilogue is modified to read the stored guard from the stack and compare
  it to the original __stack_chk_guard value. If they differ, then the
  __stack_chk_fail() function is called.

* The stack protector needs to be first on the stack (after the parameters) to
  catch any stack-smashing activities.

Front-end support will follow after a round of beta testing.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58673 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/LLVMTargetMachine.cpp

@@ -60,6 +60,11 @@ static cl::opt<cl::boolOrDefault>
 EnableFastISelOption("fast-isel", cl::Hidden,
   cl::desc("Enable the experimental \"fast\" instruction selector"));
 
+// Enable stack protectors.
+static cl::opt<int>
+EnableStackProtector("enable-stack-protector", cl::init(0),
+                     cl::desc("Use ProPolice as a stack protection method."));
+
 FileModel::Model
 LLVMTargetMachine::addPassesToEmitFile(PassManagerBase &PM,
                                        raw_ostream &Out,
@@ -165,6 +170,8 @@ bool LLVMTargetMachine::addCommonCodeGenPasses(PassManagerBase &PM, bool Fast) {
   if (!Fast)
     PM.add(createCodeGenPreparePass(getTargetLowering()));
 
+  PM.add(createStackProtectorPass(EnableStackProtector));
+
   if (PrintISelInput)
     PM.add(createPrintFunctionPass("\n\n"
                                    "*** Final LLVM Code input to ISel ***\n",