Emit Function IDs table for Control Flow Guard

Adds option /guard:cf to clang-cl and -cfguard to cc1 to emit function IDs
of functions that have their address taken into a section named .gfids$y for
compatibility with Microsoft's Control Flow Guard feature.

Differential Revision: https://reviews.llvm.org/D40531

llvm-svn: 322005

1 files changed, 45 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/WinCFGuard.cpp b/llvm/lib/CodeGen/AsmPrinter/WinCFGuard.cpp
new file mode 100644
index 0000000..18d37ca
--- /dev/null
+++ b/llvm/lib/CodeGen/AsmPrinter/WinCFGuard.cpp
@@ -0,0 +1,45 @@
+//===-- CodeGen/AsmPrinter/WinCFGuard.cpp - Control Flow Guard Impl ------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains support for writing Win64 exception info into asm files.
+//
+//===----------------------------------------------------------------------===//
+
+#include "WinCFGuard.h"
+#include "llvm/CodeGen/AsmPrinter.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/CodeGen/MachineOperand.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Metadata.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCObjectFileInfo.h"
+#include "llvm/MC/MCStreamer.h"
+
+#include <vector>
+
+using namespace llvm;
+
+WinCFGuard::WinCFGuard(AsmPrinter *A) : AsmPrinterHandler(), Asm(A) {}
+
+WinCFGuard::~WinCFGuard() {}
+
+void WinCFGuard::endModule() {
+  const Module *M = Asm->MMI->getModule();
+  std::vector<const Function *> Functions;
+  for (const Function &F : *M)
+    if (F.hasAddressTaken())
+      Functions.push_back(&F);
+  if (Functions.empty())
+    return;
+  auto &OS = *Asm->OutStreamer;
+  OS.SwitchSection(Asm->OutContext.getObjectFileInfo()->getGFIDsSection());
+  for (const Function *F : Functions)
+    OS.EmitCOFFSymbolIndex(Asm->getSymbol(F));
+}