Revert "[CFGuard] Add address-taken IAT tables and delay-load support"

This reverts commit ef4e971e5e18ae796466623df8f26265ba6bdfb5.

include/llvm/MC/MCObjectFileInfo.h

@@ -215,7 +215,6 @@ protected:
   MCSection *XDataSection = nullptr;
   MCSection *SXDataSection = nullptr;
   MCSection *GFIDsSection = nullptr;
-  MCSection *GIATsSection = nullptr;
   MCSection *GLJMPSection = nullptr;
 
   // XCOFF specific sections
@@ -399,7 +398,6 @@ public:
   MCSection *getXDataSection() const { return XDataSection; }
   MCSection *getSXDataSection() const { return SXDataSection; }
   MCSection *getGFIDsSection() const { return GFIDsSection; }
-  MCSection *getGIATsSection() const { return GIATsSection; }
   MCSection *getGLJMPSection() const { return GLJMPSection; }
 
   // XCOFF specific sections

lib/CodeGen/AsmPrinter/WinCFGuard.cpp

@@ -7,7 +7,7 @@
 //===----------------------------------------------------------------------===//
 //
 // This file contains support for writing the metadata for Windows Control Flow
-// Guard, including address-taken functions and valid longjmp targets.
+// Guard, including address-taken functions, and valid longjmp targets.
 //
 //===----------------------------------------------------------------------===//
 
@@ -17,8 +17,8 @@
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/MachineOperand.h"
 #include "llvm/IR/Constants.h"
-#include "llvm/IR/Instructions.h"
 #include "llvm/IR/Metadata.h"
+#include "llvm/IR/Instructions.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCStreamer.h"
@@ -78,49 +78,20 @@ static bool isPossibleIndirectCallTarget(const Function *F) {
   return false;
 }
 
-/// Returns true if this function should be added to the Guard Address Taken IAT
-/// Entry Table (GIATs) instead of the Guard Function ID Table (GFIDs).
-static bool isIATAddressTaken(const Function *F) {
-  if (F->hasDLLImportStorageClass()) {
-    return true;
-  }
-  return false;
-}
-
 void WinCFGuard::endModule() {
   const Module *M = Asm->MMI->getModule();
-  std::vector<const Function *> GFIDsEntries;
-  std::vector<const Function *> GIATsEntries;
-  for (const Function &F : *M) {
-    if (isPossibleIndirectCallTarget(&F)) {
-      if (isIATAddressTaken(&F)) {
-        // If the possible call target is reached via the IAT, add it to the
-        // GIATs table instead of the GFIDs table.
-        GIATsEntries.push_back(&F);
-      } else {
-        // Otherwise add it to the GFIDs table.
-        GFIDsEntries.push_back(&F);
-      }
-    }
-  }
-
-  if (GFIDsEntries.empty() && GIATsEntries.empty() && LongjmpTargets.empty())
+  std::vector<const Function *> Functions;
+  for (const Function &F : *M)
+    if (isPossibleIndirectCallTarget(&F))
+      Functions.push_back(&F);
+  if (Functions.empty() && LongjmpTargets.empty())
     return;
-
-  // Emit the symbol index of each GFIDs entry to form the GFIDs table.
   auto &OS = *Asm->OutStreamer;
   OS.SwitchSection(Asm->OutContext.getObjectFileInfo()->getGFIDsSection());
-  for (const Function *F : GFIDsEntries)
+  for (const Function *F : Functions)
     OS.EmitCOFFSymbolIndex(Asm->getSymbol(F));
 
-  // Emit the symbol index of each GIATs entry to form the GIATs table.
-  OS.SwitchSection(Asm->OutContext.getObjectFileInfo()->getGIATsSection());
-  for (const Function *F : GIATsEntries) {
-    OS.EmitCOFFSymbolIndex(Asm->OutContext.getOrCreateSymbol(
-        Twine("__imp_") + Asm->getSymbol(F)->getName()));
-  }
-
-  // Emit the symbol index of each longjmp target to form the GLJMP table.
+  // Emit the symbol index of each longjmp target.
   OS.SwitchSection(Asm->OutContext.getObjectFileInfo()->getGLJMPSection());
   for (const MCSymbol *S : LongjmpTargets) {
     OS.EmitCOFFSymbolIndex(S);

lib/MC/MCObjectFileInfo.cpp

@@ -752,11 +752,6 @@ void MCObjectFileInfo::initCOFFMCObjectFileInfo(const Triple &T) {
                                          COFF::IMAGE_SCN_MEM_READ,
                                      SectionKind::getMetadata());
 
-  GIATsSection = Ctx->getCOFFSection(".giats$y",
-                                     COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
-                                         COFF::IMAGE_SCN_MEM_READ,
-                                     SectionKind::getMetadata());
-
   GLJMPSection = Ctx->getCOFFSection(".gljmp$y",
                                      COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
                                          COFF::IMAGE_SCN_MEM_READ,

test/CodeGen/WinCFGuard/cfguard-giats.ll

@@ -1,22 +0,0 @@
-; RUN: llc < %s -mtriple=x86_64-pc-windows-msvc | FileCheck %s
-; Control Flow Guard is currently only available on Windows
-
-declare dllimport i32 @target_func()
-
-; Test address-taken functions from imported DLLs are added to the 
-; Guard Address-Taken IAT Entry table (.giats).
-define i32 @func_cf_giats() {
-entry:
-  %func_ptr = alloca i32 ()*, align 8
-  store i32 ()* @target_func, i32 ()** %func_ptr, align 8
-  %0 = load i32 ()*, i32 ()** %func_ptr, align 8
-  %1 = call i32 %0()
-  ret i32 %1
-}
-
-!llvm.module.flags = !{!0}
-!0 = !{i32 2, !"cfguard", i32 2}
-
-; CHECK-LABEL: .section .giats$y,"dr"
-; CHECK-NEXT:  .symidx __imp_target_func
-; CHECK-NOT:   .symidx

tools/llvm-readobj/COFFDumper.cpp

@@ -67,8 +67,6 @@ struct LoadConfigTables {
   uint32_t GuardFlags = 0;
   uint64_t GuardFidTableVA = 0;
   uint64_t GuardFidTableCount = 0;
-  uint64_t GuardIatTableVA = 0;
-  uint64_t GuardIatTableCount = 0;
   uint64_t GuardLJmpTableVA = 0;
   uint64_t GuardLJmpTableCount = 0;
 };
@@ -806,11 +804,6 @@ void COFFDumper::printCOFFLoadConfig() {
     }
   }
 
-  if (Tables.GuardIatTableVA) {
-    ListScope LS(W, "GuardIatTable");
-    printRVATable(Tables.GuardIatTableVA, Tables.GuardIatTableCount, 4);
-  }
-
   if (Tables.GuardLJmpTableVA) {
     ListScope LS(W, "GuardLJmpTable");
     printRVATable(Tables.GuardLJmpTableVA, Tables.GuardLJmpTableCount, 4);
@@ -895,9 +888,6 @@ void COFFDumper::printCOFFLoadConfig(const T *Conf, LoadConfigTables &Tables) {
              Conf->GuardRFVerifyStackPointerFunctionPointer);
   W.printHex("HotPatchTableOffset", Conf->HotPatchTableOffset);
 
-  Tables.GuardIatTableVA = Conf->GuardAddressTakenIatEntryTable;
-  Tables.GuardIatTableCount = Conf->GuardAddressTakenIatEntryCount;
-
   Tables.GuardLJmpTableVA = Conf->GuardLongJumpTargetTable;
   Tables.GuardLJmpTableCount = Conf->GuardLongJumpTargetCount;
 }