[clang] [llvm] [X86][CodeGen] security check cookie execute only when needed (PR #95904)

[via llvm-commits]

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@@ -0,0 +1,243 @@
+//===---- X86FixupStackProtector.cpp Fix Stack Protector Call ----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+// Stack Protector implementation inserts platform specific callback into code.
+// For windows __security_check_cookie call gets call everytime function is
+// return without fixup. Since this function is defined in runtime library, it
+// incures cost of call in dll which simply does comparison and returns most
+// time. With Fixup, We selective move to call in DLL only if comparison fails.
+//===----------------------------------------------------------------------===//
+
+#include "X86.h"
+#include "X86FrameLowering.h"
+#include "X86InstrInfo.h"
+#include "X86Subtarget.h"
+#include "llvm/CodeGen/LivePhysRegs.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/IR/Module.h"
+#include <iterator>
+
+using namespace llvm;
+
+#define DEBUG_TYPE "x86-fixup-spcall"
+
+namespace {
+
+class X86FixupStackProtectorPass : public MachineFunctionPass {
+public:
+  static char ID;
+
+  X86FixupStackProtectorPass() : MachineFunctionPass(ID) {}
+
+  StringRef getPassName() const override { return "X86 Fixup Stack Protector"; }
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  std::pair<MachineBasicBlock *, MachineInstr *>
+  getSecurityCheckerBasicBlock(MachineFunction &MF);
+
+  void getGuardCheckSequence(MachineBasicBlock *CurMBB, MachineInstr *CheckCall,
+                             MachineInstr *SeqMI[5]);
+ 
+  void SplitBasicBlock(MachineBasicBlock *CurMBB, MachineBasicBlock *NewRetMBB,
+                       MachineBasicBlock::iterator SplitIt);
+
+  void FinishBlock(MachineBasicBlock *MBB);
+
+  void FinishFunction(MachineBasicBlock *FailMBB, MachineBasicBlock *NewRetMBB);
+
+  std::pair<MachineInstr *, MachineInstr *>
+  CreateFailCheckSequence(MachineBasicBlock *CurMBB, MachineBasicBlock *FailMBB,
+                          MachineInstr *SeqMI[5]);
+};
+} // end anonymous namespace
+
+char X86FixupStackProtectorPass::ID = 0;
+
+INITIALIZE_PASS(X86FixupStackProtectorPass, DEBUG_TYPE, DEBUG_TYPE, false,
+                false)
+
+FunctionPass *llvm::createX86FixupStackProtectorPass() {
+  return new X86FixupStackProtectorPass();
+}
+
+void X86FixupStackProtectorPass::SplitBasicBlock(
+    MachineBasicBlock *CurMBB, MachineBasicBlock *NewRetMBB,
+    MachineBasicBlock::iterator SplitIt) {
+  NewRetMBB->splice(NewRetMBB->end(), CurMBB, SplitIt, CurMBB->end());
+}
+
+std::pair<MachineBasicBlock *, MachineInstr *>
+X86FixupStackProtectorPass::getSecurityCheckerBasicBlock(MachineFunction &MF) {
+  MachineBasicBlock::reverse_iterator RBegin, REnd;
+
+  for (auto &MBB : llvm::reverse(MF)) {
+    for (RBegin = MBB.rbegin(), REnd = MBB.rend(); RBegin != REnd; RBegin++) {
+      auto &MI = *RBegin;
+      if (MI.getOpcode() == X86::CALL64pcrel32 &&
+          MI.getNumExplicitOperands() == 1) {
+        auto MO = MI.getOperand(0);
+        if (MO.isGlobal()) {
+          auto Callee = dyn_cast<Function>(MO.getGlobal());
+          if (Callee && Callee->getName() == "__security_check_cookie") {
+            return std::make_pair(&MBB, &MI);
+            break;
+          }
+        }
+      }
+    }
+  }
+  return std::make_pair(nullptr, nullptr);
+}
+
+void X86FixupStackProtectorPass::getGuardCheckSequence(
+    MachineBasicBlock *CurMBB, MachineInstr *CheckCall,
+    MachineInstr *SeqMI[5]) {
+
+  MachineBasicBlock::iterator UIt(CheckCall);
+  MachineBasicBlock::reverse_iterator DIt(CheckCall);
+  // Seq From StackUp to Stack Down Is fixed.
+  // ADJCALLSTACKUP64
+  UIt++;
----------------
mahesh-attarde wrote:

done.

https://github.com/llvm/llvm-project/pull/95904