[llvm] f95a67d - [X86] Add RET-hardening Support to mitigate Load Value Injection (LVI)
Craig Topper via llvm-commits
llvm-commits at lists.llvm.org
Fri Apr 3 12:09:04 PDT 2020
Author: Scott Constable
Date: 2020-04-03T12:08:34-07:00
New Revision: f95a67d8b8a8cec326ee4a7e8427b779936d100a
URL: https://github.com/llvm/llvm-project/commit/f95a67d8b8a8cec326ee4a7e8427b779936d100a
DIFF: https://github.com/llvm/llvm-project/commit/f95a67d8b8a8cec326ee4a7e8427b779936d100a.diff
LOG: [X86] Add RET-hardening Support to mitigate Load Value Injection (LVI)
Adding a pass that replaces every ret instruction with the sequence:
pop <scratch-reg>
lfence
jmp *<scratch-reg>
where <scratch-reg> is some available scratch register, according to the
calling convention of the function being mitigated.
Differential Revision: https://reviews.llvm.org/D75935
Added:
llvm/lib/Target/X86/X86LoadValueInjectionRetHardening.cpp
llvm/test/CodeGen/X86/lvi-hardening-ret.ll
Modified:
llvm/lib/Target/X86/CMakeLists.txt
llvm/lib/Target/X86/X86.h
llvm/lib/Target/X86/X86TargetMachine.cpp
llvm/test/CodeGen/X86/O0-pipeline.ll
llvm/test/CodeGen/X86/O3-pipeline.ll
Removed:
################################################################################
diff --git a/llvm/lib/Target/X86/CMakeLists.txt b/llvm/lib/Target/X86/CMakeLists.txt
index a07b66426fbb..5df9978bf11d 100644
--- a/llvm/lib/Target/X86/CMakeLists.txt
+++ b/llvm/lib/Target/X86/CMakeLists.txt
@@ -52,6 +52,7 @@ set(sources
X86InstrInfo.cpp
X86EvexToVex.cpp
X86LegalizerInfo.cpp
+ X86LoadValueInjectionRetHardening.cpp
X86MCInstLower.cpp
X86MachineFunctionInfo.cpp
X86MacroFusion.cpp
diff --git a/llvm/lib/Target/X86/X86.h b/llvm/lib/Target/X86/X86.h
index f251cde5d253..1b6e99ae7b9b 100644
--- a/llvm/lib/Target/X86/X86.h
+++ b/llvm/lib/Target/X86/X86.h
@@ -142,6 +142,7 @@ InstructionSelector *createX86InstructionSelector(const X86TargetMachine &TM,
X86Subtarget &,
X86RegisterBankInfo &);
+FunctionPass *createX86LoadValueInjectionRetHardeningPass();
FunctionPass *createX86SpeculativeLoadHardeningPass();
void initializeEvexToVexInstPassPass(PassRegistry &);
@@ -158,6 +159,7 @@ void initializeX86DomainReassignmentPass(PassRegistry &);
void initializeX86ExecutionDomainFixPass(PassRegistry &);
void initializeX86ExpandPseudoPass(PassRegistry &);
void initializeX86FlagsCopyLoweringPassPass(PassRegistry &);
+void initializeX86LoadValueInjectionRetHardeningPassPass(PassRegistry &);
void initializeX86OptimizeLEAPassPass(PassRegistry &);
void initializeX86PartialReductionPass(PassRegistry &);
void initializeX86SpeculativeLoadHardeningPassPass(PassRegistry &);
diff --git a/llvm/lib/Target/X86/X86LoadValueInjectionRetHardening.cpp b/llvm/lib/Target/X86/X86LoadValueInjectionRetHardening.cpp
new file mode 100644
index 000000000000..9c36e86099f9
--- /dev/null
+++ b/llvm/lib/Target/X86/X86LoadValueInjectionRetHardening.cpp
@@ -0,0 +1,140 @@
+//===-- X86LoadValueInjectionRetHardening.cpp - LVI RET hardening for x86 --==//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// Description: Replaces every `ret` instruction with the sequence:
+/// ```
+/// pop <scratch-reg>
+/// lfence
+/// jmp *<scratch-reg>
+/// ```
+/// where `<scratch-reg>` is some available scratch register, according to the
+/// calling convention of the function being mitigated.
+///
+//===----------------------------------------------------------------------===//
+
+#include "X86.h"
+#include "X86InstrBuilder.h"
+#include "X86Subtarget.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/IR/Function.h"
+#include "llvm/Support/Debug.h"
+#include <bitset>
+
+using namespace llvm;
+
+#define PASS_KEY "x86-lvi-ret"
+#define DEBUG_TYPE PASS_KEY
+
+STATISTIC(NumFences, "Number of LFENCEs inserted for LVI mitigation");
+STATISTIC(NumFunctionsConsidered, "Number of functions analyzed");
+STATISTIC(NumFunctionsMitigated, "Number of functions for which mitigations "
+ "were deployed");
+
+namespace {
+
+class X86LoadValueInjectionRetHardeningPass : public MachineFunctionPass {
+public:
+ X86LoadValueInjectionRetHardeningPass() : MachineFunctionPass(ID) {}
+ StringRef getPassName() const override {
+ return "X86 Load Value Injection (LVI) Ret-Hardening";
+ }
+ bool runOnMachineFunction(MachineFunction &MF) override;
+
+ static char ID;
+};
+
+} // end anonymous namespace
+
+char X86LoadValueInjectionRetHardeningPass::ID = 0;
+
+bool X86LoadValueInjectionRetHardeningPass::runOnMachineFunction(
+ MachineFunction &MF) {
+ LLVM_DEBUG(dbgs() << "***** " << getPassName() << " : " << MF.getName()
+ << " *****\n");
+ const X86Subtarget *Subtarget = &MF.getSubtarget<X86Subtarget>();
+ if (!Subtarget->useLVIControlFlowIntegrity() || !Subtarget->is64Bit())
+ return false; // FIXME: support 32-bit
+
+ // Don't skip functions with the "optnone" attr but participate in opt-bisect.
+ const Function &F = MF.getFunction();
+ if (!F.hasOptNone() && skipFunction(F))
+ return false;
+
+ ++NumFunctionsConsidered;
+ const X86RegisterInfo *TRI = Subtarget->getRegisterInfo();
+ const X86InstrInfo *TII = Subtarget->getInstrInfo();
+ unsigned ClobberReg = X86::NoRegister;
+ std::bitset<X86::NUM_TARGET_REGS> UnclobberableGR64s;
+ UnclobberableGR64s.set(X86::RSP); // can't clobber stack pointer
+ UnclobberableGR64s.set(X86::RIP); // can't clobber instruction pointer
+ UnclobberableGR64s.set(X86::RAX); // used for function return
+ UnclobberableGR64s.set(X86::RDX); // used for function return
+
+ // We can clobber any register allowed by the function's calling convention.
+ for (const MCPhysReg *PR = TRI->getCalleeSavedRegs(&MF); auto Reg = *PR; ++PR)
+ UnclobberableGR64s.set(Reg);
+ for (auto &Reg : X86::GR64RegClass) {
+ if (!UnclobberableGR64s.test(Reg)) {
+ ClobberReg = Reg;
+ break;
+ }
+ }
+
+ if (ClobberReg != X86::NoRegister) {
+ LLVM_DEBUG(dbgs() << "Selected register "
+ << Subtarget->getRegisterInfo()->getRegAsmName(ClobberReg)
+ << " to clobber\n");
+ } else {
+ LLVM_DEBUG(dbgs() << "Could not find a register to clobber\n");
+ }
+
+ bool Modified = false;
+ for (auto &MBB : MF) {
+ MachineInstr &MI = MBB.back();
+ if (MI.getOpcode() != X86::RETQ)
+ continue;
+
+ if (ClobberReg != X86::NoRegister) {
+ MBB.erase_instr(&MI);
+ BuildMI(MBB, MBB.end(), DebugLoc(), TII->get(X86::POP64r))
+ .addReg(ClobberReg, RegState::Define)
+ .setMIFlag(MachineInstr::FrameDestroy);
+ BuildMI(MBB, MBB.end(), DebugLoc(), TII->get(X86::LFENCE));
+ BuildMI(MBB, MBB.end(), DebugLoc(), TII->get(X86::JMP64r))
+ .addReg(ClobberReg);
+ } else {
+ // In case there is no available scratch register, we can still read from
+ // RSP to assert that RSP points to a valid page. The write to RSP is
+ // also helpful because it verifies that the stack's write permissions
+ // are intact.
+ MachineInstr *Fence = BuildMI(MBB, MI, DebugLoc(), TII->get(X86::LFENCE));
+ addRegOffset(BuildMI(MBB, Fence, DebugLoc(), TII->get(X86::SHL64mi)),
+ X86::RSP, false, 0)
+ .addImm(0)
+ ->addRegisterDead(X86::EFLAGS, TRI);
+ }
+
+ ++NumFences;
+ Modified = true;
+ }
+
+ if (Modified)
+ ++NumFunctionsMitigated;
+ return Modified;
+}
+
+INITIALIZE_PASS(X86LoadValueInjectionRetHardeningPass, PASS_KEY,
+ "X86 LVI ret hardener", false, false)
+
+FunctionPass *llvm::createX86LoadValueInjectionRetHardeningPass() {
+ return new X86LoadValueInjectionRetHardeningPass();
+}
diff --git a/llvm/lib/Target/X86/X86TargetMachine.cpp b/llvm/lib/Target/X86/X86TargetMachine.cpp
index 16c3edf8769f..b2551b64eb0d 100644
--- a/llvm/lib/Target/X86/X86TargetMachine.cpp
+++ b/llvm/lib/Target/X86/X86TargetMachine.cpp
@@ -83,6 +83,7 @@ extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeX86Target() {
initializeX86SpeculativeLoadHardeningPassPass(PR);
initializeX86FlagsCopyLoweringPassPass(PR);
initializeX86CondBrFoldingPassPass(PR);
+ initializeX86LoadValueInjectionRetHardeningPassPass(PR);
initializeX86OptimizeLEAPassPass(PR);
initializeX86PartialReductionPass(PR);
}
@@ -540,6 +541,7 @@ void X86PassConfig::addPreEmitPass2() {
// Identify valid longjmp targets for Windows Control Flow Guard.
if (TT.isOSWindows())
addPass(createCFGuardLongjmpPass());
+ addPass(createX86LoadValueInjectionRetHardeningPass());
}
std::unique_ptr<CSEConfigBase> X86PassConfig::getCSEConfig() const {
diff --git a/llvm/test/CodeGen/X86/O0-pipeline.ll b/llvm/test/CodeGen/X86/O0-pipeline.ll
index 5ca3129c784d..9af81b77a70b 100644
--- a/llvm/test/CodeGen/X86/O0-pipeline.ll
+++ b/llvm/test/CodeGen/X86/O0-pipeline.ll
@@ -74,6 +74,7 @@
; CHECK-NEXT: Live DEBUG_VALUE analysis
; CHECK-NEXT: X86 Indirect Thunks
; CHECK-NEXT: Check CFA info and insert CFI instructions if needed
+; CHECK-NEXT: X86 Load Value Injection (LVI) Ret-Hardening
; CHECK-NEXT: Lazy Machine Block Frequency Analysis
; CHECK-NEXT: Machine Optimization Remark Emitter
; CHECK-NEXT: X86 Assembly Printer
diff --git a/llvm/test/CodeGen/X86/O3-pipeline.ll b/llvm/test/CodeGen/X86/O3-pipeline.ll
index f7518afc5cd5..97ce5082d4f7 100644
--- a/llvm/test/CodeGen/X86/O3-pipeline.ll
+++ b/llvm/test/CodeGen/X86/O3-pipeline.ll
@@ -184,6 +184,7 @@
; CHECK-NEXT: Live DEBUG_VALUE analysis
; CHECK-NEXT: X86 Indirect Thunks
; CHECK-NEXT: Check CFA info and insert CFI instructions if needed
+; CHECK-NEXT: X86 Load Value Injection (LVI) Ret-Hardening
; CHECK-NEXT: Lazy Machine Block Frequency Analysis
; CHECK-NEXT: Machine Optimization Remark Emitter
; CHECK-NEXT: X86 Assembly Printer
diff --git a/llvm/test/CodeGen/X86/lvi-hardening-ret.ll b/llvm/test/CodeGen/X86/lvi-hardening-ret.ll
new file mode 100644
index 000000000000..9f2b028b3034
--- /dev/null
+++ b/llvm/test/CodeGen/X86/lvi-hardening-ret.ll
@@ -0,0 +1,72 @@
+; RUN: llc -verify-machineinstrs -mtriple=x86_64-unknown < %s | FileCheck %s
+
+define dso_local void @one_instruction() #0 {
+; CHECK-LABEL: one_instruction:
+entry:
+ ret void
+; CHECK-NOT: retq
+; CHECK: popq %[[x:[^ ]*]]
+; CHECK-NEXT: lfence
+; CHECK-NEXT: jmpq *%[[x]]
+}
+
+; Function Attrs: noinline nounwind optnone uwtable
+define dso_local i32 @ordinary_function(i32 %x, i32 %y) #0 {
+; CHECK-LABEL: ordinary_function:
+entry:
+ %x.addr = alloca i32, align 4
+ %y.addr = alloca i32, align 4
+ store i32 %x, i32* %x.addr, align 4
+ store i32 %y, i32* %y.addr, align 4
+ %0 = load i32, i32* %x.addr, align 4
+ %1 = load i32, i32* %y.addr, align 4
+ %add = add nsw i32 %0, %1
+ ret i32 %add
+; CHECK-NOT: retq
+; CHECK: popq %[[x:[^ ]*]]
+; CHECK-NEXT: lfence
+; CHECK-NEXT: jmpq *%[[x]]
+}
+
+; Function Attrs: noinline nounwind optnone uwtable
+define dso_local i32 @no_caller_saved_registers_function(i32 %x, i32 %y) #1 {
+; CHECK-LABEL: no_caller_saved_registers_function:
+entry:
+ %x.addr = alloca i32, align 4
+ %y.addr = alloca i32, align 4
+ store i32 %x, i32* %x.addr, align 4
+ store i32 %y, i32* %y.addr, align 4
+ %0 = load i32, i32* %x.addr, align 4
+ %1 = load i32, i32* %y.addr, align 4
+ %add = add nsw i32 %0, %1
+ ret i32 %add
+; CHECK-NOT: retq
+; CHECK: shlq $0, (%{{[^ ]*}})
+; CHECK-NEXT: lfence
+; CHECK-NEXT: retq
+}
+
+; Function Attrs: noinline nounwind optnone uwtable
+define dso_local preserve_mostcc void @preserve_most() #0 {
+; CHECK-LABEL: preserve_most:
+entry:
+ ret void
+; CHECK-NOT: retq
+; CHECK: popq %r11
+; CHECK-NEXT: lfence
+; CHECK-NEXT: jmpq *%r11
+}
+
+; Function Attrs: noinline nounwind optnone uwtable
+define dso_local preserve_allcc void @preserve_all() #0 {
+; CHECK-LABEL: preserve_all:
+entry:
+ ret void
+; CHECK-NOT: retq
+; CHECK: popq %r11
+; CHECK-NEXT: lfence
+; CHECK-NEXT: jmpq *%r11
+}
+
+attributes #0 = { "target-features"="+lvi-cfi" }
+attributes #1 = { "no_caller_saved_registers" "target-features"="+lvi-cfi" }
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