diff options
Diffstat (limited to 'contrib/llvm-project/llvm/lib/Target/ARM/ARMSLSHardening.cpp')
-rw-r--r-- | contrib/llvm-project/llvm/lib/Target/ARM/ARMSLSHardening.cpp | 416 |
1 files changed, 416 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/Target/ARM/ARMSLSHardening.cpp b/contrib/llvm-project/llvm/lib/Target/ARM/ARMSLSHardening.cpp new file mode 100644 index 000000000000..cfcc7d5a0408 --- /dev/null +++ b/contrib/llvm-project/llvm/lib/Target/ARM/ARMSLSHardening.cpp @@ -0,0 +1,416 @@ +//===- ARMSLSHardening.cpp - Harden Straight Line Missspeculation ---------===// +// +// 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 +// +//===----------------------------------------------------------------------===// +// +// This file contains a pass to insert code to mitigate against side channel +// vulnerabilities that may happen under straight line miss-speculation. +// +//===----------------------------------------------------------------------===// + +#include "ARM.h" +#include "ARMInstrInfo.h" +#include "ARMSubtarget.h" +#include "llvm/CodeGen/IndirectThunks.h" +#include "llvm/CodeGen/MachineBasicBlock.h" +#include "llvm/CodeGen/MachineFunction.h" +#include "llvm/CodeGen/MachineFunctionPass.h" +#include "llvm/CodeGen/MachineInstr.h" +#include "llvm/CodeGen/MachineInstrBuilder.h" +#include "llvm/CodeGen/MachineOperand.h" +#include "llvm/IR/DebugLoc.h" +#include <cassert> + +using namespace llvm; + +#define DEBUG_TYPE "arm-sls-hardening" + +#define ARM_SLS_HARDENING_NAME "ARM sls hardening pass" + +namespace { + +class ARMSLSHardening : public MachineFunctionPass { +public: + const TargetInstrInfo *TII; + const ARMSubtarget *ST; + + static char ID; + + ARMSLSHardening() : MachineFunctionPass(ID) { + initializeARMSLSHardeningPass(*PassRegistry::getPassRegistry()); + } + + bool runOnMachineFunction(MachineFunction &Fn) override; + + StringRef getPassName() const override { return ARM_SLS_HARDENING_NAME; } + + void getAnalysisUsage(AnalysisUsage &AU) const override { + AU.setPreservesCFG(); + MachineFunctionPass::getAnalysisUsage(AU); + } + +private: + bool hardenReturnsAndBRs(MachineBasicBlock &MBB) const; + bool hardenIndirectCalls(MachineBasicBlock &MBB) const; + MachineBasicBlock & + ConvertIndirectCallToIndirectJump(MachineBasicBlock &MBB, + MachineBasicBlock::iterator) const; +}; + +} // end anonymous namespace + +char ARMSLSHardening::ID = 0; + +INITIALIZE_PASS(ARMSLSHardening, "arm-sls-hardening", + ARM_SLS_HARDENING_NAME, false, false) + +static void insertSpeculationBarrier(const ARMSubtarget *ST, + MachineBasicBlock &MBB, + MachineBasicBlock::iterator MBBI, + DebugLoc DL, + bool AlwaysUseISBDSB = false) { + assert(MBBI != MBB.begin() && + "Must not insert SpeculationBarrierEndBB as only instruction in MBB."); + assert(std::prev(MBBI)->isBarrier() && + "SpeculationBarrierEndBB must only follow unconditional control flow " + "instructions."); + assert(std::prev(MBBI)->isTerminator() && + "SpeculationBarrierEndBB must only follow terminators."); + const TargetInstrInfo *TII = ST->getInstrInfo(); + assert(ST->hasDataBarrier() || ST->hasSB()); + bool ProduceSB = ST->hasSB() && !AlwaysUseISBDSB; + unsigned BarrierOpc = + ProduceSB ? (ST->isThumb() ? ARM::t2SpeculationBarrierSBEndBB + : ARM::SpeculationBarrierSBEndBB) + : (ST->isThumb() ? ARM::t2SpeculationBarrierISBDSBEndBB + : ARM::SpeculationBarrierISBDSBEndBB); + if (MBBI == MBB.end() || !isSpeculationBarrierEndBBOpcode(MBBI->getOpcode())) + BuildMI(MBB, MBBI, DL, TII->get(BarrierOpc)); +} + +bool ARMSLSHardening::runOnMachineFunction(MachineFunction &MF) { + ST = &MF.getSubtarget<ARMSubtarget>(); + TII = MF.getSubtarget().getInstrInfo(); + + bool Modified = false; + for (auto &MBB : MF) { + Modified |= hardenReturnsAndBRs(MBB); + Modified |= hardenIndirectCalls(MBB); + } + + return Modified; +} + +bool ARMSLSHardening::hardenReturnsAndBRs(MachineBasicBlock &MBB) const { + if (!ST->hardenSlsRetBr()) + return false; + assert(!ST->isThumb1Only()); + bool Modified = false; + MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator(), E = MBB.end(); + MachineBasicBlock::iterator NextMBBI; + for (; MBBI != E; MBBI = NextMBBI) { + MachineInstr &MI = *MBBI; + NextMBBI = std::next(MBBI); + if (isIndirectControlFlowNotComingBack(MI)) { + assert(MI.isTerminator()); + assert(!TII->isPredicated(MI)); + insertSpeculationBarrier(ST, MBB, std::next(MBBI), MI.getDebugLoc()); + Modified = true; + } + } + return Modified; +} + +static const char SLSBLRNamePrefix[] = "__llvm_slsblr_thunk_"; + +static const struct ThunkNameRegMode { + const char* Name; + Register Reg; + bool isThumb; +} SLSBLRThunks[] = { + {"__llvm_slsblr_thunk_arm_r0", ARM::R0, false}, + {"__llvm_slsblr_thunk_arm_r1", ARM::R1, false}, + {"__llvm_slsblr_thunk_arm_r2", ARM::R2, false}, + {"__llvm_slsblr_thunk_arm_r3", ARM::R3, false}, + {"__llvm_slsblr_thunk_arm_r4", ARM::R4, false}, + {"__llvm_slsblr_thunk_arm_r5", ARM::R5, false}, + {"__llvm_slsblr_thunk_arm_r6", ARM::R6, false}, + {"__llvm_slsblr_thunk_arm_r7", ARM::R7, false}, + {"__llvm_slsblr_thunk_arm_r8", ARM::R8, false}, + {"__llvm_slsblr_thunk_arm_r9", ARM::R9, false}, + {"__llvm_slsblr_thunk_arm_r10", ARM::R10, false}, + {"__llvm_slsblr_thunk_arm_r11", ARM::R11, false}, + {"__llvm_slsblr_thunk_arm_sp", ARM::SP, false}, + {"__llvm_slsblr_thunk_arm_pc", ARM::PC, false}, + {"__llvm_slsblr_thunk_thumb_r0", ARM::R0, true}, + {"__llvm_slsblr_thunk_thumb_r1", ARM::R1, true}, + {"__llvm_slsblr_thunk_thumb_r2", ARM::R2, true}, + {"__llvm_slsblr_thunk_thumb_r3", ARM::R3, true}, + {"__llvm_slsblr_thunk_thumb_r4", ARM::R4, true}, + {"__llvm_slsblr_thunk_thumb_r5", ARM::R5, true}, + {"__llvm_slsblr_thunk_thumb_r6", ARM::R6, true}, + {"__llvm_slsblr_thunk_thumb_r7", ARM::R7, true}, + {"__llvm_slsblr_thunk_thumb_r8", ARM::R8, true}, + {"__llvm_slsblr_thunk_thumb_r9", ARM::R9, true}, + {"__llvm_slsblr_thunk_thumb_r10", ARM::R10, true}, + {"__llvm_slsblr_thunk_thumb_r11", ARM::R11, true}, + {"__llvm_slsblr_thunk_thumb_sp", ARM::SP, true}, + {"__llvm_slsblr_thunk_thumb_pc", ARM::PC, true}, +}; + +namespace { +struct SLSBLRThunkInserter : ThunkInserter<SLSBLRThunkInserter> { + const char *getThunkPrefix() { return SLSBLRNamePrefix; } + bool mayUseThunk(const MachineFunction &MF) { + // FIXME: This could also check if there are any indirect calls in the + // function to more accurately reflect if a thunk will be needed. + return MF.getSubtarget<ARMSubtarget>().hardenSlsBlr(); + } + void insertThunks(MachineModuleInfo &MMI); + void populateThunk(MachineFunction &MF); +}; +} // namespace + +void SLSBLRThunkInserter::insertThunks(MachineModuleInfo &MMI) { + // FIXME: It probably would be possible to filter which thunks to produce + // based on which registers are actually used in indirect calls in this + // function. But would that be a worthwhile optimization? + for (auto T : SLSBLRThunks) + createThunkFunction(MMI, T.Name); +} + +void SLSBLRThunkInserter::populateThunk(MachineFunction &MF) { + // FIXME: How to better communicate Register number, rather than through + // name and lookup table? + assert(MF.getName().startswith(getThunkPrefix())); + auto ThunkIt = llvm::find_if( + SLSBLRThunks, [&MF](auto T) { return T.Name == MF.getName(); }); + assert(ThunkIt != std::end(SLSBLRThunks)); + Register ThunkReg = ThunkIt->Reg; + bool isThumb = ThunkIt->isThumb; + + const TargetInstrInfo *TII = MF.getSubtarget<ARMSubtarget>().getInstrInfo(); + MachineBasicBlock *Entry = &MF.front(); + Entry->clear(); + + // These thunks need to consist of the following instructions: + // __llvm_slsblr_thunk_(arm/thumb)_rN: + // bx rN + // barrierInsts + Entry->addLiveIn(ThunkReg); + if (isThumb) + BuildMI(Entry, DebugLoc(), TII->get(ARM::tBX)) + .addReg(ThunkReg) + .add(predOps(ARMCC::AL)); + else + BuildMI(Entry, DebugLoc(), TII->get(ARM::BX)) + .addReg(ThunkReg); + + // Make sure the thunks do not make use of the SB extension in case there is + // a function somewhere that will call to it that for some reason disabled + // the SB extension locally on that function, even though it's enabled for + // the module otherwise. Therefore set AlwaysUseISBSDB to true. + insertSpeculationBarrier(&MF.getSubtarget<ARMSubtarget>(), *Entry, + Entry->end(), DebugLoc(), true /*AlwaysUseISBDSB*/); +} + +MachineBasicBlock &ARMSLSHardening::ConvertIndirectCallToIndirectJump( + MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI) const { + // Transform an indirect call to an indirect jump as follows: + // Before: + // |-----------------------------| + // | ... | + // | instI | + // | BLX rN | + // | instJ | + // | ... | + // |-----------------------------| + // + // After: + // |---------- -------------------------| + // | ... | + // | instI | + // | *call* __llvm_slsblr_thunk_mode_xN | + // | instJ | + // | ... | + // |--------------------------------------| + // + // __llvm_slsblr_thunk_mode_xN: + // |-----------------------------| + // | BX rN | + // | barrierInsts | + // |-----------------------------| + // + // The __llvm_slsblr_thunk_mode_xN thunks are created by the + // SLSBLRThunkInserter. + // This function merely needs to transform an indirect call to a direct call + // to __llvm_slsblr_thunk_xN. + MachineInstr &IndirectCall = *MBBI; + assert(isIndirectCall(IndirectCall) && !IndirectCall.isReturn()); + int RegOpIdxOnIndirectCall = -1; + bool isThumb; + switch (IndirectCall.getOpcode()) { + case ARM::BLX: // !isThumb2 + case ARM::BLX_noip: // !isThumb2 + isThumb = false; + RegOpIdxOnIndirectCall = 0; + break; + case ARM::tBLXr: // isThumb2 + case ARM::tBLXr_noip: // isThumb2 + isThumb = true; + RegOpIdxOnIndirectCall = 2; + break; + default: + llvm_unreachable("unhandled Indirect Call"); + } + + Register Reg = IndirectCall.getOperand(RegOpIdxOnIndirectCall).getReg(); + // Since linkers are allowed to clobber R12 on function calls, the above + // mitigation only works if the original indirect call instruction was not + // using R12. Code generation before must make sure that no indirect call + // using R12 was produced if the mitigation is enabled. + // Also, the transformation is incorrect if the indirect call uses LR, so + // also have to avoid that. + assert(Reg != ARM::R12 && Reg != ARM::LR); + bool RegIsKilled = IndirectCall.getOperand(RegOpIdxOnIndirectCall).isKill(); + + DebugLoc DL = IndirectCall.getDebugLoc(); + + MachineFunction &MF = *MBBI->getMF(); + auto ThunkIt = llvm::find_if(SLSBLRThunks, [Reg, isThumb](auto T) { + return T.Reg == Reg && T.isThumb == isThumb; + }); + assert(ThunkIt != std::end(SLSBLRThunks)); + Module *M = MF.getFunction().getParent(); + const GlobalValue *GV = cast<GlobalValue>(M->getNamedValue(ThunkIt->Name)); + + MachineInstr *BL = + isThumb ? BuildMI(MBB, MBBI, DL, TII->get(ARM::tBL)) + .addImm(IndirectCall.getOperand(0).getImm()) + .addReg(IndirectCall.getOperand(1).getReg()) + .addGlobalAddress(GV) + : BuildMI(MBB, MBBI, DL, TII->get(ARM::BL)).addGlobalAddress(GV); + + // Now copy the implicit operands from IndirectCall to BL and copy other + // necessary info. + // However, both IndirectCall and BL instructions implictly use SP and + // implicitly define LR. Blindly copying implicit operands would result in SP + // and LR operands to be present multiple times. While this may not be too + // much of an issue, let's avoid that for cleanliness, by removing those + // implicit operands from the BL created above before we copy over all + // implicit operands from the IndirectCall. + int ImpLROpIdx = -1; + int ImpSPOpIdx = -1; + for (unsigned OpIdx = BL->getNumExplicitOperands(); + OpIdx < BL->getNumOperands(); OpIdx++) { + MachineOperand Op = BL->getOperand(OpIdx); + if (!Op.isReg()) + continue; + if (Op.getReg() == ARM::LR && Op.isDef()) + ImpLROpIdx = OpIdx; + if (Op.getReg() == ARM::SP && !Op.isDef()) + ImpSPOpIdx = OpIdx; + } + assert(ImpLROpIdx != -1); + assert(ImpSPOpIdx != -1); + int FirstOpIdxToRemove = std::max(ImpLROpIdx, ImpSPOpIdx); + int SecondOpIdxToRemove = std::min(ImpLROpIdx, ImpSPOpIdx); + BL->RemoveOperand(FirstOpIdxToRemove); + BL->RemoveOperand(SecondOpIdxToRemove); + // Now copy over the implicit operands from the original IndirectCall + BL->copyImplicitOps(MF, IndirectCall); + MF.moveCallSiteInfo(&IndirectCall, BL); + // Also add the register called in the IndirectCall as being used in the + // called thunk. + BL->addOperand(MachineOperand::CreateReg(Reg, false /*isDef*/, true /*isImp*/, + RegIsKilled /*isKill*/)); + // Remove IndirectCallinstruction + MBB.erase(MBBI); + return MBB; +} + +bool ARMSLSHardening::hardenIndirectCalls(MachineBasicBlock &MBB) const { + if (!ST->hardenSlsBlr()) + return false; + bool Modified = false; + MachineBasicBlock::iterator MBBI = MBB.begin(), E = MBB.end(); + MachineBasicBlock::iterator NextMBBI; + for (; MBBI != E; MBBI = NextMBBI) { + MachineInstr &MI = *MBBI; + NextMBBI = std::next(MBBI); + // Tail calls are both indirect calls and "returns". + // They are also indirect jumps, so should be handled by sls-harden-retbr, + // rather than sls-harden-blr. + if (isIndirectCall(MI) && !MI.isReturn()) { + ConvertIndirectCallToIndirectJump(MBB, MBBI); + Modified = true; + } + } + return Modified; +} + + + +FunctionPass *llvm::createARMSLSHardeningPass() { + return new ARMSLSHardening(); +} + +namespace { +class ARMIndirectThunks : public MachineFunctionPass { +public: + static char ID; + + ARMIndirectThunks() : MachineFunctionPass(ID) {} + + StringRef getPassName() const override { return "ARM Indirect Thunks"; } + + bool doInitialization(Module &M) override; + bool runOnMachineFunction(MachineFunction &MF) override; + + void getAnalysisUsage(AnalysisUsage &AU) const override { + MachineFunctionPass::getAnalysisUsage(AU); + AU.addRequired<MachineModuleInfoWrapperPass>(); + AU.addPreserved<MachineModuleInfoWrapperPass>(); + } + +private: + std::tuple<SLSBLRThunkInserter> TIs; + + // FIXME: When LLVM moves to C++17, these can become folds + template <typename... ThunkInserterT> + static void initTIs(Module &M, + std::tuple<ThunkInserterT...> &ThunkInserters) { + (void)std::initializer_list<int>{ + (std::get<ThunkInserterT>(ThunkInserters).init(M), 0)...}; + } + template <typename... ThunkInserterT> + static bool runTIs(MachineModuleInfo &MMI, MachineFunction &MF, + std::tuple<ThunkInserterT...> &ThunkInserters) { + bool Modified = false; + (void)std::initializer_list<int>{ + Modified |= std::get<ThunkInserterT>(ThunkInserters).run(MMI, MF)...}; + return Modified; + } +}; + +} // end anonymous namespace + +char ARMIndirectThunks::ID = 0; + +FunctionPass *llvm::createARMIndirectThunks() { + return new ARMIndirectThunks(); +} + +bool ARMIndirectThunks::doInitialization(Module &M) { + initTIs(M, TIs); + return false; +} + +bool ARMIndirectThunks::runOnMachineFunction(MachineFunction &MF) { + LLVM_DEBUG(dbgs() << getPassName() << '\n'); + auto &MMI = getAnalysis<MachineModuleInfoWrapperPass>().getMMI(); + return runTIs(MMI, MF, TIs); +} |