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[PAC][CodeGen][ELF][AArch64] Support signed GOT #113811

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merged 6 commits into from
Nov 1, 2024
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[PAC][CodeGen][ELF][AArch64] Support signed GOT #113811

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932e36a
[PAC][CodeGen][ELF][AArch64] Support signed GOT
kovdan01 Oct 24, 2024
f0044c3
[PAC][CodeGen] Use `emitPtrauthCheckAuthenticatedValue` in `LowerMOVa…
kovdan01 Oct 24, 2024
c1dd585
[PAC][CodeGen] Fix handling of extern_weak symbols with signed GOT
kovdan01 Oct 25, 2024
a5688e5
[PAC][CodeGen] Emit trap sequence w/o FPAC on LOADgotAUTH expansion
kovdan01 Oct 25, 2024
0499aab
Merge branch 'main' into users/kovdan01/pauth-signed-got-codegen
kovdan01 Nov 1, 2024
48ce9aa
Address review comments
kovdan01 Nov 1, 2024
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151 changes: 143 additions & 8 deletions llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -169,6 +169,11 @@ class AArch64AsmPrinter : public AsmPrinter {
// adrp-add followed by PAC sign)
void LowerMOVaddrPAC(const MachineInstr &MI);

// Emit the sequence for LOADgotAUTH (load signed pointer from signed ELF GOT
// and authenticate it with, if FPAC bit is not set, check+trap sequence after
// authenticating)
void LowerLOADgotAUTH(const MachineInstr &MI);

/// tblgen'erated driver function for lowering simple MI->MC
/// pseudo instructions.
bool lowerPseudoInstExpansion(const MachineInstr *MI, MCInst &Inst);
Expand Down Expand Up @@ -873,6 +878,22 @@ void AArch64AsmPrinter::emitEndOfAsmFile(Module &M) {

OutStreamer->addBlankLine();
}

// With signed ELF GOT enabled, the linker looks at the symbol type to
// choose between keys IA (for STT_FUNC) and DA (for other types). Symbols
// for functions not defined in the module have STT_NOTYPE type by default.
// This makes linker to emit signing schema with DA key (instead of IA) for
// corresponding R_AARCH64_AUTH_GLOB_DAT dynamic reloc. To avoid that, force
// all function symbols used in the module to have STT_FUNC type. See
// https://github.com/ARM-software/abi-aa/blob/main/pauthabielf64/pauthabielf64.rst#default-signing-schema
const auto *PtrAuthELFGOTFlag = mdconst::extract_or_null<ConstantInt>(
M.getModuleFlag("ptrauth-elf-got"));
if (PtrAuthELFGOTFlag && PtrAuthELFGOTFlag->getZExtValue() == 1)
for (const GlobalValue &GV : M.global_values())
if (!GV.use_empty() && isa<Function>(GV) &&
!GV.getName().starts_with("llvm."))
OutStreamer->emitSymbolAttribute(getSymbol(&GV),
MCSA_ELF_TypeFunction);
}

// Emit stack and fault map information.
Expand Down Expand Up @@ -2068,6 +2089,10 @@ void AArch64AsmPrinter::LowerLOADauthptrstatic(const MachineInstr &MI) {

void AArch64AsmPrinter::LowerMOVaddrPAC(const MachineInstr &MI) {
const bool IsGOTLoad = MI.getOpcode() == AArch64::LOADgotPAC;
const bool IsELFSignedGOT = MI.getParent()
->getParent()
->getInfo<AArch64FunctionInfo>()
->hasELFSignedGOT();
MachineOperand GAOp = MI.getOperand(0);
const uint64_t KeyC = MI.getOperand(1).getImm();
assert(KeyC <= AArch64PACKey::LAST &&
Expand All @@ -2084,9 +2109,17 @@ void AArch64AsmPrinter::LowerMOVaddrPAC(const MachineInstr &MI) {
// Emit:
// target materialization:
// - via GOT:
// adrp x16, :got:target
// ldr x16, [x16, :got_lo12:target]
// add offset to x16 if offset != 0
// - unsigned GOT:
// adrp x16, :got:target
// ldr x16, [x16, :got_lo12:target]
// add offset to x16 if offset != 0
// - ELF signed GOT:
// adrp x17, :got:target
// add x17, x17, :got_auth_lo12:target
// ldr x16, [x17]
// aut{i|d}a x16, x17
// check+trap sequence (if no FPAC)
// add offset to x16 if offset != 0
//
// - direct:
// adrp x16, target
Expand Down Expand Up @@ -2129,13 +2162,48 @@ void AArch64AsmPrinter::LowerMOVaddrPAC(const MachineInstr &MI) {
MCInstLowering.lowerOperand(GAMOLo, GAMCLo);

EmitToStreamer(
MCInstBuilder(AArch64::ADRP).addReg(AArch64::X16).addOperand(GAMCHi));
MCInstBuilder(AArch64::ADRP)
.addReg(IsGOTLoad && IsELFSignedGOT ? AArch64::X17 : AArch64::X16)
.addOperand(GAMCHi));

if (IsGOTLoad) {
EmitToStreamer(MCInstBuilder(AArch64::LDRXui)
.addReg(AArch64::X16)
.addReg(AArch64::X16)
.addOperand(GAMCLo));
if (IsELFSignedGOT) {
EmitToStreamer(MCInstBuilder(AArch64::ADDXri)
.addReg(AArch64::X17)
.addReg(AArch64::X17)
.addOperand(GAMCLo)
.addImm(0));

EmitToStreamer(MCInstBuilder(AArch64::LDRXui)
.addReg(AArch64::X16)
.addReg(AArch64::X17)
.addImm(0));

assert(GAOp.isGlobal());
assert(GAOp.getGlobal()->getValueType() != nullptr);
unsigned AuthOpcode = GAOp.getGlobal()->getValueType()->isFunctionTy()
? AArch64::AUTIA
: AArch64::AUTDA;

EmitToStreamer(MCInstBuilder(AuthOpcode)
.addReg(AArch64::X16)
.addReg(AArch64::X16)
.addReg(AArch64::X17));

if (!STI->hasFPAC()) {
auto AuthKey = (AuthOpcode == AArch64::AUTIA ? AArch64PACKey::IA
: AArch64PACKey::DA);

emitPtrauthCheckAuthenticatedValue(AArch64::X16, AArch64::X17, AuthKey,
/*ShouldTrap=*/true,
/*OnFailure=*/nullptr);
}
} else {
EmitToStreamer(MCInstBuilder(AArch64::LDRXui)
.addReg(AArch64::X16)
.addReg(AArch64::X16)
.addOperand(GAMCLo));
}
} else {
EmitToStreamer(MCInstBuilder(AArch64::ADDXri)
.addReg(AArch64::X16)
Expand Down Expand Up @@ -2203,6 +2271,69 @@ void AArch64AsmPrinter::LowerMOVaddrPAC(const MachineInstr &MI) {
EmitToStreamer(MIB);
}

void AArch64AsmPrinter::LowerLOADgotAUTH(const MachineInstr &MI) {
Register DstReg = MI.getOperand(0).getReg();
Register AuthResultReg = STI->hasFPAC() ? DstReg : AArch64::X16;
const MachineOperand &GAMO = MI.getOperand(1);
assert(GAMO.getOffset() == 0);

MachineOperand GAHiOp(GAMO);
MachineOperand GALoOp(GAMO);
GAHiOp.addTargetFlag(AArch64II::MO_PAGE);
GALoOp.addTargetFlag(AArch64II::MO_PAGEOFF | AArch64II::MO_NC);

MCOperand GAMCHi, GAMCLo;
MCInstLowering.lowerOperand(GAHiOp, GAMCHi);
MCInstLowering.lowerOperand(GALoOp, GAMCLo);

EmitToStreamer(
MCInstBuilder(AArch64::ADRP).addReg(AArch64::X17).addOperand(GAMCHi));

EmitToStreamer(MCInstBuilder(AArch64::ADDXri)
.addReg(AArch64::X17)
.addReg(AArch64::X17)
.addOperand(GAMCLo)
.addImm(0));

EmitToStreamer(MCInstBuilder(AArch64::LDRXui)
.addReg(AuthResultReg)
.addReg(AArch64::X17)
.addImm(0));

assert(GAMO.isGlobal());
MCSymbol *UndefWeakSym;
if (GAMO.getGlobal()->hasExternalWeakLinkage()) {
UndefWeakSym = createTempSymbol("undef_weak");
EmitToStreamer(
MCInstBuilder(AArch64::CBZX)
.addReg(AuthResultReg)
.addExpr(MCSymbolRefExpr::create(UndefWeakSym, OutContext)));
}

assert(GAMO.getGlobal()->getValueType() != nullptr);
unsigned AuthOpcode = GAMO.getGlobal()->getValueType()->isFunctionTy()
? AArch64::AUTIA
: AArch64::AUTDA;
EmitToStreamer(MCInstBuilder(AuthOpcode)
.addReg(AuthResultReg)
.addReg(AuthResultReg)
.addReg(AArch64::X17));

if (GAMO.getGlobal()->hasExternalWeakLinkage())
OutStreamer->emitLabel(UndefWeakSym);

if (!STI->hasFPAC()) {
auto AuthKey =
(AuthOpcode == AArch64::AUTIA ? AArch64PACKey::IA : AArch64PACKey::DA);

emitPtrauthCheckAuthenticatedValue(AuthResultReg, AArch64::X17, AuthKey,
/*ShouldTrap=*/true,
/*OnFailure=*/nullptr);

emitMovXReg(DstReg, AuthResultReg);
}
}

const MCExpr *
AArch64AsmPrinter::lowerBlockAddressConstant(const BlockAddress &BA) {
const MCExpr *BAE = AsmPrinter::lowerBlockAddressConstant(BA);
Expand Down Expand Up @@ -2381,6 +2512,10 @@ void AArch64AsmPrinter::emitInstruction(const MachineInstr *MI) {
LowerMOVaddrPAC(*MI);
return;

case AArch64::LOADgotAUTH:
LowerLOADgotAUTH(*MI);
return;

case AArch64::BRA:
case AArch64::BLRA:
emitPtrauthBranch(MI);
Expand Down
3 changes: 3 additions & 0 deletions llvm/lib/Target/AArch64/AArch64FastISel.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -453,6 +453,9 @@ unsigned AArch64FastISel::materializeGV(const GlobalValue *GV) {
if (!Subtarget->useSmallAddressing() && !Subtarget->isTargetMachO())
return 0;

if (FuncInfo.MF->getInfo<AArch64FunctionInfo>()->hasELFSignedGOT())
return 0;

unsigned OpFlags = Subtarget->ClassifyGlobalReference(GV, TM);

EVT DestEVT = TLI.getValueType(DL, GV->getType(), true);
Expand Down
5 changes: 5 additions & 0 deletions llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
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Expand Up @@ -9598,6 +9598,11 @@ SDValue AArch64TargetLowering::getGOT(NodeTy *N, SelectionDAG &DAG,
SDValue GotAddr = getTargetNode(N, Ty, DAG, AArch64II::MO_GOT | Flags);
// FIXME: Once remat is capable of dealing with instructions with register
// operands, expand this into two nodes instead of using a wrapper node.
if (DAG.getMachineFunction()
.getInfo<AArch64FunctionInfo>()
->hasELFSignedGOT())
return SDValue(DAG.getMachineNode(AArch64::LOADgotAUTH, DL, Ty, GotAddr),
0);
return DAG.getNode(AArch64ISD::LOADgot, DL, Ty, GotAddr);
}

Expand Down
11 changes: 9 additions & 2 deletions llvm/lib/Target/AArch64/AArch64InstrInfo.td
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Expand Up @@ -1937,8 +1937,15 @@ let Predicates = [HasPAuth] in {
Sched<[WriteI, ReadI]> {
let isReMaterializable = 1;
let isCodeGenOnly = 1;
let Size = 40; // 12 fixed + 28 variable, for pointer offset, and discriminator
let Defs = [X16,X17];
let Size = 68; // 12 fixed + 56 variable, for pointer offset, discriminator and
// ELF signed GOT signed pointer authentication (if no FPAC)
let Defs = [X16,X17,NZCV];
}

def LOADgotAUTH : Pseudo<(outs GPR64common:$dst), (ins i64imm:$addr), []>,
Sched<[WriteI, ReadI]> {
let Defs = [X16,X17,NZCV];
let Size = 44;
}

// Load a signed global address from a special $auth_ptr$ stub slot.
Expand Down
10 changes: 7 additions & 3 deletions llvm/lib/Target/AArch64/AArch64MCInstLower.cpp
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Expand Up @@ -12,6 +12,7 @@
//===----------------------------------------------------------------------===//

#include "AArch64MCInstLower.h"
#include "AArch64MachineFunctionInfo.h"
#include "MCTargetDesc/AArch64MCExpr.h"
#include "Utils/AArch64BaseInfo.h"
#include "llvm/CodeGen/AsmPrinter.h"
Expand Down Expand Up @@ -185,9 +186,12 @@ MCOperand AArch64MCInstLower::lowerSymbolOperandELF(const MachineOperand &MO,
MCSymbol *Sym) const {
uint32_t RefFlags = 0;

if (MO.getTargetFlags() & AArch64II::MO_GOT)
RefFlags |= AArch64MCExpr::VK_GOT;
else if (MO.getTargetFlags() & AArch64II::MO_TLS) {
if (MO.getTargetFlags() & AArch64II::MO_GOT) {
const MachineFunction *MF = MO.getParent()->getParent()->getParent();
RefFlags |= (MF->getInfo<AArch64FunctionInfo>()->hasELFSignedGOT()
? AArch64MCExpr::VK_GOT_AUTH
: AArch64MCExpr::VK_GOT);
} else if (MO.getTargetFlags() & AArch64II::MO_TLS) {
TLSModel::Model Model;
if (MO.isGlobal()) {
const GlobalValue *GV = MO.getGlobal();
Expand Down
13 changes: 13 additions & 0 deletions llvm/lib/Target/AArch64/AArch64MachineFunctionInfo.cpp
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Expand Up @@ -72,6 +72,18 @@ static bool ShouldSignWithBKey(const Function &F, const AArch64Subtarget &STI) {
return Key == "b_key";
}

static bool HasELFSignedGOTHelper(const Function &F,
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hasELF... (fix style when adding new functions)

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Fixed, thanks! See 48ce9aa

const AArch64Subtarget *STI) {
if (!Triple(STI->getTargetTriple()).isOSBinFormatELF())
return false;
const Module *M = F.getParent();
const auto *Flag = mdconst::extract_or_null<ConstantInt>(
M->getModuleFlag("ptrauth-elf-got"));
if (Flag && Flag->getZExtValue() == 1)
return true;
return false;
}

AArch64FunctionInfo::AArch64FunctionInfo(const Function &F,
const AArch64Subtarget *STI) {
// If we already know that the function doesn't have a redzone, set
Expand All @@ -80,6 +92,7 @@ AArch64FunctionInfo::AArch64FunctionInfo(const Function &F,
HasRedZone = false;
std::tie(SignReturnAddress, SignReturnAddressAll) = GetSignReturnAddress(F);
SignWithBKey = ShouldSignWithBKey(F, *STI);
HasELFSignedGOT = HasELFSignedGOTHelper(F, STI);
// TODO: skip functions that have no instrumented allocas for optimization
IsMTETagged = F.hasFnAttribute(Attribute::SanitizeMemTag);

Expand Down
7 changes: 7 additions & 0 deletions llvm/lib/Target/AArch64/AArch64MachineFunctionInfo.h
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Expand Up @@ -177,6 +177,11 @@ class AArch64FunctionInfo final : public MachineFunctionInfo {
/// SignWithBKey modifies the default PAC-RET mode to signing with the B key.
bool SignWithBKey = false;

/// HasELFSignedGOT is true if the target binary format is ELF and the IR
/// module containing the corresponding function has "ptrauth-elf-got" flag
/// set to 1.
bool HasELFSignedGOT = false;

/// SigningInstrOffset captures the offset of the PAC-RET signing instruction
/// within the prologue, so it can be re-used for authentication in the
/// epilogue when using PC as a second salt (FEAT_PAuth_LR)
Expand Down Expand Up @@ -509,6 +514,8 @@ class AArch64FunctionInfo final : public MachineFunctionInfo {

bool shouldSignWithBKey() const { return SignWithBKey; }

bool hasELFSignedGOT() const { return HasELFSignedGOT; }

MCSymbol *getSigningInstrLabel() const { return SignInstrLabel; }
void setSigningInstrLabel(MCSymbol *Label) { SignInstrLabel = Label; }

Expand Down
32 changes: 19 additions & 13 deletions llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
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Expand Up @@ -896,6 +896,7 @@ class AArch64Operand : public MCParsedAsmOperand {
if (DarwinRefKind == MCSymbolRefExpr::VK_PAGEOFF ||
ELFRefKind == AArch64MCExpr::VK_LO12 ||
ELFRefKind == AArch64MCExpr::VK_GOT_LO12 ||
ELFRefKind == AArch64MCExpr::VK_GOT_AUTH_LO12 ||
ELFRefKind == AArch64MCExpr::VK_DTPREL_LO12 ||
ELFRefKind == AArch64MCExpr::VK_DTPREL_LO12_NC ||
ELFRefKind == AArch64MCExpr::VK_TPREL_LO12 ||
Expand Down Expand Up @@ -1007,19 +1008,20 @@ class AArch64Operand : public MCParsedAsmOperand {
int64_t Addend;
if (AArch64AsmParser::classifySymbolRef(Expr, ELFRefKind,
DarwinRefKind, Addend)) {
return DarwinRefKind == MCSymbolRefExpr::VK_PAGEOFF
|| DarwinRefKind == MCSymbolRefExpr::VK_TLVPPAGEOFF
|| (DarwinRefKind == MCSymbolRefExpr::VK_GOTPAGEOFF && Addend == 0)
|| ELFRefKind == AArch64MCExpr::VK_LO12
|| ELFRefKind == AArch64MCExpr::VK_DTPREL_HI12
|| ELFRefKind == AArch64MCExpr::VK_DTPREL_LO12
|| ELFRefKind == AArch64MCExpr::VK_DTPREL_LO12_NC
|| ELFRefKind == AArch64MCExpr::VK_TPREL_HI12
|| ELFRefKind == AArch64MCExpr::VK_TPREL_LO12
|| ELFRefKind == AArch64MCExpr::VK_TPREL_LO12_NC
|| ELFRefKind == AArch64MCExpr::VK_TLSDESC_LO12
|| ELFRefKind == AArch64MCExpr::VK_SECREL_HI12
|| ELFRefKind == AArch64MCExpr::VK_SECREL_LO12;
return DarwinRefKind == MCSymbolRefExpr::VK_PAGEOFF ||
DarwinRefKind == MCSymbolRefExpr::VK_TLVPPAGEOFF ||
(DarwinRefKind == MCSymbolRefExpr::VK_GOTPAGEOFF && Addend == 0) ||
ELFRefKind == AArch64MCExpr::VK_LO12 ||
ELFRefKind == AArch64MCExpr::VK_GOT_AUTH_LO12 ||
ELFRefKind == AArch64MCExpr::VK_DTPREL_HI12 ||
ELFRefKind == AArch64MCExpr::VK_DTPREL_LO12 ||
ELFRefKind == AArch64MCExpr::VK_DTPREL_LO12_NC ||
ELFRefKind == AArch64MCExpr::VK_TPREL_HI12 ||
ELFRefKind == AArch64MCExpr::VK_TPREL_LO12 ||
ELFRefKind == AArch64MCExpr::VK_TPREL_LO12_NC ||
ELFRefKind == AArch64MCExpr::VK_TLSDESC_LO12 ||
ELFRefKind == AArch64MCExpr::VK_SECREL_HI12 ||
ELFRefKind == AArch64MCExpr::VK_SECREL_LO12;
}

// If it's a constant, it should be a real immediate in range.
Expand Down Expand Up @@ -3308,6 +3310,7 @@ ParseStatus AArch64AsmParser::tryParseAdrpLabel(OperandVector &Operands) {
DarwinRefKind != MCSymbolRefExpr::VK_TLVPPAGE &&
ELFRefKind != AArch64MCExpr::VK_ABS_PAGE_NC &&
ELFRefKind != AArch64MCExpr::VK_GOT_PAGE &&
ELFRefKind != AArch64MCExpr::VK_GOT_AUTH_PAGE &&
ELFRefKind != AArch64MCExpr::VK_GOT_PAGE_LO15 &&
ELFRefKind != AArch64MCExpr::VK_GOTTPREL_PAGE &&
ELFRefKind != AArch64MCExpr::VK_TLSDESC_PAGE) {
Expand Down Expand Up @@ -4427,6 +4430,8 @@ bool AArch64AsmParser::parseSymbolicImmVal(const MCExpr *&ImmVal) {
.Case("got", AArch64MCExpr::VK_GOT_PAGE)
.Case("gotpage_lo15", AArch64MCExpr::VK_GOT_PAGE_LO15)
.Case("got_lo12", AArch64MCExpr::VK_GOT_LO12)
.Case("got_auth", AArch64MCExpr::VK_GOT_AUTH_PAGE)
.Case("got_auth_lo12", AArch64MCExpr::VK_GOT_AUTH_LO12)
.Case("gottprel", AArch64MCExpr::VK_GOTTPREL_PAGE)
.Case("gottprel_lo12", AArch64MCExpr::VK_GOTTPREL_LO12_NC)
.Case("gottprel_g1", AArch64MCExpr::VK_GOTTPREL_G1)
Expand Down Expand Up @@ -5800,6 +5805,7 @@ bool AArch64AsmParser::validateInstruction(MCInst &Inst, SMLoc &IDLoc,

// Only allow these with ADDXri/ADDWri
if ((ELFRefKind == AArch64MCExpr::VK_LO12 ||
ELFRefKind == AArch64MCExpr::VK_GOT_AUTH_LO12 ||
ELFRefKind == AArch64MCExpr::VK_DTPREL_HI12 ||
ELFRefKind == AArch64MCExpr::VK_DTPREL_LO12 ||
ELFRefKind == AArch64MCExpr::VK_DTPREL_LO12_NC ||
Expand Down
4 changes: 3 additions & 1 deletion llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
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Expand Up @@ -2959,7 +2959,9 @@ bool AArch64InstructionSelector::select(MachineInstr &I) {
}

if (OpFlags & AArch64II::MO_GOT) {
I.setDesc(TII.get(AArch64::LOADgot));
I.setDesc(TII.get(MF.getInfo<AArch64FunctionInfo>()->hasELFSignedGOT()
? AArch64::LOADgotAUTH
: AArch64::LOADgot));
I.getOperand(1).setTargetFlags(OpFlags);
} else if (TM.getCodeModel() == CodeModel::Large &&
!TM.isPositionIndependent()) {
Expand Down
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