llvm-project/llvm/lib/MC/MCWin64EH.cpp

597 lines
19 KiB
C++

//===- lib/MC/MCWin64EH.cpp - MCWin64EH implementation --------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCWin64EH.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCObjectStreamer.h"
#include "llvm/MC/MCSectionCOFF.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/Win64EH.h"
using namespace llvm;
// NOTE: All relocations generated here are 4-byte image-relative.
static uint8_t CountOfUnwindCodes(std::vector<WinEH::Instruction> &Insns) {
uint8_t Count = 0;
for (const auto &I : Insns) {
switch (static_cast<Win64EH::UnwindOpcodes>(I.Operation)) {
default:
llvm_unreachable("Unsupported unwind code");
case Win64EH::UOP_PushNonVol:
case Win64EH::UOP_AllocSmall:
case Win64EH::UOP_SetFPReg:
case Win64EH::UOP_PushMachFrame:
Count += 1;
break;
case Win64EH::UOP_SaveNonVol:
case Win64EH::UOP_SaveXMM128:
Count += 2;
break;
case Win64EH::UOP_SaveNonVolBig:
case Win64EH::UOP_SaveXMM128Big:
Count += 3;
break;
case Win64EH::UOP_AllocLarge:
Count += (I.Offset > 512 * 1024 - 8) ? 3 : 2;
break;
}
}
return Count;
}
static void EmitAbsDifference(MCStreamer &Streamer, const MCSymbol *LHS,
const MCSymbol *RHS) {
MCContext &Context = Streamer.getContext();
const MCExpr *Diff =
MCBinaryExpr::createSub(MCSymbolRefExpr::create(LHS, Context),
MCSymbolRefExpr::create(RHS, Context), Context);
Streamer.EmitValue(Diff, 1);
}
static void EmitUnwindCode(MCStreamer &streamer, const MCSymbol *begin,
WinEH::Instruction &inst) {
uint8_t b2;
uint16_t w;
b2 = (inst.Operation & 0x0F);
switch (static_cast<Win64EH::UnwindOpcodes>(inst.Operation)) {
default:
llvm_unreachable("Unsupported unwind code");
case Win64EH::UOP_PushNonVol:
EmitAbsDifference(streamer, inst.Label, begin);
b2 |= (inst.Register & 0x0F) << 4;
streamer.EmitIntValue(b2, 1);
break;
case Win64EH::UOP_AllocLarge:
EmitAbsDifference(streamer, inst.Label, begin);
if (inst.Offset > 512 * 1024 - 8) {
b2 |= 0x10;
streamer.EmitIntValue(b2, 1);
w = inst.Offset & 0xFFF8;
streamer.EmitIntValue(w, 2);
w = inst.Offset >> 16;
} else {
streamer.EmitIntValue(b2, 1);
w = inst.Offset >> 3;
}
streamer.EmitIntValue(w, 2);
break;
case Win64EH::UOP_AllocSmall:
b2 |= (((inst.Offset - 8) >> 3) & 0x0F) << 4;
EmitAbsDifference(streamer, inst.Label, begin);
streamer.EmitIntValue(b2, 1);
break;
case Win64EH::UOP_SetFPReg:
EmitAbsDifference(streamer, inst.Label, begin);
streamer.EmitIntValue(b2, 1);
break;
case Win64EH::UOP_SaveNonVol:
case Win64EH::UOP_SaveXMM128:
b2 |= (inst.Register & 0x0F) << 4;
EmitAbsDifference(streamer, inst.Label, begin);
streamer.EmitIntValue(b2, 1);
w = inst.Offset >> 3;
if (inst.Operation == Win64EH::UOP_SaveXMM128)
w >>= 1;
streamer.EmitIntValue(w, 2);
break;
case Win64EH::UOP_SaveNonVolBig:
case Win64EH::UOP_SaveXMM128Big:
b2 |= (inst.Register & 0x0F) << 4;
EmitAbsDifference(streamer, inst.Label, begin);
streamer.EmitIntValue(b2, 1);
if (inst.Operation == Win64EH::UOP_SaveXMM128Big)
w = inst.Offset & 0xFFF0;
else
w = inst.Offset & 0xFFF8;
streamer.EmitIntValue(w, 2);
w = inst.Offset >> 16;
streamer.EmitIntValue(w, 2);
break;
case Win64EH::UOP_PushMachFrame:
if (inst.Offset == 1)
b2 |= 0x10;
EmitAbsDifference(streamer, inst.Label, begin);
streamer.EmitIntValue(b2, 1);
break;
}
}
static void EmitSymbolRefWithOfs(MCStreamer &streamer,
const MCSymbol *Base,
const MCSymbol *Other) {
MCContext &Context = streamer.getContext();
const MCSymbolRefExpr *BaseRef = MCSymbolRefExpr::create(Base, Context);
const MCSymbolRefExpr *OtherRef = MCSymbolRefExpr::create(Other, Context);
const MCExpr *Ofs = MCBinaryExpr::createSub(OtherRef, BaseRef, Context);
const MCSymbolRefExpr *BaseRefRel = MCSymbolRefExpr::create(Base,
MCSymbolRefExpr::VK_COFF_IMGREL32,
Context);
streamer.EmitValue(MCBinaryExpr::createAdd(BaseRefRel, Ofs, Context), 4);
}
static void EmitRuntimeFunction(MCStreamer &streamer,
const WinEH::FrameInfo *info) {
MCContext &context = streamer.getContext();
streamer.EmitValueToAlignment(4);
EmitSymbolRefWithOfs(streamer, info->Function, info->Begin);
EmitSymbolRefWithOfs(streamer, info->Function, info->End);
streamer.EmitValue(MCSymbolRefExpr::create(info->Symbol,
MCSymbolRefExpr::VK_COFF_IMGREL32,
context), 4);
}
static void EmitUnwindInfo(MCStreamer &streamer, WinEH::FrameInfo *info) {
// If this UNWIND_INFO already has a symbol, it's already been emitted.
if (info->Symbol)
return;
MCContext &context = streamer.getContext();
MCSymbol *Label = context.createTempSymbol();
streamer.EmitValueToAlignment(4);
streamer.EmitLabel(Label);
info->Symbol = Label;
// Upper 3 bits are the version number (currently 1).
uint8_t flags = 0x01;
if (info->ChainedParent)
flags |= Win64EH::UNW_ChainInfo << 3;
else {
if (info->HandlesUnwind)
flags |= Win64EH::UNW_TerminateHandler << 3;
if (info->HandlesExceptions)
flags |= Win64EH::UNW_ExceptionHandler << 3;
}
streamer.EmitIntValue(flags, 1);
if (info->PrologEnd)
EmitAbsDifference(streamer, info->PrologEnd, info->Begin);
else
streamer.EmitIntValue(0, 1);
uint8_t numCodes = CountOfUnwindCodes(info->Instructions);
streamer.EmitIntValue(numCodes, 1);
uint8_t frame = 0;
if (info->LastFrameInst >= 0) {
WinEH::Instruction &frameInst = info->Instructions[info->LastFrameInst];
assert(frameInst.Operation == Win64EH::UOP_SetFPReg);
frame = (frameInst.Register & 0x0F) | (frameInst.Offset & 0xF0);
}
streamer.EmitIntValue(frame, 1);
// Emit unwind instructions (in reverse order).
uint8_t numInst = info->Instructions.size();
for (uint8_t c = 0; c < numInst; ++c) {
WinEH::Instruction inst = info->Instructions.back();
info->Instructions.pop_back();
EmitUnwindCode(streamer, info->Begin, inst);
}
// For alignment purposes, the instruction array will always have an even
// number of entries, with the final entry potentially unused (in which case
// the array will be one longer than indicated by the count of unwind codes
// field).
if (numCodes & 1) {
streamer.EmitIntValue(0, 2);
}
if (flags & (Win64EH::UNW_ChainInfo << 3))
EmitRuntimeFunction(streamer, info->ChainedParent);
else if (flags &
((Win64EH::UNW_TerminateHandler|Win64EH::UNW_ExceptionHandler) << 3))
streamer.EmitValue(MCSymbolRefExpr::create(info->ExceptionHandler,
MCSymbolRefExpr::VK_COFF_IMGREL32,
context), 4);
else if (numCodes == 0) {
// The minimum size of an UNWIND_INFO struct is 8 bytes. If we're not
// a chained unwind info, if there is no handler, and if there are fewer
// than 2 slots used in the unwind code array, we have to pad to 8 bytes.
streamer.EmitIntValue(0, 4);
}
}
void llvm::Win64EH::UnwindEmitter::Emit(MCStreamer &Streamer) const {
// Emit the unwind info structs first.
for (const auto &CFI : Streamer.getWinFrameInfos()) {
MCSection *XData = Streamer.getAssociatedXDataSection(CFI->TextSection);
Streamer.SwitchSection(XData);
::EmitUnwindInfo(Streamer, CFI.get());
}
// Now emit RUNTIME_FUNCTION entries.
for (const auto &CFI : Streamer.getWinFrameInfos()) {
MCSection *PData = Streamer.getAssociatedPDataSection(CFI->TextSection);
Streamer.SwitchSection(PData);
EmitRuntimeFunction(Streamer, CFI.get());
}
}
void llvm::Win64EH::UnwindEmitter::EmitUnwindInfo(
MCStreamer &Streamer, WinEH::FrameInfo *info) const {
// Switch sections (the static function above is meant to be called from
// here and from Emit().
MCSection *XData = Streamer.getAssociatedXDataSection(info->TextSection);
Streamer.SwitchSection(XData);
::EmitUnwindInfo(Streamer, info);
}
static int64_t GetAbsDifference(MCStreamer &Streamer, const MCSymbol *LHS,
const MCSymbol *RHS) {
MCContext &Context = Streamer.getContext();
const MCExpr *Diff =
MCBinaryExpr::createSub(MCSymbolRefExpr::create(LHS, Context),
MCSymbolRefExpr::create(RHS, Context), Context);
MCObjectStreamer *OS = (MCObjectStreamer *)(&Streamer);
int64_t value;
Diff->evaluateAsAbsolute(value, OS->getAssembler());
return value;
}
static uint32_t
ARM64CountOfUnwindCodes(const std::vector<WinEH::Instruction> &Insns) {
uint32_t Count = 0;
for (const auto &I : Insns) {
switch (static_cast<Win64EH::UnwindOpcodes>(I.Operation)) {
default:
llvm_unreachable("Unsupported ARM64 unwind code");
case Win64EH::UOP_AllocSmall:
Count += 1;
break;
case Win64EH::UOP_AllocMedium:
Count += 2;
break;
case Win64EH::UOP_AllocLarge:
Count += 4;
break;
case Win64EH::UOP_SaveFPLRX:
Count += 1;
break;
case Win64EH::UOP_SaveFPLR:
Count += 1;
break;
case Win64EH::UOP_SaveReg:
Count += 2;
break;
case Win64EH::UOP_SaveRegP:
Count += 2;
break;
case Win64EH::UOP_SaveRegPX:
Count += 2;
break;
case Win64EH::UOP_SaveRegX:
Count += 2;
break;
case Win64EH::UOP_SaveFReg:
Count += 2;
break;
case Win64EH::UOP_SaveFRegP:
Count += 2;
break;
case Win64EH::UOP_SaveFRegX:
Count += 2;
break;
case Win64EH::UOP_SaveFRegPX:
Count += 2;
break;
case Win64EH::UOP_SetFP:
Count += 1;
break;
case Win64EH::UOP_AddFP:
Count += 2;
break;
case Win64EH::UOP_Nop:
Count += 1;
break;
case Win64EH::UOP_End:
Count += 1;
break;
}
}
return Count;
}
// Unwind opcode encodings and restrictions are documented at
// https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling
static void ARM64EmitUnwindCode(MCStreamer &streamer, const MCSymbol *begin,
WinEH::Instruction &inst) {
uint8_t b, reg;
switch (static_cast<Win64EH::UnwindOpcodes>(inst.Operation)) {
default:
llvm_unreachable("Unsupported ARM64 unwind code");
case Win64EH::UOP_AllocSmall:
b = (inst.Offset >> 4) & 0x1F;
streamer.EmitIntValue(b, 1);
break;
case Win64EH::UOP_AllocMedium: {
uint16_t hw = (inst.Offset >> 4) & 0x7FF;
b = 0xC0;
b |= (hw >> 8);
streamer.EmitIntValue(b, 1);
b = hw & 0xFF;
streamer.EmitIntValue(b, 1);
break;
}
case Win64EH::UOP_AllocLarge: {
uint32_t w;
b = 0xE0;
streamer.EmitIntValue(b, 1);
w = inst.Offset >> 4;
b = (w & 0x00FF0000) >> 16;
streamer.EmitIntValue(b, 1);
b = (w & 0x0000FF00) >> 8;
streamer.EmitIntValue(b, 1);
b = w & 0x000000FF;
streamer.EmitIntValue(b, 1);
break;
}
case Win64EH::UOP_SetFP:
b = 0xE1;
streamer.EmitIntValue(b, 1);
break;
case Win64EH::UOP_AddFP:
b = 0xE2;
streamer.EmitIntValue(b, 1);
b = (inst.Offset >> 3);
streamer.EmitIntValue(b, 1);
break;
case Win64EH::UOP_Nop:
b = 0xE3;
streamer.EmitIntValue(b, 1);
break;
case Win64EH::UOP_SaveFPLRX:
b = 0x80;
b |= ((inst.Offset - 1) >> 3) & 0x3F;
streamer.EmitIntValue(b, 1);
break;
case Win64EH::UOP_SaveFPLR:
b = 0x40;
b |= (inst.Offset >> 3) & 0x3F;
streamer.EmitIntValue(b, 1);
break;
case Win64EH::UOP_SaveReg:
assert(inst.Register >= 19 && "Saved reg must be >= 19");
reg = inst.Register - 19;
b = 0xD0 | ((reg & 0xC) >> 2);
streamer.EmitIntValue(b, 1);
b = ((reg & 0x3) << 6) | (inst.Offset >> 3);
streamer.EmitIntValue(b, 1);
break;
case Win64EH::UOP_SaveRegX:
assert(inst.Register >= 19 && "Saved reg must be >= 19");
reg = inst.Register - 19;
b = 0xD4 | ((reg & 0x8) >> 3);
streamer.EmitIntValue(b, 1);
b = ((reg & 0x7) << 5) | ((inst.Offset >> 3) - 1);
streamer.EmitIntValue(b, 1);
break;
case Win64EH::UOP_SaveRegP:
assert(inst.Register >= 19 && "Saved registers must be >= 19");
reg = inst.Register - 19;
b = 0xC8 | ((reg & 0xC) >> 2);
streamer.EmitIntValue(b, 1);
b = ((reg & 0x3) << 6) | (inst.Offset >> 3);
streamer.EmitIntValue(b, 1);
break;
case Win64EH::UOP_SaveRegPX:
assert(inst.Register >= 19 && "Saved registers must be >= 19");
reg = inst.Register - 19;
b = 0xCC | ((reg & 0xC) >> 2);
streamer.EmitIntValue(b, 1);
b = ((reg & 0x3) << 6) | ((inst.Offset >> 3) - 1);
streamer.EmitIntValue(b, 1);
break;
case Win64EH::UOP_SaveFReg:
assert(inst.Register >= 8 && "Saved dreg must be >= 8");
reg = inst.Register - 8;
b = 0xDC | ((reg & 0x4) >> 2);
streamer.EmitIntValue(b, 1);
b = ((reg & 0x3) << 6) | (inst.Offset >> 3);
streamer.EmitIntValue(b, 1);
break;
case Win64EH::UOP_SaveFRegX:
assert(inst.Register >= 8 && "Saved dreg must be >= 8");
reg = inst.Register - 8;
b = 0xDE;
streamer.EmitIntValue(b, 1);
b = ((reg & 0x7) << 5) | ((inst.Offset >> 3) - 1);
streamer.EmitIntValue(b, 1);
break;
case Win64EH::UOP_SaveFRegP:
assert(inst.Register >= 8 && "Saved dregs must be >= 8");
reg = inst.Register - 8;
b = 0xD8 | ((reg & 0x4) >> 2);
streamer.EmitIntValue(b, 1);
b = ((reg & 0x3) << 6) | (inst.Offset >> 3);
streamer.EmitIntValue(b, 1);
break;
case Win64EH::UOP_SaveFRegPX:
assert(inst.Register >= 8 && "Saved dregs must be >= 8");
reg = inst.Register - 8;
b = 0xDA | ((reg & 0x4) >> 2);
streamer.EmitIntValue(b, 1);
b = ((reg & 0x3) << 6) | ((inst.Offset >> 3) - 1);
streamer.EmitIntValue(b, 1);
break;
case Win64EH::UOP_End:
b = 0xE4;
streamer.EmitIntValue(b, 1);
break;
}
}
// Populate the .xdata section. The format of .xdata on ARM64 is documented at
// https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling
static void ARM64EmitUnwindInfo(MCStreamer &streamer, WinEH::FrameInfo *info) {
// If this UNWIND_INFO already has a symbol, it's already been emitted.
if (info->Symbol)
return;
MCContext &context = streamer.getContext();
MCSymbol *Label = context.createTempSymbol();
streamer.EmitValueToAlignment(4);
streamer.EmitLabel(Label);
info->Symbol = Label;
uint32_t FuncLength = 0x0;
FuncLength = (uint32_t)GetAbsDifference(streamer, info->FuncletOrFuncEnd,
info->Begin);
if (FuncLength)
FuncLength /= 4;
uint32_t PrologCodeBytes = ARM64CountOfUnwindCodes(info->Instructions);
uint32_t TotalCodeBytes = PrologCodeBytes;
// Process epilogs.
MapVector<MCSymbol *, uint32_t> EpilogInfo;
for (auto &I : info->EpilogMap) {
MCSymbol *EpilogStart = I.first;
auto &EpilogInstrs = I.second;
uint32_t CodeBytes = ARM64CountOfUnwindCodes(EpilogInstrs);
EpilogInfo[EpilogStart] = TotalCodeBytes;
TotalCodeBytes += CodeBytes;
}
// Code Words, Epilog count, E, X, Vers, Function Length
uint32_t row1 = 0x0;
uint32_t CodeWords = TotalCodeBytes / 4;
uint32_t CodeWordsMod = TotalCodeBytes % 4;
if (CodeWordsMod)
CodeWords++;
uint32_t EpilogCount = info->EpilogMap.size();
bool ExtensionWord = EpilogCount > 31 || TotalCodeBytes > 124;
if (!ExtensionWord) {
row1 |= (EpilogCount & 0x1F) << 22;
row1 |= (CodeWords & 0x1F) << 27;
}
// E is always 0 right now, TODO: packed epilog setup
if (info->HandlesExceptions) // X
row1 |= 1 << 20;
row1 |= FuncLength & 0x3FFFF;
streamer.EmitIntValue(row1, 4);
// Extended Code Words, Extended Epilog Count
if (ExtensionWord) {
// FIXME: We should be able to split unwind info into multiple sections.
// FIXME: We should share epilog codes across epilogs, where possible,
// which would make this issue show up less frequently.
if (CodeWords > 0xFF || EpilogCount > 0xFFFF)
report_fatal_error("SEH unwind data splitting not yet implemented");
uint32_t row2 = 0x0;
row2 |= (CodeWords & 0xFF) << 16;
row2 |= (EpilogCount & 0xFFFF);
streamer.EmitIntValue(row2, 4);
}
// Epilog Start Index, Epilog Start Offset
for (auto &I : EpilogInfo) {
MCSymbol *EpilogStart = I.first;
uint32_t EpilogIndex = I.second;
uint32_t EpilogOffset =
(uint32_t)GetAbsDifference(streamer, EpilogStart, info->Begin);
if (EpilogOffset)
EpilogOffset /= 4;
uint32_t row3 = EpilogOffset;
row3 |= (EpilogIndex & 0x3FF) << 22;
streamer.EmitIntValue(row3, 4);
}
// Emit prolog unwind instructions (in reverse order).
uint8_t numInst = info->Instructions.size();
for (uint8_t c = 0; c < numInst; ++c) {
WinEH::Instruction inst = info->Instructions.back();
info->Instructions.pop_back();
ARM64EmitUnwindCode(streamer, info->Begin, inst);
}
// Emit epilog unwind instructions
for (auto &I : info->EpilogMap) {
auto &EpilogInstrs = I.second;
for (uint32_t i = 0; i < EpilogInstrs.size(); i++) {
WinEH::Instruction inst = EpilogInstrs[i];
ARM64EmitUnwindCode(streamer, info->Begin, inst);
}
}
int32_t BytesMod = CodeWords * 4 - TotalCodeBytes;
assert(BytesMod >= 0);
for (int i = 0; i < BytesMod; i++)
streamer.EmitIntValue(0xE3, 1);
if (info->HandlesExceptions)
streamer.EmitValue(
MCSymbolRefExpr::create(info->ExceptionHandler,
MCSymbolRefExpr::VK_COFF_IMGREL32, context),
4);
}
static void ARM64EmitRuntimeFunction(MCStreamer &streamer,
const WinEH::FrameInfo *info) {
MCContext &context = streamer.getContext();
streamer.EmitValueToAlignment(4);
EmitSymbolRefWithOfs(streamer, info->Function, info->Begin);
streamer.EmitValue(MCSymbolRefExpr::create(info->Symbol,
MCSymbolRefExpr::VK_COFF_IMGREL32,
context),
4);
}
void llvm::Win64EH::ARM64UnwindEmitter::Emit(MCStreamer &Streamer) const {
// Emit the unwind info structs first.
for (const auto &CFI : Streamer.getWinFrameInfos()) {
MCSection *XData = Streamer.getAssociatedXDataSection(CFI->TextSection);
Streamer.SwitchSection(XData);
ARM64EmitUnwindInfo(Streamer, CFI.get());
}
// Now emit RUNTIME_FUNCTION entries.
for (const auto &CFI : Streamer.getWinFrameInfos()) {
MCSection *PData = Streamer.getAssociatedPDataSection(CFI->TextSection);
Streamer.SwitchSection(PData);
ARM64EmitRuntimeFunction(Streamer, CFI.get());
}
}
void llvm::Win64EH::ARM64UnwindEmitter::EmitUnwindInfo(
MCStreamer &Streamer, WinEH::FrameInfo *info) const {
// Switch sections (the static function above is meant to be called from
// here and from Emit().
MCSection *XData = Streamer.getAssociatedXDataSection(info->TextSection);
Streamer.SwitchSection(XData);
ARM64EmitUnwindInfo(Streamer, info);
}