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

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//===- 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/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)) {
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)) {
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 (WinEH::FrameInfo *CFI : Streamer.getWinFrameInfos()) {
MCSection *XData = Streamer.getAssociatedXDataSection(CFI->TextSection);
Streamer.SwitchSection(XData);
::EmitUnwindInfo(Streamer, CFI);
}
// Now emit RUNTIME_FUNCTION entries.
for (WinEH::FrameInfo *CFI : Streamer.getWinFrameInfos()) {
MCSection *PData = Streamer.getAssociatedPDataSection(CFI->TextSection);
Streamer.SwitchSection(PData);
EmitRuntimeFunction(Streamer, CFI);
}
}
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);
}
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