lib/MC/MCObjectSymbolizer.cpp - llvm - Git at Google

 //===-- lib/MC/MCObjectSymbolizer.cpp -------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//

 #include "llvm/MC/MCObjectSymbolizer.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCRelocationInfo.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/Object/MachO.h"
 #include "llvm/Object/ELFObjectFile.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>

 using namespace llvm;
 using namespace object;

 //===- MCMachObjectSymbolizer ---------------------------------------------===//

 namespace {
 class MCMachObjectSymbolizer : public MCObjectSymbolizer {
   const MachOObjectFile *MOOF;
   // __TEXT;__stubs support.
   uint64_t StubsStart;
   uint64_t StubsCount;
   uint64_t StubSize;
   uint64_t StubsIndSymIndex;

 public:
   MCMachObjectSymbolizer(MCContext &Ctx, OwningPtr<MCRelocationInfo> &RelInfo,
                          const MachOObjectFile *MOOF);

   StringRef findExternalFunctionAt(uint64_t Addr) LLVM_OVERRIDE;

   void tryAddingPcLoadReferenceComment(raw_ostream &cStream,
                                        int64_t Value,
                                        uint64_t Address) LLVM_OVERRIDE;
 };
 } // End unnamed namespace


 MCMachObjectSymbolizer::
 MCMachObjectSymbolizer(MCContext &Ctx, OwningPtr<MCRelocationInfo> &RelInfo,
                        const MachOObjectFile *MOOF)
     : MCObjectSymbolizer(Ctx, RelInfo, MOOF), MOOF(MOOF),
       StubsStart(0), StubsCount(0), StubSize(0), StubsIndSymIndex(0) {

   error_code ec;
   for (section_iterator SI = MOOF->begin_sections(), SE = MOOF->end_sections();
        SI != SE; SI.increment(ec)) {
     if (ec) break;
     StringRef Name; SI->getName(Name);
     if (Name == "__stubs") {
       SectionRef StubsSec = *SI;
       if (MOOF->is64Bit()) {
         MachO::section_64 S = MOOF->getSection64(StubsSec.getRawDataRefImpl());
         StubsIndSymIndex = S.reserved1;
         StubSize = S.reserved2;
       } else {
         MachO::section S = MOOF->getSection(StubsSec.getRawDataRefImpl());
         StubsIndSymIndex = S.reserved1;
         StubSize = S.reserved2;
       }
       assert(StubSize && "Mach-O stub entry size can't be zero!");
       StubsSec.getAddress(StubsStart);
       StubsSec.getSize(StubsCount);
       StubsCount /= StubSize;
     }
   }
 }

 StringRef MCMachObjectSymbolizer::findExternalFunctionAt(uint64_t Addr) {
   // FIXME: also, this can all be done at the very beginning, by iterating over
   // all stubs and creating the calls to outside functions. Is it worth it
   // though?
   if (!StubSize)
     return StringRef();
   uint64_t StubIdx = (Addr - StubsStart) / StubSize;
   if (StubIdx >= StubsCount)
     return StringRef();

   uint32_t SymtabIdx =
     MOOF->getIndirectSymbolTableEntry(MOOF->getDysymtabLoadCommand(), StubIdx);

   StringRef SymName;
   symbol_iterator SI = MOOF->begin_symbols();
   error_code ec;
   for (uint32_t i = 0; i != SymtabIdx; ++i) {
     SI.increment(ec);
   }
   SI->getName(SymName);
   assert(SI != MOOF->end_symbols() && "Stub wasn't found in the symbol table!");
   assert(SymName.front() == '_' && "Mach-O symbol doesn't start with '_'!");
   return SymName.substr(1);
 }

 void MCMachObjectSymbolizer::
 tryAddingPcLoadReferenceComment(raw_ostream &cStream, int64_t Value,
                                 uint64_t Address) {
   if (const RelocationRef *R = findRelocationAt(Address)) {
     const MCExpr *RelExpr = RelInfo->createExprForRelocation(*R);
     if (!RelExpr || RelExpr->EvaluateAsAbsolute(Value) == false)
       return;
   }
   uint64_t Addr = Value;
   if (const SectionRef *S = findSectionContaining(Addr)) {
     StringRef Name; S->getName(Name);
     uint64_t SAddr; S->getAddress(SAddr);
     if (Name == "__cstring") {
       StringRef Contents;
       S->getContents(Contents);
       Contents = Contents.substr(Addr - SAddr);
       cStream << " ## literal pool for: "
               << Contents.substr(0, Contents.find_first_of(0));
     }
   }
 }

 //===- MCObjectSymbolizer -------------------------------------------------===//

 MCObjectSymbolizer::MCObjectSymbolizer(MCContext &Ctx,
                                        OwningPtr<MCRelocationInfo> &RelInfo,
                                        const ObjectFile *Obj)
     : MCSymbolizer(Ctx, RelInfo), Obj(Obj), SortedSections(), AddrToReloc() {
 }

 bool MCObjectSymbolizer::
 tryAddingSymbolicOperand(MCInst &MI, raw_ostream &cStream,
                          int64_t Value, uint64_t Address, bool IsBranch,
                          uint64_t Offset, uint64_t InstSize) {
   if (IsBranch) {
     StringRef ExtFnName = findExternalFunctionAt((uint64_t)Value);
     if (!ExtFnName.empty()) {
       MCSymbol *Sym = Ctx.GetOrCreateSymbol(ExtFnName);
       const MCExpr *Expr = MCSymbolRefExpr::Create(Sym, Ctx);
       MI.addOperand(MCOperand::CreateExpr(Expr));
       return true;
     }
   }

   if (const RelocationRef *R = findRelocationAt(Address + Offset)) {
     if (const MCExpr *RelExpr = RelInfo->createExprForRelocation(*R)) {
       MI.addOperand(MCOperand::CreateExpr(RelExpr));
       return true;
     }
     // Only try to create a symbol+offset expression if there is no relocation.
     return false;
   }

   // Interpret Value as a branch target.
   if (IsBranch == false)
     return false;
   uint64_t UValue = Value;
   // FIXME: map instead of looping each time?
   error_code ec;
   for (symbol_iterator SI = Obj->begin_symbols(), SE = Obj->end_symbols();
        SI != SE; SI.increment(ec)) {
     if (ec) break;
     uint64_t SymAddr; SI->getAddress(SymAddr);
     uint64_t SymSize; SI->getSize(SymSize);
     StringRef SymName; SI->getName(SymName);
     SymbolRef::Type SymType; SI->getType(SymType);
     if (SymAddr == UnknownAddressOrSize || SymSize == UnknownAddressOrSize
         || SymName.empty() || SymType != SymbolRef::ST_Function)
       continue;

     if ( SymAddr == UValue ||
         (SymAddr <= UValue && SymAddr + SymSize > UValue)) {
       MCSymbol *Sym = Ctx.GetOrCreateSymbol(SymName);
       const MCExpr *Expr = MCSymbolRefExpr::Create(Sym, Ctx);
       if (SymAddr != UValue) {
         const MCExpr *Off = MCConstantExpr::Create(UValue - SymAddr, Ctx);
         Expr = MCBinaryExpr::CreateAdd(Expr, Off, Ctx);
       }
       MI.addOperand(MCOperand::CreateExpr(Expr));
       return true;
     }
   }
   return false;
 }

 void MCObjectSymbolizer::
 tryAddingPcLoadReferenceComment(raw_ostream &cStream,
                                 int64_t Value, uint64_t Address) {
 }

 StringRef MCObjectSymbolizer::findExternalFunctionAt(uint64_t Addr) {
   return StringRef();
 }

 MCObjectSymbolizer *
 MCObjectSymbolizer::createObjectSymbolizer(MCContext &Ctx,
                                            OwningPtr<MCRelocationInfo> &RelInfo,
                                            const ObjectFile *Obj) {
   if (const MachOObjectFile *MOOF = dyn_cast<MachOObjectFile>(Obj))
     return new MCMachObjectSymbolizer(Ctx, RelInfo, MOOF);
   return new MCObjectSymbolizer(Ctx, RelInfo, Obj);
 }

 // SortedSections implementation.

 static bool SectionStartsBefore(const SectionRef &S, uint64_t Addr) {
   uint64_t SAddr; S.getAddress(SAddr);
   return SAddr < Addr;
 }

 const SectionRef *MCObjectSymbolizer::findSectionContaining(uint64_t Addr) {
   if (SortedSections.empty())
     buildSectionList();

   SortedSectionList::iterator
     EndIt = SortedSections.end(),
     It = std::lower_bound(SortedSections.begin(), EndIt,
                           Addr, SectionStartsBefore);
   if (It == EndIt)
     return 0;
   uint64_t SAddr; It->getAddress(SAddr);
   uint64_t SSize; It->getSize(SSize);
   if (Addr >= SAddr + SSize)
     return 0;
   return &*It;
 }

 const RelocationRef *MCObjectSymbolizer::findRelocationAt(uint64_t Addr) {
   if (AddrToReloc.empty())
     buildRelocationByAddrMap();

   AddrToRelocMap::const_iterator RI = AddrToReloc.find(Addr);
   if (RI == AddrToReloc.end())
     return 0;
   return &RI->second;
 }

 void MCObjectSymbolizer::buildSectionList() {
   error_code ec;
   for (section_iterator SI = Obj->begin_sections(), SE = Obj->end_sections();
                         SI != SE; SI.increment(ec)) {
     if (ec) break;

     bool RequiredForExec; SI->isRequiredForExecution(RequiredForExec);
     if (RequiredForExec == false)
       continue;
     uint64_t SAddr; SI->getAddress(SAddr);
     uint64_t SSize; SI->getSize(SSize);
     SortedSectionList::iterator It = std::lower_bound(SortedSections.begin(),
                                                       SortedSections.end(),
                                                       SAddr,
                                                       SectionStartsBefore);
     if (It != SortedSections.end()) {
       uint64_t FoundSAddr; It->getAddress(FoundSAddr);
       if (FoundSAddr < SAddr + SSize)
         llvm_unreachable("Inserting overlapping sections");
     }
     SortedSections.insert(It, *SI);
   }
 }

 void MCObjectSymbolizer::buildRelocationByAddrMap() {
   error_code ec;
   for (section_iterator SI = Obj->begin_sections(), SE = Obj->end_sections();
                         SI != SE; SI.increment(ec)) {
     if (ec) break;

     section_iterator RelSecI = SI->getRelocatedSection();
     if (RelSecI == Obj->end_sections())
       continue;

     uint64_t StartAddr; RelSecI->getAddress(StartAddr);
     uint64_t Size; RelSecI->getSize(Size);
     bool RequiredForExec; RelSecI->isRequiredForExecution(RequiredForExec);
     if (RequiredForExec == false || Size == 0)
       continue;
     for (relocation_iterator RI = SI->begin_relocations(),
                              RE = SI->end_relocations();
                              RI != RE;
                              RI.increment(ec)) {
       if (ec) break;
       // FIXME: libObject is inconsistent regarding error handling. The
       // overwhelming majority of methods always return object_error::success,
       // and assert for simple errors.. Here, ELFObjectFile::getRelocationOffset
       // asserts when the file type isn't ET_REL.
       // This workaround handles x86-64 elf, the only one that has a relocinfo.
       uint64_t Offset;
       if (Obj->isELF()) {
         const ELF64LEObjectFile *ELFObj = dyn_cast<ELF64LEObjectFile>(Obj);
         if (ELFObj == 0)
           break;
         if (ELFObj->getELFFile()->getHeader()->e_type == ELF::ET_REL) {
           RI->getOffset(Offset);
           Offset += StartAddr;
         } else {
           RI->getAddress(Offset);
         }
       } else {
         RI->getOffset(Offset);
         Offset += StartAddr;
       }
       // At a specific address, only keep the first relocation.
       if (AddrToReloc.find(Offset) == AddrToReloc.end())
         AddrToReloc[Offset] = *RI;
     }
   }
 }
	//===-- lib/MC/MCObjectSymbolizer.cpp -------------------------------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//

	#include "llvm/MC/MCObjectSymbolizer.h"
	#include "llvm/ADT/SmallString.h"
	#include "llvm/MC/MCContext.h"
	#include "llvm/MC/MCExpr.h"
	#include "llvm/MC/MCInst.h"
	#include "llvm/MC/MCRelocationInfo.h"
	#include "llvm/MC/MCSymbol.h"
	#include "llvm/Object/MachO.h"
	#include "llvm/Object/ELFObjectFile.h"
	#include "llvm/Support/raw_ostream.h"
	#include <algorithm>

	using namespace llvm;
	using namespace object;

	//===- MCMachObjectSymbolizer ---------------------------------------------===//

	namespace {
	class MCMachObjectSymbolizer : public MCObjectSymbolizer {
	const MachOObjectFile *MOOF;
	// __TEXT;__stubs support.
	uint64_t StubsStart;
	uint64_t StubsCount;
	uint64_t StubSize;
	uint64_t StubsIndSymIndex;

	public:
	MCMachObjectSymbolizer(MCContext &Ctx, OwningPtr<MCRelocationInfo> &RelInfo,
	const MachOObjectFile *MOOF);

	StringRef findExternalFunctionAt(uint64_t Addr) LLVM_OVERRIDE;

	void tryAddingPcLoadReferenceComment(raw_ostream &cStream,
	int64_t Value,
	uint64_t Address) LLVM_OVERRIDE;
	};
	} // End unnamed namespace


	MCMachObjectSymbolizer::
	MCMachObjectSymbolizer(MCContext &Ctx, OwningPtr<MCRelocationInfo> &RelInfo,
	const MachOObjectFile *MOOF)
	: MCObjectSymbolizer(Ctx, RelInfo, MOOF), MOOF(MOOF),
	StubsStart(0), StubsCount(0), StubSize(0), StubsIndSymIndex(0) {

	error_code ec;
	for (section_iterator SI = MOOF->begin_sections(), SE = MOOF->end_sections();
	SI != SE; SI.increment(ec)) {
	if (ec) break;
	StringRef Name; SI->getName(Name);
	if (Name == "__stubs") {
	SectionRef StubsSec = *SI;
	if (MOOF->is64Bit()) {
	MachO::section_64 S = MOOF->getSection64(StubsSec.getRawDataRefImpl());
	StubsIndSymIndex = S.reserved1;
	StubSize = S.reserved2;
	} else {
	MachO::section S = MOOF->getSection(StubsSec.getRawDataRefImpl());
	StubsIndSymIndex = S.reserved1;
	StubSize = S.reserved2;
	}
	assert(StubSize && "Mach-O stub entry size can't be zero!");
	StubsSec.getAddress(StubsStart);
	StubsSec.getSize(StubsCount);
	StubsCount /= StubSize;
	}
	}
	}

	StringRef MCMachObjectSymbolizer::findExternalFunctionAt(uint64_t Addr) {
	// FIXME: also, this can all be done at the very beginning, by iterating over
	// all stubs and creating the calls to outside functions. Is it worth it
	// though?
	if (!StubSize)
	return StringRef();
	uint64_t StubIdx = (Addr - StubsStart) / StubSize;
	if (StubIdx >= StubsCount)
	return StringRef();

	uint32_t SymtabIdx =
	MOOF->getIndirectSymbolTableEntry(MOOF->getDysymtabLoadCommand(), StubIdx);

	StringRef SymName;
	symbol_iterator SI = MOOF->begin_symbols();
	error_code ec;
	for (uint32_t i = 0; i != SymtabIdx; ++i) {
	SI.increment(ec);
	}
	SI->getName(SymName);
	assert(SI != MOOF->end_symbols() && "Stub wasn't found in the symbol table!");
	assert(SymName.front() == '_' && "Mach-O symbol doesn't start with '_'!");
	return SymName.substr(1);
	}

	void MCMachObjectSymbolizer::
	tryAddingPcLoadReferenceComment(raw_ostream &cStream, int64_t Value,
	uint64_t Address) {
	if (const RelocationRef *R = findRelocationAt(Address)) {
	const MCExpr RelExpr = RelInfo->createExprForRelocation(R);
	if (!RelExpr \|\| RelExpr->EvaluateAsAbsolute(Value) == false)
	return;
	}
	uint64_t Addr = Value;
	if (const SectionRef *S = findSectionContaining(Addr)) {
	StringRef Name; S->getName(Name);
	uint64_t SAddr; S->getAddress(SAddr);
	if (Name == "__cstring") {
	StringRef Contents;
	S->getContents(Contents);
	Contents = Contents.substr(Addr - SAddr);
	cStream << " ## literal pool for: "
	<< Contents.substr(0, Contents.find_first_of(0));
	}
	}
	}

	//===- MCObjectSymbolizer -------------------------------------------------===//

	MCObjectSymbolizer::MCObjectSymbolizer(MCContext &Ctx,
	OwningPtr<MCRelocationInfo> &RelInfo,
	const ObjectFile *Obj)
	: MCSymbolizer(Ctx, RelInfo), Obj(Obj), SortedSections(), AddrToReloc() {
	}

	bool MCObjectSymbolizer::
	tryAddingSymbolicOperand(MCInst &MI, raw_ostream &cStream,
	int64_t Value, uint64_t Address, bool IsBranch,
	uint64_t Offset, uint64_t InstSize) {
	if (IsBranch) {
	StringRef ExtFnName = findExternalFunctionAt((uint64_t)Value);
	if (!ExtFnName.empty()) {
	MCSymbol *Sym = Ctx.GetOrCreateSymbol(ExtFnName);
	const MCExpr *Expr = MCSymbolRefExpr::Create(Sym, Ctx);
	MI.addOperand(MCOperand::CreateExpr(Expr));
	return true;
	}
	}

	if (const RelocationRef *R = findRelocationAt(Address + Offset)) {
	if (const MCExpr RelExpr = RelInfo->createExprForRelocation(R)) {
	MI.addOperand(MCOperand::CreateExpr(RelExpr));
	return true;
	}
	// Only try to create a symbol+offset expression if there is no relocation.
	return false;
	}

	// Interpret Value as a branch target.
	if (IsBranch == false)
	return false;
	uint64_t UValue = Value;
	// FIXME: map instead of looping each time?
	error_code ec;
	for (symbol_iterator SI = Obj->begin_symbols(), SE = Obj->end_symbols();
	SI != SE; SI.increment(ec)) {
	if (ec) break;
	uint64_t SymAddr; SI->getAddress(SymAddr);
	uint64_t SymSize; SI->getSize(SymSize);
	StringRef SymName; SI->getName(SymName);
	SymbolRef::Type SymType; SI->getType(SymType);
	if (SymAddr == UnknownAddressOrSize \|\| SymSize == UnknownAddressOrSize
	\|\| SymName.empty() \|\| SymType != SymbolRef::ST_Function)
	continue;

	if ( SymAddr == UValue \|\|
	(SymAddr <= UValue && SymAddr + SymSize > UValue)) {
	MCSymbol *Sym = Ctx.GetOrCreateSymbol(SymName);
	const MCExpr *Expr = MCSymbolRefExpr::Create(Sym, Ctx);
	if (SymAddr != UValue) {
	const MCExpr *Off = MCConstantExpr::Create(UValue - SymAddr, Ctx);
	Expr = MCBinaryExpr::CreateAdd(Expr, Off, Ctx);
	}
	MI.addOperand(MCOperand::CreateExpr(Expr));
	return true;
	}
	}
	return false;
	}

	void MCObjectSymbolizer::
	tryAddingPcLoadReferenceComment(raw_ostream &cStream,
	int64_t Value, uint64_t Address) {
	}

	StringRef MCObjectSymbolizer::findExternalFunctionAt(uint64_t Addr) {
	return StringRef();
	}

	MCObjectSymbolizer *
	MCObjectSymbolizer::createObjectSymbolizer(MCContext &Ctx,
	OwningPtr<MCRelocationInfo> &RelInfo,
	const ObjectFile *Obj) {
	if (const MachOObjectFile *MOOF = dyn_cast<MachOObjectFile>(Obj))
	return new MCMachObjectSymbolizer(Ctx, RelInfo, MOOF);
	return new MCObjectSymbolizer(Ctx, RelInfo, Obj);
	}

	// SortedSections implementation.

	static bool SectionStartsBefore(const SectionRef &S, uint64_t Addr) {
	uint64_t SAddr; S.getAddress(SAddr);
	return SAddr < Addr;
	}

	const SectionRef *MCObjectSymbolizer::findSectionContaining(uint64_t Addr) {
	if (SortedSections.empty())
	buildSectionList();

	SortedSectionList::iterator
	EndIt = SortedSections.end(),
	It = std::lower_bound(SortedSections.begin(), EndIt,
	Addr, SectionStartsBefore);
	if (It == EndIt)
	return 0;
	uint64_t SAddr; It->getAddress(SAddr);
	uint64_t SSize; It->getSize(SSize);
	if (Addr >= SAddr + SSize)
	return 0;
	return &*It;
	}

	const RelocationRef *MCObjectSymbolizer::findRelocationAt(uint64_t Addr) {
	if (AddrToReloc.empty())
	buildRelocationByAddrMap();

	AddrToRelocMap::const_iterator RI = AddrToReloc.find(Addr);
	if (RI == AddrToReloc.end())
	return 0;
	return &RI->second;
	}

	void MCObjectSymbolizer::buildSectionList() {
	error_code ec;
	for (section_iterator SI = Obj->begin_sections(), SE = Obj->end_sections();
	SI != SE; SI.increment(ec)) {
	if (ec) break;

	bool RequiredForExec; SI->isRequiredForExecution(RequiredForExec);
	if (RequiredForExec == false)
	continue;
	uint64_t SAddr; SI->getAddress(SAddr);
	uint64_t SSize; SI->getSize(SSize);
	SortedSectionList::iterator It = std::lower_bound(SortedSections.begin(),
	SortedSections.end(),
	SAddr,
	SectionStartsBefore);
	if (It != SortedSections.end()) {
	uint64_t FoundSAddr; It->getAddress(FoundSAddr);
	if (FoundSAddr < SAddr + SSize)
	llvm_unreachable("Inserting overlapping sections");
	}
	SortedSections.insert(It, *SI);
	}
	}

	void MCObjectSymbolizer::buildRelocationByAddrMap() {
	error_code ec;
	for (section_iterator SI = Obj->begin_sections(), SE = Obj->end_sections();
	SI != SE; SI.increment(ec)) {
	if (ec) break;

	section_iterator RelSecI = SI->getRelocatedSection();
	if (RelSecI == Obj->end_sections())
	continue;

	uint64_t StartAddr; RelSecI->getAddress(StartAddr);
	uint64_t Size; RelSecI->getSize(Size);
	bool RequiredForExec; RelSecI->isRequiredForExecution(RequiredForExec);
	if (RequiredForExec == false \|\| Size == 0)
	continue;
	for (relocation_iterator RI = SI->begin_relocations(),
	RE = SI->end_relocations();
	RI != RE;
	RI.increment(ec)) {
	if (ec) break;
	// FIXME: libObject is inconsistent regarding error handling. The
	// overwhelming majority of methods always return object_error::success,
	// and assert for simple errors.. Here, ELFObjectFile::getRelocationOffset
	// asserts when the file type isn't ET_REL.
	// This workaround handles x86-64 elf, the only one that has a relocinfo.
	uint64_t Offset;
	if (Obj->isELF()) {
	const ELF64LEObjectFile *ELFObj = dyn_cast<ELF64LEObjectFile>(Obj);
	if (ELFObj == 0)
	break;
	if (ELFObj->getELFFile()->getHeader()->e_type == ELF::ET_REL) {
	RI->getOffset(Offset);
	Offset += StartAddr;
	} else {
	RI->getAddress(Offset);
	}
	} else {
	RI->getOffset(Offset);
	Offset += StartAddr;
	}
	// At a specific address, only keep the first relocation.
	if (AddrToReloc.find(Offset) == AddrToReloc.end())
	AddrToReloc[Offset] = *RI;
	}
	}
	}