llvm-6502/lib/MC/MCObjectSymbolizer.cpp
Rafael Espindola efdbec8b0a Simplify the handling of iterators in ObjectFile.
None of the object file formats reported error on iterator increment. In
retrospect, that is not too surprising: no object format stores symbols or
sections in a linked list or other structure that requires chasing pointers.
As a consequence, all error checking can be done on begin() and end().

This reduces the text segment of bin/llvm-readobj in my machine from 521233 to
518526 bytes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200442 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-30 02:49:50 +00:00

297 lines
10 KiB
C++

//===-- 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/ELFObjectFile.h"
#include "llvm/Object/MachO.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) {
for (section_iterator SI = MOOF->begin_sections(), SE = MOOF->end_sections();
SI != SE; ++SI) {
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();
for (uint32_t i = 0; i != SymtabIdx; ++i)
++SI;
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?
for (symbol_iterator SI = Obj->begin_symbols(), SE = Obj->end_symbols();
SI != SE; ++SI) {
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() {
for (section_iterator SI = Obj->begin_sections(), SE = Obj->end_sections();
SI != SE; ++SI) {
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() {
for (section_iterator SI = Obj->begin_sections(), SE = Obj->end_sections();
SI != SE; ++SI) {
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) {
// 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;
}
}
}