Add MCSymbolizer for symbolic/annotated disassembly.
This is a basic first step towards symbolization of disassembled
instructions. This used to be done using externally provided (C API)
callbacks. This patch introduces:
- the MCSymbolizer class, that mimics the same functions that were used
in the X86 and ARM disassemblers to symbolize immediate operands and
to annotate loads based off PC (for things like c string literals).
- the MCExternalSymbolizer class, which implements the old C API.
- the MCRelocationInfo class, which provides a way for targets to
translate relocations (either object::RelocationRef, or disassembler
C API VariantKinds) to MCExprs.
- the MCObjectSymbolizer class, which does symbolization using what it
finds in an object::ObjectFile. This makes simple symbolization (with
no fancy relocation stuff) work for all object formats!
- x86-64 Mach-O and ELF MCRelocationInfos.
- A basic ARM Mach-O MCRelocationInfo, that provides just enough to
support the C API VariantKinds.
Most of what works in otool (the only user of the old symbolization API
that I know of) for x86-64 symbolic disassembly (-tvV) works, namely:
- symbol references: call _foo; jmp 15 <_foo+50>
- relocations: call _foo-_bar; call _foo-4
- __cf?string: leaq 193(%rip), %rax ## literal pool for "hello"
Stub support is the main missing part (because libObject doesn't know,
among other things, about mach-o indirect symbols).
As for the MCSymbolizer API, instead of relying on the disassemblers
to call the tryAdding* methods, maybe this could be done automagically
using InstrInfo? For instance, even though PC-relative LEAs are used
to get the address of string literals in a typical Mach-O file, a MOV
would be used in an ELF file. And right now, the explicit symbolization
only recognizes PC-relative LEAs. InstrInfo should have already have
most of what is needed to know what to symbolize, so this can
definitely be improved.
I'd also like to remove object::RelocationRef::getValueString (it seems
only used by relocation printing in objdump), as simply printing the
created MCExpr is definitely enough (and cleaner than string concats).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182625 91177308-0d34-0410-b5e6-96231b3b80d8
2013-05-24 00:39:57 +00:00
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//===-- lib/MC/MCObjectSymbolizer.cpp -------------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/MC/MCObjectSymbolizer.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCInst.h"
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#include "llvm/MC/MCRelocationInfo.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/Object/MachO.h"
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#include "llvm/Object/ELF.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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using namespace object;
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//===- MCMachObjectSymbolizer ---------------------------------------------===//
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namespace {
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class MCMachObjectSymbolizer : public MCObjectSymbolizer {
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public:
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MCMachObjectSymbolizer(MCContext &Ctx, OwningPtr<MCRelocationInfo> &RelInfo,
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const object::MachOObjectFile *MachOOF)
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: MCObjectSymbolizer(Ctx, RelInfo, MachOOF)
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{}
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void tryAddingPcLoadReferenceComment(raw_ostream &cStream,
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int64_t Value, uint64_t Address) {
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AddrToRelocMap::iterator RI = AddrToReloc.find(Address);
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if (RI != AddrToReloc.end()) {
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const MCExpr *RelExpr = RelInfo->createExprForRelocation(RI->second);
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if (!RelExpr || RelExpr->EvaluateAsAbsolute(Value) == false)
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return;
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}
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uint64_t Addr = Value;
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AddrToSectionMap::const_iterator SI = AddrToSection.find(Addr);
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if (SI.valid()) {
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DataRefImpl DRI; DRI.p = *SI;
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SectionRef S(DRI, Obj);
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StringRef Name; S.getName(Name);
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if (Name == "__cstring") {
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StringRef Contents;
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S.getContents(Contents);
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Contents = Contents.substr(Addr - SI.start());
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cStream << " ## literal pool for: "
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<< Contents.substr(0, Contents.find_first_of(0));
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}
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}
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}
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};
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} // End unnamed namespace
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//===- MCObjectSymbolizer -------------------------------------------------===//
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MCObjectSymbolizer::MCObjectSymbolizer(MCContext &Ctx,
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OwningPtr<MCRelocationInfo> &RelInfo,
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const ObjectFile *Obj)
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: MCSymbolizer(Ctx, RelInfo), Obj(Obj),
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AddrToSectionAllocator(), AddrToSection(AddrToSectionAllocator),
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AddrToReloc() {
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error_code ec;
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for (section_iterator SI = Obj->begin_sections(),
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SE = Obj->end_sections();
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SI != SE;
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SI.increment(ec)) {
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if (ec) break;
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2013-05-30 03:05:14 +00:00
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section_iterator RelSecI = SI->getRelocatedSection();
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if (RelSecI == Obj->end_sections())
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continue;
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uint64_t StartAddr; RelSecI->getAddress(StartAddr);
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uint64_t Size; RelSecI->getSize(Size);
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bool RequiredForExec; RelSecI->isRequiredForExecution(RequiredForExec);
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Add MCSymbolizer for symbolic/annotated disassembly.
This is a basic first step towards symbolization of disassembled
instructions. This used to be done using externally provided (C API)
callbacks. This patch introduces:
- the MCSymbolizer class, that mimics the same functions that were used
in the X86 and ARM disassemblers to symbolize immediate operands and
to annotate loads based off PC (for things like c string literals).
- the MCExternalSymbolizer class, which implements the old C API.
- the MCRelocationInfo class, which provides a way for targets to
translate relocations (either object::RelocationRef, or disassembler
C API VariantKinds) to MCExprs.
- the MCObjectSymbolizer class, which does symbolization using what it
finds in an object::ObjectFile. This makes simple symbolization (with
no fancy relocation stuff) work for all object formats!
- x86-64 Mach-O and ELF MCRelocationInfos.
- A basic ARM Mach-O MCRelocationInfo, that provides just enough to
support the C API VariantKinds.
Most of what works in otool (the only user of the old symbolization API
that I know of) for x86-64 symbolic disassembly (-tvV) works, namely:
- symbol references: call _foo; jmp 15 <_foo+50>
- relocations: call _foo-_bar; call _foo-4
- __cf?string: leaq 193(%rip), %rax ## literal pool for "hello"
Stub support is the main missing part (because libObject doesn't know,
among other things, about mach-o indirect symbols).
As for the MCSymbolizer API, instead of relying on the disassemblers
to call the tryAdding* methods, maybe this could be done automagically
using InstrInfo? For instance, even though PC-relative LEAs are used
to get the address of string literals in a typical Mach-O file, a MOV
would be used in an ELF file. And right now, the explicit symbolization
only recognizes PC-relative LEAs. InstrInfo should have already have
most of what is needed to know what to symbolize, so this can
definitely be improved.
I'd also like to remove object::RelocationRef::getValueString (it seems
only used by relocation printing in objdump), as simply printing the
created MCExpr is definitely enough (and cleaner than string concats).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182625 91177308-0d34-0410-b5e6-96231b3b80d8
2013-05-24 00:39:57 +00:00
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if (RequiredForExec == false || Size == 0)
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continue;
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AddrToSection.insert(StartAddr, StartAddr + Size - 1,
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SI->getRawDataRefImpl().p);
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for (relocation_iterator RI = SI->begin_relocations(),
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RE = SI->end_relocations();
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RI != RE;
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RI.increment(ec)) {
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if (ec) break;
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// FIXME: libObject is inconsistent regarding error handling. The
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// overwhelming majority of methods always return object_error::success,
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// and assert for simple errors.. Here, ELFObjectFile::getRelocationOffset
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// asserts when the file type isn't ET_REL.
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// This workaround handles x86-64 elf, the only one that has a relocinfo.
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uint64_t Offset;
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if (Obj->isELF()) {
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const ELF64LEObjectFile *ELFObj = dyn_cast<ELF64LEObjectFile>(Obj);
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if (ELFObj == 0)
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break;
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if (ELFObj->getElfHeader()->e_type == ELF::ET_REL) {
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RI->getOffset(Offset);
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Offset += StartAddr;
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} else {
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RI->getAddress(Offset);
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}
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} else {
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RI->getOffset(Offset);
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Offset += StartAddr;
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}
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// At a specific address, only keep the first relocation.
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if (AddrToReloc.find(Offset) == AddrToReloc.end())
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AddrToReloc[Offset] = *RI;
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}
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}
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}
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bool MCObjectSymbolizer::
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tryAddingSymbolicOperand(MCInst &MI, raw_ostream &cStream,
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int64_t Value, uint64_t Address, bool IsBranch,
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uint64_t Offset, uint64_t InstSize) {
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AddrToRelocMap::iterator RI = AddrToReloc.find(Address + Offset);
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if (RI != AddrToReloc.end()) {
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if (const MCExpr *RelExpr = RelInfo->createExprForRelocation(RI->second)) {
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MI.addOperand(MCOperand::CreateExpr(RelExpr));
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return true;
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}
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// Only try to create a symbol+offset expression if there is no relocation.
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return false;
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}
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// Interpret Value as a branch target.
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if (IsBranch == false)
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return false;
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uint64_t UValue = Value;
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// FIXME: map instead of looping each time?
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error_code ec;
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for (symbol_iterator SI = Obj->begin_symbols(),
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SE = Obj->end_symbols();
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SI != SE;
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SI.increment(ec)) {
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if (ec) break;
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uint64_t SymAddr; SI->getAddress(SymAddr);
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uint64_t SymSize; SI->getSize(SymSize);
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StringRef SymName; SI->getName(SymName);
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SymbolRef::Type SymType; SI->getType(SymType);
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if (SymAddr == UnknownAddressOrSize || SymSize == UnknownAddressOrSize
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|| SymName.empty() || SymType != SymbolRef::ST_Function)
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continue;
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if ( SymAddr == UValue ||
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(SymAddr <= UValue && SymAddr + SymSize > UValue)) {
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MCSymbol *Sym = Ctx.GetOrCreateSymbol(SymName);
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const MCExpr *Expr = MCSymbolRefExpr::Create(Sym, Ctx);
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if (SymAddr != UValue) {
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const MCExpr *Off = MCConstantExpr::Create(UValue - SymAddr, Ctx);
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Expr = MCBinaryExpr::CreateAdd(Expr, Off, Ctx);
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}
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MI.addOperand(MCOperand::CreateExpr(Expr));
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return true;
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}
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}
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return false;
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}
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void MCObjectSymbolizer::
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tryAddingPcLoadReferenceComment(raw_ostream &cStream,
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int64_t Value, uint64_t Address) {
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}
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MCObjectSymbolizer *
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MCObjectSymbolizer::createObjectSymbolizer(MCContext &Ctx,
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OwningPtr<MCRelocationInfo> &RelInfo,
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const ObjectFile *Obj) {
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if (const MachOObjectFile *MachOOF = dyn_cast<MachOObjectFile>(Obj)) {
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return new MCMachObjectSymbolizer(Ctx, RelInfo, MachOOF);
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}
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return new MCObjectSymbolizer(Ctx, RelInfo, Obj);
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}
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