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llvm-mirror/include/llvm/MC/MCRelocationInfo.h
Ahmed Bougacha 6979d48fa4 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).

llvm-svn: 182625
2013-05-24 00:39:57 +00:00

56 lines
1.7 KiB
C++

//==-- llvm/MC/MCRelocationInfo.h --------------------------------*- C++ -*-==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file declares the MCRelocationInfo class, which provides methods to
// create MCExprs from relocations, either found in an object::ObjectFile
// (object::RelocationRef), or provided through the C API.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_MC_MCRELOCATIONINFO_H
#define LLVM_MC_MCRELOCATIONINFO_H
#include "llvm/Support/Compiler.h"
namespace llvm {
namespace object {
class RelocationRef;
}
class MCExpr;
class MCContext;
/// \brief Create MCExprs from relocations found in an object file.
class MCRelocationInfo {
MCRelocationInfo(const MCRelocationInfo &) LLVM_DELETED_FUNCTION;
void operator=(const MCRelocationInfo &) LLVM_DELETED_FUNCTION;
protected:
MCContext &Ctx;
public:
MCRelocationInfo(MCContext &Ctx);
virtual ~MCRelocationInfo();
/// \brief Create an MCExpr for the relocation \p Rel.
/// \returns If possible, an MCExpr corresponding to Rel, else 0.
virtual const MCExpr *createExprForRelocation(object::RelocationRef Rel);
/// \brief Create an MCExpr for the target-specific \p VariantKind.
/// The VariantKinds are defined in llvm-c/Disassembler.h.
/// Used by MCExternalSymbolizer.
/// \returns If possible, an MCExpr corresponding to VariantKind, else 0.
virtual const MCExpr *createExprForCAPIVariantKind(const MCExpr *SubExpr,
unsigned VariantKind);
};
}
#endif