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llvm-mirror/lib/Object/Binary.cpp
Georgii Rymar 04b897752e Recommit: [llvm-readelf/obj] - Allow dumping of ELF header even if some elements are corrupt.
This is recommit for D90903 with fixes for BB:
1) Used std::move<> when returning Expected<> (http://lab.llvm.org:8011/#/builders/112/builds/913)
2) Fixed the name of temporarily file in the file-headers.test (http://lab.llvm.org:8011/#/builders/36/builds/1269)
   (a local old temporarily file was used before)

For creating `ELFObjectFile` instances we have the factory method
`ELFObjectFile<ELFT>::create(MemoryBufferRef Object)`.

The problem of this method is that it scans the section header to locate some sections.
When a file is truncated or has broken fields in the ELF header, this approach does
not allow us to create the `ELFObjectFile` and dump the ELF header.

This is https://bugs.llvm.org/show_bug.cgi?id=40804

This patch suggests a solution - it allows to delay scaning sections in the
`ELFObjectFile<ELFT>::create`. It now allows user code to call an object
initialization (`initContent()`) later. With that it is possible,
for example, for dumpers just to dump the file header and exit.
By default initialization is still performed as before, what helps to keep
the logic of existent callers untouched.

I've experimented with different approaches when worked on this patch.
I think this approach is better than doing initialization of sections (i.e. scan of them)
on demand, because normally users of `ELFObjectFile` API expect to work with a valid object.
In most cases when a section header table can't be read (because of an error), we don't
have to continue to work with object. So we probably don't need to implement a more complex API.

Differential revision: https://reviews.llvm.org/D90903
2020-11-09 12:53:53 +03:00

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//===- Binary.cpp - A generic binary file ---------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines the Binary class.
//
//===----------------------------------------------------------------------===//
#include "llvm/Object/Binary.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/BinaryFormat/Magic.h"
#include "llvm/Object/Archive.h"
#include "llvm/Object/Error.h"
#include "llvm/Object/MachOUniversal.h"
#include "llvm/Object/Minidump.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Object/TapiUniversal.h"
#include "llvm/Object/WindowsResource.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include <algorithm>
#include <memory>
#include <system_error>
using namespace llvm;
using namespace object;
Binary::~Binary() = default;
Binary::Binary(unsigned int Type, MemoryBufferRef Source)
: TypeID(Type), Data(Source) {}
StringRef Binary::getData() const { return Data.getBuffer(); }
StringRef Binary::getFileName() const { return Data.getBufferIdentifier(); }
MemoryBufferRef Binary::getMemoryBufferRef() const { return Data; }
Expected<std::unique_ptr<Binary>> object::createBinary(MemoryBufferRef Buffer,
LLVMContext *Context,
bool InitContent) {
file_magic Type = identify_magic(Buffer.getBuffer());
switch (Type) {
case file_magic::archive:
return Archive::create(Buffer);
case file_magic::elf:
case file_magic::elf_relocatable:
case file_magic::elf_executable:
case file_magic::elf_shared_object:
case file_magic::elf_core:
case file_magic::macho_object:
case file_magic::macho_executable:
case file_magic::macho_fixed_virtual_memory_shared_lib:
case file_magic::macho_core:
case file_magic::macho_preload_executable:
case file_magic::macho_dynamically_linked_shared_lib:
case file_magic::macho_dynamic_linker:
case file_magic::macho_bundle:
case file_magic::macho_dynamically_linked_shared_lib_stub:
case file_magic::macho_dsym_companion:
case file_magic::macho_kext_bundle:
case file_magic::coff_object:
case file_magic::coff_import_library:
case file_magic::pecoff_executable:
case file_magic::bitcode:
case file_magic::xcoff_object_32:
case file_magic::xcoff_object_64:
case file_magic::wasm_object:
return ObjectFile::createSymbolicFile(Buffer, Type, Context, InitContent);
case file_magic::macho_universal_binary:
return MachOUniversalBinary::create(Buffer);
case file_magic::windows_resource:
return WindowsResource::createWindowsResource(Buffer);
case file_magic::pdb:
// PDB does not support the Binary interface.
return errorCodeToError(object_error::invalid_file_type);
case file_magic::unknown:
case file_magic::coff_cl_gl_object:
// Unrecognized object file format.
return errorCodeToError(object_error::invalid_file_type);
case file_magic::minidump:
return MinidumpFile::create(Buffer);
case file_magic::tapi_file:
return TapiUniversal::create(Buffer);
}
llvm_unreachable("Unexpected Binary File Type");
}
Expected<OwningBinary<Binary>>
object::createBinary(StringRef Path, LLVMContext *Context, bool InitContent) {
ErrorOr<std::unique_ptr<MemoryBuffer>> FileOrErr =
MemoryBuffer::getFileOrSTDIN(Path, /*FileSize=*/-1,
/*RequiresNullTerminator=*/false);
if (std::error_code EC = FileOrErr.getError())
return errorCodeToError(EC);
std::unique_ptr<MemoryBuffer> &Buffer = FileOrErr.get();
Expected<std::unique_ptr<Binary>> BinOrErr =
createBinary(Buffer->getMemBufferRef(), Context, InitContent);
if (!BinOrErr)
return BinOrErr.takeError();
std::unique_ptr<Binary> &Bin = BinOrErr.get();
return OwningBinary<Binary>(std::move(Bin), std::move(Buffer));
}