Exceptions.cpp | Explore in Territory

//===- bolt/Core/Exceptions.cpp - Helpers for C++ exceptions --------------===//
//
// 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 implements functions for handling C++ exception meta data.
//
// Some of the code is taken from examples/ExceptionDemo
//
//===----------------------------------------------------------------------===//

#include "bolt/Core/Exceptions.h"
#include "bolt/Core/BinaryFunction.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/DebugInfo/DWARF/DWARFDebugFrame.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Errc.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include <map>

#undef  DEBUG_TYPE
#define DEBUG_TYPE …

usingnamespacellvm::dwarf;

namespace opts {

extern llvm::cl::OptionCategory BoltCategory;

extern llvm::cl::opt<unsigned> Verbosity;

static llvm::cl::opt<bool>
    PrintExceptions("print-exceptions",
                    llvm::cl::desc("print exception handling data"),
                    llvm::cl::Hidden, llvm::cl::cat(BoltCategory));

} // namespace opts

namespace llvm {
namespace bolt {

// Read and dump the .gcc_exception_table section entry.
//
// .gcc_except_table section contains a set of Language-Specific Data Areas -
// a fancy name for exception handling tables. There's one  LSDA entry per
// function. However, we can't actually tell which function LSDA refers to
// unless we parse .eh_frame entry that refers to the LSDA.
// Then inside LSDA most addresses are encoded relative to the function start,
// so we need the function context in order to get to real addresses.
//
// The best visual representation of the tables comprising LSDA and
// relationships between them is illustrated at:
//   https://github.com/itanium-cxx-abi/cxx-abi/blob/master/exceptions.pdf
// Keep in mind that GCC implementation deviates slightly from that document.
//
// To summarize, there are 4 tables in LSDA: call site table, actions table,
// types table, and types index table (for indirection). The main table contains
// call site entries. Each call site includes a PC range that can throw an
// exception, a handler (landing pad), and a reference to an entry in the action
// table. The handler and/or action could be 0. The action entry is a head
// of a list of actions associated with a call site. The action table contains
// all such lists (it could be optimized to share list tails). Each action could
// be either to catch an exception of a given type, to perform a cleanup, or to
// propagate the exception after filtering it out (e.g. to make sure function
// exception specification is not violated). Catch action contains a reference
// to an entry in the type table, and filter action refers to an entry in the
// type index table to encode a set of types to filter.
//
// Call site table follows LSDA header. Action table immediately follows the
// call site table.
//
// Both types table and type index table start at the same location, but they
// grow in opposite directions (types go up, indices go down). The beginning of
// these tables is encoded in LSDA header. Sizes for both of the tables are not
// included anywhere.
//
// We have to parse all of the tables to determine their sizes. Then we have
// to parse the call site table and associate discovered information with
// actual call instructions and landing pad blocks.
//
// For the purpose of rewriting exception handling tables, we can reuse action,
// and type index tables in their original binary format.
//
// Type table could be encoded using position-independent references, and thus
// may require relocation.
//
// Ideally we should be able to re-write LSDA in-place, without the need to
// allocate a new space for it. Sadly there's no guarantee that the new call
// site table will be the same size as GCC uses uleb encodings for PC offsets.
//
// Note: some functions have LSDA entries with 0 call site entries.
Error BinaryFunction::parseLSDA(ArrayRef<uint8_t> LSDASectionData,
                                uint64_t LSDASectionAddress) { … }

void BinaryFunction::updateEHRanges() { … }

const uint8_t DWARF_CFI_PRIMARY_OPCODE_MASK = …;

CFIReaderWriter::CFIReaderWriter(BinaryContext &BC,
                                 const DWARFDebugFrame &EHFrame)
    : … { … }

bool CFIReaderWriter::fillCFIInfoFor(BinaryFunction &Function) const { … }

std::vector<char> CFIReaderWriter::generateEHFrameHeader(
    const DWARFDebugFrame &OldEHFrame, const DWARFDebugFrame &NewEHFrame,
    uint64_t EHFrameHeaderAddress,
    std::vector<uint64_t> &FailedAddresses) const { … }

Error EHFrameParser::parseCIE(uint64_t StartOffset) { … }

Error EHFrameParser::parseFDE(uint64_t CIEPointer,
                              uint64_t StartStructureOffset) { … }

Error EHFrameParser::parse() { … }

Error EHFrameParser::parse(DWARFDataExtractor Data, uint64_t EHFrameAddress,
                           PatcherCallbackTy PatcherCallback) { … }

} // namespace bolt
} // namespace llvm
llvm/bolt/lib/Core/Exceptions.cpp
