llvm/llvm/include/llvm/DebugInfo/GSYM/GsymCreator.h

//===- GsymCreator.h --------------------------------------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_DEBUGINFO_GSYM_GSYMCREATOR_H
#define LLVM_DEBUGINFO_GSYM_GSYMCREATOR_H

#include <functional>
#include <memory>
#include <mutex>
#include <thread>

#include "llvm/ADT/AddressRanges.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/DebugInfo/GSYM/FileEntry.h"
#include "llvm/DebugInfo/GSYM/FunctionInfo.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/Path.h"

namespace llvm {

namespace gsym {
class FileWriter;
class OutputAggregator;

/// GsymCreator is used to emit GSYM data to a stand alone file or section
/// within a file.
///
/// The GsymCreator is designed to be used in 3 stages:
/// - Create FunctionInfo objects and add them
/// - Finalize the GsymCreator object
/// - Save to file or section
///
/// The first stage involves creating FunctionInfo objects from another source
/// of information like compiler debug info metadata, DWARF or Breakpad files.
/// Any strings in the FunctionInfo or contained information, like InlineInfo
/// or LineTable objects, should get the string table offsets by calling
/// GsymCreator::insertString(...). Any file indexes that are needed should be
/// obtained by calling GsymCreator::insertFile(...). All of the function calls
/// in GsymCreator are thread safe. This allows multiple threads to create and
/// add FunctionInfo objects while parsing debug information.
///
/// Once all of the FunctionInfo objects have been added, the
/// GsymCreator::finalize(...) must be called prior to saving. This function
/// will sort the FunctionInfo objects, finalize the string table, and do any
/// other passes on the information needed to prepare the information to be
/// saved.
///
/// Once the object has been finalized, it can be saved to a file or section.
///
/// ENCODING
///
/// GSYM files are designed to be memory mapped into a process as shared, read
/// only data, and used as is.
///
/// The GSYM file format when in a stand alone file consists of:
///   - Header
///   - Address Table
///   - Function Info Offsets
///   - File Table
///   - String Table
///   - Function Info Data
///
/// HEADER
///
/// The header is fully described in "llvm/DebugInfo/GSYM/Header.h".
///
/// ADDRESS TABLE
///
/// The address table immediately follows the header in the file and consists
/// of Header.NumAddresses address offsets. These offsets are sorted and can be
/// binary searched for efficient lookups. Addresses in the address table are
/// stored as offsets from a 64 bit base address found in Header.BaseAddress.
/// This allows the address table to contain 8, 16, or 32 offsets. This allows
/// the address table to not require full 64 bit addresses for each address.
/// The resulting GSYM size is smaller and causes fewer pages to be touched
/// during address lookups when the address table is smaller. The size of the
/// address offsets in the address table is specified in the header in
/// Header.AddrOffSize. The first offset in the address table is aligned to
/// Header.AddrOffSize alignment to ensure efficient access when loaded into
/// memory.
///
/// FUNCTION INFO OFFSETS TABLE
///
/// The function info offsets table immediately follows the address table and
/// consists of Header.NumAddresses 32 bit file offsets: one for each address
/// in the address table. This data is aligned to a 4 byte boundary. The
/// offsets in this table are the relative offsets from the start offset of the
/// GSYM header and point to the function info data for each address in the
/// address table. Keeping this data separate from the address table helps to
/// reduce the number of pages that are touched when address lookups occur on a
/// GSYM file.
///
/// FILE TABLE
///
/// The file table immediately follows the function info offsets table. The
/// encoding of the FileTable is:
///
/// struct FileTable {
///   uint32_t Count;
///   FileEntry Files[];
/// };
///
/// The file table starts with a 32 bit count of the number of files that are
/// used in all of the function info, followed by that number of FileEntry
/// structures. The file table is aligned to a 4 byte boundary, Each file in
/// the file table is represented with a FileEntry structure.
/// See "llvm/DebugInfo/GSYM/FileEntry.h" for details.
///
/// STRING TABLE
///
/// The string table follows the file table in stand alone GSYM files and
/// contains all strings for everything contained in the GSYM file. Any string
/// data should be added to the string table and any references to strings
/// inside GSYM information must be stored as 32 bit string table offsets into
/// this string table. The string table always starts with an empty string at
/// offset zero and is followed by any strings needed by the GSYM information.
/// The start of the string table is not aligned to any boundary.
///
/// FUNCTION INFO DATA
///
/// The function info data is the payload that contains information about the
/// address that is being looked up. It contains all of the encoded
/// FunctionInfo objects. Each encoded FunctionInfo's data is pointed to by an
/// entry in the Function Info Offsets Table. For details on the exact encoding
/// of FunctionInfo objects, see "llvm/DebugInfo/GSYM/FunctionInfo.h".
class GsymCreator { … };

} // namespace gsym
} // namespace llvm

#endif // LLVM_DEBUGINFO_GSYM_GSYMCREATOR_H