// -*- mode: C++ -*-
// Copyright (c) 2010, Google Inc.
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//
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
// macho_reader.h: A class for parsing Mach-O files.
#ifndef BREAKPAD_COMMON_MAC_MACHO_READER_H_
#define BREAKPAD_COMMON_MAC_MACHO_READER_H_
#include <mach-o/loader.h>
#include <mach-o/fat.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include <map>
#include <string>
#include <vector>
#include "common/byte_cursor.h"
namespace google_breakpad {
namespace mach_o {
using std::map;
using std::string;
using std::vector;
// The Mac headers don't specify particular types for these groups of
// constants, but defining them here provides some documentation
// value. We also give them the same width as the fields in which
// they appear, which makes them a bit easier to use with ByteCursors.
typedef uint32_t Magic;
typedef uint32_t FileType;
typedef uint32_t FileFlags;
typedef uint32_t LoadCommandType;
typedef uint32_t SegmentFlags;
typedef uint32_t SectionFlags;
// A parser for fat binary files, used to store universal binaries.
// When applied to a (non-fat) Mach-O file, this behaves as if the
// file were a fat file containing a single object file.
class FatReader {
public:
// A class for reporting errors found while parsing fat binary files. The
// default definitions of these methods print messages to stderr.
class Reporter {
public:
// Create a reporter that attributes problems to |filename|.
explicit Reporter(const string &filename) : filename_(filename) { }
virtual ~Reporter() { }
// The data does not begin with a fat binary or Mach-O magic number.
// This is a fatal error.
virtual void BadHeader();
// The Mach-O fat binary file ends abruptly, without enough space
// to contain an object file it claims is present.
virtual void MisplacedObjectFile();
// The file ends abruptly: either it is not large enough to hold a
// complete header, or the header implies that contents are present
// beyond the actual end of the file.
virtual void TooShort();
private:
// The filename to which the reader should attribute problems.
string filename_;
};
// Create a fat binary file reader that uses |reporter| to report problems.
explicit FatReader(Reporter *reporter) : reporter_(reporter) { }
// Read the |size| bytes at |buffer| as a fat binary file. On success,
// return true; on failure, report the problem to reporter_ and return
// false.
//
// If the data is a plain Mach-O file, rather than a fat binary file,
// then the reader behaves as if it had found a fat binary file whose
// single object file is the Mach-O file.
bool Read(const uint8_t *buffer, size_t size);
// Return an array of 'struct fat_arch' structures describing the
// object files present in this fat binary file. Set |size| to the
// number of elements in the array.
//
// Assuming Read returned true, the entries are validated: it is
// safe to assume that the offsets and sizes in each 'struct
// fat_arch' refer to subranges of the bytes passed to Read.
//
// If there are no object files in this fat binary, then this
// function can return NULL.
//
// The array is owned by this FatReader instance; it will be freed when
// this FatReader is destroyed.
//
// This function returns a C-style array instead of a vector to make it
// possible to use the result with OS X functions like NXFindBestFatArch,
// so that the symbol dumper will behave consistently with other OS X
// utilities that work with fat binaries.
const struct fat_arch *object_files(size_t *count) const {
*count = object_files_.size();
if (object_files_.size() > 0)
return &object_files_[0];
return NULL;
}
private:
// We use this to report problems parsing the file's contents. (WEAK)
Reporter *reporter_;
// The contents of the fat binary or Mach-O file we're parsing. We do not
// own the storage it refers to.
ByteBuffer buffer_;
// The magic number of this binary, in host byte order.
Magic magic_;
// The list of object files in this binary.
// object_files_.size() == fat_header.nfat_arch
vector<struct fat_arch> object_files_;
};
// A segment in a Mach-O file. All these fields have been byte-swapped as
// appropriate for use by the executing architecture.
struct Segment {
// The ByteBuffers below point into the bytes passed to the Reader that
// created this Segment.
ByteBuffer section_list; // This segment's section list.
ByteBuffer contents; // This segment's contents.
// This segment's name.
string name;
// The address at which this segment should be loaded in memory. If
// bits_64 is false, only the bottom 32 bits of this value are valid.
uint64_t vmaddr;
// The size of this segment when loaded into memory. This may be larger
// than contents.Size(), in which case the extra area will be
// initialized with zeros. If bits_64 is false, only the bottom 32 bits
// of this value are valid.
uint64_t vmsize;
// The maximum and initial VM protection of this segment's contents.
uint32_t maxprot;
uint32_t initprot;
// The number of sections in section_list.
uint32_t nsects;
// Flags describing this segment, from SegmentFlags.
uint32_t flags;
// True if this is a 64-bit section; false if it is a 32-bit section.
bool bits_64;
};
// A section in a Mach-O file. All these fields have been byte-swapped as
// appropriate for use by the executing architecture.
struct Section {
// This section's contents. This points into the bytes passed to the
// Reader that created this Section.
ByteBuffer contents;
// This section's name.
string section_name; // section[_64].sectname
// The name of the segment this section belongs to.
string segment_name; // section[_64].segname
// The address at which this section's contents should be loaded in
// memory. If bits_64 is false, only the bottom 32 bits of this value
// are valid.
uint64_t address;
// The contents of this section should be loaded into memory at an
// address which is a multiple of (two raised to this power).
uint32_t align;
// Flags from SectionFlags describing the section's contents.
uint32_t flags;
// We don't support reading relocations yet.
// True if this is a 64-bit section; false if it is a 32-bit section.
bool bits_64;
};
// A map from section names to Sections.
typedef map<string, Section> SectionMap;
// A reader for a Mach-O file.
//
// This does not handle fat binaries; see FatReader above. FatReader
// provides a friendly interface for parsing data that could be either a
// fat binary or a Mach-O file.
class Reader {
public:
// A class for reporting errors found while parsing Mach-O files. The
// default definitions of these member functions print messages to
// stderr.
class Reporter {
public:
// Create a reporter that attributes problems to |filename|.
explicit Reporter(const string &filename) : filename_(filename) { }
virtual ~Reporter() { }
// Reporter functions for fatal errors return void; the reader will
// definitely return an error to its caller after calling them
// The data does not begin with a Mach-O magic number, or the magic
// number does not match the expected value for the cpu architecture.
// This is a fatal error.
virtual void BadHeader();
// The data contained in a Mach-O fat binary (|cpu_type|, |cpu_subtype|)
// does not match the expected CPU architecture
// (|expected_cpu_type|, |expected_cpu_subtype|).
virtual void CPUTypeMismatch(cpu_type_t cpu_type,
cpu_subtype_t cpu_subtype,
cpu_type_t expected_cpu_type,
cpu_subtype_t expected_cpu_subtype);
// The file ends abruptly: either it is not large enough to hold a
// complete header, or the header implies that contents are present
// beyond the actual end of the file.
virtual void HeaderTruncated();
// The file's load command region, as given in the Mach-O header, is
// too large for the file.
virtual void LoadCommandRegionTruncated();
// The file's Mach-O header claims the file contains |claimed| load
// commands, but the I'th load command, of type |type|, extends beyond
// the end of the load command region, as given by the Mach-O header.
// If |type| is zero, the command's type was unreadable.
virtual void LoadCommandsOverrun(size_t claimed, size_t i,
LoadCommandType type);
// The contents of the |i|'th load command, of type |type|, extend beyond
// the size given in the load command's header.
virtual void LoadCommandTooShort(size_t i, LoadCommandType type);
// The LC_SEGMENT or LC_SEGMENT_64 load command for the segment named
// |name| is too short to hold the sections that its header says it does.
// (This more specific than LoadCommandTooShort.)
virtual void SectionsMissing(const string &name);
// The segment named |name| claims that its contents lie beyond the end
// of the file.
virtual void MisplacedSegmentData(const string &name);
// The section named |section| in the segment named |segment| claims that
// its contents do not lie entirely within the segment.
virtual void MisplacedSectionData(const string §ion,
const string &segment);
// The LC_SYMTAB command claims that symbol table contents are located
// beyond the end of the file.
virtual void MisplacedSymbolTable();
// An attempt was made to read a Mach-O file of the unsupported
// CPU architecture |cpu_type|.
virtual void UnsupportedCPUType(cpu_type_t cpu_type);
private:
string filename_;
};
// A handler for sections parsed from a segment. The WalkSegmentSections
// member function accepts an instance of this class, and applies it to
// each section defined in a given segment.
class SectionHandler {
public:
virtual ~SectionHandler() { }
// Called to report that the segment's section list contains |section|.
// This should return true if the iteration should continue, or false
// if it should stop.
virtual bool HandleSection(const Section §ion) = 0;
};
// A handler for the load commands in a Mach-O file.
class LoadCommandHandler {
public:
LoadCommandHandler() { }
virtual ~LoadCommandHandler() { }
// When called from WalkLoadCommands, the following handler functions
// should return true if they wish to continue iterating over the load
// command list, or false if they wish to stop iterating.
//
// When called from LoadCommandIterator::Handle or Reader::Handle,
// these functions' return values are simply passed through to Handle's
// caller.
//
// The definitions provided by this base class simply return true; the
// default is to silently ignore sections whose member functions the
// subclass doesn't override.
// COMMAND is load command we don't recognize. We provide only the
// command type and a ByteBuffer enclosing the command's data (If we
// cannot parse the command type or its size, we call
// reporter_->IncompleteLoadCommand instead.)
virtual bool UnknownCommand(LoadCommandType type,
const ByteBuffer &contents) {
return true;
}
// The load command is LC_SEGMENT or LC_SEGMENT_64, defining a segment
// with the properties given in |segment|.
virtual bool SegmentCommand(const Segment &segment) {
return true;
}
// The load command is LC_SYMTAB. |entries| holds the array of nlist
// entries, and |names| holds the strings the entries refer to.
virtual bool SymtabCommand(const ByteBuffer &entries,
const ByteBuffer &names) {
return true;
}
// Add handler functions for more load commands here as needed.
};
// Create a Mach-O file reader that reports problems to |reporter|.
explicit Reader(Reporter *reporter)
: reporter_(reporter) { }
// Read the given data as a Mach-O file. The reader retains pointers
// into the data passed, so the data should live as long as the reader
// does. On success, return true; on failure, return false.
//
// At most one of these functions should be invoked once on each Reader
// instance.
bool Read(const uint8_t *buffer,
size_t size,
cpu_type_t expected_cpu_type,
cpu_subtype_t expected_cpu_subtype);
bool Read(const ByteBuffer &buffer,
cpu_type_t expected_cpu_type,
cpu_subtype_t expected_cpu_subtype) {
return Read(buffer.start,
buffer.Size(),
expected_cpu_type,
expected_cpu_subtype);
}
// Return this file's characteristics, as found in the Mach-O header.
cpu_type_t cpu_type() const { return cpu_type_; }
cpu_subtype_t cpu_subtype() const { return cpu_subtype_; }
FileType file_type() const { return file_type_; }
FileFlags flags() const { return flags_; }
// Return true if this is a 64-bit Mach-O file, false if it is a 32-bit
// Mach-O file.
bool bits_64() const { return bits_64_; }
// Return true if this is a big-endian Mach-O file, false if it is
// little-endian.
bool big_endian() const { return big_endian_; }
// Apply |handler| to each load command in this Mach-O file, stopping when
// a handler function returns false. If we encounter a malformed load
// command, report it via reporter_ and return false. Return true if all
// load commands were parseable and all handlers returned true.
bool WalkLoadCommands(LoadCommandHandler *handler) const;
// Set |segment| to describe the segment named |name|, if present. If
// found, |segment|'s byte buffers refer to a subregion of the bytes
// passed to Read. If we find the section, return true; otherwise,
// return false.
bool FindSegment(const string &name, Segment *segment) const;
// Apply |handler| to each section defined in |segment|. If |handler| returns
// false, stop iterating and return false. If all calls to |handler| return
// true and we reach the end of the section list, return true.
bool WalkSegmentSections(const Segment &segment, SectionHandler *handler)
const;
// Clear |section_map| and then populate it with a map of the sections
// in |segment|, from section names to Section structures.
// Each Section's contents refer to bytes in |segment|'s contents.
// On success, return true; if a problem occurs, report it and return false.
bool MapSegmentSections(const Segment &segment, SectionMap *section_map)
const;
private:
// Used internally.
class SegmentFinder;
class SectionMapper;
// We use this to report problems parsing the file's contents. (WEAK)
Reporter *reporter_;
// The contents of the Mach-O file we're parsing. We do not own the
// storage it refers to.
ByteBuffer buffer_;
// True if this file is big-endian.
bool big_endian_;
// True if this file is a 64-bit Mach-O file.
bool bits_64_;
// This file's cpu type and subtype.
cpu_type_t cpu_type_; // mach_header[_64].cputype
cpu_subtype_t cpu_subtype_; // mach_header[_64].cpusubtype
// This file's type.
FileType file_type_; // mach_header[_64].filetype
// The region of buffer_ occupied by load commands.
ByteBuffer load_commands_;
// The number of load commands in load_commands_.
uint32_t load_command_count_; // mach_header[_64].ncmds
// This file's header flags.
FileFlags flags_;
};
} // namespace mach_o
} // namespace google_breakpad
#endif // BREAKPAD_COMMON_MAC_MACHO_READER_H_