Add MachOImageReader and its test

util/mac/mach_o_image_reader.h

+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_UTIL_MAC_MACH_O_IMAGE_READER_H_
+#define CRASHPAD_UTIL_MAC_MACH_O_IMAGE_READER_H_
+
+#include <mach/mach.h>
+#include <stdint.h>
+
+#include <map>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "util/misc/initialization_state_dcheck.h"
+#include "util/misc/uuid.h"
+#include "util/stdlib/pointer_container.h"
+#include "util/mac/process_types.h"
+
+namespace crashpad {
+
+class MachOImageSegmentReader;
+class ProcessReader;
+
+//! \brief A reader for Mach-O images mapped into another process.
+//!
+//! This class is capable of reading both 32-bit (`mach_header`/`MH_MAGIC`) and
+//! 64-bit (`mach_header_64`/`MH_MAGIC_64`) images based on the bitness of the
+//! remote process.
+class MachOImageReader {
+ public:
+  MachOImageReader();
+  ~MachOImageReader();
+
+  //! \brief Reads the Mach-O image file’s load commands from another process.
+  //!
+  //! This method must only be called once on an object. This method must be
+  //! called successfully before any other method in this class may be called.
+  //!
+  //! \param[in] process_reader The reader for the remote process.
+  //! \param[in] address The address, in the remote process’ address space,
+  //!     where the `mach_header` or `mach_header_64` at the beginning of the
+  //!     image to be read is located. This address can be determined by reading
+  //!     the remote process’ dyld information (see
+  //!     util/mac/process_types/dyld_images.proctype).
+  //! \param[in] name The module’s name, a string to be used in logged messages.
+  //!     This string is for diagnostic purposes only, and may be empty.
+  //!
+  //! \return `true` if the image was read successfully, including all load
+  //!     commands. `false` otherwise, with an appropriate message logged.
+  bool Initialize(ProcessReader* process_reader,
+                  mach_vm_address_t address,
+                  const std::string& name);
+
+  //! \brief Returns the Mach-O file type.
+  //!
+  //! This value comes from the `filetype` field of the `mach_header` or
+  //! `mach_header_64`. Common values include `MH_EXECUTE`, `MH_DYLIB`,
+  //! `MH_DYLINKER`, and `MH_BUNDLE`.
+  uint32_t FileType() const { return file_type_; }
+
+  //! \brief Returns the Mach-O image’s load address.
+  //!
+  //! This is the value passed as \a address to Initialize().
+  mach_vm_address_t Address() const { return address_; }
+
+  //! \brief Returns the mapped size of the Mach-O image’s __TEXT segment.
+  //!
+  //! Note that this is returns only the size of the __TEXT segment, not of any
+  //! other segment. This is because the interface only allows one load address
+  //! and size to be reported, but Mach-O image files may consist of multiple
+  //! discontiguous segments. By convention, the __TEXT segment is always mapped
+  //! at the beginning of a Mach-O image file, and it is the most useful for the
+  //! expected intended purpose of collecting data to obtain stack backtraces.
+  //! The implementation insists during initialization that the __TEXT segment
+  //! be mapped at the beginning of the file.
+  //!
+  //! In practice, discontiguous segments are only found for images that have
+  //! loaded out of the dyld shared cache, but the __TEXT segment’s size is
+  //! returned for modules that loaded with contiguous segments as well for
+  //! consistency.
+  mach_vm_size_t Size() const { return size_; }
+
+  //! \brief Returns the Mach-O image’s “slide,” the difference between its
+  //!     actual load address and its preferred load address.
+  //!
+  //! “Slide” is computed by subtracting the __TEXT segment’s preferred load
+  //! address from its actual load address. It will be reported as a positive
+  //! offset when the actual load address is greater than the preferred load
+  //! address. The preferred load address is taken to be the segment’s reported
+  //! `vmaddr` value.
+  mach_vm_size_t Slide() const { return slide_; }
+
+  //! \brief Obtain segment information by segment name.
+  //!
+  //! \param[in] segment_name The name of the segment to search for, for
+  //!     example, `"__TEXT"`.
+  //! \param[out] address The actual address that the segment was loaded at in
+  //!     memory, taking any “slide” into account if the segment did not load at

[Robert Sesek, 2014/09/04 13:18:42]

A similar \note about how address may differ from
MachOImageSegmentReader::vmaddr() could be useful.

+  //!     its preferred address as stored in the Mach-O image file. This
+  //!     parameter can be `NULL`.
+  //! \param[out] size The actual size of the segment as loaded at in memory.
+  //!     This value takes any expansion of the segment into account, which
+  //!     occurs when a nonsliding segment in a sliding image loads at its
+  //!     preferred address but grows by the value of the slide. This parameter
+  //!     can be `NULL`.
+  //!
+  //! \return A pointer to the segment information if it was found, or `NULL` if
+  //!     it was not found.
+  const MachOImageSegmentReader* GetSegmentByName(
+      const std::string& segment_name,
+      mach_vm_address_t* address,
+      mach_vm_size_t* size) const;
+
+  //! \brief Obtain section information by segment and section name.
+  //!
+  //! \param[in] segment_name The name of the segment to search for, for
+  //!     example, `"__TEXT"`.
+  //! \param[in] section_name The name of the section within the segment to
+  //!     search for, for example, `"__text"`.
+  //! \param[out] address The actual address that the section was loaded at in
+  //!     memory, taking any “slide” into account if the section did not load at
+  //!     its preferred address as stored in the Mach-O image file. This
+  //!     parameter can be `NULL`.
+  //!
+  //! \return A pointer to the section information if it was found, or `NULL` if
+  //!     it was not found.
+  //!
+  //! No parameter is provided for the section’s size, because it can be
+  //! obtained from the returned process_types::section::size field.
+  //!
+  //! \note The process_types::section::addr field gives the section’s preferred
+  //!     load address as stored in the Mach-O image file, and is not adjusted
+  //!     for any “slide” that may have occurred when the image was loaded. Use
+  //!     \a address to obtain the section’s actual load address.
+  const process_types::section* GetSectionByName(
+      const std::string& segment_name,
+      const std::string& section_name,
+      mach_vm_address_t* address) const;
+
+  //! \brief Obtain section information by section index.
+  //!
+  //! \param[in] index The index of the section to return, in the order that it
+  //!     appears in the segment load commands. This is a 1-based index,
+  //!     matching the section number values used for `nlist::n_sect`.
+  //! \param[out] address The actual address that the section was loaded at in
+  //!     memory, taking any “slide” into account if the section did not load at
+  //!     its preferred address as stored in the Mach-O image file. This
+  //!     parameter can be `NULL`.
+  //!
+  //! \return A pointer to the section information. If \a index is out of range,

[Robert Sesek, 2014/09/04 13:18:42]

This is a behavior difference from MachOImageSegmentReader::GetSectionAtIndex().

+  //!     logs a warning and returns `NULL`.
+  //!
+  //! No parameter is provided for the section’s size, because it can be
+  //! obtained from the returned process_types::section::size field.
+  //!
+  //! \note The process_types::section::addr field gives the section’s preferred
+  //!     load address as stored in the Mach-O image file, and is not adjusted
+  //!     for any “slide” that may have occurred when the image was loaded. Use
+  //!     \a address to obtain the section’s actual load address.
+  const process_types::section* GetSectionAtIndex(
+      size_t index,
+      mach_vm_address_t* address) const;
+
+  //! \brief Returns a Mach-O dylib image’s current version.
+  //!
+  //! This information comes from the `dylib_current_version` field of a dylib’s
+  //! `LC_ID_DYLIB` load command. For dylibs without this load command, `0` will
+  //! be returned.
+  //!
+  //! This method may only be called on Mach-O images for which FileType()
+  //! returns `MH_DYLIB`.
+  uint32_t DylibVersion() const;
+
+  //! \brief Returns a Mach-O image’s source version.
+  //!
+  //! This information comes from a Mach-O image’s `LC_SOURCE_VERSION` load
+  //! command. For Mach-O images without this load command, `0` will be
+  //! returned.
+  uint64_t SourceVersion() const { return source_version_; }
+
+  //! \brief Returns a Mach-O image’s UUID.
+  //!
+  //! This information comes from a Mach-O image’s `LC_UUID` load command. For
+  //! Mach-O images without this load command, a zeroed-out UUID value will be
+  //! returned.
+  void UUID(struct UUID* uuid) const;

[Robert Sesek, 2014/09/04 13:18:42]

Why `struct UUID` instead of just `UUID`?

+
+  //! \brief Returns the dynamic linker’s pathname.
+  //!
+  //! The dynamic linker is normally /usr/lib/dyld.
+  //!
+  //! For executable images (those with file type `MH_EXECUTE`), this is the
+  //! name provided in the `LC_LOAD_DYLINKER` load command, if any. For dynamic
+  //! linker images (those with file type `MH_DYLINKER`), this is the name
+  //! provided in the `LC_ID_DYLINKER` load command. In other cases, this will
+  //! be empty.
+  std::string DylinkerName() const { return dylinker_name_; }
+
+ private:
+  // A generic helper routine for the other Read*Command() methods.
+  template <typename T>
+  bool ReadLoadCommand(mach_vm_address_t load_command_address,
+                       const std::string& load_command_info,
+                       uint32_t expected_load_command_id,
+                       T* load_command);
+
+  // The Read*Command() methods are subroutines called by Initialize(). They are
+  // responsible for reading a single load command. They may update
+  // |initialization_data| or the member fields of their MachOImageReader

[Robert Sesek, 2014/09/04 13:18:42]

What's |initialization_data|?

+  // object. If they can’t make sense of a load command, they return false.
+  bool ReadSegmentCommand(mach_vm_address_t load_command_address,
+                          const std::string& load_command_info);
+  bool ReadSymTabCommand(mach_vm_address_t load_command_address,
+                         const std::string& load_command_info);
+  bool ReadDySymTabCommand(mach_vm_address_t load_command_address,
+                           const std::string& load_command_info);
+  bool ReadIdDylibCommand(mach_vm_address_t load_command_address,
+                          const std::string& load_command_info);
+  bool ReadDylinkerCommand(mach_vm_address_t load_command_address,
+                           const std::string& load_command_info);
+  bool ReadUUIDCommand(mach_vm_address_t load_command_address,
+                       const std::string& load_command_info);
+  bool ReadSourceVersionCommand(mach_vm_address_t load_command_address,
+                                const std::string& load_command_info);
+  bool ReadUnexpectedCommand(mach_vm_address_t load_command_address,
+                             const std::string& load_command_info);
+
+  PointerVector<MachOImageSegmentReader> segments_;
+  std::map<std::string, size_t> segment_map_;
+  std::string module_info_;
+  std::string dylinker_name_;
+  struct UUID uuid_;
+  mach_vm_address_t address_;
+  mach_vm_size_t size_;
+  mach_vm_size_t slide_;
+  uint64_t source_version_;
+  scoped_ptr<process_types::symtab_command> symtab_command_;
+  scoped_ptr<process_types::dysymtab_command> dysymtab_command_;
+  scoped_ptr<process_types::dylib_command> id_dylib_command_;
+  ProcessReader* process_reader_;  // weak
+  uint32_t file_type_;
+  InitializationStateDcheck initialized_;
+
+  DISALLOW_COPY_AND_ASSIGN(MachOImageReader);
+};
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_MAC_MACH_O_IMAGE_READER_H_