Add MachOImageSegmentReader

util/mac/mach_o_image_segment_reader.h

Index: util/mac/mach_o_image_segment_reader.h
diff --git a/util/mac/mach_o_image_segment_reader.h b/util/mac/mach_o_image_segment_reader.h
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+++ b/util/mac/mach_o_image_segment_reader.h
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+// 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_SEGMENT_READER_H_
+#define CRASHPAD_UTIL_MAC_MACH_O_IMAGE_SEGMENT_READER_H_
+
+#include <mach/mach.h>
+#include <stdint.h>
+#include <sys/types.h>
+
+#include <map>
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "util/mac/process_types.h"
+#include "util/misc/initialization_state_dcheck.h"
+
+namespace crashpad {
+
+class ProcessReader;
+
+//! \brief A reader for LC_SEGMENT or LC_SEGMENT_64 load commands in Mach-O
+//!     images mapped into another process.
+//!
+//! This class is capable of reading both LC_SEGMENT and LC_SEGMENT_64 based on
+//! the bitness of the remote process.
+//!
+//! A MachOImageSegmentReader will normally be instantiated by a
+//! MachOImageReader.
+class MachOImageSegmentReader {
+ public:
+  MachOImageSegmentReader();
+  ~MachOImageSegmentReader();
+
+  //! \brief Reads the segment load command 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] load_command_address The address, in the remote process’
+  //!     address space, where the LC_SEGMENT or LC_SEGMENT_64 load command
+  //!     to be read is located. This address is determined by a Mach-O image
+  //!     reader, such as MachOImageReader, as it walks Mach-O load commands.
+  //! \param[in] load_command_info A string to be used in logged messages. This
+  //!     string is for diagnostic purposes only, and may be empty.
+  //!
+  //! \return `true` if the load command was read successfully. `false`
+  //!     otherwise, with an appropriate message logged.
+  bool Initialize(ProcessReader* process_reader,
+                  mach_vm_address_t load_command_address,
+                  const std::string& load_command_info);
+
+  //! \brief Returns the segment’s name.
+  //!
+  //! The segment’s name is taken from the load command’s `segname` field.
+  //! Common segment names are `"__TEXT"`, `"__DATA"`, and `"__LINKEDIT"`.
+  //! Symbolic constants for these common names are defined in
+  //! `<mach-o/loader.h>`.
+  std::string Name() const;
+
+  //! \brief The segment’s preferred load address.
+  //!
+  //! \return The segment’s preferred load address as stored in the Mach-O file.
+  //!
+  //! \note This value is not adjusted for any “slide” that may have occurred
+  //!     when the image was loaded.
+  //!
+  //! \sa MachOImageReader::GetSegmentByName()
+  mach_vm_address_t vmaddr() const { return segment_command_.vmaddr; }
+
+  //! \brief Returns the segment’s size as mapped into memory.
+  mach_vm_size_t vmsize() const { return segment_command_.vmsize; }
+
+  //! \brief Returns the file offset of the mapped segment in the file from
+  //!     which it was mapped.
+  //!
+  //! The file offset is the difference between the beginning of the
+  //! `mach_header` or `mach_header_64` and the beginning of the segment’s
+  //! mapped region. For segments that are not mapped from a file (such as
+  //! `"__PAGEZERO"` segments), this will be `0`.
+  mach_vm_size_t fileoff() const { return segment_command_.fileoff; }
+
+  //! \brief Returns the number of sections in the segment.
+  //!
+  //! This will return `0` for a segment without any sections, typical for
+  //! `"__PAGEZERO"` and `"__LINKEDIT"` segments.
+  //!
+  //! Although the Mach-O file format uses a `uint32_t` for this field, there is
+  //! an overall limit of 255 sections in an entire Mach-O image file (not just
+  //! in a single segment) imposed by the symbol table format. Symbols will not
+  //! be able to reference anything in a section beyond the first 255 in a
+  //! Mach-O image file.
+  uint32_t nsects() const { return segment_command_.nsects; }
+
+  //! \brief Obtain section information by section name.
+  //!
+  //! \param[in] section_name The name of the section to search for, without the
+  //!     leading segment name. For example, use `"__text"`, not
+  //!     `"__TEXT,__text"` or `"__TEXT.__text"`.
+  //!
+  //! \return A pointer to the section information if it was found, or `NULL` if
+  //!     it was not found.
+  //!
+  //! \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.
+  //!
+  //! \sa MachOImageReader::GetSectionByName()
+  const process_types::section* GetSectionByName(
+      const std::string& section_name) 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 command. Unlike
+  //!     MachOImageReader::GetSectionAtIndex(), this is a 0-based index. This
+  //!     parameter must be in the range of valid indices aas reported by
+  //!     nsects().
+  //!
+  //! \return A pointer to the section information. If \a index is out of range,
+  //!     execution is aborted.
+  //!
+  //! \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.
+  //!
+  //! \sa MachOImageReader::GetSectionAtIndex()
+  const process_types::section* GetSectionAtIndex(size_t index) const;
+
+  //! \brief Returns a segment name string.
+  //!
+  //! Segment names may be 16 characters long, and are not necessarily
+  //! `NUL`-terminated. This function will return a segment name based on up to
+  //! the first 16 characters found at \a segment_name_c.
+  static std::string SegmentNameString(const char* segment_name_c);
+
+  //! \brief Returns a section name string.
+  //!
+  //! Section names may be 16 characters long, and are not necessarily
+  //! `NUL`-terminated. This function will return a section name based on up to
+  //! the first 16 characters found at \a section_name_c.
+  static std::string SectionNameString(const char* section_name_c);
+
+  //! \brief Returns a segment and section name string.
+  //!
+  //! A segment and section name string is composed of a segment name string
+  //! (see SegmentNameString()) and a section name string (see
+  //! SectionNameString()) separated by a comma. An example is
+  //! `"__TEXT,__text"`.
+  static std::string SegmentAndSectionNameString(const char* segment_name_c,
+                                                 const char* section_name_c);
+
+ private:
+  //! \brief The internal implementation of Name().
+  //!
+  //! This is identical to Name() but does not perform the
+  //! InitializationStateDcheck check. It may be called during initialization
+  //! provided that the caller only does so after segment_command_ has been
+  //! read successfully.
+  std::string NameInternal() const;
+
+  // The segment command data read from the remote process.
+  process_types::segment_command segment_command_;
+
+  // Section structures read from the remote process in the order that they are
+  // given in the remote process.
+  std::vector<process_types::section> sections_;
+
+  // Maps section names to indices into the sections_ vector.
+  std::map<std::string, size_t> section_map_;
+
+  InitializationStateDcheck initialized_;
+
+  DISALLOW_COPY_AND_ASSIGN(MachOImageSegmentReader);
+};
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_MAC_MACH_O_IMAGE_SEGMENT_READER_H_