Add MachOImageReader and its test

util/mac/mach_o_image_segment_reader.cc

 // 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,
@@ skipping 176 matching lines @@
   return &sections_[iterator->second];
 }
 
 const process_types::section* MachOImageSegmentReader::GetSectionAtIndex(
     size_t index) const {
   INITIALIZATION_STATE_DCHECK_VALID(initialized_);
   CHECK_LT(index, sections_.size());
   return &sections_[index];
 }
 
+bool MachOImageSegmentReader::SegmentSlides() const {
+  INITIALIZATION_STATE_DCHECK_VALID(initialized_);
+
+  // These are the same rules that the kernel uses to identify __PAGEZERO. See
+  // 10.9.4 xnu-2422.110.17/bsd/kern/mach_loader.c load_segment().
+  return !(segment_command_.vmaddr == 0 && segment_command_.filesize == 0 &&
+           segment_command_.vmsize != 0 &&
+           (segment_command_.initprot & VM_PROT_ALL) == VM_PROT_NONE &&
+           (segment_command_.maxprot & VM_PROT_ALL) == VM_PROT_NONE);
+}
+
 // static
 std::string MachOImageSegmentReader::SegmentNameString(
     const char* segment_name_c) {
   // This is used to interpret the segname field of both the segment_command and
   // section structures, so be sure that they’re identical.
   COMPILE_ASSERT(sizeof(process_types::segment_command::segname) ==
                      sizeof(process_types::section::segname),
                  sizes_must_be_equal);
 
   return SizeLimitedCString(segment_name_c,
@@ skipping 14 matching lines @@
   return base::StringPrintf("%s,%s",
                             SegmentNameString(segment_name_c).c_str(),
                             SectionNameString(section_name_c).c_str());
 }
 
 std::string MachOImageSegmentReader::NameInternal() const {
   return SegmentNameString(segment_command_.segname);
 }
 
 }  // namespace crashpad