mac: Emit dyld info from the memory dump provider.

components/tracing/common/process_metrics_memory_dump_provider.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/tracing/common/process_metrics_memory_dump_provider.h"
 
 #include <fcntl.h>
 #include <stdint.h>
 
 #include <map>
@@ skipping 10 matching lines @@
 #include "base/trace_event/memory_dump_manager.h"
 #include "base/trace_event/process_memory_dump.h"
 #include "base/trace_event/process_memory_maps.h"
 #include "base/trace_event/process_memory_totals.h"
 #include "build/build_config.h"
 
 #if defined(OS_MACOSX)
 #include <libproc.h>
 #include <mach/mach.h>
 #include <mach/mach_vm.h>
+#include <mach/shared_region.h>
 #include <sys/param.h>
 
 #include "base/numerics/safe_math.h"
 #endif  // defined(OS_MACOSX)
 
 namespace tracing {
 
 namespace {
 
 base::LazyInstance<
@@ skipping 209 matching lines @@
       return false;
     if (info.is_submap) {
       size = 0;
       ++depth;
       continue;
     }
 
     if (info.share_mode == SM_COW && info.ref_count == 1)
       info.share_mode = SM_PRIVATE;
 
+    // Ignore regions in the dyld shared cache.

[Mark Mentovai, 2017/02/03 23:17:13]

Anyone can come along and map something else in this region to hide from our
statistic gathering, accidentally or on purpose. Are there other characteristics
of the region that we can check to make sure that this is likely to be the dyld
shared cache region? A dedicated user_tag, perhaps? The fact that the top-level
entry is a submap? Anything else?

+    if (address >= SHARED_REGION_BASE_X86_64 &&
+        address < (SHARED_REGION_BASE_X86_64 + SHARED_REGION_SIZE_X86_64) &&
+        info.share_mode != SM_PRIVATE) {
+      continue;
+    }
+
     VMRegion region;
     uint64_t dirty_bytes = info.pages_dirtied * PAGE_SIZE;
     uint64_t clean_bytes =
         (info.pages_resident - info.pages_reusable - info.pages_dirtied) *
         PAGE_SIZE;
     switch (info.share_mode) {
       case SM_LARGE_PAGE:
       case SM_PRIVATE:
         region.byte_stats_private_dirty_resident = dirty_bytes;
         region.byte_stats_private_clean_resident = clean_bytes;
@@ skipping 193 matching lines @@
 #endif
 }
 
 void ProcessMetricsMemoryDumpProvider::SuspendFastMemoryPolling() {
 #if defined(OS_LINUX) || defined(OS_ANDROID)
   fast_polling_statm_fd_.reset();
 #endif
 }
 
 }  // namespace tracing