base/android/library_loader/library_prefetcher.h

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_ANDROID_LIBRARY_LOADER_LIBRARY_PREFETCHER_H_
   6 #define BASE_ANDROID_LIBRARY_LOADER_LIBRARY_PREFETCHER_H_
   7
   8 #include <jni.h>
   9
  10 #include <stdint.h>
  11 #include <string>
  12
  13 #include "base/debug/proc_maps_linux.h"
  14 #include "base/gtest_prod_util.h"
  15
  16 namespace base {
  17 namespace android {
  18
  19 // Forks and waits for a process prefetching the native library. This is done in
  20 // a forked process for the following reasons:
  21 // - Isolating the main process from mistakes in the parsing. If the parsing
  22 //   returns an incorrect address, only the forked process will crash.
  23 // - Not inflating the memory used by the main process uselessly, which could
  24 //   increase its likelihood to be killed.
  25 // The forked process has background priority and, since it is not declared to
  26 // the Android runtime, can be killed at any time, which is not an issue here.
  27 class BASE_EXPORT NativeLibraryPrefetcher {
  28  public:
  29   // Finds the ranges matching the native library, forks a low priority
  30   // process pre-fetching these ranges and wait()s for it.
  31   // Returns true for success.
  32   static bool ForkAndPrefetchNativeLibrary();
  33
  34  private:
  35   using AddressRange = std::pair<uintptr_t, uintptr_t>;
  36   // Returns true if the region matches native code or data.
  37   static bool IsGoodToPrefetch(const base::debug::MappedMemoryRegion& region);
  38   // Filters the regions to keep only libchrome ranges if possible.
  39   static void FilterLibchromeRangesOnlyIfPossible(
  40       const std::vector<base::debug::MappedMemoryRegion>& regions,
  41       std::vector<AddressRange>* ranges);
  42   // Finds the ranges matching the native library in /proc/self/maps.
  43   // Returns true for success.
  44   static bool FindRanges(std::vector<AddressRange>* ranges);
  45
  46   FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
  47                            TestIsGoodToPrefetchNoRange);
  48   FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
  49                            TestIsGoodToPrefetchUnreadableRange);
  50   FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
  51                            TestIsGoodToPrefetchSkipSharedRange);
  52   FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
  53                            TestIsGoodToPrefetchLibchromeRange);
  54   FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
  55                            TestIsGoodToPrefetchBaseApkRange);
  56   FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
  57                            TestFilterLibchromeRangesOnlyIfPossibleNoLibchrome);
  58   FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
  59                            TestFilterLibchromeRangesOnlyIfPossibleHasLibchrome);
  60
  61   DISALLOW_IMPLICIT_CONSTRUCTORS(NativeLibraryPrefetcher);
  62 };
  63
  64 }  // namespace android
  65 }  // namespace base
  66
  67 #endif  // BASE_ANDROID_LIBRARY_LOADER_LIBRARY_PREFETCHER_H_