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Commit de5cd8cc authored by Christopher Ferris's avatar Christopher Ferris
Browse files

Fix global finding logic. 

Recently, the maps for an elf in memory might show up looking like:

  f0000-f1000 0 r-- /system/lib/libc.so
  f1000-f2000 0 ---
  f2000-f3000 1000 r-x /system/lib/libc.so
  f3000-f4000 2000 rw- /system/lib/libc.so

That empty map was confusing the logic when looking for a global
variable. Now this case is handled properly.

New unit test added for this case.

Bug: 147910661

Test: Ran unit tests.
Test: Ran original failing test 137-cfi.
Change-Id: Ida2e96d1da5e1bf61f41646949fe5a2d405c0d61
parent a78d0cb7

libunwindstack/Global.cpp

+18 −20
Original line number Diff line number Diff line
@@ -70,12 +70,16 @@ void Global::FindAndReadVariable(Maps* maps, const char* var_str) { 
  // This also works:

  //   f0000-f2000 0 r-- /system/lib/libc.so

  //   f2000-f3000 2000 rw- /system/lib/libc.so

  MapInfo* map_start = nullptr;

  // It is also possible to see empty maps after the read-only like so:

  //   f0000-f1000 0 r-- /system/lib/libc.so

  //   f1000-f2000 0 ---

  //   f2000-f3000 1000 r-x /system/lib/libc.so

  //   f3000-f4000 2000 rw- /system/lib/libc.so

  MapInfo* map_zero = nullptr;

  for (const auto& info : *maps) {

    if (map_start != nullptr && map_start->name == info->name) {

      if (info->offset != 0 &&

          (info->flags & (PROT_READ | PROT_WRITE)) == (PROT_READ | PROT_WRITE)) {

        Elf* elf = map_start->GetElf(memory_, arch());

    if (info->offset != 0 && (info->flags & (PROT_READ | PROT_WRITE)) == (PROT_READ | PROT_WRITE) &&

        map_zero != nullptr && Searchable(info->name) && info->name == map_zero->name) {

      Elf* elf = map_zero->GetElf(memory_, arch());

      uint64_t ptr;

      if (elf->GetGlobalVariableOffset(variable, &ptr) && ptr != 0) {

        uint64_t offset_end = info->offset + info->end - info->start;
@@ -86,14 +90,8 @@ void Global::FindAndReadVariable(Maps* maps, const char* var_str) { 
          }

        }

      }

        map_start = nullptr;

      }

    } else {

      map_start = nullptr;

    }

    if (map_start == nullptr && (info->flags & PROT_READ) && info->offset == 0 &&

        Searchable(info->name)) {

      map_start = info.get();

    } else if (info->offset == 0 && !info->name.empty()) {

      map_zero = info.get();

    }

  }

}

libunwindstack/tests/DexFilesTest.cpp

+26 −1
Original line number Diff line number Diff line
@@ -64,7 +64,11 @@ class DexFilesTest : public ::testing::Test { 
                       "f000-11000 r--p 00000000 00:00 0 /fake/elf3\n"

                       "100000-110000 rw-p 00f1000 00:00 0 /fake/elf3\n"

                       "200000-210000 rw-p 0002000 00:00 0 /fake/elf3\n"

                       "300000-400000 rw-p 0003000 00:00 0 /fake/elf3\n"));

                       "300000-400000 rw-p 0003000 00:00 0 /fake/elf3\n"

                       "500000-501000 r--p 0000000 00:00 0 /fake/elf4\n"

                       "501000-502000 ---p 0000000 00:00 0\n"

                       "503000-510000 rw-p 0003000 00:00 0 /fake/elf4\n"

                       "510000-520000 rw-p 0010000 00:00 0 /fake/elf4\n"));

    ASSERT_TRUE(maps_->Parse());



    // Global variable in a section that is not readable.
@@ -81,6 +85,11 @@ class DexFilesTest : public ::testing::Test { 
    map_info = maps_->Get(kMapGlobal);

    ASSERT_TRUE(map_info != nullptr);

    CreateFakeElf(map_info, 0xf1800, 0xf1000, 0xf1000, 0x10000);



    // Global variable set in this map, but there is an empty map before rw map.

    map_info = maps_->Get(kMapGlobalAfterEmpty);

    ASSERT_TRUE(map_info != nullptr);

    CreateFakeElf(map_info, 0x3800, 0x3000, 0x3000, 0xd000);

  }



  void SetUp() override {
@@ -102,6 +111,8 @@ class DexFilesTest : public ::testing::Test { 
  static constexpr size_t kMapGlobalRw = 6;

  static constexpr size_t kMapDexFileEntries = 7;

  static constexpr size_t kMapDexFiles = 8;

  static constexpr size_t kMapGlobalAfterEmpty = 9;

  static constexpr size_t kMapDexFilesAfterEmpty = 12;



  std::shared_ptr<Memory> process_memory_;

  MemoryFake* memory_;
@@ -328,4 +339,18 @@ TEST_F(DexFilesTest, get_method_information_global_skip_zero_64) { 
  EXPECT_EQ(0x123U, method_offset);

}



TEST_F(DexFilesTest, get_method_information_with_empty_map) {

  std::string method_name = "nothing";

  uint64_t method_offset = 0x124;

  MapInfo* info = maps_->Get(kMapDexFilesAfterEmpty);



  WriteDescriptor32(0x503800, 0x506000);

  WriteEntry32(0x506000, 0, 0, 0x510000);

  WriteDex(0x510000);



  dex_files_->GetMethodInformation(maps_.get(), info, 0x510100, &method_name, &method_offset);

  EXPECT_EQ("Main.<init>", method_name);

  EXPECT_EQ(0U, method_offset);

}



}  // namespace unwindstack