Overview

source
- art/runtime/gc/space/image_space.h
- art/runtime/gc/space/image_space.cc
数据结构
- ImageSpace
- ImageSpaceLoader
- OatFile
- VdexFile
- OatDexFile

ImageSpace的加载

流程

ImageSpace.png

LoadBootImage()

BootImage是虚拟机启动时，在Heap初始化阶段加载的.

Runtime::Init()
- gc::Heap::Heap()
  - ImageSpace::LoadBootImage()
    - ImageSpace::CreateBootImage()
    - ImageSpace::ExtractMultiImageLocations()
ImageSpace::CreateBootImage()
- MarkZygoteStart()
- FindImageFilenameImpl()
- 判断
  - found_image && has_system && has_cache
    - 若ChecksumsMatch()匹配，则会Load
      - ImageSpaceLoader::Load()
  - found_image && !has_system && has_cache
    - ImageSpaceLoader::Load()
  - found_image && has_system && !relocate
    - 此分支应该进不来.
    - relocate默认是需要的
```
bool ShouldRelocate() const {
  return must_relocate_ && CanRelocate();
}
- must_relocate_为true
static constexpr bool kDefaultMustRelocate = true
RUNTIME_OPTIONS_KEY (bool,                Relocate,                       kDefaultMustRelocate)

- CanRelocate()为true
bool Runtime::CanRelocate() const {
  return !IsAotCompiler() || compiler_callbacks_->IsRelocationPossible();
}
```
    - ImageSpaceLoader::Load()
  - found_image && has_system && relocate
    - RelocateImage()
    - ImageSpaceLoader::Load()
  - !has_system
    - GenerateImage()
    - ImageSpaceLoader::Load()

space::ImageSpace::ExtractMultiImageLocations()
- 使用":"分割bootclasspath字符串
- 获取input_image_file_nameiamge[0]的common suffix，即 "boot.art"
- 从images[1]开始，将/system/framework/xxx.art存储image_file_names
- 后面ImageSpace::LoadBootImage()会在for()执行多次CreateBootImage()
RelocateImage()
- ChooseRelocationOffsetDelta()
- patchoat
GenerateImage()
- ChooseRelocationOffsetDelta()
- dex2oat

ImageSpaceLoader::Load()

ImageSpaceLoader::Load()
- ImageSpaceLoader::Init()
ImageSpaceLoader::Init()
- OS::OpenFileForReading(image_filename))
- LoadImageFile(): 加载art文件
  - MemMap::MapFileAtAddress()
    - MemMap::MapInternal()
      - mmap()
  - 映射文件大小为image_size_, 只包括ImageHeader+data, 不包括padding + bitmap部分.
- image_bitmap_map(MemMap::MapFileAtAddress())
- RelocateInPlace()
- space(new ImageSpace())
- ImageSpaceLoader::OpenOatFile()
  - oat_file(OatFile::Open())
    - OatFileBase::OpenOatFile<>
      - new kOatFileBaseSubType()
        
        new DlOpenOatFile()
        
        new ElfOatFile()
      - LoadVdex(): 加载VdexFile文件
        
        OatFileBase::LoadVdex()
      - PreLoad()
        
        DlOpenOatFile::PreLoad()
        
        ElfOatFile::PreLoad()
      - Load(): 加载OatFile文件
        
        DlOpenOatFile::Load()->DlOpenOatFile::Dlopen()->android_dlopen_ext()
        
        ElfOatFile::ElfFileOpen()
        
        ElfFile::Open()
        
        ElfFile::Load()
      - OatFileBase::ComputeFields()
        
        begin_ = FindDynamicSymbolAddress("oatdata")
        
        end_ = FindDynamicSymbolAddress("oatlastword")
        
        end_ += sizeof(uint32_t)
        
        bss_begin_ = FindDynamicSymbolAddress("oatbss")
        
        bss_end_ += sizeof(uint32_t)
        
        bss_roots_ = FindDynamicSymbolAddress("oatbssroots")
      - PreSetup()
        
        DlOpenOatFile::PreSetup()
        
        ElfOatFile::PreSetup() 空
      - Setup()
        
        OatFileBase::Setup()
        
        OatDexFile* oat_dex_file = new OatDexFile()
        
        TypeLookupTable::Open()
        
        oat_dex_files_.Put(key, oat_dex_file)
      - space->ValidateOatFile()
- space->oat_file_non_owned_ = space->oat_file_.get()

实验

boot_image_spaces_内容

elem[0 ] = {ImageSpace* = 0x74da427600, OatFile* = 0x74da4fb2c0, begin_ = 0x6fb4a000, name = /data/dalvik-cache/arm64/system@[email protected]}
elem[1 ] = {ImageSpace* = 0x74da427680, OatFile* = 0x74da4cb140, begin_ = 0x6fdf1000, name = /data/dalvik-cache/arm64/system@[email protected]}
elem[2 ] = {ImageSpace* = 0x74da427700, OatFile* = 0x74da4cb000, begin_ = 0x6fef7000, name = /data/dalvik-cache/arm64/system@[email protected]}
elem[3 ] = {ImageSpace* = 0x74da427780, OatFile* = 0x74da4cb280, begin_ = 0x6ff41000, name = /data/dalvik-cache/arm64/system@[email protected]}
elem[4 ] = {ImageSpace* = 0x74da427800, OatFile* = 0x74da4cb3c0, begin_ = 0x6ff77000, name = /data/dalvik-cache/arm64/system@[email protected]}
elem[5 ] = {ImageSpace* = 0x74da427880, OatFile* = 0x74da4cb500, begin_ = 0x6ff7b000, name = /data/dalvik-cache/arm64/system@[email protected]}
elem[6 ] = {ImageSpace* = 0x74da427900, OatFile* = 0x74da4cb640, begin_ = 0x6ffbe000, name = /data/dalvik-cache/arm64/system@[email protected]}
elem[7 ] = {ImageSpace* = 0x74da427980, OatFile* = 0x74da4cb780, begin_ = 0x6fff9000, name = /data/dalvik-cache/arm64/system@[email protected]}
elem[8 ] = {ImageSpace* = 0x74da427a00, OatFile* = 0x74da4cb8c0, begin_ = 0x70786000, name = /data/dalvik-cache/arm64/system@[email protected]}
elem[9 ] = {ImageSpace* = 0x74da427b00, OatFile* = 0x74da4cba00, begin_ = 0x707f2000, name = /data/dalvik-cache/arm64/system@[email protected]}
elem[10] = {ImageSpace* = 0x74da427b80, OatFile* = 0x74da4cbb40, begin_ = 0x707fb000, name = /data/dalvik-cache/arm64/system@[email protected]}
elem[11] = {ImageSpace* = 0x74da427c00, OatFile* = 0x74da4cbc80, begin_ = 0x70803000, name = /data/dalvik-cache/arm64/system@[email protected]}
elem[12] = {ImageSpace* = 0x74da427c80, OatFile* = 0x74da4cbdc0, begin_ = 0x70827000, name = /data/dalvik-cache/arm64/system@[email protected]}
elem[13] = {ImageSpace* = 0x74da427d00, OatFile* = 0x74da4cbf00, begin_ = 0x7084f000, name = /data/dalvik-cache/arm64/system@[email protected]}
elem[14] = {ImageSpace* = 0x74da427d80, OatFile* = 0x74da4cc040, begin_ = 0x70850000, name = /data/dalvik-cache/arm64/system@[email protected]}

第一个ImageSpace

$39 = (art::gc::space::ImageSpace) {
   = {
     = {
       = {
        _vptr$Space = 0x74da3df070 , 
        name_ = {
          > = {}, 
          members of std::__1::basic_string, std::__1::allocator >: 
          __r_ = {
            , std::__1::allocator >::__rep, std::__1::allocator, 2>> = {
              > = {}, 
              members of std::__1::__libcpp_compressed_pair_imp, std::__1::allocator >::__rep, std::__1::allocator, 2>: 
              __first_ = {
                {
                  __l = {
                    __cap_ = 0x41, 
                    __size_ = 0x32, 
                    __data_ = 0x74da4f59c0
                  }, 
                  __s = {
                    {
                      __size_ = 0x41, 
                      __lx = 0x41
                    }, 
                    __data_ = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x32, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0xc0, 0x59, 0x4f, 0xda, 0x74, 0x0, 0x0, 0x0}
                  }, 
                  __r = {
                    __words = {0x41, 0x32, 0x74da4f59c0}
                  }
                }
              }
            }, }, 
          static npos = 0xffffffffffffffff
        }, 
        gc_retention_policy_ = 0x0
      }, 
      members of art::gc::space::ContinuousSpace: 
      begin_ = 0x6fb4a000, 
      end_ = {
        > = {
          > = {
            __a_ = 0x6fc49940
          }, }, }, 
      limit_ = 0x6fc49940
    }, 
    members of art::gc::space::MemMapSpace: 
    mem_map_ = {
      __ptr_ = {
        , 2>> = {
          > = {}, 
          members of std::__1::__libcpp_compressed_pair_imp, 2>: 
          __first_ = 0x74da4e6e20
        }, }
    }
  }, 
  members of art::gc::space::ImageSpace: 
  static bitmap_index_ = {
    > = {
      > = {
        > = {
          __a_ = 0x10
        }, }, }, }, 
  live_bitmap_ = {
    __ptr_ = {
      *, std::__1::default_delete >, 2>> = {
         >> = {}, 
        members of std::__1::__libcpp_compressed_pair_imp*, std::__1::default_delete >, 2>: 
        __first_ = 0x74da4f5880
      }, }
  }, 
  oat_file_ = {
    __ptr_ = {
      , 2>> = {
        > = {}, 
        members of std::__1::__libcpp_compressed_pair_imp, 2>: 
        __first_ = 0x0
      }, }
  }, 
  oat_file_non_owned_ = 0x74da4fb2c0, 
  image_location_ = {
    > = {}, 
    members of std::__1::basic_string, std::__1::allocator >: 
    __r_ = {
      , std::__1::allocator >::__rep, std::__1::allocator, 2>> = {
        > = {}, 
        members of std::__1::__libcpp_compressed_pair_imp, std::__1::allocator >::__rep, std::__1::allocator, 2>: 
        __first_ = {
          {
            __l = {
              __cap_ = 0x21, 
              __size_ = 0x1a, 
              __data_ = 0x74da4d0780
            }, 
            __s = {
              {
                __size_ = 0x21, 
                __lx = 0x21
              }, 
              __data_ = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1a, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x80, 0x7, 0x4d, 0xda, 0x74, 0x0, 0x0, 0x0}
            }, 
            __r = {
              __words = {0x21, 0x1a, 0x74da4d0780}
            }
          }
        }
      }, }, 
    static npos = 0xffffffffffffffff
  }
}

(gdb) x/1sb 0x74da4d0780
0x74da4d0780:   "/system/framework/boot.art"

(gdb) x/1sb 0x74da4f59c0
0x74da4f59c0:   "/data/dalvik-cache/arm64/system@[email protected]"

boot.art的maps文件
6fb4a000-6fdf1000 rw-p 00000000 fd:00 278018                             /data/dalvik-cache/arm64/system@[email protected]
... ...
74deb2c000-74deb30000 r--p 002a7000 fd:00 278018                         /data/dalvik-cache/arm64/system@[email protected]

ImageSpace

Overview

ImageSpace的加载

流程

LoadBootImage()

ImageSpaceLoader::Load()

实验

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