System.loadLibrary("Unix, Native Code and why bother")

Transcript

1. System.loadLibrary( “Unix, Native Code and why bother”)

2. Library static shared static dynamic loading (.o, .a, ...) (.so,

   .dll, .dylib, ...)

3. Program A Program B static libs (.a) static libs (.a)

   static linking compile-time

4. Program A Program B Program A Program B static libs

   (.a) static libs (.a) shared libs (.so) static linking dynamic linking compile-time run-time

5. Library static shared bookstore library Paul Richter

6. source code compiler

7. source code compiler objects (.o) .o .o .o .a archive

   .o

8. source code compiler linker objects (.o) .o .o .o .a

   archive .o executable .so .so .so .so

9. source code compiler linker loader objects (.o) .o .o .o

   .a archive .o executable in-memory image .so .so .so .so

10. Building the objects

11. lib1.c

12. main.c

13. Static Libraries

14. Static Libraries

15. Shared Libraries: Static Loading

16. Shared Libraries: Static Loading LD_LIBRARY_PATH

17. Shared Libraries: Dynamic Loading

18. main.c

19. main.c

20. Android

21. Kernel Display driver USB driver Camera driver WiFi driver Power

    Mgmt. Binder IPC ... Application Framework Apps Home Contacts Dialer Clock Your app 3rd party app ... Activity Manager Window Manager Package Manager Location Manager View System Content Providers ... Libraries Android Runtime (Dalvik/ART) Core Libraries Dalvik Virtual Machine (DVM) Surface Manager OpenGL Media Framework SQLite WebKit SSL ... Bionic

22. Kernel Display driver USB driver Camera driver WiFi driver Power

    Mgmt. Binder IPC ...

23. Kernel Display driver USB driver Camera driver WiFi driver Power

    Mgmt. Binder IPC ... Libraries Surface Manager OpenGL Media Framework SQLite WebKit SSL ... Bionic

24. Android Bionic

25. Bionic libc libm libdl Linker libstdc++

26. Bionic libc libm libdl Linker libstdc++ License Size Speed

27. Bionic libc libm libdl Linker libstdc++ BSD + Rewritten code

    + Android specific services

28. Bionic libc libm libdl Linker libstdc++

29. Bionic libc libm libdl Linker libstdc++ Completely from scratch! dlopen()

    dlsym() dlerror() dlclose() {

30. Bionic libc libm libdl Linker libstdc++

31. Kernel Display driver USB driver Camera driver WiFi driver Power

    Mgmt. Binder IPC ... Libraries Android Runtime (Dalvik/ART) Core Libraries Dalvik Virtual Machine (DVM) Surface Manager OpenGL Media Framework SQLite WebKit SSL ... Bionic

32. Kernel Display driver USB driver Camera driver WiFi driver Power

    Mgmt. Binder IPC ... Application Framework Apps Home Contacts Dialer Clock Your app 3rd party app ... Activity Manager Window Manager Package Manager Location Manager View System Content Providers ... Libraries Android Runtime (Dalvik/ART) Core Libraries Dalvik Virtual Machine (DVM) Surface Manager OpenGL Media Framework SQLite WebKit SSL ... Bionic

33. Kernel Audio driver Application Framework Apps Your app Media Player

    Libraries Android Runtime (Dalvik/ART) Core Libraries Dalvik Virtual Machine (DVM) Media Framework Media Player Audio Flinger libaudio.so JNI dlopen()

34. System.loadLibrary

35. System.loadLibrary Runtime.loadLibrary

36. Runtime.java

37. Runtime.java

38. None
39. None

40. Win: main.dll Linux: libmain.so Mac: libmain.dylib

41. None

42. LD_LIBRARY_PATH

43. Runtime.java

44. //TODO Runtime::doLoad Runtime.java

45. //TODO Runtime::doLoad

46. //TODO Runtime::doLoad LD_LIBRARY_PATH

47. ClassLoader search (for application libraries) VM search (for system libraries)

48. Runtime.java

49. Workaround for zygote’s LD_LIBRARY_PATH Runtime.java

50. Runtime.cpp

51. Native.cpp

52. Native.cpp

53. Native.cpp

54. Kernel Application Framework Apps Your app Runtime.java Libraries Android Runtime

    Dalvik Virtual Machine (DVM) Native.cpp Runtime.cpp yourlib.so JNI dlopen()

55. We learned... • Static vs Shared Libraries • Dynamic Loading

    • Library paths (+ difference on android) • Android’s internals ◦ Bionic ◦ Dynamic Loading with Dalvik ◦ System.loadLibrary

56. Thanks! @juliozynger soundcloud.com/jobs