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

Presented at AppDevCon (Amsterdam) 2018

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