1. Adventures with Mono Runtime on Mobile Platforms
.NET Stammtisch Linz
Bernhard Urban
beurba@microsoft.com
https://www.xamarin.com
https://www.mono-project.com
July 23, 2019
foundation
1 / 13

2. 2 / 13

3. Xamarin
3 / 13

4. The Mono Runtime — Overview
Execution modes
4 / 13

5. The Mono Runtime — Overview
Execution modes
Just-In-Time compiler
4 / 13

6. The Mono Runtime — Overview
Execution modes
Just-In-Time compiler
Ahead-Of-Time compiler
4 / 13

7. The Mono Runtime — Overview
Execution modes
Just-In-Time compiler
Ahead-Of-Time compiler
normal AOT
4 / 13

8. The Mono Runtime — Overview
Execution modes
Just-In-Time compiler
Ahead-Of-Time compiler
normal AOT
FullAOT
4 / 13

9. The Mono Runtime — Overview
Execution modes
Just-In-Time compiler
Ahead-Of-Time compiler
normal AOT
FullAOT
Interpreter
4 / 13

10. The Mono Runtime — Overview
Execution modes
Just-In-Time compiler
Ahead-Of-Time compiler
normal AOT
FullAOT
Interpreter
Supported platforms
4 / 13

11. The Mono Runtime — Overview
Execution modes
Just-In-Time compiler
Ahead-Of-Time compiler
normal AOT
FullAOT
Interpreter
Supported platforms
Linux, macOS, Windows, *BSD, AIX, IBM i, . . .
4 / 13

12. The Mono Runtime — Overview
Execution modes
Just-In-Time compiler
Ahead-Of-Time compiler
normal AOT
FullAOT
Interpreter
Supported platforms
Linux, macOS, Windows, *BSD, AIX, IBM i, . . .
iOS, tvOS, watchOS & Android
4 / 13

13. The Mono Runtime — Overview
Execution modes
Just-In-Time compiler
Ahead-Of-Time compiler
normal AOT
FullAOT
Interpreter
Supported platforms
Linux, macOS, Windows, *BSD, AIX, IBM i, . . .
iOS, tvOS, watchOS & Android
XBox, PlayStation, WiiU, . . .
4 / 13

14. The Mono Runtime — Overview
Execution modes
Just-In-Time compiler
Ahead-Of-Time compiler
normal AOT
FullAOT
Interpreter
Supported platforms
Linux, macOS, Windows, *BSD, AIX, IBM i, . . .
iOS, tvOS, watchOS & Android
XBox, PlayStation, WiiU, . . .
amd64, x86, armv7, armv8, powerpc, s390x
4 / 13

15. The Mono Runtime — Overview
Execution modes
Just-In-Time compiler
Ahead-Of-Time compiler
normal AOT
FullAOT
Interpreter
Supported platforms
Linux, macOS, Windows, *BSD, AIX, IBM i, . . .
iOS, tvOS, watchOS & Android
XBox, PlayStation, WiiU, . . .
amd64, x86, armv7, armv8, powerpc, s390x
WebAssembly
4 / 13

16. Embedding the Mono Runtime
Embedding Mono
link Mono into your application
5 / 13

17. Embedding the Mono Runtime
Embedding Mono
link Mono into your application
allows execution of .NET, e.g. useful for scripting
5 / 13

18. Embedding the Mono Runtime
Embedding Mono
link Mono into your application
allows execution of .NET, e.g. useful for scripting
Users
5 / 13

19. Embedding the Mono Runtime
Embedding Mono
link Mono into your application
allows execution of .NET, e.g. useful for scripting
Users
Game Studios
5 / 13

20. Embedding the Mono Runtime
Embedding Mono
link Mono into your application
allows execution of .NET, e.g. useful for scripting
Users
Game Studios
Unity
5 / 13

21. Embedding the Mono Runtime
Embedding Mono
link Mono into your application
allows execution of .NET, e.g. useful for scripting
Users
Game Studios
Unity
Blazor: check out https://learn-blazor.com/
5 / 13

22. Embedding the Mono Runtime
Embedding Mono
link Mono into your application
allows execution of .NET, e.g. useful for scripting
Users
Game Studios
Unity
Blazor: check out https://learn-blazor.com/
Xamarin.Android & Xamarin.iOS
5 / 13

23. Platform & Device landscape
iOS on iPhone/iPad.
6 / 13

24. Platform & Device landscape
iOS on iPhone/iPad.
armv7: FullAOT.
6 / 13

25. Platform & Device landscape
iOS on iPhone/iPad.
armv7: FullAOT.
arm64: FullAOT and interpreter.
6 / 13

26. Platform & Device landscape
iOS on iPhone/iPad.
armv7: FullAOT.
arm64: FullAOT and interpreter.
x86: JIT.
6 / 13

27. Platform & Device landscape
iOS on iPhone/iPad.
armv7: FullAOT.
arm64: FullAOT and interpreter.
x86: JIT.
x86 64: JIT.
6 / 13

28. FullAOT
7 / 13

29. FullAOT
iOS does not allow JIT compilation
7 / 13

30. FullAOT
iOS does not allow JIT compilation
Normal AOT uses JIT occasionally at runtime
7 / 13

31. FullAOT
iOS does not allow JIT compilation
Normal AOT uses JIT occasionally at runtime
All trampolines and wrappers must be included in the AOT image
7 / 13

32. FullAOT
iOS does not allow JIT compilation
Normal AOT uses JIT occasionally at runtime
All trampolines and wrappers must be included in the AOT image
Side-effect: System.Reflection.Emit does not work
7 / 13

33. What about generics?
8 / 13

34. What about generics?
public T return_t<T> (T arg) {
return arg;
}
8 / 13

35. What about generics?
public T return_t<T> (T arg) {
return arg;
}
// "Generic sharing for value types"
public void return_t (T& ret, T& arg, ptr hidden_arg) {
int size = rgctx_fetch (hidden_arg);
memcpy (ret, arg, size);
}
8 / 13

36. What about generics?
public T return_t<T> (T arg) {
return arg;
}
// "Generic sharing for value types"
public void return_t (T& ret, T& arg, ptr hidden_arg) {
int size = rgctx_fetch (hidden_arg);
memcpy (ret, arg, size);
}
int i = return_t<int> (5);
8 / 13

37. What about generics?
public T return_t<T> (T arg) {
return arg;
}
// "Generic sharing for value types"
public void return_t (T& ret, T& arg, ptr hidden_arg) {
int size = rgctx_fetch (hidden_arg);
memcpy (ret, arg, size);
}
int i = return_t<int> (5);
// calling chain
caller
⇒ callee
8 / 13

38. What about generics?
public T return_t<T> (T arg) {
return arg;
}
// "Generic sharing for value types"
public void return_t (T& ret, T& arg, ptr hidden_arg) {
int size = rgctx_fetch (hidden_arg);
memcpy (ret, arg, size);
}
int i = return_t<int> (5);
// calling chain
caller
⇒ gsharedvt_arg_trampoline
⇒ callee
8 / 13

39. What about generics?
public T return_t<T> (T arg) {
return arg;
}
// "Generic sharing for value types"
public void return_t (T& ret, T& arg, ptr hidden_arg) {
int size = rgctx_fetch (hidden_arg);
memcpy (ret, arg, size);
}
int i = return_t<int> (5);
// calling chain
caller
⇒ gsharedvt_arg_trampoline
⇒ gsharedvt_in_trampoline
⇒ callee
8 / 13

40. System.Reflection.Emit?
System.ExecutionEngineException:
Attempting to JIT compile method MyClass:DynamicallyGeneratedMethod ()
9 / 13

41. System.Reflection.Emit?
System.ExecutionEngineException:
Attempting to JIT compile method MyClass:DynamicallyGeneratedMethod ()
9 / 13

42. System.Reflection.Emit?
System.ExecutionEngineException:
Attempting to JIT compile method MyClass:DynamicallyGeneratedMethod ()
Runtime interpreter enables System.Reflection.Emit
9 / 13

43. System.Reflection.Emit?
System.ExecutionEngineException:
Attempting to JIT compile method MyClass:DynamicallyGeneratedMethod ()
Runtime interpreter enables System.Reflection.Emit
Faster “inner dev loop”
No need to run the AOT compiler
Smaller app bundle size ⇒ faster deploy
9 / 13

44. System.Reflection.Emit?
System.ExecutionEngineException:
Attempting to JIT compile method MyClass:DynamicallyGeneratedMethod ()
Runtime interpreter enables System.Reflection.Emit
Faster “inner dev loop”
No need to run the AOT compiler
Smaller app bundle size ⇒ faster deploy
Best of both worlds: “Mixed Mode” with FullAOT
9 / 13

45. System.Reflection.Emit?
System.ExecutionEngineException:
Attempting to JIT compile method MyClass:DynamicallyGeneratedMethod ()
Runtime interpreter enables System.Reflection.Emit
Faster “inner dev loop”
No need to run the AOT compiler
Smaller app bundle size ⇒ faster deploy
Best of both worlds: “Mixed Mode” with FullAOT
Ships with upcoming release of Xamarin.iOS (Preview available)
9 / 13

46. Platform & Device landscape
iOS on iPhone/iPad.
armv7: FullAOT.
arm64: FullAOT and interpreter.
x86: JIT.
x86 64: JIT.
tvOS on Apple TV.
10 / 13

47. Platform & Device landscape
iOS on iPhone/iPad.
armv7: FullAOT.
arm64: FullAOT and interpreter.
x86: JIT.
x86 64: JIT.
tvOS on Apple TV.
arm64: FullAOT and interpreter.
10 / 13

48. Platform & Device landscape
iOS on iPhone/iPad.
armv7: FullAOT.
arm64: FullAOT and interpreter.
x86: JIT.
x86 64: JIT.
tvOS on Apple TV.
arm64: FullAOT and interpreter.
x86 64: JIT.
10 / 13

49. Platform & Device landscape
iOS on iPhone/iPad.
armv7: FullAOT.
arm64: FullAOT and interpreter.
x86: JIT.
x86 64: JIT.
tvOS on Apple TV.
arm64: FullAOT and interpreter.
x86 64: JIT.
watchOS on Apple Watch.
10 / 13

50. Platform & Device landscape
iOS on iPhone/iPad.
armv7: FullAOT.
arm64: FullAOT and interpreter.
x86: JIT.
x86 64: JIT.
tvOS on Apple TV.
arm64: FullAOT and interpreter.
x86 64: JIT.
watchOS on Apple Watch.
armv7k: FullAOT and bitcode.
10 / 13

51. Platform & Device landscape
iOS on iPhone/iPad.
armv7: FullAOT.
arm64: FullAOT and interpreter.
x86: JIT.
x86 64: JIT.
tvOS on Apple TV.
arm64: FullAOT and interpreter.
x86 64: JIT.
watchOS on Apple Watch.
armv7k: FullAOT and bitcode.
arm64 32: interpreter (WIP) and bitcode.
10 / 13

52. Platform & Device landscape
iOS on iPhone/iPad.
armv7: FullAOT.
arm64: FullAOT and interpreter.
x86: JIT.
x86 64: JIT.
tvOS on Apple TV.
arm64: FullAOT and interpreter.
x86 64: JIT.
watchOS on Apple Watch.
armv7k: FullAOT and bitcode.
arm64 32: interpreter (WIP) and bitcode.
x86: JIT.
10 / 13

53. Xamarin.Android
Simliar to Linux, except for interop between C# and Java
Two Garbage collectors have to work together
11 / 13

54. Xamarin.Android
Simliar to Linux, except for interop between C# and Java
Two Garbage collectors have to work together
War story: Samsung Galaxy S7
11 / 13

55. Xamarin.Android
Simliar to Linux, except for interop between C# and Java
Two Garbage collectors have to work together
War story: Samsung Galaxy S7
First bug report: “Xamarin.Android apps on the Samsung Galaxy S7
fails to start with the error System.ExecutionEngineException
SIGILL“.
11 / 13

56. Xamarin.Android
Simliar to Linux, except for interop between C# and Java
Two Garbage collectors have to work together
War story: Samsung Galaxy S7
First bug report: “Xamarin.Android apps on the Samsung Galaxy S7
fails to start with the error System.ExecutionEngineException
SIGILL“.
Co-worker in the US got the device.
11 / 13

57. Xamarin.Android
Simliar to Linux, except for interop between C# and Java
Two Garbage collectors have to work together
War story: Samsung Galaxy S7
First bug report: “Xamarin.Android apps on the Samsung Galaxy S7
fails to start with the error System.ExecutionEngineException
SIGILL“.
Co-worker in the US got the device. He could not reproduce it.
11 / 13

58. Xamarin.Android
Simliar to Linux, except for interop between C# and Java
Two Garbage collectors have to work together
War story: Samsung Galaxy S7
First bug report: “Xamarin.Android apps on the Samsung Galaxy S7
fails to start with the error System.ExecutionEngineException
SIGILL“.
Co-worker in the US got the device. He could not reproduce it.
US edition: Ships with Snapdragon 820.
11 / 13

59. Xamarin.Android
Simliar to Linux, except for interop between C# and Java
Two Garbage collectors have to work together
War story: Samsung Galaxy S7
First bug report: “Xamarin.Android apps on the Samsung Galaxy S7
fails to start with the error System.ExecutionEngineException
SIGILL“.
Co-worker in the US got the device. He could not reproduce it.
US edition: Ships with Snapdragon 820.
World edition: Ships with Exynos 8890.
11 / 13

60. Xamarin.Android
Simliar to Linux, except for interop between C# and Java
Two Garbage collectors have to work together
War story: Samsung Galaxy S7
First bug report: “Xamarin.Android apps on the Samsung Galaxy S7
fails to start with the error System.ExecutionEngineException
SIGILL“.
Co-worker in the US got the device. He could not reproduce it.
US edition: Ships with Snapdragon 820.
World edition: Ships with Exynos 8890.
Could reproduce it with Xamarin Test Cloud.
11 / 13

61. War story: Samsung Galaxy S7
$ grep SIGILL *.log
custom_01.log:E/mono (13964): SIGILL at ip=0x0000007f4f15e8d0
custom_02.log:E/mono (13088): SIGILL at ip=0x0000007f8ff76cc0
custom_03.log:E/mono (12824): SIGILL at ip=0x0000007f68e93c70
custom_04.log:E/mono (12876): SIGILL at ip=0x0000007f4b3d55f0
custom_05.log:E/mono (13008): SIGILL at ip=0x0000007f8df1e8d0
custom_06.log:E/mono (14093): SIGILL at ip=0x0000007f6c21edf0
12 / 13

62. War story: Samsung Galaxy S7
$ grep SIGILL *.log
custom_01.log:E/mono (13964): SIGILL at ip=0x0000007f4f15e8d0
custom_02.log:E/mono (13088): SIGILL at ip=0x0000007f8ff76cc0
custom_03.log:E/mono (12824): SIGILL at ip=0x0000007f68e93c70
custom_04.log:E/mono (12876): SIGILL at ip=0x0000007f4b3d55f0
custom_05.log:E/mono (13008): SIGILL at ip=0x0000007f8df1e8d0
custom_06.log:E/mono (14093): SIGILL at ip=0x0000007f6c21edf0
void __clear_cache (char *address, size_t size) {
static int cache_line_size = 0;
if (!cache_line_size)
cache_line_size = get_current_cpu_cache_line_size ();
for (int i = 0; i < size; i += cache_line_size)
flush_cache_line (address + i);
}

63. War story: Samsung Galaxy S7
$ grep SIGILL *.log
custom_01.log:E/mono (13964): SIGILL at ip=0x0000007f4f15e8d0
custom_02.log:E/mono (13088): SIGILL at ip=0x0000007f8ff76cc0
custom_03.log:E/mono (12824): SIGILL at ip=0x0000007f68e93c70
custom_04.log:E/mono (12876): SIGILL at ip=0x0000007f4b3d55f0
custom_05.log:E/mono (13008): SIGILL at ip=0x0000007f8df1e8d0
custom_06.log:E/mono (14093): SIGILL at ip=0x0000007f6c21edf0
void __clear_cache (char *address, size_t size) {
static int cache_line_size = 0;
if (!cache_line_size)
cache_line_size = get_current_cpu_cache_line_size ();
for (int i = 0; i < size; i += cache_line_size)
flush_cache_line (address + i);
}

64. War story: Samsung Galaxy S7
$ grep SIGILL *.log
custom_01.log:E/mono (13964): SIGILL at ip=0x0000007f4f15e8d0
custom_02.log:E/mono (13088): SIGILL at ip=0x0000007f8ff76cc0
custom_03.log:E/mono (12824): SIGILL at ip=0x0000007f68e93c70
custom_04.log:E/mono (12876): SIGILL at ip=0x0000007f4b3d55f0
custom_05.log:E/mono (13008): SIGILL at ip=0x0000007f8df1e8d0
custom_06.log:E/mono (14093): SIGILL at ip=0x0000007f6c21edf0
void __clear_cache (char *address, size_t size) {
static int cache_line_size = 0;
if (!cache_line_size)
cache_line_size = get_current_cpu_cache_line_size ();
for (int i = 0; i < size; i += cache_line_size)
flush_cache_line (address + i);
}
12 / 13

65. War story: Samsung Galaxy S7
$ grep SIGILL *.log
custom_01.log:E/mono (13964): SIGILL at ip=0x0000007f4f15e8d0
custom_02.log:E/mono (13088): SIGILL at ip=0x0000007f8ff76cc0
custom_03.log:E/mono (12824): SIGILL at ip=0x0000007f68e93c70
custom_04.log:E/mono (12876): SIGILL at ip=0x0000007f4b3d55f0
custom_05.log:E/mono (13008): SIGILL at ip=0x0000007f8df1e8d0
custom_06.log:E/mono (14093): SIGILL at ip=0x0000007f6c21edf0
void __clear_cache (char *address, size_t size) {
static int cache_line_size = 0;
if (!cache_line_size)
cache_line_size = get_current_cpu_cache_line_size ();
for (int i = 0; i < size; i += cache_line_size)
flush_cache_line (address + i);
}
64byte buckets:
0x00-0x3f: always flushed
0x40-0x7f: only flushed when cacheline size is 64 byte.
0x80-0xbf: always flushed
0xc0-0xff: only flushed when cacheline size is 64 byte.
12 / 13

66. Thanks
Visit us
https://www.mono-project.com
Chat with us
https://gitter.im/mono/mono
Mail me
beurba@microsoft.com
foundation
13 / 13