A presentation on writing your own .NET profiler to use for IL rewriting as presented at DDD Melbourne 2. Uses ATL (C++) and code from OpenCover.

1. .NET Profilers aren’t scary shaun.wilde@commonvision.com.au shaun_wilde@hotmail.com @scubamunki Email: Email: Twitter:

2. Who am I? Specialize in providing project teams with the necessary frameworks and personnel during the critical early stages of the project. shaun.wilde@commonvision.com.au shaun_wilde@hotmail.com @scubamunki Email: Email: Twitter:

3. CoverageEye.NET Originally hosted on GotDotNet PartCover Originally hosted on SourceForge Forked to GitHub https://github.com/sawilde/partcover.net4 OpenCover Hosted on GitHub https://github.com/sawilde/opencover How did I get here?

4. Profilers: What are they good for? Quick review of some commercial and open source .NET profilers Overview of the profiler API Code and Demos Basics of IL rewriting Code and Demos II Introducing new classes and methods Code and Demos III Extras (If time permits) .NET Profilers aren’t (that) scary

5. Profilers: What are they good for?

6. Monitor Load/Unload Events Application Domains Assemblies Modules Classes JIT Compilation Events Monitor threads, remotingand native/managed transitions Monitor GC events Monitor exceptions Monitor method enter/leave Monitor the runtime

7. Get the names and signatures of classes and methods Read the IL for methods (functions) Memory allocations Types Garbage Collection Call graphs Interrogate the runtime

8. Dynamically create new classes and methods Rewrite the IL of existing methods Allocate memory Work with the GC Interact with the runtime

9. Commercial Redgate ANTS NCover(was originally Open Source) JetBrainsdotCover/dotTrace CLRProfiler4 (Microsoft with Source Code) Commercial and Open Source Profilers* (*Obviously this list is not complete)

10. Open Source Nprof http://code.google.com/p/nprof/ SlimTune http://code.google.com/p/slimtune/ PartCover https://github.com/sawilde/partcover.net4 OpenCover https://github.com/sawilde/opencover Commercial and Open Source Profilers* (*Obviously this list is not complete)

11. System.Reflection.Emit .NET Framework Mono.Cecil https://github.com/mono/cecil Other IL (Re)Writing Methods

12. Important Interfaces Implementation and Registration Overview of the Profiler API

13. In-process COM object i.e. a DLL Native code i.e. unmanaged code Free threaded i.e. the developer is responsible for any required synchronisation 32/64 bit Like for like Implementation

15. .NET Runtime through the ages

16. ICorProfilerCallback 69 Methods ICorProfilerInfo 33 Methods IMetaDataImport 64 Methods IMetaDataEmit 49 Methods .NET1

17. ICorProfilerCallback2 8 Methods ICorProfilerInfo2 21 Methods IMetaDataImport2 64 Methods IMetaDataEmit2 49 Methods .NET2

18. ICorProfilerCallback3 3 Methods ICorProfilerInfo3 14 Methods .NET4

19. How much?

20. Register the COM Object Use Environment variables c:>set COR_ENABLE_PROFILING=1 c:>set COR_PROFILER=MyProfiler.Profiler Instantiation

22. Need to be side-by-side CLR awarePick one Pick first Pick all/many RunSxS http://archive.msdn.microsoft.com/RunSxS .NET4

23. Silverlight support CORECLR_ENABLE_PROFILING CORECLR_PROFILER CORECLR_PROFILER_PATH .NET4

24. Creating an ATL COM object with required interfaces Demo 1

30. Create host and target processes Launch Target with Profiler Simple Target Demo 2

37. Requesting and handling events ICorProfilerInfo::SetEventMask COR_PRF_MONITOR_MODULE_LOADS COR_PRF_MONITOR_JIT_COMPILATION COR_PRF_DISABLE_INLINING COR_PRF_DISABLE_OPTIMIZATIONS Demo 3

42. Getting assembly and method names Interfaces ICorProfilerInfo3 IMetaDataImport2 Demo 4

50. What is a Method? Headers Sections Clauses The Method Body Operations Branches The Stack Debug vs. Release Basics of IL Rewriting

51. Tiny and Fat Methods

54. Tiny and Fat Sections

56. Tiny and Fat Clauses

58. 5 Types of Clauses COR_ILEXCEPTION_CLAUSE_NONE COR_ILEXCEPTION_CLAUSE_FILTER COR_ILEXCEPTION_CLAUSE_FINALLY COR_ILEXCEPTION_CLAUSE_FAULT COR_ILEXCEPTION_CLAUSE_DUPLICATED Clauses

59. Try/Catch Code in handler block is called if an exception of the type expected is thrown from code that is contained in the try block. (needs rewording) COR_ILEXCEPTION_CLAUSE_NONE

60. Variation on Try/Catch VB.NET only COR_ILEXCEPTION_CLAUSE_FILTER

61. Try/Finally Code in handler block always called regardless of how the associated try block is exited. COR_ILEXCEPTION_CLAUSE_FINALLY

62. Try/Fault Code in handler block is only called if an exception has occurred in the corresponding try block. The exception continues on… IL Only? COR_ILEXCEPTION_CLAUSE_FAULT

63. A Mystery // duplicated clause.. this clause was duplicated down to a funclet which was pulled out of line COR_ILEXCEPTION_CLAUSE_DUPLICATED

65. The Method Body Operations Branches The Stack Debug vs. Release The Method Body

66. Contains all the information needed to interpret and write IL Canonical Name String Name Stack Behaviour Parameter Size Length Bytes Control Flow OPCODE.DEF

69. OPCODE.DEF

70. OPCODE.DEF

71. Is there a difference? Debug vs. Release

74. Headers Stack size Method Size Clauses Offsets Lengths Branches Size of Jump Considerations when adding IL

75. Make … Tiny headers Fat Tiny sections Fat Tiny clauses Fat Short branches Long Cheat… Use the parser from OpenCover Common approach when adding IL

76. Leverage the OpenCover parser Demo 5

83. Add a new Type Exception Define Constructor (.ctor) Throw new Type Add extra IL to TargetMethod Adding new classes and methods I

84. Interfaces IMetaDataEmit2 IMetaDataAssemblyEmit Adding New Classes and Methods

88. IL DASM

97. Complicated Intensive Hmmmm……

104. Sequence Points PDB Files IL Rewriting Points out of sync Debugging

108. The End Demo code https://github.com/sawilde/DDD2011_ProfilerDemo