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MMLite Part I: The Gospel

MMLite Part I: The Gospel. Your Favorite Preacher. Freedom. You can never make them all happy make it replaceable! Do *I* need that ? make it optional! avoid architectural restrictions (MMU, interrupts,…) Interfaces should not mandate functionality think hard!. Components.

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MMLite Part I: The Gospel

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  1. MMLitePart I: The Gospel Your Favorite Preacher

  2. Freedom • You can never make them all happy • make it replaceable! • Do *I* need that ? • make it optional! • avoid architectural restrictions (MMU, interrupts,…) • Interfaces should not mandate functionality • think hard!

  3. Components • A Component is code + static data + a number of objects • Leads to modularity: formal interfaces, multiple implementations, configurability, replaceability (mutation) • A componentized system is easily scalable • Minimalism rules.

  4. Objects Objects Objects.. • Operating Systems die young or live very, very long lives => Software Engineering • No DLL hell • Stress dynamic over static configuration • Location independence • No exposed Messages • Reuse of code and interfaces

  5. Base Component • “Kernel” is a very bad word • Build-up is easy, scale-down impossible • The “minimal” set of objects/APIs depends on your whole system requirements • Both static and dynamic configurability are necessary features • Security and modularity are different issues • VM and IPC are loaded on-demand

  6. Programming Model(s) • Small config must still be usable • People don’t like fakes • Objects are popular • Threading is not that easy • Use passive objects

  7. Why COM ? • It was there • Explicit refcounting (unmanaged code) • IUnknown is useful per-se (Namespace) • Typechecked and versioning • ..but we don’t need the whole enchilada • No Registry, CoCreateInstance, Class IIDs, IIDs as names, IDispatch, Monikers, ….

  8. NameSpaces • Uniform naming (instead of Registry, Filesystems, Device trees, Web, ….) • Register() the IUnknown of an object in the NameSpace, Bind() to it from somewhere else and you got an IPC. • Register an INameSpace to extend the NameSpace • Leverage simple tools (dir,type,…)

  9. Virtual Machines • An OS cannot be language-dependent • Base supports unmanaged (C/C++) code • VMs are implemented on top (URT!) • Doing it upsy-turvy has been proven wrong (Inferno, JavaMachine).

  10. Scheduling • State of the art real-time (Time Constraints) • TimeSharing • FixedPriority • ..do your own if you don’t like it!

  11. Synchronization • Mutexes (locks), Condition Variables, lock-free primitives • Well established in academia • Simple and efficient • Precisely defined interactions with scheduling and time constraints • Can build all others (cf. Herlihy) on top (events, semaphores,monitors,…)

  12. Device Driver Model • One word: don’t.

  13. Tools • Live with what is provided, cannot port VC to all processors. • We do DLLs by hand, if necessary • Code is ANSI-C, no MSFT “extensions” • Debug on simulators (NT&VC,vendor’s) • Extend simulators with full-system simulation (peripherals!)

  14. Part II: Instructions for Use

  15. Start from nothing • “Just the initialization code, please.” • Add a heap manager.. • … a scheduler... • … a namespace… • … a loader… • … then go a-la carte, including VM & IPC

  16. Initialization & MachDep code • MD code gets control first, then calls the MI Initialization function [kinit.c] • But it could do its own [h8\_kinit.c] • MD code lives separately, can be macros • A MI file foo.cincludes a MD file _foo.c when it strongly expects MD code. • All MD code filenames start with “_”

  17. MD code in Base • 64bit math, unless int64XXX.c does it • Context switch [_schedul.c] & thread creation [_thread.c] • CompareAndSwap [_atomic.c] • Interrupts [_pic.c,_timer.c] • Debug I/O [_debug.c] • Startup initialization [_start.s]

  18. Heap Managers • Anything that provides the IHeap interface • The obvious, plus Extract() • FreeList [heap.c] • Bitmap [bm_heap.c] • AllocOnly [no_heap.c]

  19. Schedulers • Separate from thread manager [thread.c] and from synchronization [mutex.c, condtn.c, atomic.c] • Not exposed in NameSpace (for now?) • Constraints [cb_sched.c] • RoundRobin [rr_sched.c] • None, placeholder [no_sched.c] • ..or ask Equator for theirs

  20. Namespaces • Think of it as an extensible directory, or a filing system for live objects • Per-process CurrentNameSpace() • Root in Base [namespc.c] • Demand-Loading in cobmgr • Filesystems [romfs.c, memdev.c, drivers/fatfs.c, mips/_hostfs.c]

  21. Loaders • Implicitly part of IProcess/IModule • AIF for ARM [arm_ldr.c] • ELF for MIPS and Equator [elf_ldr.c] • LIFE for TriMedia [life_ldr.c] • PE for x86 [pe_ldr.c]

  22. VM & IPC • Both are on-demand loadable objects • VM [src/vm] features: • Skiplist for ranges • 3 (instead of 2) separate concepts - virtual address, TLB, and physical address • IVMFactory, IVMSpace, IVMMapping, IVMView, IVTLB • IPC is work-in-progress [src/ipc]

  23. Interrupts & I/O • AddDevice() both adds and removes ISRs • No DPCs, no priorities, no nesting • An ISR takes an object argument • An ISR can only ConditionInterruptSignal() • AtomicQueues are useful • IDMA Interface

  24. The RTL • DLL-style linking into Base • Deprecated but necessary for sharing the compiler’s builtins and for bootstrapping e.g. CurrentXXX() • AtomicXXX, MutexXXX, ConditionXXX, Constraints, Sleep/Delay, some other constructors.

  25. ANSI C stdio/lib • Built as a static library • Primarily used for debug • Some minor omissions

  26. Networking Stack • BSD4.4Lite based • UDP,TCP,MCAST,IGMP,Routing,DHCP,DNS,UPnP • Old: XNS,CCITT,OSI • Winsock 1.1 interface • Native interfaces (IEndPoint/INetDevice) • Needs trimming and interface revision

  27. Device Drivers • 23 sample drivers, real-time safe, for typical PC peripherals. • IDevice/INetDevice interfaces, derive from IFile. • Both C and C++, common base class code in C++ • Autoconfig example also. • MIDI, audio, GbEthernet, host pkt interface..

  28. Other stuff • Atomic Queues • NT style Events • Look in the Talisman CD (DirectX) • Doom

  29. Apps are objects • Objects are all created equal • Performance tuning is a system-wide exercise...no barriers • Security might require VM protection • COB Namespace & programming model • ..or just use your regular main(argc,argv)

  30. The Source Trees • Components publish their interfaces in the /MMLite/inc directory. • Sources and private includes ..are somewhere under /MMLite/src. • Compilers&co under /tools. • Tools we own (&sources) are under /MMLite/mstools.

  31. Build process • Command scripts drive [mkall.bat, mkit.bat] • Per-processor makefiles (e.g. arm.mak) with lots of common.mak • Per-directory arm.mak file includes the top level arm.def • Environment variables: MMLITE_SDK, BUILD_ROOT, ARM_TOOLS, KIND

  32. Testing • Lots of little regression tests [src/tests] • Each one is pass/fail [calls DebugBreak()] • All run in sequence [alltests.c], or by hand • Normal startup code will run “init.exe” • If you can run Doom you are not doomed

  33. NT Stuff • Generic driver for intelligent I/O cards (Alteon&Philips) • SAN datapump (ucode) for GbEther card • VIA Interface and NDIS driver • Support and debugging tools • Shared Spinlocks • Net packet driver for NT-based simulator

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