Microkernel-based operating system development

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Microkernel-based operating system development Senko Rašić

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operating system (OS): A part of software that manages hardware resources and provides a safe environment for processes to execute in.

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the micro-kernel idea: Hardware drivers and operating system services are regular processes. The kernel has only the required basic functionality

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intensive inter-process comunication + slow IPC calls = bad performance

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mainstream systems: Monolithic kernels with some elements of microkernel design ongoing research: L4, Exokernel, ...

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L4 microkernel  recursive address spaces  highly optimized IPC L4Ka::Pistachio – an implementation by the University of Karlsruhe

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Open Source software  availability  community  malleability

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Hasenpfeffer  based on L4 microkernel  set of servers cooperating through IPC calls  maximal reuse of available open source components (NIH syndrome avoidance)

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Inter-process communication  server and client processes  communication interface  IDL4 generates server and client stubs interface File { boolean Read(in Capability_t cap,in unsigned long offset, out byteseq_t buffer, inout unsigned long size); unsigned long Size(in Capability_t cap); ... }

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Remote procedure calls

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capability: The privilege to invoke a specific RPC.

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Naming system

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Name system

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Features  program loading and execution (ELF)  multiprocessing, multithreading  standard C library available  hard disk (IDE) support  TinyScheme i TinyBasic programming languages

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3rd party components  IDE disk driver  display output, keyboard input  C library  TinyScheme interpreter  TinyBasic interpreter

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System boot

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Software Development Kit  Linux system  GNU C/C++ compiler  L4Ka::Pistachio development environment

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Testing  QEMU  VMWare Workstation  L4 KDB (Kernel Debugger) Test environment: − floppy disk image for OS boot (using grub) − IDE disk image with ext2 filesystem

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QEMU & KDB in action

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Software development #include #include #define SECOND 1000000UL int main(int argc, char *argv[]) { char buf[1024]; L4_Sleep(L4_TimePeriod(4 * SECOND)); printf("Hello, I'm %s!\nWho are you: ", argv[0]); fgets(buf, 1023, stdin); printf("Howdy, %s\n", buf); return 0; }

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Software development  Standard C source code  Build system config (scons) − based on L4 system build system  Build and creation of floppy image  System boot configuration  Virtual machine execution and testing

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Software development

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In summary developed system: − rudimentary − extensable microkernel: − good base for future development open source: − availability − malleability