Principles of Operating Systems: Design & Applications

1. Principles of Operating Systems: Design & Applications Chapter 3 Inferno Structure and Initialization

2. Objectives • understand where Inferno fits into the history of operating system development • have an appreciation for its position as a descendant of CTSS, Multics, UNIX, and Plan 9 • understand key concepts that are probably unfamiliar: per-process name spaces, everything as a file server, and Styx

3. Objectives (cont.)‏ • have a mental picture of how the major components of Inferno are organized and how the source code is organized • understand the division of labor between host-dependent and host-independent initialization • understand how and why the first kproc and the first user process are created “by hand”

4. Objectives (cont.)‏ • understand how the system goes from its starting point to time-sharing • understand that the initial user process becomes the ancestor of all other processes that run during the lifetime of the system • understand how the system call mechanism of Inferno differs from that of most other systems

5. Inferno History • Multics begat UNIX–Ken Thompson and Dennis Ritchie: 1969 • UNIX begat Plan 9–Ken Thompson and Rob Pike • Plan 9 begat Inferno • Vita Nuova purchased Inferno • Vita Nuova open sourced Inferno Principles of Operating Systems: Design & Applications 5

6. Inferno Concepts • Native and Hosted operation • Hosted on FreeBSD, HP-UX, Irix, Linux, Mac OS X, Windows NT, Plan 9, Solaris, and Unixware • Native on CerfCube 1110, CerfCube 250, CerfCube 405, MPC8xx FADS development board, Ipaq , Brightstar ipEngine, JavaStation 1, Arm 7 evaluator kit, IBM PC compatibles, Embedded Planet RPXLite MPC823 Principles of Operating Systems: Design & Applications 6

7. Inferno Concepts (cont.)‏ • Per-process name spaces • Can assemble name space from separate files and directories • Name spaces can be inherited • Everything is a file server • Extends the UNIX idea that (almost) everything is a file • Directories and files provided by file servers • File servers both built in to the kernel and run as normal applications Principles of Operating Systems: Design & Applications 7

8. Inferno Concepts (cont.)‏ • Styx • Used by all File servers • Limbo and Dis • All apps written in Limbo • Limbo compiled to Dis • Dis runs the same on all host OSs and hardware • Just-in-time compilers for most platforms Principles of Operating Systems: Design & Applications 8

9. Inferno Structure Principles of Operating Systems: Design & Applications 9

10. Source Directory Structure Principles of Operating Systems: Design & Applications 10

11. Inferno Initialization • Process command line arguments and environment parameters • Identify the host owner • Do host OS-specific initialization • Create first kernel process • Initialize devices • Build initial name space Principles of Operating Systems: Design & Applications 11

12. Inferno Initialization (cont.)‏ • Create second kproc to run Dis VM • Create initial floating-point state • Initialize the Dis VM • Load the initial Dis module and set it to ready • Start the Dis VM Principles of Operating Systems: Design & Applications 12

13. In emu/port/main.c: main()‏ Process Parameters: if((p = getenv("INFERNO")) != nil || (p = getenv("ROOT")) != nil)‏ strecpy(rootdir, rootdir+sizeof(rootdir), p); opt = getenv("EMU"); if(opt != nil && *opt != '\0') { enva[0] = "emu"; envc = tokenize(opt, &enva[1], sizeof(enva)-1) + 1; enva[envc] = 0; option(envc, enva, envusage); } option(argc, argv, usage); Principles of Operating Systems: Design & Applications 13

14. In emu/port/main.c: main()‏ Set Initial Host Owner eve = strdup("inferno"); Call Host OS-Specific Initialization libinit(imod); Principles of Operating Systems: Design & Applications 14

15. In emu/Linux/os.c: libinit()‏ Create First kproc p = newproc(); p->kstack = stackalloc(p, &tos); pw = getpwuid(getuid()); if(pw != nil)‏ kstrdup(&eve, pw->pw_name); else print("cannot getpwuid\n"); p->env->uid = getuid(); p->env->gid = getgid(); executeonnewstack(tos, emuinit, imod); Principles of Operating Systems: Design & Applications 15

16. In emu/port/main.c: emuinit()‏ Initialize Devices chandevinit(); Create Name Space Root e->pgrp->slash = namec("#/", Atodir, 0, 0); cnameclose(e->pgrp->slash->name); e->pgrp->slash->name = newcname("/"); e->pgrp->dot = cclone(e->pgrp->slash); Principles of Operating Systems: Design & Applications 16

17. In emu/port/main.c: emuinit()‏ Open Standard Input, Output, and Error if(kopen("#c/cons", OREAD) != 0)‏ fprint(2, "failed to make fd0 from #c/cons: %r\n"); kopen("#c/cons", OWRITE); kopen("#c/cons", OWRITE); Principles of Operating Systems: Design & Applications 17

18. In emu/port/main.c: emuinit()‏ Create Initial Name Space kbind("#U", "/", MAFTER|MCREATE); setid(eve, 0); kbind("#^", "/dev", MBEFORE); /* snarf */ kbind("#^", "/chan", MBEFORE); kbind("#m", "/dev", MBEFORE); /* pointer */ kbind("#c", "/dev", MBEFORE); kbind("#p", "/prog", MREPL); kbind("#d", "/fd", MREPL); kbind("#I", "/net", MAFTER); /* will fail on Plan 9 */ Principles of Operating Systems: Design & Applications 18

19. In emu/port/main.c: emuinit()‏ Create First Dis Interpreter kproc("main", disinit, imod, KPDUPFDG|KPDUPPG|KPDUPENVG); Principles of Operating Systems: Design & Applications 19

20. In emu/port/dis.c: disinit()‏ Create Initial Floating Point State Fpinit(); Fpsave(&up->env->fpu); Initialize Dis VM opinit(); modinit(); excinit(); Principles of Operating Systems: Design & Applications 20

21. In emu/port/dis.c: disinit()‏ Load Initial Module root = load(initmod); Schedule Initial Module p = schedmod(root); Start the Virtual Machine vmachine(nil); Principles of Operating Systems: Design & Applications 21

22. System Calls • Apps see ordinary cross-module function calls • System calls in module, Sys • Sys module built in to kernel • Calls kernel functionality with normal function calls Principles of Operating Systems: Design & Applications 22

23. Summary • Inferno derives from a long line of research operating systems • Inferno has a number of unique features • Initialization covers everything from beginning to time-sharing • System calls implemented through special module Principles of Operating Systems: Design & Applications 23

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