Mezzano Operating System Documentation

The Mezzano compiler backend processes optimized ASTs into Intermediate Representation (IR) instructions, which are then converted to assembly.

Key design concepts:

• Instruction Structure: Instructions are linked via an intrusive doubly-linked list. Basic blocks are implicit, started by a label instruction and ended by a terminator-instruction.
• Function Entry: The first instruction in any function must be an argument-setup-instruction.
• Data Flow: Uses virtual-register (vreg) objects. In SSA form, a vreg is defined exactly once. Physical registers (preg) can be used directly, but they cannot be live over basic block boundaries until after register allocation.
• Lexical Variables: Represented by the lexical-variable class. They are explicitly bound and unbound and are not converted to SSA form to preserve debug lifetime information.
• Multiple Values: Handled outside the vreg/preg system using target-specific multiple value registers. They can only be live over a small set of instructions.

The line editor supports standard navigation and editing commands:

Navigation

• C-F or Right-Arrow: Move forward one character.
• C-B or Left-Arrow: Move backward one character.
• C-A or Home: Move to the beginning of the line.
• C-E or End: Move to the end of the line.
• M-F: Move forward one word.
• M-B: Move backward one word.
• M-P or Up-Arrow: Find previous matching history item.
• M-N or Down-Arrow: Find next matching history item.

Editing

• C-D or Delete: Delete the next character.
• Backspace: Delete the previous character.
• M-D: Delete the next word.
• M-Backspace: Delete the previous word.
• C-K: Delete from the cursor to the end of the line.
• Tab: Cycle through completions for the current symbol.

Debugging

• C-C: Enter the debugger using BREAK.
• C-G: Invoke the most recent ABORT restart (clears input and returns to prompt).

To run ANSI regression tests, load the test initialization, configure the runtime to handle specific test cases (like disabling certain notes), and execute the tests using regression-test:do-tests.

To skip a specific test during execution, use: (throw 'rt::*in-test* nil)

(in-package :cl-user)
(load (merge-pathnames "ansi-test/init.lsp" (user-homedir-pathname)) :verbose t :print t)
(rt:disable-note :nil-vectors-are-strings)
(mapc #'rt:rem-test
      '(cl-test::make-array.23 ; Exhausts memory
        cl-test::make-array.28 ; Stack overflows
        cl-test::print.cons.7 ; Missing circularity detection
        cl-test::print.vector.circle.1 ; Stack overflows
        ;; These all take ages.
        cl-test::find-all-symbols.1
        cl-test::do-all-symbols.1
        cl-test::do-all-symbols.2
        cl-test::do-all-symbols.3
        cl-test::do-all-symbols.4
        cl-test::bignum.float.compare.7
        cl-test::bignum.float.compare.8
        cl-test::rational.double-float.random.compare.1
        cl-test::rational.long-float.random.compare.1
        cl-test::print.vector.random.1
        ))
;; Since we're evaluating lots, better to avoid the compiler
(setf mezzano.internals::*eval-hook* 'mezzano.full-eval:eval-in-lexenv)
(time (regression-test:do-tests))

To use kboot as a secondary bootloader within a dual-boot system, copy kboot.bin into your /boot directory and create a kboot.cfg file in /boot.

kboot.cfg allows you to define different boot entries. Common options include:

• video_mode: Sets the resolution (e.g., lfb:1440x900).
• mezzano <partition> <options>: Specifies the partition (e.g., hd0,2) and boot modes.
• video-console: Displays console messages directly on the background window.
• freestanding: Runs Mezzano in memory without paging or snapshots (useful for read-only media).
• no-detect: Disables most hardware detection (useful for troubleshooting).

set "timeout" 5

entry "Mezzano - hardware detection with video console" {
      set "video_mode" "lfb:1440x900"
      mezzano "hd0,2" "video-console"
}

entry "Mezzano - hardware detection" {
      set "video_mode" "lfb:1440x900"
      mezzano "hd0,2"
}

entry "Mezzano - freestanding with video console" {
      set "video_mode" "lfb:1440x900"
      mezzano "hd0,2" "freestanding" "no-detect" "video-console"
}

entry "Mezzano - freestanding" {
      set "video_mode" "lfb:1440x900"
      mezzano "hd0,2" "freestanding"  "no-detect"
}