Raymii.org

Table of Contents

• Compiling Vi with Cosmopolitan
• Run Vi in QEMU
• Patches for viless

This guide shows you how to run Vi without an operating system, bare metal. This is a follow up on my article from 2014 where I made a custom linux distro that would Boot to Vim, VIM as PID 1. This time we go further, we boot into Vi without an operating system. This is made possible by Cosmopolitan, a libc that outputs a POSIX-approved polyglot format that runs natively on Linux + Mac + Windows + FreeBSD + OpenBSD + NetBSD + BIOS with the best possible performance and the tiniest footprint imaginable.

Here is a screenshot of bare metal Vi:

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The article Vim as PID 1, Boot to Vim recently hit the front page of HackerNews and one of the commenters stated the following:

I bet it wouldn't be too extremely hard to port Vim to cosmopolitan and run it without an OS (BIOS mode in cosmopolitan). (by etaioinshrdlu )

Turns out, that's mostly possible. Not actual Vim, but a minimal Vi clone compiles just fine and runs without any OS.

Super cool, fast startup time, the only thing it lacks is filesystem support, so you cannot save or load your files. But hey, who needs that?

I'm compiling a small Vi clone, viless, which is the BusyBox Vi clone but patched to run without BusyBox, and a few patches by me to make it compile inside cosmopolitan.

Compiling Vi with Cosmopolitan

These instructions are based on the instructions on the cosmopolitan source. I'm running them on a Debian 11 system, but Ubuntu should work too.

Make sure you can compile C code and have git:

apt install build-essential git unzip

Clone the Vi code:

git clone https://github.com/RaymiiOrg/viless

Test if you can compile it:

cd viless
make

You should have an executable vi binary in the current folder. Try to run it:

./vi

Exit with :q!. If that all worked you can continue with the cosmopolitan part.

Download the required files:

 wget https://justine.lol/cosmopolitan/cosmopolitan-amalgamation-2.2.zip

Unzip cosmopolitan:

unzip cosmopolitan-amalgamation-2.2.zip

Compile Vi with the cosmopolitan runtime:

gcc -g -Os -static -nostdlib -nostdinc -fno-pie -no-pie -mno-red-zone \
    -fno-omit-frame-pointer -pg -mnop-mcount -mno-tls-direct-seg-refs \
    -gdwarf-4   \
    -o vi.com.dbg \
    vi.c \
    -fuse-ld=bfd -Wl,-T,ape.lds -Wl,--gc-sections   \
    -include cosmopolitan.h crt.o ape-no-modify-self.o cosmopolitan.a

Use objcopy to make the actual binary you can run:

objcopy -S -O binary vi.com.dbg vi.com

The file vi.com should be executable on your linux system, but also on all the platforms stated above.

Run Vi in QEMU

On the same Ubuntu machine, make sure you've installed qemu:

sudo apt install qemu-system-x86

Then execute the following command to boot your freshly created vi.com disk(?):

 qemu-system-x86_64 -m 16 -nographic -drive file=vi.com,format=raw,index=0,media=disk

This will launch you into Vi. Exit with CTRL+A, X (to exit QEMU). If you want to have a separate window as I did in the screenshots, remove the -nographic option and in the window that pops up, select the View menu, then choose serial0.

I currently only have a Raspberry Pi 4 as my main desktop so I cannot try booting from a floppy or USB drive on real hardware. If you can, please let me know if it works. You will probably not see anything on the screen but on the serial port.

Update: I've loaned an x86 laptop and the vi.com file runs when written to disk using dd:

# replace /dev/sdX with your USB device
dd if=vi.com of=/dev/sdX conv=notrunc 

The vi.com file I compiled is available for download.

You could try to compile the actual Vim and see if that works. If you do, please let me know about it!

Patches for viless

These are the changes I made to viless to make it compile with Cosmopolitan:

From 96aa85f886249ad7fd097a413c28ca4771c0326e Mon Sep 17 00:00:00 2001
From: Remy van Elst <RaymiiOrg@users.noreply.github.com>
Date: Sat, 22 Apr 2023 20:27:05 +0200
Subject: [PATCH] Patches for cosmopolitan

---
 vi.c | 60 ++----------------------------------------------------------
 1 file changed, 2 insertions(+), 58 deletions(-)

diff --git a/vi.c b/vi.c
index 1d7f9ac..4e959fc 100644
--- a/vi.c
+++ b/vi.c
@@ -22,27 +22,14 @@
  * A true "undo" facility
  * An "ex" line oriented mode- maybe using "cmdedit"
  */
+ 
+#define STANDALONE

 #ifdef STANDALONE
 #define BB_VER "version 2.62"
 #define BB_BT "brent@mbari.org"

 #define _GNU_SOURCE
-#include <stdarg.h>
-#include <string.h>
-#include <stdio.h>
-#include <unistd.h>
-#include <stdlib.h>
-#include <setjmp.h>
-#include <sys/ioctl.h>
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-#include <signal.h>
-#include <errno.h>
-#include <ctype.h>
-#include <termios.h>
-#include <poll.h>

 #define vi_main            main
 #define CONFIG_FEATURE_VI_MAX_LEN 4096
@@ -104,8 +91,6 @@ typedef signed char smallint;

 #endif

-#include <limits.h>
-
 /* the CRASHME code is unmaintained, and doesn't currently build */
 #define ENABLE_FEATURE_VI_CRASHME 0

@@ -509,22 +494,6 @@ void *xzalloc(size_t size)
    return memset(xmalloc(size), 0, size);
 }

-void *xstrdup(const char *s)
-{
-   void *ptr = strdup(s);
-   if (ptr) return ptr;
-   perror("strdup");
-   exit(66);
-}
-
-void *xstrndup(const char *s, size_t n)
-{
-   void *ptr = strndup(s, n);
-   if (ptr) return ptr;
-   perror("strndup");
-   exit(67);
-}
-
 void *xrealloc(void *old, size_t size)
 {
    void *ptr = realloc(old, size);
@@ -2475,31 +2444,6 @@ static int rawmode(void)
    tcsetattr(0, TCSANOW, &term_vi);

    unsigned tics = 1;
-    switch (cfgetispeed(&term_vi)) {
-   case B600:
-       tics = 2;
-       break;
-   case B300:
-       tics = 4;
-       break;
-   case B200:
-       tics = 6;
-       break;
-   case B150:
-       tics = 7;
-       break;
-   case B134:
-       tics = 8;
-       break;
-   case B110:
-       tics = 10;
-       break;
-   case B75:
-       tics = 15;
-       break;
-   case B50:
-       tics = 21;
-   } //determines how long to wait for ESCAPE sequences
    ticsPerChar = tics;
    return 0;
 }

Tags: bare-metal , bios , blog , compile , cosmopolitan , libc , uefi , vi , vim