It’s just been really busy with this move, unpacking and the usual losing things, finding things and breaking things.

In the middle of it all, I found something online, that I want to at least do some proper article thing about… As it’s been really exciting, and goes back to the first month I started this blog.

Outside of NeXTSTEP, the other i386 commercial version of Mach 2.5 surfaced, the Mt Xinu version!

Even better, a few years ago, I had stumbled onto the source code for 2.5 buried on the 4th disc of the CSRG set, and with a LOT of luck and persistence I can confirm that the sources are complete enough to build.

loading vmunix.sys
rearranging symbols
text	data	bss	dec	hex
389088	45564	101364	536016	82dd0
ln vmunix.sys vmunix; ln vmunix vmunix.I386x.STD+WS-afs-nfs

However, as luck always has it, start.s in the i386 code does something weird at the 3GB mark causing a triple fault on any kind of modern emulation/virtualization setup.

    / Fix up the 1st, 3 giga and last entries in the page directory
    mov     $EXT(kpde), %ebx
    and     $MASK, %ebx

    mov     $EXT(kpte), %eax
    and     $0xffff000, %eax
    or      $0x1, %eax

    mov     %eax, (%ebx)
    mov     %eax, 3072(%ebx)        / 3 giga -- C0000000

    mov     $EXT(kpde), %edx
    and     $MASK, %edx

Not all that sure why, but at least on Bochs, I can see the triple fault.

00036527018d[CPU0  ] page walk for address 0x0000000000101122
00036527018d[CPU0  ] page walk for address 0x00000000e0000011
00036527018d[CPU0  ] PDE: entry not present
00036527018d[CPU0  ] page fault for address 00000000e0000011 @ 0000000000101124
00036527018d[CPU0  ] exception(0x0e): error_code=0002
00036527018d[CPU0  ] interrupt(): vector = 0e, TYPE = 3, EXT = 1
00036527018d[CPU0  ] page walk for address 0x00000000c0161370
00036527018d[CPU0  ] PDE: entry not present
00036527018d[CPU0  ] page fault for address 00000000c0161370 @ 0000000000101122
00036527018d[CPU0  ] exception(0x0e): error_code=0000
00036527018d[CPU0  ] exception(0x08): error_code=0000
00036527018d[CPU0  ] interrupt(): vector = 08, TYPE = 3, EXT = 1
00036527018d[CPU0  ] page walk for address 0x00000000c0161340
00036527018d[CPU0  ] PDE: entry not present
00036527018d[CPU0  ] page fault for address 00000000c0161340 @ 0000000000101122
00036527018d[CPU0  ] exception(0x0e): error_code=0000
00036527018i[CPU0  ] CPU is in protected mode (active)
00036527018i[CPU0  ] CS.mode = 32 bit
00036527018i[CPU0  ] SS.mode = 32 bit
00036527018i[CPU0  ] EFER   = 0x00000000
00036527018i[CPU0  ] | EAX=e0000011  EBX=0015f000  ECX=00161dc1  EDX=0015f000
00036527018i[CPU0  ] | ESP=0000efbc  EBP=0000efbc  ESI=00193fb8  EDI=00009d84
00036527018i[CPU0  ] | IOPL=0 id vip vif ac vm RF nt of df if tf SF zf af PF cf
00036527018i[CPU0  ] | SEG sltr(index|ti|rpl)     base    limit G D
00036527018i[CPU0  ] |  CS:0028( 0005| 0|  0) 00000000 ffffffff 1 1
00036527018i[CPU0  ] |  DS:0020( 0004| 0|  0) 00000000 ffffffff 1 1
00036527018i[CPU0  ] |  SS:0010( 0002| 0|  0) 00001000 0000ffff 0 1
00036527018i[CPU0  ] |  ES:0020( 0004| 0|  0) 00000000 ffffffff 1 1
00036527018i[CPU0  ] |  FS:0000( 0005| 0|  0) 00000000 0000ffff 0 0
00036527018i[CPU0  ] |  GS:0000( 0005| 0|  0) 00000000 0000ffff 0 0
00036527018i[CPU0  ] | EIP=00101122 (00101122)
00036527018i[CPU0  ] | CR0=0xe0000011 CR2=0xc0161340
00036527018i[CPU0  ] | CR3=0x00000000 CR4=0x00000000
00036527018i[CPU0  ] 0x0000000000101122>> add byte ptr ds:[eax], al : 0000
00036527018d[SIM   ] searching for component 'cpu' in list 'bochs'
00036527018d[SIM   ] searching for component 'reset_on_triple_fault' in list 'cpu'
00036527018e[CPU0  ] exception(): 3rd (14) exception with no resolution, shutdown status is 00h, resetting

Mach 3.0 doesn’t do this, so I’ll have to dig far deeper into start.s which is kind of really beyond me.

Building a boot disk … is involved. 😐

rm -rf /usr/src/mach25-i386/obj
mkdir /usr/src/mach25-i386/obj
cd /usr/src/mach25-i386/standi386at/boot
make fdboot
/home/user/mkfs /dev/rfloppy 2880 18 2 4096 512 32 1
dd if=/usr/src/mach25-i386/obj/standi386at/boot/boot.fd of=/dev/rfd0d
/home/user/fsck -y /dev/rfloppy
cd /usr/src/mach25-i386/
make
mount /dev/floppy /mnt
cp /usr/src/mach25-i386/obj/STD+WS-afs-nfs/vmunix /mnt
sync
umount /mnt
/home/user/fsck -y /dev/rfloppy

So, I’m not all that dead. For anyone super impatient, you can download my VMDK here, which runs on Qemu & VMware, it includes a serial terminal on COM1 so you can use a real terminal, and if you are like me, uuencode/uudecode files in & out of the system. As always read the 404 page for the current username/password.