Saturday, October 31, 2009

Playground extension

Carey Schug did me another favor. This time he provided access to a SparcServer-20 which he has at home! Now I can compare a virtual SS-20 with a real one. So, the little bugs, beware of me!
Thanks, Carey!

Sunday, October 25, 2009

Another small improvement in SCSI emulation

The message

Error: Inquiry (STANDARD) buffer size 5 is less than 36 (TODO: only 5 required)

was quite annoying, so I attacked it. I used to have a hack which explicitly implemented
inquiry with the allocation size length == 5.
But it turned out that the clean fix is quite trivial, the specification says "if the allocation length of the command descriptor block (CDB) is too small to transfer all of the parameters, the additional length shall not be adjusted to reflect the truncation", so the clean fix for this problem is not longer than the code telling about "TODO". :) Will send the patch upstream. Now probe-scsi in OBP looks really nice:

ok probe-scsi
Target 0
Target 1
Target 2
Unit 0 Removable Read Only device QEMU QEMU CD-ROM 0.11

Saturday, October 24, 2009

Greetings, Professor Falken

Success! I've managed to boot Solaris 2.5.1/sparc under qemu! It takes long. I started it on my machine (E8200@2.66GHz) yesterday at 18:31, and today at 03:24, I finally got the "#":

WARNING: clock gained 4900 days -- CHECK AND RESET THE DATE!
# ls
a devices kernel opt root.proto var
bin etc kvm platform sbin
cdrom export lib proc tmp
dev home mnt reconfigure usr
# uname -a
SunOS 5.5.1 Generic sun4m sparc SUNW,SPARCstation-20

Woo-hoo! Currently I can boot it in a single user mode only, as in normal mode it fails on non-existing SX framebuffer.

Does anyone know how to change module "exclude" list from the adb session?

P.S. 4900 days - didn't notice first, that the date was so special. Hope to boot Solaris 9 earlier than 4900 days after its release date. :)

Saturday, October 17, 2009

Can't invoke /etc/init, error 14

Solaris boots the kernel now. The next stop is booting /etc/init . With Solaris 2.6 I get

Can't invoke /etc/init, error 14

After searching the Net, I found that the error number is 2 if /sbin/init is missing, and 8 if /sbin/init has an incorrect executable format. But what is 14? Is this the errno 14, aka EFAULT? Is this a message from the init, or from the kernel?

Sunday, October 11, 2009

The second bug in the qemu sparc CPU emulation

Mitch Bradley found a bug in the Sparc CPU emulation. I gave him access to my qemu session and he stepped through the code. Is sort of shame, I haven't done it myself, as I thought about it 2 weeks ago.

This bug is actually much more heavy than the previous one. While the previous one affected only the hand crafted assembly code, this one should hit the compiled code as well: the handling of carry flag in subxcc instruction is wrong. And, yes, it's RISC architecture, so this instruction is also used for comparison...

I'm really astonished that Linux/sparc is working under qemu since years. Of course Linux may be just more robust, but it also may mean that gcc doesn't use some sparcv8 instructions, and is therefore inefficient.

Saturday, October 10, 2009

The OBP author is here and still cares

Mitch Bradley (OBP author) explained how OBP space* commands are working. While the emulation is meanwhile working properly for this commands, it is nevertheless great to know that the father still cares about his child.

And, speaking of children, Mitch is also the author of OLPC firmware and OLPC Forth tutorial I mentioned before.

Sunday, October 4, 2009

A little improvement of SCSI disk emulation

NetBSD complained:

sd3: mode sense (4) returned nonsense; using fictitious geometry

SunOS 4.1.4 complains:

sd3: non-CCS device found at target 0 lun 0 on esp0

I was hoping that this is the same bug, so I tried to investigate. It's always easier to work when the sources are available. It turned out that NetBSD expects a block descriptor for mode pages, which wasn't implemented in qemu, and is probably mandatory for SCSI-2 disks. The specs are unclear: they don't explicitly say "optional" or "mandatory" in chapters 9.1.2 and 9.3.3.

Anyway, I implemented the block descriptor, and the NetBSD bug is gone. But this was in vain: the SunOS bug is still there, the Solaris bootblk problem is also un-affected.

Will send the patch upstream though. A small improvement is still an improvement.