[Qemu-devel] Re: Fun with sparc (was Re: qemu-ppc can't run static uClibc binaries.)

[Blue Swirl <blauwirbel@gmail.com>]

On 2/20/10, Rob Landley <rob@landley.net> wrote:
> On Thursday 18 February 2010 05:21:16 Artyom Tarasenko wrote:
>  > 2010/2/17 Rob Landley <rob@landley.net>:
>  > > But it does imply that qemu is capable of decently running _something_ on
>  > > sparc, so the problems I'm seeing are more likely to be uClibc or
>  > > toolchain issues.
>  >
>  > qemu-sparc can decently run debian-40r8: gcc and all the other stuff
>  > seem to work.
>  >
>  > Most versions of the NetBSD boot. Some require the original OBP
>  > though. The only known to me version which definetely doesn't boot is
>  > 3.0.2.
>  >
>  > Also since the last dma fix Solaris 2.4-2.5.1 seems to be also fully
>  > functional. Don't have a suitable compiler to check whether it's
>  > working under Solaris though.
>  >
>  > Debian-40r8 should have all the necessary stuff to build the uClibc
>  > toolchain, right?
>
>  So I did a network install of that Debian image into a 4 gig disk image, and
>  made some progress.
>
>  First a quick bug report: qemu-system-sparc tries to set the video window to
>  900 pixels vertical, but my laptop's display is only 800 pixels tall, and the
>  window manager trims it a bit more than that for the toolbar.  The kernel
>  booting up seems to think the graphics window is still its original size
>  renders text off the bottom of it.  But for some reason I can grab the window
>  and resize it, and when I do this the emulated kernel's frame buffer gets the
>  update and resizes its console to show the correct number of lines of text for
>  the new size!  (So my question is, why didn't it get the size right when the
>  window manager first resized it before I manually resized it again?)
>
>  Anyway: yay emulated sparc debian, I installed it, got a reasonable
>  environment going, extracted my root filesystem image under there and chrooted
>  into it... and everything worked fine.  (Well, trying to run a dynamically
>  linked "hello world" still died with a bus error, but using the static busybox
>  I could mount a tmpfs and list its contents, which I never could before.)
>
>  My plan had been to use sparc-debian's copy of gdb to track down why the
>  binaries were going funky... but in that environment, they were behaving
>  themselves.  Same binaries, built with the same toolchain, same qemu-system-
>  sparc, same -M and -cpu and so on...
>
>  So I think "A-ha!  Booting a different kernel!  That's gotta be it!"
>
>  The debian-sparc image is using a 2.6.18 kernel (and I'm using a 2.6.32
>  kernel), but it installed the relevant .config in /boot, so I copied that out
>  with scp, did a "make oldconfig" up to 2.6.32 (holding down the enter key until
>  it shut up), stripped out all the modules and disabled module support, put
>  back in CONFIG_SERIAL_SUNZILOG_CONSOLE=y and friends, procfs, sysfs, and tmpfs
>  (strange things to have as modules?), and CONFIG_SQUASHFS (that's my default
>  root filesystem format).
>
>  I booted the result up with init=/bin/ash, did a "mount -t tmpfs /tmp /tmp",
>  and then:
>
>   / # ls -l /tmp
>   Illegal instruction
>
>  It's still misbehaving.  Huh.
>
>  This is as close as I can get to the debian kernel config without adding module
>  support to my images (which is unnecessary complication for what they do).  I
>  can try an ext2 root filesystem image but I don't see how that would cause
>  this.
>
>  The part I don't understand is that same busybox binary, built with the same
>  toolchain, worked just fine under the Debian kernel.  I'd blame my toolchain,
>  but in a slightly different context THE BINARIES WORKED...
>
>  I don't understand what's going wrong here.  Did the kernel break on sparc
>  sometime between 2.6.18 and 2.6.32 and nobody noticed?  Is sparc using
>  software emulated floating point at the kernel level and that's configured as a
>  module?  (Except I don't think busybox ls uses floating point...)

Sparc32 is not maintained anymore so maybe it broke at some point.
There was some discussion a few years ago.

>  Do any sparc people understand what's going on here?  My next step is to grab
>  a 2.6.18 kernel and try to get _that_ to work with the tweaked debian config
>  (and an ext2 root filesystem since squashfs wasn't merged back then and had a
>  format change when it was merged).  But I'm mostly flailing around blind
>  here...

I'm also trying different kernels using my .config. But already 2.6.12
hangs in ESP probe.