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

[Artyom Tarasenko]

2010/2/20 Blue Swirl <address@hidden>:
> On 2/20/10, Rob Landley <address@hidden> wrote:
>> On Thursday 18 February 2010 05:21:16 Artyom Tarasenko wrote:
>>  > 2010/2/17 Rob Landley <address@hidden>:
>>  > > 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.

Does it work on a real hw? 2.6.18 definitely does.
We still have bug(s) in ESP though: Solaris also hangs in ESP probe
after a soft reset in OBP.

-- 
Regards,
Artyom Tarasenko

solaris/sparc under qemu blog: http://tyom.blogspot.com/