Re: [Qemu-devel] svn 6658 broke powerpc.

[Rob Landley <rob@landley.net>]

On Thursday 19 March 2009 12:48:09 Blue Swirl wrote:
> On 3/19/09, Rob Landley <rob@landley.net> wrote:
> > On Wednesday 18 March 2009 14:11:19 Blue Swirl wrote:
> >  > On 3/18/09, Rob Landley <rob@landley.net> wrote:
> >  > > On Wednesday 18 March 2009 03:41:05 Alexander Graf wrote:
> >  > >  > On 18.03.2009, at 00:57, Rob Landley wrote:
> >  > >  > > Up through svn 6657, I could boot a powerpc kernel with
> >  > >  > > -kernel. That commit
> >  > >  > > changed it so now it says:
> >  > >  > > invalid/unsupported opcode: 00 - 00 - 00 (00000000) fff18f00 1
> >  > >  > > invalid/unsupported opcode: 00 - 00 - 00 (00000000) fff18f04 1
> >  > >  > > invalid/unsupported opcode: 00 - 0c - 06 (00009198) 00009214 0
> >  > >  > >
> >  > >  > > And dies.
> >  > >  > >
> >  > >  > > You can grab a test kernel from
> >  > >  > > http://landley.net/zImage-powerpc and try
> >  > >  > > booting it (out of the qemu source directory, this is assuming
> >  > >  > > you've built it
> >  > >  > > but haven't installed it yet) via:
> >  > >  > >
> >  > >  > > ppc-softmmu/qemu-system-ppc -kernel zImage-powerpc \
> >  > >  > >  -append "console=ttyS0 panic=1" -nographic -no-reboot -L
> >  > >  > > pc-bios
> >  > >  > >
> >  > >  > > With svn 6657, it works.  (You get kernel boot messages up
> >  > >  > > until it panics and
> >  > >  > > dies because it can't find the root filesystem).  With 6658 it
> >  > >  > > dies immediately with the above error message.
> >  > >  > >
> >  > >  > > Unfortunately, this means that the 0.10.0 release doesn't work
> >  > >  > > for powerpc for
> >  > >  > > me, but svn a couple days _before_ the release did.
> >  > >  >
> >  > >  > That specific commit shouldn't have changed anything with respect
> >  > >  > to ppc32 emulation. The one where your command broken is the
> >  > >  > openBIOS update.
> >  > >
> >  > > The commit I pointed to is the openbios update, yes.
> >  > >
> >  > >  > Please try again without -nographic.
> >  > >
> >  > > It does indeed work without nographic.  (It doesn't do anything
> >  > > _useful_ for me without nographic, since I'm scripting the emulated
> >  > > kernel's behavior through stdin and stdout, but allowing it to pop
> >  > > up an SDL window does make it out of openbios and into the kernel.)
> >  >
> >  > The kernel makes the equivalent of the following calls to OF
> >  > interface: finddevice("/") = 0x11d5c
> >  > finddevice("/chosen") = 0x1197c
> >  > finddevice("/openprom") = 0x11b3c
> >  > getprop(0x11b3c, "model", 0x78efeb0, 0x40) = 0xf
> >  > getprop(0x11d5c, "stdout", 0x78efea0, 0x4) = 0x4
> >  > instance-to-path(0x86ea0, 0x12ad0dc, 0xff) where it crashes because
> >  > memmove overwrites all memory.
> >  >
> >  > But where does this 0x86ea0 come from?
> >
> > No idea, but it worked with the previous openbios, and without
> > --nographic. This is a 2.6.28.8 kernel built with the attached .config.
> >
> >  By the way, while binary searching the openbios repository to figure out
> >  exactly what commit between 450 and 463 actually caused it to stop
> > working, and I hit a fun little OpenBios hiccup in the top level Makefile
> > of current OpenBios svn:
> >
> >  build:
> >     @printf "Building..."
> >     @for dir in $(ODIRS); do \
> >         $(MAKE) -C $$dir > $$dir/build.log 2>&1 && echo "ok." || \
> >         ( echo "error:"; tail -15 $$$dir/build.log; exit 1 ) \
> >     done
> >
> >  You have one too many $ before dir/build.log in the error message, so
> > the error message you get is
> >
> >   Building...error:
> >   tail: cannot open `/build.log' for reading: No such file or directory
> >   make: *** [build] Error 1
>
> I must always have used build-verbose. Should be fixed soon.
>
> >  Which took about 15 minutes of head scratching for a newbie like me to
> > track down.  (The actual problem was that your
> > config/examples/cross-ppc_rules.xml hardwires TARGET=powerpc-linux-gnu-
> > and my cross compiler just uses powerpc- as the prefix, and overriding
> > TARGET on the make command line doesn't work because you use recursive
> > make, and you aren't doing the ?= conditional assignments that won't
> > overwrite existing environment variable values.  I more or less expected
> > it and was running the thing the first time so it would tell me what
> > cross compiler name it expected when it died unable to find it.  Easy
> > enough to fix by just editing the darn file, but a mention of it in the
> > README wouldn't go amiss...)
>
> But my tools also use different prefix, powerpc-elf-
> (powerpc-unknown-elf). I compile using:
>
> make build-verbose TARGET=powerpc-elf-
>
> without problems.

Eh, maybe I typoed something.  But it would still be nice if the README could 
mention TARGET.  (Or, for that matter, build-verbose.)

> About the OpenBIOS problem, I've done further debugging. The crash can
> be reproduced with (-nographic -prom-env auto-boot?=false):

And we are beyond my area of expertise.

When I grab openbios-qemu.elf built from svn 479, rename it qemu-system-ppc, 
and then fire up qemu with "-L ." it complains it can't find "video.x".  Ok, 
fine, add video.x to the current directory (that's powerpc code?) and try 
again, and it goes:

>> =============================================================
>> OpenBIOS 1.0 [Mar 19 2009 02:56]
>> Configuration device id QEMU version 1 machine id 2
>> CPUs: 1
>> Memory: 128M
>> UUID: 00000000-0000-0000-0000-000000000000
>> CPU type PowerPC,750
Welcome to OpenBIOS v1.0 built on Mar 19 2009 02:56

>> File not found
>> *** Boot failure! No secondary bootloader specified ***

Which is at least a _different_ error, but I have no idea what I did wrong...

I tried building a known working version, but svn is being stroppy:

> $ svn update -r 450
> svn: Target path does not exist

No _idea_ what that means, but apparently svn won't back up from current HEAD 
to target 450 without a fight, and won't explain why either.  Google is not 
helpful here, it talks about merging branches...

Rob