Re: qemu/m68k

Hi Greg,
Greg Ungerer wrote,

> Hi Waldemar,
> 
> On 22/08/14 06:25, Waldemar Brodkorb wrote:
> >>>Do you have a suggestion why I get a segfault after first executed
> >>>command? Similar behaviour Thomas Petazzoni have seen, while he was
> >>>trying to run buildroot in Qemu/m68k. See here:
> >>>http://lists.busybox.net/pipermail/buildroot/2012-April/052585.html
> >>
> >>No, I haven't seen that behavior. Is it a hush problem?
> >>Maybe try a simpler shell to see if you get the same result.
> >
> >Okay, it seems a problem with my uClibc version or configuration.
> >Still investigating. But using the sash from uClinux works fine
> >with my own kernel.
> 
> Ok, at least that gives you a working base to go from.

Okay, after further investigation and deeper digging in the uClinux
buildsystem I found partially a solution to my problem.
uCLinux uses a gcc wrapper and is linking executables with
-nostdlib and manually adding the needed C libraries and startup
files. 
I have just used -static, but this pulled in crtbegin.o and crtend.o
from gcc. I now use a gcc wrapper with a modified spec file, so that
crtbegin.o/crtend.o is not added to my binary.
Furthermore I added following patch to my gcc:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54584

Both changes required to create a working BFLT executable.
Otherwise elf2flt seems to pick up the data section of crtbegin.o,
which ends up with a BFLT file with a wrong data start.

I can provide more details and output of readelf of the sh.gdb files,
if required. I am not sure if this can be fixed in the linker script
used by elf2flt. 

But I still don't get an interactive shell working. I use simpleinit
and sash. The output of Qemu is:
Starting Linux (built with OpenADK).
Freeing unused kernel memory: 432K (401a0000 - 4020c000)
Shell invoked to run file: /etc/rc
Command: echo Starting OpenADK
Starting OpenADK
Command: hostname openadk
Command: mount -t proc proc /proc
Command: mount -t sysfs sys /sys
Command: mkdir -m 755 /dev/pts
Command: mount -t devpts devpts /dev/pts
Command: mount -t tmpfs -o size=8M tmpfs /tmp
Command: chmod 1777 /tmp
Command: mkdir -p /var/log
Command: mkdir -p /var/run
Command: mkdir -p /var/tmp
Command: mdev -s
Command: mount
rootfs on / type rootfs (rw)
devtmpfs on /dev type devtmpfs (rw,relatime,mode=0755)
proc on /proc type proc (rw,relatime)
sys on /sys type sysfs (rw,relatime)
devpts on /dev/pts type devpts (rw,relatime,mode=600)
tmpfs on /tmp type tmpfs (rw,relatime,size=8M)
Command: ifconfig lo 127.0.0.1 up
Execution Finished, Exiting

openadk login: Kernel panic - not syncing: Attempted to kill init!
exitcode=0x0000000b

My inittab is:
s0:linux:/sbin/getty -L -n 38400 ttyS0
1:linux:/sbin/getty -L -n 38400 ttyS1

I have taken a look into the coldfire example from qemu.org. They
are using simpleinit and busybox msh. I tried busybox hush, instead
of sash, but without success. msh seems no longer available in
busybox. Does uClinux provide a interactive shell? 

(need to try the uClinx system with the gdb method. I am just using kernel with initramfs
piggyback) 
 
> >>>qemu: hardware error: mcf_fec_read: Bad address 0x1c4
> >>
> >>Hmmm, yeah, it does stop there. Not sure why. I will need to look
> >>more closely at that.
> >
> >Did you found anything?
> 
> Yep. The problem is that the FEC driver is writing to registers
> that don't exist in the FEC hardware module on the ColdFire
> family. Support for some of the extended registers used on
> the FEC are used on ARM implementations, and they had added
> support for those in more recent years.
> 
> I never picked those up on real hardware. Accesses to those
> on addresses cause no (visible) problems.
> 
> Anyway, attached is a patch I propose to fix it. I will be
> sending this to the linux net-dev list soon.
 
Great! I will test it really soon. Or may be your upcoming patch.
 
thanks
 Waldemar
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