Pid 1 crashing under L4Linux

Uwe Geuder 5vwrpnxfb7 at snkmail.com
Wed Jul 9 00:23:52 CEST 2014


Hi!

I'm pretty new to L4 so I hope this is not an FAQ. I tried to search
the forum archives but couldn't find an answer.

I'm using L4 on an i.MX6 device. Building fiasco, L4Re and L4Linux
succeeded without any errors as far as I can tell. A small ramdisk
containing busybox works fine and I can play around on the command
line. (The system actually has framebuffer support, so I can even
get something on the screen.)

Now I replaced the small "demo" ramdisk by one containing a bigger
distro.  This bigger ramdisk runs without problems on a native Linux
kernel.

However, on L4Linux I always get

> RAMDISK: ext2 filesystem found at block 0
> RAMDISK: Loading 262144KiB [1 disk] into ram disk... 
> EXT4-fs (ram0): couldn't mount as ext3 due to feature incompatibilities
> EXT4-fs (ram0): couldn't mount as ext2 due to feature incompatibilities
> EXT4-fs (ram0): mounted filesystem with ordered data mode. Opts: (null)
> VFS: Mounted root (ext4 filesystem) readonly on device 1:0.
> Freeing unused kernel memory: 116K (022f9000 - 02316000)
> Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004
> 
> CPU: 0 PID: 1 Comm: sh Not tainted 3.14.0-l4 #7
> [<0200c47c>] (unwind_backtrace) from [<02005618>] (show_stack+0x10/0x14)
> [<02005618>] (show_stack) from [<02238d08>] (panic+0x8c/0x1c8)
> [<02238d08>] (panic) from [<020186bc>] (complete_and_exit+0x0/0x1c)
> [<020186bc>] (complete_and_exit) from [<00000001>] (0x1)
> panic: going to sleep forever, bye
> l4linux | panic: going to sleep forever, bye
> 

The stack trace is the same for init=/bin/sh and the default
systemd. Looks like for some reason user space processes in this setup
just crash pretty soon.

The console log before that looks pretty unsuspicious to me. But I can
of course post it should it be necessary to understand what is going
on.

What comes to my mind is that my user space is built for armv7tnhl, i. e. 
thumb instruction set, NEON, and hard-float. 

> -march=armv7-a -mfloat-abi=hard -mfpu=neon -mthumb

Can any of these options be a problem under L4?

(The small busybox ramdisk, which works fine was built by a colleague
of mine who is on holidays at the moment. I'm not sure how he built
it, but I assume it's neither hard-float nor thumb. Well, I could
disassemble something to be sure I guess...)

If armv7tnhl does not cause obvious problems, do you have any
debugging hints/pointers how to find out why/where pid 1 is crashing?
Address 0x1 is nonsense I suppose, but if tells anything then that
the processor is in thumb mode. Which is what I would expect from my
user space.

Regards,

Uwe Geuder
Nomovok Ltd.
Tampere, Finland
uwe.gxuder at nomovok.com (bot test: humans correct 1 obvious spelling error)






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