Custom ramdisk

Adam Lackorzynski adam at os.inf.tu-dresden.de
Tue Apr 1 00:29:04 CEST 2014


On Tue Apr 01, 2014 at 02:17:29 +0400, Tim Komarov wrote:
> 01.04.2014, 02:03, "Adam Lackorzynski" <adam at os.inf.tu-dresden.de>:
> > Hi,
> >
> > On Mon Mar 31, 2014 at 20:07:34 +0400, Tim Komarov wrote:
> >
> >> šI use Pandaboard for my practising with Fiasco.OC and L4Linux.
> >>
> >> š1) I got a problem with booting L4Linux with my own ramdisk. When I use 18 mb ramdisk, I got the following error:
> >>
> >> šreading image.elf ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ
> >>
> >> š24691072 bytes read ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ
> >> š## Starting application at 0x81000000 ...
> >> š...
> >> š,,,[Everything is usual]
> >> š,,,
> >>
> >> šNET: Registered protocol family 17
> >> šList of all partitions:
> >> šNo filesystem could mount root, tried: šext3 ext2 ext4 cramfs
> >> šKernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(1,0)
> >> šCPU: 0 PID: 1 Comm: swapper Not tainted 3.13.0-l4 #1
> >> š[<0200c624>] (unwind_backtrace+0x0/0xec) from [<020054c0>] (show_stack+0x10/0x14)
> >> š[<020054c0>] (show_stack+0x10/0x14) from [<0222e63c>] (panic+0x7c/0x1b8)
> >> š[<0222e63c>] (panic+0x7c/0x1b8) from [<022f2c40>] (mount_block_root+0x25c/0x29c)
> >> š[<022f2c40>] (mount_block_root+0x25c/0x29c) from [<022f2f44>] (prepare_namespace+0x160/0)
> >> š[<022f2f44>] (prepare_namespace+0x160/0x1b4) from [<022f2894>] (kernel_init_freeable+0x1)
> >> š[<022f2894>] (kernel_init_freeable+0x174/0x1b8) from [<0222ccf0>] (kernel_init+0x8/0x118)
> >> š[<0222ccf0>] (kernel_init+0x8/0x118) from [<020077d4>] (ret_from_fork+0x14/0x20)
> >> š[<020077d4>] (ret_from_fork+0x14/0x20) from [<00000000>] ( š(null))
> >> španic: going to sleep forever, bye
> >>
> >> šTo make ramdisk I simply create a file, write 18 Mb of zeroes to it
> >> š(with dd), create in that file ext2 partition and copy there files
> >> šfrom ramdisk-arm.rd
> >>
> >> šSo, what should I do to get a proper working ramdisk?
> >
> > Hmm, is the expected ramdisk size big enough? I.e. a ramdisk_size=18500
> > on the cmdline could help here. (On the other side the according error
> > message is missing, so maybe not.)
> 
> Yes, in this case in lua configuration file I put 19000. So, that's
> not the reason of my problem. Would you be so kind to write an example
> ( with particular commands ) of making suitable ramdisk for l4linux?
> May be I am wrong with it... If you did, I would be happy!

Sounds ok what you did, i.e. create a file of size of your choice, mkfs
file, loop-mount, copy in your files, unmount, and done. Nothing more,
nothing less.
I'd rather say it's somehow the same issue as with the even bigger
ramdisk, i.e. some parts missing, overwritten, or similar. You could use
a smaller ramdisk and load another one via l4bdds driver and see any
effect of a large image to be loaded.



Adam
-- 
Adam                 adam at os.inf.tu-dresden.de
  Lackorzynski         http://os.inf.tu-dresden.de/~adam/



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