linux-kernel - RFC: initramfs unpack point and rules

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Date:	Thu, 05 Apr 2007 14:34:39 +0200
From:	Krzysztof Halasa <khc@...waw.pl>
To:	<linux-kernel@...r.kernel.org>
Subject: RFC: initramfs unpack point and rules

Hi,

I recently got a BSOD bootup problem with external initramfs (it's
ARM but it seems it doesn't matter).

--------------------------------------------------------------------------

First problem: initramfs is unpacked way before console drivers
are initialized, so you aren't going to see the panic():

init/initramfs.c:static int __init populate_rootfs(void)
...
		printk(KERN_INFO "Unpacking initramfs...");
		err = unpack_to_rootfs((char *)initrd_start,
			initrd_end - initrd_start, 0);
		if (err)
			panic(err);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
		printk(" done\n");
		free_initrd();

I wonder why is initramfs unpacked that early, before most drivers?
I'd expect it much later in the boot sequence, just before userspace
and initial devices (/dev/console etc) are needed. Should it be moved
there? populate_rootfs() unpacks both builtin and external initramfs.

--------------------------------------------------------------------------

Second problem:
RedBoot> exec -r 0x800000 -s 8000000 -c "console=ttyS0,115200"      

Using base address 0x00030000 and length 0x001eea08
Uncompressing Linux...............................done, booting the kernel.
[nothing then]

Obviously I didn't want to specify the exact size and expected inflate
to determine it by itself. I think a valid gzipped cpio image, followed
by some junk, should not be a problem here. Currently, unpack_to_rootfs()
does the job but returns "bad gzip magic numbers" error message - I think
I should change it to return that message only for first initramfs header
and return a success if some junk is spotted after a valid end of
compressed data.

Opinions?
-- 
Krzysztof Halasa
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