Re: [PATCH] Long linux kernel command lines

From: Jan Alsenz <janalsenz@student.ethz.ch>
To: The development of GRUB 2 <grub-devel@gnu.org>
Subject: Re: [PATCH] Long linux kernel command lines
Date: Tue, 10 Feb 2009 21:09:59 +0100	[thread overview]
Message-ID: <4991DF17.9030002@student.ethz.ch> (raw)
In-Reply-To: <4991DC4D.4060802@gmail.com>

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Hi!

I also don't know the exact details, it sure would be better to have some kind
of detection!

But the limit I set is not that arbitrary:
--- Quote from Documentation/kernel-parameters.txt ---
The number of kernel parameters is not limited, but the length of the
complete command line (parameters including spaces etc.) is limited to
a fixed number of characters. This limit depends on the architecture
and is between 256 and 4096 characters. It is defined in the file
./include/asm/setup.h as COMMAND_LINE_SIZE.
--- Quote end ---

And from what I've seen in the kernel code the maximum supported length is
copied from lh.cmd_line_ptr into kernel space and processed.

Greets,

Jan

phcoder schrieb:
> Hello!
> I don't know the linux booting protocol in details but it looks like you
> patch replaces one arbitrary limit (256) by another (4096). Is there any
> way of avoiding any arbitrary limit at all wothout modyfiing boot protocol?
> Thanks
> Vladimir 'phcoder' Serbinenko
> Jan Alsenz wrote:
>> Hello!
>>
>> I just noticed, that the pc linux loader (loader/i386/pc/linux.c) always
>> truncates the kernel command line to less than 256 characters.
>> Well since I needed a longer command line, I fixed this problem.
>>
>> I found a patch on this list from last year (
>> http://lists.gnu.org/archive/html/grub-devel/2008-05/msg00005.html ),
>> which apparently was lost in some other discussion.
>> I didn't use it, because I think my version works better with older
>> kernels.
>>
>> I tested this on my machine and it worked without a problem with a
>> 2.6.27 kernel.
>>
>> It would be great if you could add this (or something like it), so I can
>> switch to the official version again.
>>
>> Thanks and Regards,
>>
>> Jan
>>
>>
>> ------------------------------------------------------------------------
>>
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>> Grub-devel@gnu.org
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> 
> 
> 
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