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zuki
n00b
Joined: 05 Sep 2003
Posts: 32
Location: Kahla/Thuringia/Germany
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 Posted: Tue Nov 27, 2007 11:47 am Post subject: gentoo-sources-2.6.23-r2 kernel append line max 153 chars |
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Hi,
I have tested the newest gentoo-sources. I dont know if this is a bug of the gentoo part or of the kernel it self. The append line will be cut to 153 chars, but the Documentation/i386/boot.txt say 255. Anyone with the same problem?
cat /proc/cmdline | wc -c
results in 153 if the appendline is bigger than 153 chars...
greetings mario[/code]
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mjf55
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Joined: 25 Aug 2007
Posts: 372
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| Posted: Sun Dec 02, 2007 10:46 am Post subject: |
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Key phrases from Documentation/i386/boot.txt
| Code: | | Protocol 2.06: (Kernel 2.6.22) Added a field that contains the size of the boot command line |
| Code: | The kernel command line is a null-terminated string. The maximum length can be retrieved from the field cmdline_size. Before protocol version 2.06, the maximum was 255 characters. A string that is too long will be automatically truncated by the kernel.
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| Code: | Field name: cmdline_size
Type: read
Offset/size: 0x238/4
Protocol: 2.06+
The maximum size of the command line without the terminating zero. This means that the command line can contain at most cmdline_size characters. With protocol version 2.05 and earlier, the maximum size was 255.
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So, with kernel 2.6.22 the cmd line length is no longer 255, but a different value defined by cmdline_size
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zuki
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Joined: 05 Sep 2003
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Location: Kahla/Thuringia/Germany
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| Posted: Tue Dec 18, 2007 1:47 pm Post subject: |
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Hi,
thanks for the answer. But where to specify the cmdline_size? In 2.6.23-gentoo-r3 I got the same:
| Code: |
#cat /proc/cmdline | wc -c
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153 chars. Not more. The cmdline is cutted after char 153.
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zuki
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mjf55
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Joined: 25 Aug 2007
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| Posted: Wed Dec 19, 2007 2:10 pm Post subject: |
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Just to clarify, The bug posted above has to do with CONFIG_CMDLINE not passing parameters to the kernel. not to do with cmd line length.
The <256 characters appears to work as designed (no comment on the design, I am NOT qualified) per my previous post here.
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