linux-kernel - Re: [patch 03/26] Dynamic kernel command-line

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Message-ID: <20070118152326.GC31418@flint.arm.linux.org.uk>
Date:	Thu, 18 Jan 2007 15:23:26 +0000
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Tomas Carnecky <tom@...ervice.com>
Cc:	Bernhard Walle <bwalle@...e.de>, linux-kernel@...r.kernel.org,
	Alon Bar-Lev <alon.barlev@...il.com>
Subject: Re: [patch 03/26] Dynamic kernel command-line - arm

On Thu, Jan 18, 2007 at 04:31:51PM +0100, Tomas Carnecky wrote:
> Russell King wrote:
> > On Thu, Jan 18, 2007 at 01:58:52PM +0100, Bernhard Walle wrote: 
> >> -static char command_line[COMMAND_LINE_SIZE];
> >> +static char __initdata command_line[COMMAND_LINE_SIZE];
> > 
> > Uninitialised data is placed in the BSS.  Adding __initdata to BSS
> > data causes grief.
> > 
> 
> Static variables are implicitly initialized to zero. Does that also
> count as initialization?

No.  As I say, they're placed in the BSS.  The BSS is zeroed as part of
the C runtime initialisation.

If you want to place a variable in a specific section, it must be
explicitly initialised.  Eg,

static char __initdata command_line[COMMAND_LINE_SIZE] = "";

However, there is a bigger question here: that is the tradeoff between
making this variable part of the on-disk kernel image, but throw away
the memory at runtime, or to leave it in the BSS where it will not be
part of the on-disk kernel image, but will not be thrown away at
runtime.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
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