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

Russell King
2007-01-18T15:23:36Z

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/