Re: [PATCH] Force UNIX domain sockets to be built in

Adrian Bunk
2007-12-31T14:43:21Z

On Mon, Dec 31, 2007 at 02:26:42PM +0100, Bodo Eggert wrote:
> On Mon, 31 Dec 2007, Adrian Bunk wrote:
> > On Mon, Dec 31, 2007 at 01:09:43PM +0100, Bodo Eggert wrote:
>
> > > As suggested by Adrian Bunk, UNIX domain sockets should always be built in
> > > on normal systems. This is especially true since udev needs these sockets
> > > and fails to run if UNIX=m.
> > >
> > > Signed-Off-By: Bodo Eggert <7eggert@gmx.de>
> > >
> > > ---
> > > Last minute change: I decided against making it a bool because embedded
> > > folks might depend on a small kernel image. Edited in the patch below.
> > >...
> >
> > Is this just a purely theoretical thought or is this a reasonable use
> > case people actually use in practice?
>
> For now, it's a theoretical thought, but having an embedded device, I can
> see the reason for $EVERYTHING=m there.

The only advantage I see is that the kernel image you have to flash
can be made smaller - with the disadvantage that the running kernel
is bigger by more than 10%.

If you don't believe me, try it yourself:
Build all drivers statically into your kernel, and then compare the
vmlinux sizes with CONFIG_MODULES=n and CONFIG_MODULES=y.

> > After all, changing it to a bool will allow us to make the kernel image
> > for nearly everyone smaller by a few hundred bytes...
>
> I can't see why optionally building it as a module would force us to make
> the kernel bigger. It may be a little more ugly to support =m, but thats it,
> isn't it?

On architectures like x86 where __exit code is freed at runtime
af_unix_exit() makes your kernel image (but not the running kernel)
bigger.

With CONFIG_MODULES=y the 13 EXPORT_SYMBOL's that only exist for the
theoretical possibility of CONIG_UNIX=m waste a few hundred bytes
of memory.

cu
Adrian

--

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"Only a promise," Lao Er said.
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