linux-kernel - Re: [RFC PATCH 00/35] remove in-kernel syscall invocations

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Date:   Mon, 12 Mar 2018 20:30:54 +0100
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org, luto@...nel.org,
        torvalds@...ux-foundation.org, viro@...iv.linux.org.uk,
        akpm@...ux-foundation.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC PATCH 00/35] remove in-kernel syscall invocations

On Mon, Mar 12, 2018 at 08:32:56AM +0100, Ingo Molnar wrote:
> 
> * Dominik Brodowski <linux@...inikbrodowski.net> wrote:
> 
> > I'm a bit more unsure about these remaining patches. They use inline stubs
> > named ksys_xyzzy() which (mostly) call fs-internal functions. Another
> > alternative would be to define these in fs/*, but then we'd get more and
> > more indirections.
> > 
> > 	syscalls: do not call sys_unlink() within the kernel
> > 	syscalls: do not call sys_rmdir() within the kernel
> > 	syscalls: do not call sys_mkdir{,at}() within the kernel
> > 	syscalls: do not call sys_symlink{,at}() within the kernel
> > 	syscalls: do not call sys_mknod{,at}() within the kernel
> > 	syscalls: do not call sys_link{,at}() within the kernel
> > 	syscalls: do not call sys_{f,}chmod{at,}() within the kernel
> > 	syscalls: do not call sys_{f,}access{,at}() within the kernel
> > 	syscalls: do not call sys_ftruncate() within the kernel
> > 	syscalls: do not call sys_{,l,f}chown() within the kernel
> > 	syscalls: do not call sys_close() within the kernel
> 
> >  72 files changed, 572 insertions(+), 274 deletions(-)
> 
> Just curious, have you done a before/after vmlinux /usr/bin/size comparison?
> How do these changes impact generated code?
> 
> My expectation would be for there to be a noticeable decrease in text size.

Unfortunately, no:

   text	   data	    bss	    dec	    hex	filename
10352515	6598692	13344972	30296179	1ce4873	vmlinux-v4.16-rc5
10352845	6598852	13344972	30296669	1ce4a5d	vmlinux-v4.16-rc5-patch23
10352942	6598948	13344972	30296862	1ce4b1e	vmlinux-v4.16-rc5-patch35

Thanks,
	Dominik