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

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Date:   Tue, 13 Mar 2018 06:48:13 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Dominik Brodowski <linux@...inikbrodowski.net>
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


* Dominik Brodowski <linux@...inikbrodowski.net> wrote:

> 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

Maybe it's due to the new helpers - still, the changes in size are very small so 
this isn't a showstopper.

Thanks,

	Ingo