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Date: Wed, 8 May 2024 13:40:38 +0200
From: Joel Granados <j.granados@samsung.com>
To: Thomas =?utf-8?Q?Wei=C3=9Fschuh?= <linux@weissschuh.net>
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Subject: Re: [PATCH v3 00/11] sysctl: treewide: constify ctl_table argument
 of sysctl handlers
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On Fri, May 03, 2024 at 04:09:40PM +0200, Thomas Wei=DFschuh wrote:
> Hey Joel,
>=20
=2E..
> > # Motivation
> > As I read it, the motivation for these constification efforts are:
> > 1. It provides increased safety: Having things in .rodata section reduc=
es the
> >    attack surface. This is especially relevant for structures that have=
 function
> >    pointers (like ctl_table); having these in .rodata means that these =
pointers
> >    always point to the "intended" function and cannot be changed.
> > 2. Compiler optimizations: This was just a comment in the patchsets tha=
t I have
> >    mentioned ([3,4,5]). Do you know what optimizations specifically? Do=
es it
> >    have to do with enhancing locality for the data in .rodata? Do you h=
ave other
> >    specific optimizations in mind?
>=20
> I don't know about anything that would make it faster.
> It's more about safety and transmission of intent to API users,
> especially callback implementers.
Noted.

=2E..
> > # Show the move
> > I created [8] because there is no easy way to validate which objects ma=
de it
> > into .rodata. I ran [8] for your Dec 2nd patcheset [7] and there are le=
ss in
> > .rodata than I expected (the results are in [9]) Why is that? Is it som=
ething
> > that has not been posted to the lists yet?=20
>=20
> Constifying the APIs only *allows* the actual table to be constified
> themselves.
> Then each table definition will have to be touched and "const" added.
That is what I thought. thx for clarifying.

>=20
> See patches 17 and 18 in [7] for two examples.
>=20
> Some tables in net/ are already "const" as the static definitions are
> never registered themselves but only their copies are.
>=20
=2E..

best

--=20

Joel Granados

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