linux-kernel - Re: [PATCH] zram: constify attribute

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20170703120415.GB836@jagdpanzerIV.localdomain>
Date:   Mon, 3 Jul 2017 21:04:15 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Arvind Yadav <arvind.yadav.cs@...il.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        minchan@...nel.org, ngupta@...are.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] zram: constify attribute_group structures.

On (07/03/17 16:00), Arvind Yadav wrote:
> On Monday 03 July 2017 02:30 PM, Sergey Senozhatsky wrote:
> > On (07/03/17 11:43), Arvind Yadav wrote:
> > > attribute_groups are not supposed to change at runtime. All functions
> > > working with attribute_groups provided by <linux/sysfs.h> work with const
> > > attribute_group. So mark the non-const structs as const.
> > > 
> > > File size before:
> > >     text	   data	    bss	    dec	    hex	filename
> > >     8293	    841	      4	   9138	   23b2	drivers/block/zram/zram_drv.o
> > > 
> > > File size After adding 'const':
> > >     text	   data	    bss	    dec	    hex	filename
> > >     8357	    777	      4	   9138	   23b2	drivers/block/zram/zram_drv.o
> > sorry, what exactly is the improvement here?
> > we grew .text bigger, why should we be happy about it?
> Yes, .text size is increased but .data size got decreased.
> Overall size will be same. the text segment is often read-only,
> to prevent a program from accidentally modifying its instructions.

well, to the best of my knowledge, nothing in C standard guarantees
that a variable with a C keyword 'const' will be placed into .text
or .rodata. not even sure if all gcc versions have the same opinion
on this.

but ok, we can move that struct to one of the RO sections (up to the
compiler to decide).

	-ss