linux-kernel - Re: No more bits in vm_area_struct's vm

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

Date:	Tue, 29 Sep 2009 01:14:03 +0900 (JST)
From:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
To:	"Hugh Dickins" <hugh.dickins@...cali.co.uk>
Cc:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
	"Wu Fengguang" <fengguang.wu@...el.com>,
	"Nigel Cunningham" <ncunningham@...a.org.au>,
	"LKML" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: No more bits in vm_area_struct's vm_flags.

Hugh Dickins wrote:
> On Mon, 28 Sep 2009, KAMEZAWA Hiroyuki wrote:
>>
>> What I dislike is making vm_flags to be long long ;)
>
> Why?
I'm sorry if my "dislike" sounds too strong.

Every time I see long long in the kernel, my concern is
"do I need spinlock to access this for 32bit arch ? is it safe ?".
(And it makes binary=>disassemble=>C (by eyes) a bit difficult)
Then, I don't like long long personally.

Another reason is some other calls like test_bit() cannot be used against
long long. (even if it's not used _now_)

Maybe vm->vm_flags will not require extra locks because
it can be protected by bigger lock as mmap_sem. Then, please make it
to be long long if its's recommended.

keeping vm_flags to be 32bit may makes vma_merge() ugly.
If so, long long is  a choice.

Thanks,
-Kame

> Hugh
>

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/