linux-kernel - Re: linux page table

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]

Message-ID: <alpine.LNX.2.00.1209022026100.20709@pobox.suse.cz>
Date:	Sun, 2 Sep 2012 20:26:56 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Xin Tong <xerox.time.tech@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: linux page table

On Sun, 2 Sep 2012, Xin Tong wrote:

> >> 3. can two different processes have their CR3 being the same value
> >> even though they have different first level page tables ?
> >
> > Yes, if they are created by clone(CLONE_VM). In such case they share the
> > same mm_struct, and therefore mm_struct->pgd (which is exactly what is
> > loaded into cr3 in switch_mm()) is the same.
> >
> 
> Is this the COW mechanism in linux. what if the cloned process need to
> have set of its own pages later. do the CR3s for the 2 processes
> become different at that point ?

That is a different story. COW is applied on fork() (i.e. spawning new 
process), not on clone(CLONE_VM) (i.e. spawning new thread).

-- 
Jiri Kosina
SUSE Labs
--
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/