linux-kernel - Re: [Xen-devel] [PATCH 2/2] x86: add pte_set_flags/clear

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:	Fri, 23 Jan 2009 13:05:27 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Jan Beulich <jbeulich@...ell.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Xen-devel <xen-devel@...ts.xensource.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Nick Piggin <nickpiggin@...oo.com.au>
Subject: Re: [Xen-devel] [PATCH 2/2] x86: add pte_set_flags/clear_flags	 for
 pteflag manipulation

Jan Beulich wrote:
> I think a comment (or event a BUG_ON()) should be added here to make
> clear that this absolutely must not be used to toggle the present bit. I
> even view toggling _PAGE_PSE as dangerous this way.
>
> And alternative would be to make these macros and #undef them (or keep
> them inline functions but add destructive #define-s) after all their users.
>   

I don't see any particular problem with changing PSE or even Present 
with these functions; they don't operate on live in-memory ptes, so its 
not like they could ever be used to modify a pte unless followed with 
some kind of set_pte operation.  It is unwise to change any pte flag 
without knowing what you're doing (though P or PSE would probably have 
less subtle effects than some of the others).

But it probably wouldn't hurt to have a __ prefix to indicate they're 
"internal" and not for general use.

    J
--
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/