linux-kernel - Re: [PATCH 00/12] [RFC] x86: Memory Protection Keys

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: <554BBFA8.3010607@sr71.net>
Date:	Thu, 07 May 2015 12:40:24 -0700
From:	Dave Hansen <dave@...1.net>
To:	Ingo Molnar <mingo@...nel.org>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
CC:	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH 00/12] [RFC] x86: Memory Protection Keys

On 05/07/2015 12:26 PM, Ingo Molnar wrote:
> The Valgrind usecase looks somewhat legit, albeit not necessarily for 
> multithreaded apps: there you generally really want protection changes 
> to be globally visible, such as publishing the effects of free() or 
> malloc().

I guess we could theoretically have an IPC of some kind that voluntarily
broadcasts changes so that we can be guaranteed that other threads see it.

> Also, will apps/libraries bother if it's not a standard API and if it 
> only runs on very fresh CPUs?

It's always a problem with new CPU features.

I've thought a bit about trying to "emulate" the feature on older CPUs
using good ol' mprotect() so that we could have an API that folks can
use _today_, but that would get magically fast on future CPUs.  But, the
problem with that is the thread-local aspect.

mprotect() is fundamentally process-wide and protection keys right are
fundamentally thread-local.  Those things are going to be hard to
reconcile unless we do something slightly extreme like having per-thread
page tables.
--
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/