linux-kernel - Re: [PATCH 1/8] PM: Opportunistic suspend support.

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 for Android: free password hash cracker in your pocket

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

Message-ID: <1274895611.4467.805.camel@mulgrave.site>
Date:	Wed, 26 May 2010 12:40:11 -0500
From:	James Bottomley <James.Bottomley@...e.de>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Arve Hjønnevåg <arve@...roid.com>,
	Florian Mickler <florian@...kler.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Alan Stern <stern@...land.harvard.edu>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Randy Dunlap <rdunlap@...otime.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Tejun Heo <tj@...nel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Nigel Cunningham <nigel@...onice.net>,
	Ming Lei <tom.leiming@...il.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Maxim Levitsky <maximlevitsky@...il.com>,
	linux-doc@...r.kernel.org, Matthew Garrett <mjg59@...f.ucam.org>,
	Greg KH <gregkh@...e.de>, tytso@....edu
Subject: Re: [PATCH 1/8] PM: Opportunistic suspend support.

On Wed, 2010-05-26 at 20:25 +0300, Pekka Enberg wrote:
> Hi James,
> 
> On Wed, 2010-05-26 at 13:29 +0300, Pekka Enberg wrote:
> >> Yup, I don't quite get Arve's argument either. C code can interact
> >> with Java code (and vice versa) just fine in userspace.
> 
> On Wed, May 26, 2010 at 7:18 PM, James Bottomley
> <James.Bottomley@...e.de> wrote:
> > This is an incorrect statement.  It's possible for java to call C via
> > the JNI, even though there are quite a few gotchas that mean not just
> > *any* C code can do it (been there, tripped over some of them, although
> > they were all ultimately ironed out).  It's very difficult for C to call
> > directly into Java without being specially coded because it involves
> > creating and managing a JVM (so in general, arbitrary C code can't do
> > this).  The usual way we do C -> Java is process to process via some
> > intermediary like RPC or Corba or SOAP (or even JSON) ... which gets
> > very messy for a mobile device.
> 
> Incorrect statement how exactly? A JVM can do mmap(), for example,
> just fine through FileChannel.map() so there's no need for
> heavy-weight RPC.

Incorrect in that an arbitrary C application can't link to a java API.
mmap and some other messaging (like signals) is just another form of
IPC ... the list I gave wasn't exhaustive.

>  Furthermore, the whole discussion is moot anyway as
> Android runs Dalvik which can be hacked to support whatever
> communication mechanism is the best choice here.
> 
> So can we drop the whole "we need to do it in kernel because Java is
> hard" nonsense and concentrate on real issues?

I've lost you.  This argument seems to hinge on whether or not you
believe that suspend in any form is a solution to the rogue app
problem ... whether it's implemented in Java or C is an ancillary issue.

James


--
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/