netdev - Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops callsites to make them patchable

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: <20070319.120854.30182994.davem@davemloft.net>
Date:	Mon, 19 Mar 2007 12:08:54 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	ak@...e.de
Cc:	virtualization@...ts.linux-foundation.org, jbeulich@...ell.com,
	jeremy@...p.org, ak@....de, xen-devel@...ts.xensource.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	chrisw@...s-sol.org, virtualization@...ts.osdl.org,
	anthony@...emonkey.ws, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, mingo@...e.hu
Subject: Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops
 callsites to make them patchable

From: Andi Kleen <ak@...e.de>
Date: Mon, 19 Mar 2007 11:57:28 +0100

> On Monday 19 March 2007 00:46, Jeremy Fitzhardinge wrote:
> > Andi Kleen wrote:
> > For example, say we wanted to put a general call for sti into entry.S,
> > where its expected it won't touch any registers.  In that case, we'd
> > have a sequence like:
> >
> >     push %eax
> >     push %ecx
> >     push %edx
> >     call paravirt_cli
> >     pop %edx
> >     pop %ecx
> >     pop %eax
> 
> This cannot right now be expressed as inline assembly in the unwinder at all 
> because there is no way to inject the push/pops into the compiler generated
> ehframe tables.
> 
> [BTW I plan to resubmit the unwinder with some changes]

It's inability to handle sequences like the above sounds to me like
a very good argument to _not_ merge the unwinder back into the tree.

To me, that unwinder is nothing but trouble, it severly limits what
cases you can use special calling conventions via inline asm (and we
have done that on several occaisions) and even ignoring that the
unwinder only works half the time.

Please don't subject us to another couple months of hair-pulling only
to have Linus yank the thing out again, there are certainly more
useful things to spend time on :-)
-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html