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  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:	Mon, 19 Mar 2007 13:06:14 -0700
From:	Jeremy Fitzhardinge <>
To:	David Miller <>
Subject: Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops
 callsites to make them patchable

David Miller wrote:
> Another point worth making is that for function calls you
> can fix things up lazily if you want.
> [...]
> In fact forget I mentioned this idea :)

OK :)  I think we'll only ever want to bind to a hypervisor once, since
the underlying hypervisor can't change on the fly (well, in principle it
might if you migrate, but you'll have more problems than just dealing
with the hook points).  And lazy binding doesn't buy much; I think its
much better to get it all out of the way at once, and then throw the
reloc info away.

> As another note, I do agree with Linus about the register usage
> arguments.  It is important.  I think it's been mentioned but what you
> could do is save nothing (so that "sti" and "cli" are just that and
> cost nothing), but the more complicated versions save and restore
> enough registers to operate.

Right, that's pretty much what we do now.

> It all depends upon what you're trying to do.  For example, it's
> easy to use patching to make different PTE layouts be supportable
> in the same kernel image.  We do this on sparc64 since sun4v
> has a different PTE layout than sun4u, you can see the code in
> asm-sparc64/pgtable.h for details (search for "sun4v_*_patch")

I see.  We want to do something conceptually like this, but we need to
handle more than just adjusting which of two constants to use as a
mask.  For example, Xen needs to run pfns through a pfn->mfn (machine
frame number) conversion and back when making/unpacking pagetable entries.

To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to
More majordomo info at

Powered by blists - more mailing lists