This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] [PATCH 6 of 8] Xen: remove run_in_exception_handler() an

To: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 6 of 8] Xen: remove run_in_exception_handler() and recode its only caller
From: Keir Fraser <keir.xen@xxxxxxxxx>
Date: Mon, 07 Mar 2011 15:44:51 +0000
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Mon, 07 Mar 2011 07:46:55 -0800
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:user-agent:date:subject:from:to:cc:message-id :thread-topic:thread-index:in-reply-to:mime-version:content-type :content-transfer-encoding; bh=Og8AG6KdPorAoMz6IKuqTjUN8wSE8rlsM61D5XufxrM=; b=ckesYZJpGfEPvrIELXaOFoagTQh0sKbQbH2X1W4efpL/23V3QTor4Bv9OZizvziCc/ WzIzcX5ohHDG40ebU4ecpMxhbFcd48X5XBFhnQJa5/B2B9oglsa/u+borBSHUtl4fJUP A0KuyYRsrc9VtMMuFrhNHj99MZt52DOI8Mm+U=
Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=user-agent:date:subject:from:to:cc:message-id:thread-topic :thread-index:in-reply-to:mime-version:content-type :content-transfer-encoding; b=bwFhweRjasdnaggnraGwuTlvYJSG+y68fiTdsT7gdtiZQuHtMDbDpDtsNy+EX8qOWO s4XfZ7GAyplsfgQCYrpS8iXdMrhIPUy7nZuH1veMsm1gxtrsBEgn0KHVmVmes9q+PXeh 1MBFIqyWnFDzC26VoZf2FfDDR77RgOuMSQiY0=
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <20110307153841.GA28479@xxxxxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: Acvc3piG4uH2rIf2pECJxxB7QttHnw==
Thread-topic: [Xen-devel] [PATCH 6 of 8] Xen: remove run_in_exception_handler() and recode its only caller
User-agent: Microsoft-Entourage/
On 07/03/2011 15:38, "Tim Deegan" <Tim.Deegan@xxxxxxxxxx> wrote:

> At 15:15 +0000 on 07 Mar (1299510944), Keir Fraser wrote:
>> On 07/03/2011 15:05, "Keir Fraser" <keir.xen@xxxxxxxxx> wrote:
>>> On 07/03/2011 11:26, "Tim Deegan" <Tim.Deegan@xxxxxxxxxx> wrote:
>>>> (dump_execution_state()) as its own bug-trap.
>>>> This is needed to compile xen with clang, which can't handle using a
>>>> function name in an asm immediate.
>>> Actually run_in_exception_handler() does have another user, in ns16550.c.
>>> Although non-essential, it makes the 'd' debug key much more useful when
>>> running the UART in polled mode.
>>> So I suggest we keep run_in_exception_handler but modify it to pass the
>>> function pointer in (say) rAX.
>> Like the attached patch (against latest tip).
> Sorry, I had missed that other user.  I'll see if I can find a way to
> make clang use the function address directly; if not, I'd be inclined to
> have dump_execution_state have its own ID anyway, to keep %rax valid(er)
> in BUG()s.

But actually dump_execution_state() isn't used for BUGs and WARNs and
ASSERTs. In fact it's practically dead on x86 -- it's used in one rather
unlikely ACPI error function, and also in __bug/__warn which are never used
on x86. And that's it. Actually the user of run_in_exception_handler() in
ns16550.c is really the only one we care about!

 -- Keir

> Tim.
>>> I think we won't easily be able to use
>>> BUG_STR() logic but r_i_e_h is only used (directly or indirectly) in a few
>>> places so the BUG_STR optimisation is unimportant. The only other
>>> disadvantage is that rAX is less interesting in the state dump, but any
>>> value the function pointer displaces can still be found in the stack dump,
>>> albeit with likely a little extra effort.
>>> Sound good?
>>>  -- Keir 
>>>> Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
>>>> _______________________________________________
>>>> Xen-devel mailing list
>>>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>>>> http://lists.xensource.com/xen-devel

Xen-devel mailing list

<Prev in Thread] Current Thread [Next in Thread>