From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH] xen/arm: Init traps very early Date: Wed, 28 May 2014 14:58:24 +0100 Message-ID: <5385EB80.5050905@linaro.org> References: <1401283983-19843-1-git-send-email-julien.grall@linaro.org> <5385E956.1040104@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1WpeNE-0006Zg-Uz for xen-devel@lists.xenproject.org; Wed, 28 May 2014 13:58:33 +0000 Received: by mail-wi0-f175.google.com with SMTP id f8so3693917wiw.8 for ; Wed, 28 May 2014 06:58:28 -0700 (PDT) In-Reply-To: <5385E956.1040104@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Andrew Cooper Cc: naresh.bhat@linaro.org, xen-devel@lists.xenproject.org, stefano.stabellini@citrix.com, ian.campbell@citrix.com, tim@xen.org List-Id: xen-devel@lists.xenproject.org Hi Andrew, On 05/28/2014 02:49 PM, Andrew Cooper wrote: > On 28/05/14 14:33, Julien Grall wrote: >> The function init_traps setups the handler taken when Xen hits a BUG_ON/ASSERT. >> >> If an error happen before init_traps is called, we loose the backtrace. >> >> As the function doesn't require any specific setup, we can call it just >> after Xen has jumped in C code. >> >> Signed-off-by: Julien Grall >> --- >> xen/arch/arm/setup.c | 3 +-- >> 1 file changed, 1 insertion(+), 2 deletions(-) >> >> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c >> index b9ce7a9..5bf8686 100644 >> --- a/xen/arch/arm/setup.c >> +++ b/xen/arch/arm/setup.c >> @@ -666,6 +666,7 @@ void __init start_xen(unsigned long boot_phys_offset, >> struct domain *dom0; >> >> setup_cache(); >> + init_traps(); > > Having recently redone this in x86, it must be after > set_processor_id(0), set_current() for debug sanity, and after > percpu_init_areas() for future proofing. Even though it doesn't harm to call before (the stack will be corrupted), I agree to call init_traps after set_processor_id(0), and therefore percpu_init_areas. But we don't need to have set_current correctly set up. The trap entries won't save anything about the guest if the exception are taken from HYP mode. -- Julien Grall