Date: Tue, 26 Mar 2013 09:50:09 +0100
From: Anton Arapov <anton@redhat.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
        LKML <linux-kernel@vger.kernel.org>, Josh Stone <jistone@redhat.com>,
        Frank Eigler <fche@redhat.com>, Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@elte.hu>,
        Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
        adrian.m.negreanu@intel.com, Torsten.Polle@gmx.de
Subject: Re: [PATCH 4/7] uretprobes: return probe entry, prepare_uretprobe()
Message-ID: <20130326085009.GC22603@bandura.brq.redhat.com>
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 <1363957745-6657-5-git-send-email-anton@redhat.com>
 <20130324152651.GC17037@redhat.com>
 <20130326084533.GB22603@bandura.brq.redhat.com>
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On Tue, Mar 26, 2013 at 09:45:33AM +0100, Anton Arapov wrote:
> On Sun, Mar 24, 2013 at 04:26:51PM +0100, Oleg Nesterov wrote:
> > On 03/22, Anton Arapov wrote:
> [snip]
> > And ->dirty looks confusing... perhaps ->chained ?
> > 
> > 		ri = kzalloc(...);
> > 		if (!ri)
> > 			return;
> > 
> > 		ret_vaddr = arch_uretprobe_hijack_return_addr(...);
> > 		if (ret_vaddr == -1)
> > 			goto err;
> > 
> > 		if (ret_vaddr == trampoline_vaddr) {
> > 			if (!utask->return_instances) {
> > 				// This situation is not possible.
> > 				// (not sure we should send SIGSEGV)
> > 				pr_warn(...);
> > 				goto err;
> > 			}
> 
>   If we don't send SIGSEGV, does it make sense to restore the original
> return address that was just hijacked? So that we just decline setting
> the breakpoint for this very case.

disregard this one. we have no address to restore at that moment. :) 

> Anton.
> 
> > 
> > 			ri->chained = true;
> > 			ret_vaddr = utask->return_instances->orig_ret_vaddr;
> > 		}
> > 
> > 		fill-ri-and-add-push-it;
> > 		return;
> > 
> > 	err:
> > 		kfree(ri);
> > 		return;
> > 
> > Oleg.
> > 
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