linux-kernel - Re: [PATCH 2/2] ppc64le save_stack_trace_tsk_reliable (Was: HAVE_RELIABLE

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Date:   Fri, 9 Mar 2018 16:54:12 +0100
From:   Torsten Duwe <duwe@....de>
To:     Balbir Singh <bsingharora@...il.com>
Cc:     Miroslav Benes <mbenes@...e.cz>,
        Michael Ellerman <mpe@...erman.id.au>,
        Jiri Kosina <jkosina@...e.cz>, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, live-patching@...r.kernel.org
Subject: Re: [PATCH 2/2] ppc64le save_stack_trace_tsk_reliable (Was:
 HAVE_RELIABLE_STACKTRACE)

On Fri, 9 Mar 2018 08:43:33 +1100
Balbir Singh <bsingharora@...il.com> wrote:

> On Tue, 27 Feb 2018 17:09:24 +0100
> Torsten Duwe <duwe@....de> wrote:

> > +save_stack_trace_tsk_reliable(struct task_struct *tsk,
> > +                              struct stack_trace *trace)  
> 
> Just double checking this is called under the task_rq_lock, so its
> safe to call task_stack_page() as opposed to try_get_task_stack()

Yes. IIRC a comment at the call site mentioned it.

[...]
> > +	if (sp < stack_page + sizeof(struct thread_struct)
> > +	    || sp > stack_page + THREAD_SIZE -
> > STACK_FRAME_OVERHEAD)
> > +		return 1;  
> 
> Some of this is already present in validate_sp(), it also validates
> irq stacks, should we just reuse that?

This goes a bit along one of Josh's points; I'll answer there, OK?

[...]

> Looks good to me otherwise.
> 
> Acked-by: Balbir Singh <bsingharora@...il.com>
Thanks.

	Torsten