linux-kernel - Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in save_stack_trace

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Date:   Thu, 15 Sep 2016 13:37:41 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>, Jann Horn <jann@...jh.net>
Subject: Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in
 save_stack_trace_tsk()

On Thu, Sep 15, 2016 at 11:04:47AM -0700, Andy Lutomirski wrote:
> On Wed, Sep 14, 2016 at 11:35 AM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> > On Wed, Sep 14, 2016 at 11:22:00AM -0700, Andy Lutomirski wrote:
> >> On Wed, Sep 14, 2016 at 7:55 AM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> >> > On Tue, Sep 13, 2016 at 02:29:28PM -0700, Andy Lutomirski wrote:
> >> >> This will prevent a crash if the target task dies before or while
> >> >> dumping its stack once we start freeing task stacks early.
> >> >>
> >> >> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> >> >
> >> > Do we need a similar patch for show_stack()?
> >>
> >> Probably.  Shouldn't it go in show_stack_log_lvl() instead, though?
> >
> > Yeah, that would probably be better.
> 
> This code is a colossal mess.  I really hope that, some day, we can
> clarify which entry points are used only in dumpstack*.c and which are
> used elsewhere.  Creating an arch/x86/kernel/dumpstack.h or just
> merging the three files and removing all the intermediate crap from
> the headers could help a lot.

Agreed, it's a mess, though it's improving with some of my changes.
dumpstack_32.c and dumpstack_64.c will be shrinking, with dump_trace()
getting removed.  And they'll be shrinking even more with Linus's
suggestion to remove show_stack_log_lvl().  Then maybe we can look at
merging those two files into dumpstack.c with an #ifdef to separate the
subarch differences.

-- 
Josh