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Re: [PATCH 03/19] x86/dumpstack: remove unnecessary stack pointer arguments

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On Thu, Jul 21, 2016 at 02:56:52PM -0700, Andy Lutomirski wrote:
> On Thu, Jul 21, 2016 at 2:21 PM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > When calling show_stack_log_lvl() or dump_trace() with a regs argument,
> > providing a stack pointer or frame pointer is redundant.
> >
> 
> > diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
> > index 358fe1c..c533b8b 100644
> > --- a/arch/x86/kernel/dumpstack_32.c
> > +++ b/arch/x86/kernel/dumpstack_32.c
> > @@ -122,7 +122,7 @@ void show_regs(struct pt_regs *regs)
> >                 u8 *ip;
> >
> >                 pr_emerg("Stack:\n");
> > -               show_stack_log_lvl(NULL, regs, &regs->sp, 0, KERN_EMERG);
> > +               show_stack_log_lvl(NULL, regs, NULL, 0, KERN_EMERG);
> 
> This is weird -- note the &.  You're at some risk of exposing a bug in
> x86_32's kernel_stack_pointer() function, which is a mess.  (I don't
> see why it's written the way it is -- the actual return stack pointer
> given a pt_regs is quite well defined -- if regs->cs & 3 != 0, then
> it's regs->sp, else it's &regs->sp.)
> 
> That being said, this isn't a big deal, so:
> 
> Reviewed-by: Andy Lutomirski <luto@kernel.org>
> 
> If you want to make this all a bit more reliably on x86_32, you could
> fix kernel_stack_pointer().

Ok.  The whole '&regs->sp' thing threw me for a loop.  I have no idea
what kernel_stack_pointer() is trying to do.  I just assumed it was
correct.  I'll take a look at it and try to fix it in another patch.

-- 
Josh

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Thread

[PATCH 03/19] x86/dumpstack: remove unnecessary stack pointer arguments Josh Poimboeuf <jpoimboe@redhat.com> - 2016-07-21 23:30 +0200
  Re: [PATCH 03/19] x86/dumpstack: remove unnecessary stack pointer arguments Andy Lutomirski <luto@amacapital.net> - 2016-07-22 00:00 +0200
    Re: [PATCH 03/19] x86/dumpstack: remove unnecessary stack pointer  arguments Josh Poimboeuf <jpoimboe@redhat.com> - 2016-07-22 03:50 +0200
      Re: [PATCH 03/19] x86/dumpstack: remove unnecessary stack pointer arguments Andy Lutomirski <luto@amacapital.net> - 2016-07-22 04:30 +0200
      Re: [PATCH 03/19] x86/dumpstack: remove unnecessary stack pointer arguments Brian Gerst <brgerst@gmail.com> - 2016-07-22 05:10 +0200

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