linux-kernel - Re: [PATCH] xtensa: improve stack dumping

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Date:   Thu, 07 Nov 2019 06:45:25 -0800
From:   Joe Perches <joe@...ches.com>
To:     Petr Mladek <pmladek@...e.com>, Max Filippov <jcmvbkbc@...il.com>
Cc:     "open list:TENSILICA XTENSA PORT (xtensa)" 
        <linux-xtensa@...ux-xtensa.org>, Chris Zankel <chris@...kel.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Dmitry Safonov <dima@...sta.com>
Subject: Re: [PATCH] xtensa: improve stack dumping

On Thu, 2019-11-07 at 15:38 +0100, Petr Mladek wrote:
> On Wed 2019-11-06 16:21:51, Max Filippov wrote:
> > On Wed, Nov 6, 2019 at 2:34 PM Joe Perches <joe@...ches.com> wrote:
> > > > @@ -512,10 +510,12 @@ void show_stack(struct task_struct *task, unsigned long *sp)
> > > >       for (i = 0; i < kstack_depth_to_print; i++) {
> > > >               if (kstack_end(sp))
> > > >                       break;
> > > > -             pr_cont(" %08lx", *sp++);
> > > > +             sprintf(buf + (i % 8) * 9, " %08lx", *sp++);
> > > >               if (i % 8 == 7)
> > > > -                     pr_cont("\n");
> > > > +                     pr_info("%s\n", buf);
> > > >       }
> > > > +     if (i % 8)
> > > > +             pr_info("%s\n", buf);
> > > 
> > > Could this be done using hex_dump_to_buffer
> > > by precalculating kstack_end ?
> > 
> > I've got this, but it doesn't look very attractive to me:
> > 
> > void show_stack(struct task_struct *task, unsigned long *sp)
> > {
> >         unsigned long *stack;
> >         int len;
> > 
> >         if (!sp)
> >                 sp = stack_pointer(task);
> >         stack = sp;
> > 
> >         len = min((-(unsigned long)stack) & (THREAD_SIZE - 4),
> >                   kstack_depth_to_print * 4ul);
> > 
> >         pr_info("Stack:\n");
> > 
> >         for (; len > 0; len -= 32) {
> >                 char buf[9 * 8 + 1];
> > 
> >                 hex_dump_to_buffer(sp, min(len, 32), 32, 4,
> >                                    buf, sizeof(buf), false);
> >                 pr_info(" %08lx:  %s\n", (unsigned long)sp, buf);
> >                 sp += 8;
> >         }
> 
> I wonder if the cycle actually could get replaced by a single call:
> 
> 	print_hex_dump(KERN_INFO, "", DUMP_PREFIX_OFFSET,
> 		       16, 1, sp, len, false);

I think it could be using 4 and not 1 to keep the same output
of a u32 instead of spaces between bytes.