linux-kernel - Re: [uClinux-dev] Re: [PATCH] NOMMU: add [stack] label to per-process maps output

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Date:	Thu, 17 Dec 2009 17:49:04 -0500
From:	Mike Frysinger <vapier.adi@...il.com>
To:	uClinux development list <uclinux-dev@...inux.org>
Cc:	linux-kernel@...r.kernel.org, Greg Ungerer <gerg@...inux.org>,
	uclinux-dist-devel@...ckfin.uclinux.org,
	David McCullough <davidm@...pgear.com>
Subject: Re: [uClinux-dev] Re: [PATCH] NOMMU: add [stack] label to per-process 
	maps output

On Wed, Dec 16, 2009 at 11:59, David Howells wrote:
> Mike Frysinger wrote:
>> +             if (vma->vm_start <= mm->start_brk &&
>> +                             vma->vm_end >= mm->brk) {
>
> Hmmm...  That ought to involve mm->start_stack somewhere...  (Or, more
> probably, task->stack_start:-/)

with MMU, the [heap] (i.e. brk) and [stack] are different mappings.
under NOMMU, they're the same mapping, except that no one uses the brk
and the "heap" is really all of dynamic kernel memory.  so we have to
avoid the brk/[heap] check and simply copy over the [stack] one:
    } else if (mm) {
        if (vma->vm_start <= mm->start_stack &&
                vma->vm_end >= mm->start_stack) {
            pad_len_spaces(m, len);
            seq_puts(m, "[stack]");
        }
    }

the semi-annoying thing is that FLAT combines a whole lot of stuff
(including the stack) into the same mapping giving us the output:
root:/> cat /proc/155/maps
029f0000-029f9000 rwxp 00000000 00:00 0          [stack]

but i guess this is no worse than the current ?
-mike
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