Re: [rfc 1/3] fs, proc: Add start_data, end_data, start_brk membersto /proc/$pid/stat

[Kees Cook]

On Thu, Dec 1, 2011 at 11:28 PM, Cyrill Gorcunov <gorcunov@xxxxxxxxx> wrote:
> On Fri, Dec 02, 2011 at 03:24:06AM +0300, Alexey Dobriyan wrote:
>> > > +         cputime_to_clock_t(cgtime),
>> > > +         mm ? (permitted ? mm->start_data : 1) : 0,
>> > > +         mm ? (permitted ? mm->end_data : 1) : 0,
>> > > +         mm ? (permitted ? mm->start_brk : 1) : 0);
>> > >   if (mm)
>> > >           mmput(mm);
>> > >   return 0;
>> >
>> > Thanks for using "permitted" here. :)
>>
>> And these are new fields, so "1" hack is unnecessary.
>
> I perhaps miss some history here, you mean just print 0
> instead of 1, right?

The history is that when "0" is seen for start_code, tools like "ps"
assumed the process was a kernel thread, so "1" was used as a hack to
not break userspace reporting. So yeah, since this is a new field,
it's fine to just do:

+         (mm && permitted) ? mm->start_data : 0,
+         (mm && permitted) ? mm->end_data : 0,
+         (mm && permitted) ? mm->start_brk : 0,

-Kees

-- 
Kees Cook
ChromeOS Security
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