"ps -e" without procfs(5)

Kostik Belousov kostikbel at gmail.com
Tue Oct 25 08:25:07 UTC 2011

On Tue, Oct 25, 2011 at 12:13:10AM +0300, Mikolaj Golub wrote:
> On Sun, 16 Oct 2011 20:10:05 +0300 Kostik Belousov wrote:
>  KB> In my opinion, the way to implement the feature is to (re)use
>  KB> linprocfs_doargv() and provide another kern.proc sysctl to retrieve the
>  KB> argv and env vectors. Then, ps(1) and procstat(1) can use it, as well as
>  KB> procfs and linprocfs inside the kernel.
> Thanks! I am testing a patch (without auxv vector so far) and have some
> questions.
> Original ps -e returns environment only for user owned processes (the access is
> restricted by the permissions of /proc/pid/mem file). My kern.proc.env sysctl
> does not have such a restriction. I suppose I should add it? What function I
> could use for this?
> BTW, linprocfs allows to read other user's environment.
linprocfs uses p_cansee() to check the permissions. There are sysctls
security.bsd.see_other_{ug}ids that control the behaviour.

I believe that the new sysctl shall use the same check.

>  KB> While you are at the code, it would be useful to also export the auxv vector,
>  KB> which is immediately before env.
> It looks I can find the location of auxv but what about the size? Or do you
> propose to extend struct ps_strings to store location and size of auxv? I
> could do this way...

No, extending ps_strings is not needed and it is too radical change.
The auxv vector must end by the AT_NULL aux entry. You can also artificially
limit the amount of read aux vectors to, say, 256, which is much more then
it is currently defined.
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