Re: Documenting ptrace access mode checking

[Michael Kerrisk (man-pages)]

Hi Oleg,

On 06/22/2016 11:51 PM, Oleg Nesterov wrote:
> On 06/21, Eric W. Biederman wrote:
> > Adding Oleg just because he seems to do most of the ptrace related
> > maintenance these days.
>
> so I have to admit that I never even tried to actually understand
> ptrace_may_access ;)
>
> > We certainly need something that gives a high level view so people
> > reading the man page can know what to expect.   If you get down into the
> > weeds we run the danger of people beginning to think they can depend
> > upon bugs in the implementation.
>
> Personally I agree. I think "man ptrace" shouldn't not tell too much
> about kernel internals.

See my other replies on this topic. Somehow, we need a way of
describing the behavior that user-space sees. I think it's
inevitable that that means talking about what;s going on
"under the hood".

Regarding Eric's point that "we run the danger of people beginning
to think they can depend upon bugs in the implementation": when it
comes to breaking the ABI, the presence or absence of documentation
doesn't save us on that point (Linus has a few times made his position
wrt to documentation clear).

Cheers,

Michael

--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/