[Bug libc/16291] feature request: provide simpler ways to compute stack and tls boundaries

["konstantin.s.serebryany at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=16291

--- Comment #32 from Kostya Serebryany <konstantin.s.serebryany at gmail dot com> ---
> Instead of a callback could we use a systemtap probe with the right
> arguments? We have precedent set for adding probes to libc and it would be
> easy to do with the current infrastructure and low-overhead.

I admit I have not investigated systemtap properly (need to install a newer
Linux distro first). However, from what I see systemtap is not enabled by
default 
in glibc build and requires extra packages to be installed on the system.
Which means that some lsan/msan users will be left behind 
(those who can't install extra packages) and we'll be forced to keep the hack
for the fallback, which defeats the purpose of having the right solution. 

Besides there is a consistency reason (which is not necessary relevant for
you).
Sanitizers already heavily rely on interposition for many cases, 
including all cases where glibc has systemtap hooks, but not limited to that.
Even if we used systemtap for pthread events, at least one hook
is not usable for us (in pthread_create, we actually replace one of the
parameters, which systemtap does not allow, afaict).

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