Re: [PATCH origin/google/grte/v5-2.27/master] nptl: use mmap and munmap for stack allocation

[Florian Weimer <fweimer@redhat.com>]

* Nilay Vaish via Libc-alpha:

> We made this change so that we can capture thread stack allocations.
> __mmap and __munmap cannot be overridden at runtime.  mmap and munmap
> can be overidden at runtime and we are thus able to capture when either
> of these functions were called.

Not sure if you are proposing this for general discussion?

This will need localplt.data updates on all architectures to avoid
check-localplt failures.  It also introduces a linknamespace issue with
C11 thread support: technically, an application using C11 threads could
define mmap or munmap symbols for arbitrary use (and different behavior)
because those names are not reserved in C11.

If this is intended to become a supported interface, perhaps we should
document it in the manual.  On the other hand, I do not see how this
could work in general, especially not with static linking.  glibc may
have to call mmap in certain places where the process or thread is not
fully initialized.

Thanks,
Florian