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

[Nilay Vaish <nilayvaish@google.com>]

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Hi Florian, this patch is only meant for the google/grte branch.

Thanks!

On Wed, Oct 26, 2022 at 12:37 AM Florian Weimer <fweimer@redhat.com> wrote:

> * 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
>
>