[PATCH] Linux: Remove rseq support

[Szabolcs Nagy]

The 07/17/2020 09:47, Florian Weimer wrote:
> * Szabolcs Nagy:
> 
> > the test is doing its thing.
> >
> > its testing an internal contract about static tls usage
> > as documented in the commit message.
> >
> > 192 bytes is reserved for the libc (this was decided with
> > rseq in mind), this is larger than needed so that we don't
> > have to change the contract often: doing that affects
> > stack usage too and how the tls optimizations are done etc.
> >
> > if we change the contract the test should change too, and
> > we should adjust the size reserved for optimizations too:
> > the idea was to keep static tls usage the same for now,
> > just allocate them into separate buckets of libc, ie tls
> > and tls optimizations.
> 
> In the rseq revert, I changed the libc estimate to 160 bytes (from 192).
> How should I adjust the test so that it again tests its objectives?

the contract was carefully designed not to change the
overall static tls use for now, otherwise existing
applications that abuse static tls would start failing.

i think we want existing applications to work and only
force new applications to use the new tunables.

if you change the contract you have to come up with
a new design and a test for that design, e.g. if
you no longer care about old applications that dlopen
a lot of ie tls then the test should behave accordingly.