Bringing rseq back into glibc

[Cristian Rodríguez]

On Thu, Nov 18, 2021 at 7:17 AM Florian Weimer via Libc-alpha
<libc-alpha@sourceware.org> wrote:

> 4. Add public symbols __rseq_abi_offset, __rseq_abi_size (currently 32
>    or 0), __rseq_abi_flags (currently 0).  __rseq_abi_offset is the
>    offset to add to the thread pointer (see __builtin_thread_pointer) to
>    get to the rseq area.  They will be public ABI symbols.  These
>    variables are initialized before user code runs, and changing the
>    results in undefined behavior.

Why not then __get_rseq_whatwever functions and not variables ? or
maybe writing to these variables results in a compiler or linker error
instead of UB ?