Restartable sequences in glibc

librseq can be used as an alternative way to register rseq for cases where the libc does not handle rseq. It requires the application to explicitly call a register/unregister API at the beginning/end of each thread's lifetime. It is compatible with the glibc-2.35+ ABI as well and will let glibc handle rseq registration in those cases. See https://git.kernel.org/pub/scm/libs/librseq/librseq.git/