> Further no known libc implementation making use of sa_restorer.
I don't know if this is relevant, but Linus recently tried
changing the sa_restorer behaviour in the linux-2.5 kernel and
later had to back out the change. The following lines are from
Move x86 signal handler return stub to the vsyscall page, and stop
honoring the SA_RESTORER information.
Re-instate the SA_RESTORER functionality, since it seems that some
programs still depend on it and in fact do install a different
signal restorer than the standard kernel version.