> The de-facto ABI for signal delivery and sigreturn is unfortunately
One sure 100% compatible way would be to only change the signal layout once
the application used anything that needs XSAVE/XRSTOR. But implementing
that would be likely complicated and I'm not sure it's worth it.
I don't remember that much breakage when the FXSAVE support was
introduced on i386. That already changed these data structures.
That sounds easy enough. x86-64 right now doesn't use signal vsyscalls but
there is no principle reason it can't.