On Mon, Jan 27, 2014 at 2:06 PM, Andy Lutomirski <l...@amacapital.net> wrote: > > It's not just ip and sp -- cs matters here, too, I think.
For signal *delivery*, CS will always be __USER_CS, and %rcx can be crap, so sysret should be fine. We could easily check that %rip is valid in the whole slow-path instead of saying "return 1 if we did do_signal()". Now, it's a different thing wrt signal handler *return*, because at that point we really cannot return with some random value in %rcx. We absolutely do need to use 'iretq' in that whole [rt_]sigreturn() path, but on x86-64 that is all handled by the system call itself (see the stub_*_sigreturn stuff in entry_64.S) and it very much uses iret explicitly (the 32-bit case also does that, by forcing the sigreturn to be done with an "int 0x80" instruction - we could change that to use syscall+iret, but frankly, I'm not all that inclined to care, although it might be worth trying to do just to unify the models a bit). Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/