Signal handling tune up.

[Christopher Faylor]

On Fri, Aug 29, 2003 at 10:19:22AM -0400, Pierre A. Humblet wrote:
>Christopher Faylor wrote:
>>I was heartened to see that zsh did not crash when I sicc'ed this
>>program on it -- until I tried to type something at the zsh prompt and
>>saw that it was hung.  The reason was that the recursive signal call
>>stuff was still not right.  We were restoring the return address
>>incorrectly.  AFAICT, we really do have to use the stored
>>retaddr_on_stack to rectify setup_handler's inappropriate "fixup" of
>>the return address.  Restoring it to 36(%%esp) wasn't right.
>
>Wow.  What was wrong?  After you noticed that one could remove
>movl    %%esp,%%ebp
>addl    $36,%%ebp
>before the call to set_process_mask, I though eveything made perfect
>sense.  After returning from the (user) signal handler and pulling off
>the argument, both the esp and ebp should be exactly as before the
>call.  It that's not true, the whole stack model of programming breaks
>down.

The code that was there put the return address of the nested call onto the
stack for the return of the initial signal handler.  I just changed it
to mimic what call_signal_handler_now does.

cgf