hurd: set sigaction for signal preemptors in arch-independent file

Instead of having the arch-specific trampoline setup code detect whether
preemption happened or not, we'd rather pass it the sigaction. In the
future, this may also allow to change sa_flags from post_signal().

hurd/hurd/signal.h

@@ -327,7 +327,8 @@ extern void _hurd_internal_post_signal (struct hurd_sigstate *ss,
 
 struct machine_thread_all_state;
 extern struct sigcontext *
-_hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler,
+_hurd_setup_sighandler (struct hurd_sigstate *ss, const struct sigaction *action,
+			__sighandler_t handler,
 			int signo, struct hurd_signal_detail *detail,
 			int rpc_wait, struct machine_thread_all_state *state);
 

hurd/hurdsig.c

@@ -624,6 +624,13 @@ post_signal (struct hurd_sigstate *ss,
   enum { stop, ignore, core, term, handle } act;
   int ss_suspended;
 
+  /* sigaction for preemptors */
+  struct sigaction preempt_sigaction = {
+    .sa_flags = SA_RESTART
+  };
+
+  struct sigaction *action;
+
   /* Mark the signal as pending.  */
   void mark_pending (void)
     {
@@ -780,12 +787,17 @@ post_signal (struct hurd_sigstate *ss,
     /* Ignore the signal altogether.  */
     act = ignore;
   else if (handler != SIG_ERR)
+    {
       /* Run the preemption-provided handler.  */
+      action = &preempt_sigaction;
       act = handle;
+    }
   else
     {
       /* No preemption.  Do normal handling.  */
 
+      action = & _hurd_sigstate_actions (ss) [signo];
+
       if (!untraced && __sigismember (&_hurdsig_traced, signo))
 	{
 	  /* We are being traced.  Stop to tell the debugger of the signal.  */
@@ -800,7 +812,7 @@ post_signal (struct hurd_sigstate *ss,
 	  return NULL;
 	}
 
-      handler = _hurd_sigstate_actions (ss) [signo].sa_handler;
+      handler = action->sa_handler;
 
       if (handler == SIG_DFL)
 	/* Figure out the default action for this signal.  */
@@ -1072,7 +1084,7 @@ post_signal (struct hurd_sigstate *ss,
 
 	/* Call the machine-dependent function to set the thread up
 	   to run the signal handler, and preserve its old context.  */
-	scp = _hurd_setup_sighandler (ss, handler, signo, detail,
+	scp = _hurd_setup_sighandler (ss, action, handler, signo, detail,
 				      wait_for_reply, &thread_state);
 	if (scp == NULL)
 	  goto sigbomb;
@@ -1111,8 +1123,6 @@ post_signal (struct hurd_sigstate *ss,
 	    }
 	}
 
-	struct sigaction *action = & _hurd_sigstate_actions (ss) [signo];
-
 	/* Backdoor extra argument to signal handler.  */
 	scp->sc_error = detail->error;
 

sysdeps/mach/hurd/i386/trampoline.c

@@ -80,7 +80,8 @@ static void fill_ucontext (ucontext_t *uc, const struct sigcontext *sc)
 }
 
 struct sigcontext *
-_hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler,
+_hurd_setup_sighandler (struct hurd_sigstate *ss, const struct sigaction *action,
+			__sighandler_t handler,
 			int signo, struct hurd_signal_detail *detail,
 			volatile int rpc_wait,
 			struct machine_thread_all_state *state)
@@ -90,7 +91,6 @@ _hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler,
   void firewall (void);
   extern const void _hurd_intr_rpc_msg_cx_sp;
   extern const void _hurd_intr_rpc_msg_sp_restored;
-  const struct sigaction *action;
   void *volatile sigsp;
   struct sigcontext *scp;
   struct
@@ -123,11 +123,6 @@ _hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler,
       siginfo_t siginfo;
     } *stackframe;
 
-  /* sigaction for preemptors */
-  static const struct sigaction legacy_sigaction = {
-    .sa_flags = SA_RESTART
-  };
-
   if (ss->context)
     {
       /* We have a previous sigcontext that sigreturn was about
@@ -170,14 +165,6 @@ _hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler,
      the SP on sigreturn.  */
     state->basic.uesp = state->basic.ecx;
 
-  action = & _hurd_sigstate_actions (ss) [signo];
-  if ( (action->sa_flags & SA_SIGINFO)
-        && handler != (__sighandler_t) action->sa_sigaction
-   || !(action->sa_flags & SA_SIGINFO)
-        && handler != action->sa_handler)
-    /* A signal preemptor took over, use legacy semantic.  */
-    action = &legacy_sigaction;
-
   if ((action->sa_flags & SA_ONSTACK)
       && !(ss->sigaltstack.ss_flags & (SS_DISABLE|SS_ONSTACK)))
     {