------------------------------------------------------------------------------
--                                                                          --
--                 GNU ADA RUNTIME LIBRARY (GNARL) COMPONENTS               --
--                                                                          --
--           S Y S T E M . I N T E R R U P T _ M A N A G E M E N T          --
--                                                                          --
--                                  B o d y                                 --
--                         (Version for new GNARL)                          --
--                                                                          --
--                             $Revision: 1.1 $                             --
--                                                                          --
--            Copyright (C) 1991 - 1997 Florida State University            --
--                                                                          --
-- GNARL is free software; you can  redistribute it  and/or modify it under --
-- terms of the  GNU General Public License as published  by the Free Soft- --
-- ware  Foundation;  either version 2,  or (at your option) any later ver- --
-- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
-- for  more details.  You should have  received  a copy of the GNU General --
-- Public License  distributed with GNARL; see file COPYING.  If not, write --
-- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
-- MA 02111-1307, USA.                                                      --
--                                                                          --
-- As a special exception,  if other files  instantiate  generics from this --
-- unit, or you link  this unit with other files  to produce an executable, --
-- this  unit  does not  by itself cause  the resulting  executable  to  be --
-- covered  by the  GNU  General  Public  License.  This exception does not --
-- however invalidate  any other reasons why  the executable file  might be --
-- covered by the  GNU Public License.                                      --
--                                                                          --
-- GNARL was developed by the GNARL team at Florida State University. It is --
-- now maintained by Ada Core Technologies Inc. in cooperation with Florida --
-- State University (http://www.gnat.com).                                  --
--                                                                          --
------------------------------------------------------------------------------

--  This is the DEC Unix 4.0 version of this package.

--  PLEASE DO NOT add any dependences on other packages.
--  This package is designed to work with or without tasking support.

--  Make a careful study of all signals available under the OS,
--  to see which need to be reserved, kept always unmasked,
--  or kept always unmasked.
--  Be on the lookout for special signals that
--  may be used by the thread library.

with Ada.Exceptions;
--  used for Raise_Exception
--           Exception_ID

with Interfaces.C;
--  used for int

with System.Error_Reporting;
--  used for Shutdown

with System.OS_Interface;
--  used for various Constants, Signal and types

package body System.Interrupt_Management is

   use Interfaces.C;
   use System.Error_Reporting;
   use System.OS_Interface;

   type Interrupt_List is array (Interrupt_ID range <>) of Interrupt_ID;
   Exception_Interrupts : constant Interrupt_List :=
     (SIGFPE, SIGILL, SIGSEGV, SIGBUS);

   ----------------------
   -- Notify_Exception --
   ----------------------

   --  This function identifies the Ada exception to be raised using
   --  the information when the system received a synchronous signal.
   --  Since this function is machine and OS dependent, different code
   --  has to be provided for different target.

   --  Following code is intended for Solaris on Sparcstation.

   procedure Notify_Exception
     (signo   : Signal;
      info    : access siginfo_t;
      context : access ucontext_t);

   procedure Notify_Exception
     (signo   : Signal;
      info    : access siginfo_t;
      context : access ucontext_t)
   is
      Current_Exception : Ada.Exceptions.Exception_Id;

   begin

      --  As long as we are using a longjmp to return control to the
      --  exception handler on the runtime stack, we are safe. The original
      --  signal mask (the one we had before coming into this signal catching
      --  function) will be restored by the longjmp. Therefore, raising
      --  an exception in this handler should be a safe operation.

      --  Check that treatment of exception propagation here
      --  is consistent with treatment of the abort signal in
      --  System.Task_Primitives.Operations.

      case signo is
         when SIGFPE =>
            case info.si_code is
               when  FPE_INTDIV |
                     FPE_INTOVF |
                     FPE_FLTDIV |
                     FPE_FLTOVF |
                     FPE_FLTUND |
                     FPE_FLTRES |
                     FPE_FLTINV |
                     FPE_FLTSUB =>
               raise Constraint_Error;
               when others =>
                  pragma Assert (Shutdown ("Unexpected SIGFPE signal"));
                  null;
            end case;
         when SIGILL =>
            raise Storage_Error;
         when SIGSEGV =>
            raise Storage_Error;
         when SIGBUS =>
            raise Storage_Error;
         when others =>
            pragma Assert (Shutdown ("Unexpected signal"));
            null;
      end case;
   end Notify_Exception;

   ----------------
   -- Initialize --
   ----------------

   procedure Initialize is
      act     : aliased struct_sigaction;
      old_act : aliased struct_sigaction;
      mask    : aliased sigset_t;
      Result  : Interfaces.C.int;

   begin

      Abort_Task_Interrupt := SIGABRT;
      --  Change this if you want to use another signal for task abort.
      --  SIGTERM might be a good one.

      act.sa_handler := Notify_Exception'Address;

      act.sa_flags := 8;
      --  Set sa_flags to SA_NODEFER so that during the handler execution
      --  we do not change the Signal_Mask to be masked for the Signal.
      --  This is a temporary fix to the problem that the Signal_Mask is
      --  not restored after the exception (longjmp) from the handler.
      --  The right fix should be made in sigsetjmp so that we save
      --  the Signal_Set and restore it after a longjmp.
      --  In that case, this field should be changed back to 0. ??? (Dong-Ik)

      Result := sigemptyset (mask'Access);
      pragma Assert (Result = 0
        or else Shutdown ("GNULLI failure---sigemptyset"));

      for I in Exception_Interrupts'Range loop
         Result := sigaddset (mask'Access, Signal (Exception_Interrupts (I)));
         pragma Assert (Result = 0
           or else Shutdown ("GNULLI failure---sigaddset"));
      end loop;

      act.sa_mask := mask;

      for I in Exception_Interrupts'Range loop
         Keep_Unmasked (Exception_Interrupts (I)) := True;
         Result :=
           sigaction
             (Signal (Exception_Interrupts (I)), act'Access, old_act'Access);
         pragma Assert (Result = 0
           or else Shutdown ("GNULLI failure---sigaction"));
      end loop;

      Keep_Unmasked (Abort_Task_Interrupt) := true;
      Keep_Unmasked (SIGBUS)  := true;
      --  Reserve this not to interfere with thread scheduling

      --  ??? consider adding this to interrupt exceptions
      --  Keep_Unmasked (SIGALRM) := true;
      --  An earlier version had a comment about SIGALRM needing to be unmasked
      --  in at least one thread for cond_timedwait to work.
      --  It is unclear whether this is true for Solaris threads, FSU threads,
      --  both, or maybe just an old version of FSU threads. ????

      Reserve := Keep_Unmasked or Keep_Masked;
      Reserve (SIGALRM) := true;
      Reserve (SIGSTOP) := true;
      Reserve (SIGKILL) := true;

      Reserve (SIGCHLD) := true;
      Reserve (SIGPWR) := true;
      Reserve (SIGWINCH) := true;
      Reserve (SIGURG) := true;
      Reserve (SIGTSTP) := true;
      Reserve (SIGCONT) := true;
      Reserve (SIGTTIN) := true;
      Reserve (SIGTTOU) := true;

      --  Above signals should not be disturbed. Found through experiments.
      --  Below, we provide a "c" routine to demonstarete above signals
      --  behave abnormally when we mix the use of a "sigaction" and a
      --  "sigwait" (even if they are not simultaneously used).
      --  #include <sys/types.h>
      --  #include <signal.h>
      --  #include <stdio.h>
      --  #include <unistd.h>
      --  #include <errno.h>
      --  #include <sys/ddi.h>
      --
      --  main(argc, argv)
      --      int argc;
      --      char *argv;
      --  {
      --    sigset_t  set;
      --    struct sigaction act;
      --    int signal;
      --    int ret;
      --
      --    act.sa_handler = SIG_DFL;
      --    act.sa_flags = 0;
      --
      --    for (signal=1;signal < 44;signal++) {
      --      if (signal != SIGSEGV && signal != SIGFPE     &&
      --          signal != SIGILL  && signal != SIGLWP     &&
      --          signal != SIGBUS  && signal != SIGABRT    &&
      --          signal != SIGALRM && signal != SIGSTOP    &&
      --          signal != SIGKILL && signal != SIGWAITING) {
      --
      --        /* Following signals act wrong when included in the test */
      --        if (signal != SIGCHLD   && signal != SIGPWR  &&
      --            signal != SIGWINCH  && signal != SIGURG  &&
      --            signal != SIGTSTP   && signal != SIGCONT &&
      --            signal != SIGTTIN   && signal != SIGTTOU &&
      --            signal != SIGFREEZE && signal != SIGTHAW) {
      --
      --            printf ("%d\n", signal);
      --            if (sigaction (signal, &act, NULL))
      --              printf ("Error sigaction %d \n", errno);
      --
      --            if (sigemptyset (&set))
      --               printf ("Error sigemptyset %d \n", errno);
      --            if (sigaddset (&set, signal))
      --               printf ("Error sigaddset\n %d ", errno);
      --            if (sigprocmask (SIG_BLOCK, &set, NULL))
      --               printf ("Error sigprocmask\n %d ", errno);
      --
      --            if (kill (getpid(), signal))
      --               printf ("Error kill %d \n", errno);
      --
      --            ret = sigwait (&set);
      --
      --            if (ret != signal)
      --               printf ("Error sigwait : Wrong wake up %d \n", errno);
      --
      --            if (sigprocmask (SIG_UNBLOCK, &set, NULL))
      --               printf ("Error sigprocmask\n %d ", errno);
      --        }
      --      }
      --    }
      --  }


      Reserve := Reserve or Keep_Unmasked or Keep_Masked;
      Reserve (0) := true;
      --  We do not have Signal 0 in reality. We just use this value
      --  to identify not existing signals (see s-intnam.ads). Therefore,
      --  Signal 0 should not be used in all signal related operations hence
      --  mark it as reserved.
   end Initialize;

begin
   Initialize;
end System.Interrupt_Management;
