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------------------------------------------------------------------------------

--                                                                          --

--                 GNAT RUN-TIME 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                                 --

--                                                                          --

--          Copyright (C) 1992-2005, Free Software Foundation, Inc.         --

--                                                                          --

-- 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,  51  Franklin  Street,  Fifth  Floor, --

-- Boston, MA 02110-1301, 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.       --

-- Extensive contributions were provided by Ada Core Technologies, Inc.     --

--                                                                          --

------------------------------------------------------------------------------

--  This is the POSIX threads version of this package

--  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.

--  Since this is a multi target file, the signal <-> exception mapping

--  is simple minded. If you need a more precise and target specific

--  signal handling, create a new s-intman.adb that will fit your needs.

--  This file assumes that:

--    SIGFPE, SIGILL, SIGSEGV and SIGBUS exist. They are mapped as follows:

--      SIGPFE  => Constraint_Error

--      SIGILL  => Program_Error

--      SIGSEGV => Storage_Error

--      SIGBUS  => Storage_Error

--    SIGINT exists and will be kept unmasked unless the pragma

--     Unreserve_All_Interrupts is specified anywhere in the application.

--    System.OS_Interface contains the following:

--      SIGADAABORT: the signal that will be used to abort tasks.

--      Unmasked: the OS specific set of signals that should be unmasked in

--                all the threads. SIGADAABORT is unmasked by

--                default

--      Reserved: the OS specific set of signals that are reserved.

with Interfaces.C;

--  used for int and other types

with System.OS_Interface;

--  used for various Constants, Signal and types

package body System.Interrupt_Management is

   use Interfaces.C;

   use System.OS_Interface;

   type Interrupt_List is array (Interrupt_ID range <>) of Interrupt_ID;

   Exception_Interrupts : constant Interrupt_List :=

     (SIGFPE, SIGILL, SIGSEGV, SIGBUS);

   Unreserve_All_Interrupts : Interfaces.C.int;

   pragma Import

     (C, Unreserve_All_Interrupts, "__gl_unreserve_all_interrupts");

   -----------------------

   -- Local Subprograms --

   -----------------------

   function State (Int : Interrupt_ID) return Character;

   pragma Import (C, State, "__gnat_get_interrupt_state");

   --  Get interrupt state. Defined in init.c

   --  The input argument is the interrupt number,

   --  and the result is one of the following:

   User    : constant Character := 'u';

   Runtime : constant Character := 'r';

   Default : constant Character := 's';

   --    'n'   this interrupt not set by any Interrupt_State pragma

   --    'u'   Interrupt_State pragma set state to User

   --    'r'   Interrupt_State pragma set state to Runtime

   --    's'   Interrupt_State pragma set state to System (use "default"

   --           system handler)

   procedure Notify_Exception

     (signo    : Signal;

      siginfo  : System.Address;

      ucontext : System.Address);

   --  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.

   ----------------------

   -- Notify_Exception --

   ----------------------

   Signal_Mask : aliased sigset_t;

   --  The set of signals handled by Notify_Exception

   procedure Notify_Exception

     (signo    : Signal;

      siginfo  : System.Address;

      ucontext : System.Address)

   is

      pragma Unreferenced (siginfo);

      --  The GCC unwinder requires adjustments to the signal's machine

      --  context to be able to properly unwind through the signal handler.

      --  This is achieved by the target specific subprogram below, provided

      --  by init.c to be usable by the non-tasking handler also.

      procedure Adjust_Context_For_Raise

        (signo    : Signal;

         ucontext : System.Address);

      pragma Import

        (C, Adjust_Context_For_Raise, "__gnat_adjust_context_for_raise");

      Result  : Interfaces.C.int;

   begin

      --  With the __builtin_longjmp, the signal mask is not restored, so we

      --  need to restore it explicitely.

      Result := pthread_sigmask (SIG_UNBLOCK, Signal_Mask'Access, null);

      pragma Assert (Result = 0);

      --  Perform the necessary context adjustments required by the GCC/ZCX

      --  unwinder, harmless in the SJLJ case.

      Adjust_Context_For_Raise (signo, ucontext);

      --  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 =>

            raise Constraint_Error;

         when SIGILL =>

            raise Program_Error;

         when SIGSEGV =>

            raise Storage_Error;

         when SIGBUS =>

            raise Storage_Error;

         when others =>

            null;

      end case;

   end Notify_Exception;

   ----------------

   -- Initialize --

   ----------------

   Initialized : Boolean := False;

   procedure Initialize is

      act     : aliased struct_sigaction;

      old_act : aliased struct_sigaction;

      Result  : System.OS_Interface.int;

   begin

      if Initialized then

         return;

      end if;

      Initialized := True;

      --  Need to call pthread_init very early because it is doing signal

      --  initializations.

      pthread_init;

      Abort_Task_Interrupt := SIGADAABORT;

      act.sa_handler := Notify_Exception'Address;

      act.sa_flags := SA_SIGINFO;

      --  Setting SA_SIGINFO asks the kernel to pass more than just the signal

      --  number argument to the handler when it is called. The set of extra

      --  parameters includes a pointer to the interrupted context, which the

      --  ZCX propagation scheme needs.

      --  Most man pages for sigaction mention that sa_sigaction should be set

      --  instead of sa_handler when SA_SIGINFO is on.  In practice, the two

      --  fields are actually union'ed and located at the same offset.

      --  On some targets, we 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.

      --  Since SA_NODEFER is obsolete, instead we reset explicitely

      --  the mask in the exception handler.

      Result := sigemptyset (Signal_Mask'Access);

      pragma Assert (Result = 0);

      --  Add signals that map to Ada exceptions to the mask.

      for J in Exception_Interrupts'Range loop

         if State (Exception_Interrupts (J)) /= Default  then

            Result :=

            sigaddset (Signal_Mask'Access, Signal (Exception_Interrupts (J)));

            pragma Assert (Result = 0);

         end if;

      end loop;

      act.sa_mask := Signal_Mask;

      pragma Assert (Keep_Unmasked = (Interrupt_ID'Range => False));

      pragma Assert (Reserve = (Interrupt_ID'Range => False));

      --  Process state of exception signals

      for J in Exception_Interrupts'Range loop

         if State (Exception_Interrupts (J)) /= User then

            Keep_Unmasked (Exception_Interrupts (J)) := True;

            Reserve (Exception_Interrupts (J)) := True;

            if State (Exception_Interrupts (J)) /= Default then

               Result :=

                 sigaction

                 (Signal (Exception_Interrupts (J)), act'Unchecked_Access,

                  old_act'Unchecked_Access);

               pragma Assert (Result = 0);

            end if;

         end if;

      end loop;

      if State (Abort_Task_Interrupt) /= User then

         Keep_Unmasked (Abort_Task_Interrupt) := True;

         Reserve (Abort_Task_Interrupt) := True;

      end if;

      --  Set SIGINT to unmasked state as long as it is not in "User"

      --  state. Check for Unreserve_All_Interrupts last

      if State (SIGINT) /= User then

         Keep_Unmasked (SIGINT) := True;

         Reserve (SIGINT) := True;

      end if;

      --  Check all signals for state that requires keeping them

      --  unmasked and reserved

      for J in Interrupt_ID'Range loop

         if State (J) = Default or else State (J) = Runtime then

            Keep_Unmasked (J) := True;

            Reserve (J) := True;

         end if;

      end loop;

      --  Add the set of signals that must always be unmasked for this target

      for J in Unmasked'Range loop

         Keep_Unmasked (Interrupt_ID (Unmasked (J))) := True;

         Reserve (Interrupt_ID (Unmasked (J))) := True;

      end loop;

      --  Add target-specific reserved signals

      for J in Reserved'Range loop

         Reserve (Interrupt_ID (Reserved (J))) := True;

      end loop;

      --  Process pragma Unreserve_All_Interrupts. This overrides any

      --  settings due to pragma Interrupt_State:

      if Unreserve_All_Interrupts /= 0 then

         Keep_Unmasked (SIGINT) := False;

         Reserve (SIGINT) := False;

      end if;

      --  We do not have Signal 0 in reality. We just use this value

      --  to identify non-existent signals (see s-intnam.ads). Therefore,

      --  Signal 0 should not be used in all signal related operations hence

      --  mark it as reserved.

      Reserve (0) := True;

   end Initialize;

end System.Interrupt_Management;