gcc/ada/sigtramp.h

   1 /****************************************************************************
   2  *                                                                          *
   3  *                         GNAT COMPILER COMPONENTS                         *
   4  *                                                                          *
   5  *                             S I G T R A M P                              *
   6  *                                                                          *
   7  *                              C Header File                               *
   8  *                                                                          *
   9  *          Copyright (C) 2011-2015, Free Software Foundation, Inc.         *
  10  *                                                                          *
  11  * GNAT is free software;  you can  redistribute it  and/or modify it under *
  12  * terms of the  GNU General Public License as published  by the Free Soft- *
  13  * ware  Foundation;  either version 3,  or (at your option) any later ver- *
  14  * sion.  GNAT is distributed in the hope that it will be useful, but WITH- *
  15  * OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY *
  16  * or FITNESS FOR A PARTICULAR PURPOSE.                                     *
  17  *                                                                          *
  18  * As a special exception under Section 7 of GPL version 3, you are granted *
  19  * additional permissions described in the GCC Runtime Library Exception,   *
  20  * version 3.1, as published by the Free Software Foundation.               *
  21  *                                                                          *
  22  * You should have received a copy of the GNU General Public License and    *
  23  * a copy of the GCC Runtime Library Exception along with this program;     *
  24  * see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    *
  25  * <http://www.gnu.org/licenses/>.                                          *
  26  *                                                                          *
  27  * GNAT was originally developed  by the GNAT team at  New York University. *
  28  * Extensive contributions were provided by Ada Core Technologies Inc.      *
  29  *                                                                          *
  30  ****************************************************************************/
  31
  32 /* On targets where this is implemented, we resort to a signal trampoline to
  33    set up the DWARF Call Frame Information that lets unwinders walk through
  34    the signal frame up into the interrupted user code.  This file introduces
  35    the relevant declarations.  It should only be #included on targets that do
  36    implement the signal trampoline.  */
  37
  38 #ifdef __cplusplus
  39 extern "C" {
  40 #endif
  41
  42 /* This typedef signature sometimes conflicts with the sighandler_t from
  43    system headers so call it something unique.  */
  44 typedef void __sigtramphandler_t (int signo, void *siginfo, void *sigcontext);
  45
  46 #if defined(__vxworks) && (CPU == SIMNT || CPU == SIMPENTIUM || CPU == SIMLINUX)
  47 /* Vxsim requires a specially compiled handler.  */
  48 extern void __gnat_sigtramp_vxsim (int signo, void *siginfo, void *sigcontext,
  49                                    __sigtramphandler_t * handler);
  50 #else
  51 extern void __gnat_sigtramp (int signo, void *siginfo, void *sigcontext,
  52                              __sigtramphandler_t * handler);
  53 #endif
  54
  55 /* The signal trampoline is to be called from an established signal handler.
  56    It sets up the DWARF CFI and calls HANDLER (SIGNO, SIGINFO, SIGCONTEXT).
  57
  58    The trampoline construct makes it so that the unwinder jumps over it + the
  59    signal handler + the kernel frame.  For a typical backtrace from the raise
  60    function:
  61
  62      #0  __gnat_Unwind_RaiseException
  63      #1  Raise_From_Signal_Handler
  64      #2  __gnat_map_signal
  65      #3  __gnat_sigtramp
  66      #4  __gnat_error_handler
  67      #5  <kernel frame>
  68      #6  interrupted function
  69
  70    The unwinder will unwind frames 0, 1 and 2 as usual.  But the CFI of frame
  71    3 is set up as if the caller of frame 3 was frame 6 so, when frame 3 is
  72    unwound, the unwinder ends up in frame 6 directly.  It's possible to do so
  73    because the kernel has saved the context of frame 6 and passed it on to
  74    __gnat_error_handler and __gnat_sigtramp.  */
  75
  76 #ifdef __cplusplus
  77 }
  78 #endif