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) 2011-2014, 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 handler
  33    trampoline to set-up the DWARF Call Frame Information that let unwinders
  34    walk through the signal frame up into the interrupted application code.
  35    This file introduces the relevant declarations.  */
  36
  37 /* This file should only be #included on targets that do implement the
  38    trampoline, which needs to expose the following interface:  */
  39
  40 #ifdef __cplusplus
  41 extern "C" {
  42 #endif
  43
  44 #ifdef __ANDROID__
  45 #include <stdlib.h>
  46 #include <asm/signal.h>
  47 #include <asm/sigcontext.h>
  48
  49 /* Android SDK doesn't define these structs */
  50 typedef struct sigcontext mcontext_t;
  51
  52 typedef struct ucontext
  53   {
  54     unsigned long uc_flags;
  55     struct ucontext *uc_link;
  56     stack_t uc_stack;
  57     mcontext_t uc_mcontext;
  58 } ucontext_t;
  59 #endif
  60
  61   /* This typedef signature sometimes conflicts with the sighandler_t from
  62      system headers so call it something unique.  */
  63   typedef void __sigtramphandler_t (int signo, void *siginfo, void *sigcontext);
  64
  65   void __gnat_sigtramp  (int signo, void *siginfo, void *sigcontext,
  66                          __sigtramphandler_t * handler);
  67
  68   /* To be called from an established signal handler.  Setup the DWARF CFI
  69      bits letting unwinders walk through the signal frame up into the
  70      interrupted application code, and then call HANDLER (SIGNO, SIGINFO,
  71      SIGCONTEXT).
  72
  73      The sigtramp construct makes it so that the unwinder jumps over it + the
  74      signal handler + the kernel frame. For a typical backtrace from the raise
  75      function:
  76
  77      #0  __gnat_Unwind_RaiseException
  78      #1  Raise_From_Signal_Handler
  79      #2  __gnat_map_signal
  80      #3  __gnat_sigtramp
  81      #4  __gnat_error_handler
  82      #5  <kernel frame>
  83      #6  interrupted function
  84
  85      The unwinder will unwind frames 0, 1 and 2 as usual. But the CFI of frame
  86      3 is set up as if the caller of frame 3 was frame 6 so, when frame 3 is
  87      unwound, the unwinder ends up in frame 6 directly. It's possible to do so
  88      since the kernel has saved the context of frame 6 and passed it on to
  89      __gnat_sigtramp.  */
  90
  91 #ifdef __cplusplus
  92 }
  93 #endif