gdb/i386ly-tdep.c

   1 /* Target-dependent code for Intel 386 running LynxOS.
   2    Copyright 1993 Free Software Foundation, Inc.
   3
   4    This file is part of GDB.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include "defs.h"
  22 #include "inferior.h"
  23 #include "target.h"
  24 #include "gdbcore.h"
  25
  26 /* Return the PC of the caller from the call frame.  Assumes the subr prologue
  27    has already been executed, and the frame pointer setup.  If this is the
  28    outermost frame, we check to see if we are in a system call by examining the
  29    previous instruction.  If so, then the return PC is actually at SP+4 because
  30    system calls use a different calling sequence.  */
  31
  32 CORE_ADDR
  33 i386lynx_saved_pc_after_call (struct frame_info *frame)
  34 {
  35   char opcode[7];
  36   static const unsigned char call_inst[] =
  37   {0x9a, 0, 0, 0, 0, 8, 0};     /* lcall 0x8,0x0 */
  38
  39   read_memory (frame->pc - 7, opcode, 7);
  40   if (memcmp (opcode, call_inst, 7) == 0)
  41     return read_memory_integer (read_register (SP_REGNUM) + 4, 4);
  42
  43   return read_memory_integer (read_register (SP_REGNUM), 4);
  44 }