gdb/nindy-tdep.c

   1 /* Target-machine dependent code for the NINDY monitor running on the Intel 960
   2    Copyright (C) 1991 Free Software Foundation, Inc.
   3    Contributed by Intel Corporation.
   4
   5 This file is part of GDB.
   6
   7 This program is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 2 of the License, or
  10 (at your option) any later version.
  11
  12 This program is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with this program; if not, write to the Free Software
  19 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  20
  21 /* Miscellaneous NINDY-dependent routines.
  22    Some replace macros normally defined in "tm.h".  */
  23
  24 #include "defs.h"
  25 #include "symtab.h"
  26 #include "frame.h"
  27 #include "gdbcore.h"
  28
  29 /* 'start_frame' is a variable in the NINDY runtime startup routine
  30    that contains the frame pointer of the 'start' routine (the routine
  31    that calls 'main').  By reading its contents out of remote memory,
  32    we can tell where the frame chain ends:  backtraces should halt before
  33    they display this frame.  */
  34
  35 int
  36 nindy_frame_chain_valid (chain, curframe)
  37     unsigned int chain;
  38     struct frame_info *curframe;
  39 {
  40         struct symbol *sym;
  41         struct minimal_symbol *msymbol;
  42
  43         /* crtnindy.o is an assembler module that is assumed to be linked
  44          * first in an i80960 executable.  It contains the true entry point;
  45          * it performs startup up initialization and then calls 'main'.
  46          *
  47          * 'sf' is the name of a variable in crtnindy.o that is set
  48          *      during startup to the address of the first frame.
  49          *
  50          * 'a' is the address of that variable in 80960 memory.
  51          */
  52         static char sf[] = "start_frame";
  53         CORE_ADDR a;
  54
  55
  56         chain &= ~0x3f; /* Zero low 6 bits because previous frame pointers
  57                            contain return status info in them.  */
  58         if ( chain == 0 ){
  59                 return 0;
  60         }
  61
  62         sym = lookup_symbol(sf, 0, VAR_NAMESPACE, (int *)NULL,
  63                                   (struct symtab **)NULL);
  64         if ( sym != 0 ){
  65                 a = SYMBOL_VALUE (sym);
  66         } else {
  67                 msymbol = lookup_minimal_symbol (sf, NULL, NULL);
  68                 if (msymbol == NULL)
  69                         return 0;
  70                 a = SYMBOL_VALUE_ADDRESS (msymbol);
  71         }
  72
  73         return ( chain != read_memory_integer(a,4) );
  74 }