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mem-break.c revision 1.1 
      1 /* Simulate breakpoints by patching locations in the target system, for GDB.
      2 
      3    Copyright (C) 1990-2014 Free Software Foundation, Inc.
      4 
      5    Contributed by Cygnus Support.  Written by John Gilmore.
      6 
      7    This file is part of GDB.
      8 
      9    This program is free software; you can redistribute it and/or modify
     10    it under the terms of the GNU General Public License as published by
     11    the Free Software Foundation; either version 3 of the License, or
     12    (at your option) any later version.
     13 
     14    This program is distributed in the hope that it will be useful,
     15    but WITHOUT ANY WARRANTY; without even the implied warranty of
     16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     17    GNU General Public License for more details.
     18 
     19    You should have received a copy of the GNU General Public License
     20    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
     21 
     22 #include "defs.h"
     23 #include "symtab.h"
     24 #include "breakpoint.h"
     25 #include "inferior.h"
     26 #include "target.h"
     27 #include <string.h>
     28 
     29 
     30 /* Insert a breakpoint on targets that don't have any better
     31    breakpoint support.  We read the contents of the target location
     32    and stash it, then overwrite it with a breakpoint instruction.
     33    BP_TGT->placed_address is the target location in the target
     34    machine.  BP_TGT->shadow_contents is some memory allocated for
     35    saving the target contents.  It is guaranteed by the caller to be
     36    long enough to save BREAKPOINT_LEN bytes (this is accomplished via
     37    BREAKPOINT_MAX).  */
     38 
     39 int
     40 default_memory_insert_breakpoint (struct gdbarch *gdbarch,
     41 				  struct bp_target_info *bp_tgt)
     42 {
     43   int val;
     44   const unsigned char *bp;
     45   gdb_byte *readbuf;
     46 
     47   /* Determine appropriate breakpoint contents and size for this address.  */
     48   bp = gdbarch_breakpoint_from_pc
     49        (gdbarch, &bp_tgt->placed_address, &bp_tgt->placed_size);
     50   if (bp == NULL)
     51     error (_("Software breakpoints not implemented for this target."));
     52 
     53   /* Save the memory contents in the shadow_contents buffer and then
     54      write the breakpoint instruction.  */
     55   bp_tgt->shadow_len = bp_tgt->placed_size;
     56   readbuf = alloca (bp_tgt->placed_size);
     57   val = target_read_memory (bp_tgt->placed_address, readbuf,
     58 			    bp_tgt->placed_size);
     59   if (val == 0)
     60     {
     61       memcpy (bp_tgt->shadow_contents, readbuf, bp_tgt->placed_size);
     62       val = target_write_raw_memory (bp_tgt->placed_address, bp,
     63 				     bp_tgt->placed_size);
     64     }
     65 
     66   return val;
     67 }
     68 
     69 
     70 int
     71 default_memory_remove_breakpoint (struct gdbarch *gdbarch,
     72 				  struct bp_target_info *bp_tgt)
     73 {
     74   return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
     75 				  bp_tgt->placed_size);
     76 }
     77 
     78 
     79 int
     80 memory_insert_breakpoint (struct gdbarch *gdbarch,
     81 			  struct bp_target_info *bp_tgt)
     82 {
     83   return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt);
     84 }
     85 
     86 int
     87 memory_remove_breakpoint (struct gdbarch *gdbarch,
     88 			  struct bp_target_info *bp_tgt)
     89 {
     90   return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt);
     91 }
     92