gdb/mem-break.c

   1 /* Simulate breakpoints by patching locations in the target system, for GDB.
   2
   3    Copyright (C) 1990-2016 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 /* Insert a breakpoint on targets that don't have any better
  28    breakpoint support.  We read the contents of the target location
  29    and stash it, then overwrite it with a breakpoint instruction.
  30    BP_TGT->placed_address is the target location in the target
  31    machine.  BP_TGT->shadow_contents is some memory allocated for
  32    saving the target contents.  It is guaranteed by the caller to be
  33    long enough to save BREAKPOINT_LEN bytes (this is accomplished via
  34    BREAKPOINT_MAX).  */
  35
  36 int
  37 default_memory_insert_breakpoint (struct gdbarch *gdbarch,
  38                                   struct bp_target_info *bp_tgt)
  39 {
  40   CORE_ADDR addr = bp_tgt->reqstd_address;
  41   const unsigned char *bp;
  42   gdb_byte *readbuf;
  43   int bplen;
  44   int val;
  45
  46   /* Determine appropriate breakpoint contents and size for this address.  */
  47   bp = gdbarch_breakpoint_from_pc (gdbarch, &addr, &bplen);
  48
  49   bp_tgt->placed_address = addr;
  50   bp_tgt->placed_size = bplen;
  51
  52   /* Save the memory contents in the shadow_contents buffer and then
  53      write the breakpoint instruction.  */
  54   readbuf = (gdb_byte *) alloca (bplen);
  55   val = target_read_memory (addr, readbuf, bplen);
  56   if (val == 0)
  57     {
  58       /* These must be set together, either before or after the shadow
  59          read, so that if we're "reinserting" a breakpoint that
  60          doesn't have a shadow yet, the breakpoint masking code inside
  61          target_read_memory doesn't mask out this breakpoint using an
  62          unfilled shadow buffer.  The core may be trying to reinsert a
  63          permanent breakpoint, for targets that support breakpoint
  64          conditions/commands on the target side for some types of
  65          breakpoints, such as target remote.  */
  66       bp_tgt->shadow_len = bplen;
  67       memcpy (bp_tgt->shadow_contents, readbuf, bplen);
  68
  69       val = target_write_raw_memory (addr, bp, bplen);
  70     }
  71
  72   return val;
  73 }
  74
  75
  76 int
  77 default_memory_remove_breakpoint (struct gdbarch *gdbarch,
  78                                   struct bp_target_info *bp_tgt)
  79 {
  80   return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
  81                                   bp_tgt->placed_size);
  82 }
  83
  84
  85 int
  86 memory_insert_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch,
  87                           struct bp_target_info *bp_tgt)
  88 {
  89   return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt);
  90 }
  91
  92 int
  93 memory_remove_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch,
  94                           struct bp_target_info *bp_tgt,
  95                           enum remove_bp_reason reason)
  96 {
  97   return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt);
  98 }
  99
 100 int
 101 memory_validate_breakpoint (struct gdbarch *gdbarch,
 102                             struct bp_target_info *bp_tgt)
 103 {
 104   CORE_ADDR addr = bp_tgt->placed_address;
 105   const gdb_byte *bp;
 106   int val;
 107   int bplen;
 108   gdb_byte cur_contents[BREAKPOINT_MAX];
 109   struct cleanup *cleanup;
 110   int ret;
 111
 112   /* Determine appropriate breakpoint contents and size for this
 113      address.  */
 114   bp = gdbarch_breakpoint_from_pc (gdbarch, &addr, &bplen);
 115
 116   if (bp == NULL || bp_tgt->placed_size != bplen)
 117     return 0;
 118
 119   /* Make sure we see the memory breakpoints.  */
 120   cleanup = make_show_memory_breakpoints_cleanup (1);
 121   val = target_read_memory (addr, cur_contents, bplen);
 122
 123   /* If our breakpoint is no longer at the address, this means that
 124      the program modified the code on us, so it is wrong to put back
 125      the old value.  */
 126   ret = (val == 0 && memcmp (bp, cur_contents, bplen) == 0);
 127
 128   do_cleanups (cleanup);
 129   return ret;
 130 }