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   if (bp == NULL)
  49     error (_("Software breakpoints not implemented for this target."));
  50
  51   bp_tgt->placed_address = addr;
  52   bp_tgt->placed_size = bplen;
  53
  54   /* Save the memory contents in the shadow_contents buffer and then
  55      write the breakpoint instruction.  */
  56   readbuf = (gdb_byte *) alloca (bplen);
  57   val = target_read_memory (addr, readbuf, bplen);
  58   if (val == 0)
  59     {
  60       /* These must be set together, either before or after the shadow
  61          read, so that if we're "reinserting" a breakpoint that
  62          doesn't have a shadow yet, the breakpoint masking code inside
  63          target_read_memory doesn't mask out this breakpoint using an
  64          unfilled shadow buffer.  The core may be trying to reinsert a
  65          permanent breakpoint, for targets that support breakpoint
  66          conditions/commands on the target side for some types of
  67          breakpoints, such as target remote.  */
  68       bp_tgt->shadow_len = bplen;
  69       memcpy (bp_tgt->shadow_contents, readbuf, bplen);
  70
  71       val = target_write_raw_memory (addr, bp, bplen);
  72     }
  73
  74   return val;
  75 }
  76
  77
  78 int
  79 default_memory_remove_breakpoint (struct gdbarch *gdbarch,
  80                                   struct bp_target_info *bp_tgt)
  81 {
  82   return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
  83                                   bp_tgt->placed_size);
  84 }
  85
  86
  87 int
  88 memory_insert_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch,
  89                           struct bp_target_info *bp_tgt)
  90 {
  91   return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt);
  92 }
  93
  94 int
  95 memory_remove_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch,
  96                           struct bp_target_info *bp_tgt)
  97 {
  98   return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt);
  99 }
 100
 101 int
 102 memory_validate_breakpoint (struct gdbarch *gdbarch,
 103                             struct bp_target_info *bp_tgt)
 104 {
 105   CORE_ADDR addr = bp_tgt->placed_address;
 106   const gdb_byte *bp;
 107   int val;
 108   int bplen;
 109   gdb_byte cur_contents[BREAKPOINT_MAX];
 110   struct cleanup *cleanup;
 111   int ret;
 112
 113   /* Determine appropriate breakpoint contents and size for this
 114      address.  */
 115   bp = gdbarch_breakpoint_from_pc (gdbarch, &addr, &bplen);
 116
 117   if (bp == NULL || bp_tgt->placed_size != bplen)
 118     return 0;
 119
 120   /* Make sure we see the memory breakpoints.  */
 121   cleanup = make_show_memory_breakpoints_cleanup (1);
 122   val = target_read_memory (addr, cur_contents, bplen);
 123
 124   /* If our breakpoint is no longer at the address, this means that
 125      the program modified the code on us, so it is wrong to put back
 126      the old value.  */
 127   ret = (val == 0 && memcmp (bp, cur_contents, bplen) == 0);
 128
 129   do_cleanups (cleanup);
 130   return ret;
 131 }