gdb/mem-break.c

   1 /* Simulate breakpoints by patching locations in the target system, for GDB.
   2
   3    Copyright (C) 1990-2020 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 "gdbarch.h"
  28
  29 /* Insert a breakpoint on targets that don't have any better
  30    breakpoint support.  We read the contents of the target location
  31    and stash it, then overwrite it with a breakpoint instruction.
  32    BP_TGT->placed_address is the target location in the target
  33    machine.  BP_TGT->shadow_contents is some memory allocated for
  34    saving the target contents.  It is guaranteed by the caller to be
  35    long enough to save BREAKPOINT_LEN bytes (this is accomplished via
  36    BREAKPOINT_MAX).  */
  37
  38 int
  39 default_memory_insert_breakpoint (struct gdbarch *gdbarch,
  40                                   struct bp_target_info *bp_tgt)
  41 {
  42   CORE_ADDR addr = bp_tgt->placed_address;
  43   const unsigned char *bp;
  44   gdb_byte *readbuf;
  45   int bplen;
  46   int val;
  47
  48   /* Determine appropriate breakpoint contents and size for this address.  */
  49   bp = gdbarch_sw_breakpoint_from_kind (gdbarch, bp_tgt->kind, &bplen);
  50
  51   /* Save the memory contents in the shadow_contents buffer and then
  52      write the breakpoint instruction.  */
  53   readbuf = (gdb_byte *) alloca (bplen);
  54   val = target_read_memory (addr, readbuf, bplen);
  55   if (val == 0)
  56     {
  57       /* These must be set together, either before or after the shadow
  58          read, so that if we're "reinserting" a breakpoint that
  59          doesn't have a shadow yet, the breakpoint masking code inside
  60          target_read_memory doesn't mask out this breakpoint using an
  61          unfilled shadow buffer.  The core may be trying to reinsert a
  62          permanent breakpoint, for targets that support breakpoint
  63          conditions/commands on the target side for some types of
  64          breakpoints, such as target remote.  */
  65       bp_tgt->shadow_len = bplen;
  66       memcpy (bp_tgt->shadow_contents, readbuf, bplen);
  67
  68       val = target_write_raw_memory (addr, bp, bplen);
  69     }
  70
  71   return val;
  72 }
  73
  74
  75 int
  76 default_memory_remove_breakpoint (struct gdbarch *gdbarch,
  77                                   struct bp_target_info *bp_tgt)
  78 {
  79   int bplen;
  80
  81   gdbarch_sw_breakpoint_from_kind (gdbarch, bp_tgt->kind, &bplen);
  82
  83   return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
  84                                   bplen);
  85 }
  86
  87
  88 int
  89 memory_insert_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch,
  90                           struct bp_target_info *bp_tgt)
  91 {
  92   return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt);
  93 }
  94
  95 int
  96 memory_remove_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch,
  97                           struct bp_target_info *bp_tgt,
  98                           enum remove_bp_reason reason)
  99 {
 100   return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt);
 101 }
 102
 103 int
 104 memory_validate_breakpoint (struct gdbarch *gdbarch,
 105                             struct bp_target_info *bp_tgt)
 106 {
 107   CORE_ADDR addr = bp_tgt->placed_address;
 108   const gdb_byte *bp;
 109   int val;
 110   int bplen;
 111   gdb_byte cur_contents[BREAKPOINT_MAX];
 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)
 118     return 0;
 119
 120   /* Make sure we see the memory breakpoints.  */
 121   scoped_restore restore_memory
 122     = make_scoped_restore_show_memory_breakpoints (1);
 123   val = target_read_memory (addr, cur_contents, bplen);
 124
 125   /* If our breakpoint is no longer at the address, this means that
 126      the program modified the code on us, so it is wrong to put back
 127      the old value.  */
 128   return (val == 0 && memcmp (bp, cur_contents, bplen) == 0);
 129 }