gdb/mem-break.c

   1 /* Simulate breakpoints by patching locations in the target system, for GDB.
   2
   3    Copyright (C) 1990-2024 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 "symtab.h"
  23 #include "breakpoint.h"
  24 #include "inferior.h"
  25 #include "target.h"
  26 #include "gdbarch.h"
  27
  28 /* Insert a breakpoint on targets that don't have any better
  29    breakpoint support.  We read the contents of the target location
  30    and stash it, then overwrite it with a breakpoint instruction.
  31    BP_TGT->placed_address is the target location in the target
  32    machine.  BP_TGT->shadow_contents is some memory allocated for
  33    saving the target contents.  It is guaranteed by the caller to be
  34    long enough to save BREAKPOINT_LEN bytes (this is accomplished via
  35    BREAKPOINT_MAX).  */
  36
  37 int
  38 default_memory_insert_breakpoint (struct gdbarch *gdbarch,
  39                                   struct bp_target_info *bp_tgt)
  40 {
  41   CORE_ADDR addr = bp_tgt->placed_address;
  42   const unsigned char *bp;
  43   gdb_byte *readbuf;
  44   int bplen;
  45   int val;
  46
  47   /* Determine appropriate breakpoint contents and size for this address.  */
  48   bp = gdbarch_sw_breakpoint_from_kind (gdbarch, bp_tgt->kind, &bplen);
  49
  50   /* Save the memory contents in the shadow_contents buffer and then
  51      write the breakpoint instruction.  */
  52   readbuf = (gdb_byte *) alloca (bplen);
  53   val = target_read_memory (addr, readbuf, bplen);
  54   if (val == 0)
  55     {
  56       /* These must be set together, either before or after the shadow
  57          read, so that if we're "reinserting" a breakpoint that
  58          doesn't have a shadow yet, the breakpoint masking code inside
  59          target_read_memory doesn't mask out this breakpoint using an
  60          unfilled shadow buffer.  The core may be trying to reinsert a
  61          permanent breakpoint, for targets that support breakpoint
  62          conditions/commands on the target side for some types of
  63          breakpoints, such as target remote.  */
  64       bp_tgt->shadow_len = bplen;
  65       memcpy (bp_tgt->shadow_contents, readbuf, bplen);
  66
  67       val = target_write_raw_memory (addr, bp, bplen);
  68     }
  69
  70   return val;
  71 }
  72
  73
  74 int
  75 default_memory_remove_breakpoint (struct gdbarch *gdbarch,
  76                                   struct bp_target_info *bp_tgt)
  77 {
  78   int bplen;
  79
  80   gdbarch_sw_breakpoint_from_kind (gdbarch, bp_tgt->kind, &bplen);
  81
  82   return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
  83                                   bplen);
  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                           enum remove_bp_reason reason)
  98 {
  99   return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt);
 100 }
 101
 102 int
 103 memory_validate_breakpoint (struct gdbarch *gdbarch,
 104                             struct bp_target_info *bp_tgt)
 105 {
 106   CORE_ADDR addr = bp_tgt->placed_address;
 107   const gdb_byte *bp;
 108   int val;
 109   int bplen;
 110   gdb_byte cur_contents[BREAKPOINT_MAX];
 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)
 117     return 0;
 118
 119   /* Make sure we see the memory breakpoints.  */
 120   scoped_restore restore_memory
 121     = make_scoped_restore_show_memory_breakpoints (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   return (val == 0 && memcmp (bp, cur_contents, bplen) == 0);
 128 }