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mem-break.c revision 1.1.1.9 
      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 }
    129