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mem-break.c revision 1.1.1.8 
      1 /* Simulate breakpoints by patching locations in the target system, for GDB.
      2 
      3    Copyright (C) 1990-2023 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 }
    130