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mem-break.c revision 1.6.4.1 
      1 /* Simulate breakpoints by patching locations in the target system, for GDB.
      2 
      3    Copyright (C) 1990-2017 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->placed_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_sw_breakpoint_from_kind (gdbarch, bp_tgt->kind, &bplen);
     48 
     49   /* Save the memory contents in the shadow_contents buffer and then
     50      write the breakpoint instruction.  */
     51   readbuf = (gdb_byte *) alloca (bplen);
     52   val = target_read_memory (addr, readbuf, bplen);
     53   if (val == 0)
     54     {
     55       /* These must be set together, either before or after the shadow
     56 	 read, so that if we're "reinserting" a breakpoint that
     57 	 doesn't have a shadow yet, the breakpoint masking code inside
     58 	 target_read_memory doesn't mask out this breakpoint using an
     59 	 unfilled shadow buffer.  The core may be trying to reinsert a
     60 	 permanent breakpoint, for targets that support breakpoint
     61 	 conditions/commands on the target side for some types of
     62 	 breakpoints, such as target remote.  */
     63       bp_tgt->shadow_len = bplen;
     64       memcpy (bp_tgt->shadow_contents, readbuf, bplen);
     65 
     66       val = target_write_raw_memory (addr, bp, bplen);
     67     }
     68 
     69   return val;
     70 }
     71 
     72 
     73 int
     74 default_memory_remove_breakpoint (struct gdbarch *gdbarch,
     75 				  struct bp_target_info *bp_tgt)
     76 {
     77   int bplen;
     78 
     79   gdbarch_sw_breakpoint_from_kind (gdbarch, bp_tgt->kind, &bplen);
     80 
     81   return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
     82 				  bplen);
     83 }
     84 
     85 
     86 int
     87 memory_insert_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch,
     88 			  struct bp_target_info *bp_tgt)
     89 {
     90   return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt);
     91 }
     92 
     93 int
     94 memory_remove_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch,
     95 			  struct bp_target_info *bp_tgt,
     96 			  enum remove_bp_reason reason)
     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)
    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 }
    132