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mem-break.c revision 1.1.1.4 
      1 /* Simulate breakpoints by patching locations in the target system, for GDB.
      2 
      3    Copyright (C) 1990-2016 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->reqstd_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_breakpoint_from_pc (gdbarch, &addr, &bplen);
     48   if (bp == NULL)
     49     error (_("Software breakpoints not implemented for this target."));
     50 
     51   bp_tgt->placed_address = addr;
     52   bp_tgt->placed_size = bplen;
     53 
     54   /* Save the memory contents in the shadow_contents buffer and then
     55      write the breakpoint instruction.  */
     56   readbuf = (gdb_byte *) alloca (bplen);
     57   val = target_read_memory (addr, readbuf, bplen);
     58   if (val == 0)
     59     {
     60       /* These must be set together, either before or after the shadow
     61 	 read, so that if we're "reinserting" a breakpoint that
     62 	 doesn't have a shadow yet, the breakpoint masking code inside
     63 	 target_read_memory doesn't mask out this breakpoint using an
     64 	 unfilled shadow buffer.  The core may be trying to reinsert a
     65 	 permanent breakpoint, for targets that support breakpoint
     66 	 conditions/commands on the target side for some types of
     67 	 breakpoints, such as target remote.  */
     68       bp_tgt->shadow_len = bplen;
     69       memcpy (bp_tgt->shadow_contents, readbuf, bplen);
     70 
     71       val = target_write_raw_memory (addr, bp, bplen);
     72     }
     73 
     74   return val;
     75 }
     76 
     77 
     78 int
     79 default_memory_remove_breakpoint (struct gdbarch *gdbarch,
     80 				  struct bp_target_info *bp_tgt)
     81 {
     82   return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
     83 				  bp_tgt->placed_size);
     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   struct cleanup *cleanup;
    112   int ret;
    113 
    114   /* Determine appropriate breakpoint contents and size for this
    115      address.  */
    116   bp = gdbarch_breakpoint_from_pc (gdbarch, &addr, &bplen);
    117 
    118   if (bp == NULL || bp_tgt->placed_size != bplen)
    119     return 0;
    120 
    121   /* Make sure we see the memory breakpoints.  */
    122   cleanup = make_show_memory_breakpoints_cleanup (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   ret = (val == 0 && memcmp (bp, cur_contents, bplen) == 0);
    129 
    130   do_cleanups (cleanup);
    131   return ret;
    132 }
    133