gdb/mem-break.c

   1 /* Simulate breakpoints by patching locations in the target system, for GDB.
   2
   3    Copyright 1990, 1991, 1992, 1993, 1995, 1997, 1998, 1999, 2000,
   4    2002 Free Software Foundation, Inc.
   5
   6    Contributed by Cygnus Support.  Written by John Gilmore.
   7
   8    This file is part of GDB.
   9
  10    This program is free software; you can redistribute it and/or modify
  11    it under the terms of the GNU General Public License as published by
  12    the Free Software Foundation; either version 2 of the License, or
  13    (at your option) any later version.
  14
  15    This program is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18    GNU General Public License for more details.
  19
  20    You should have received a copy of the GNU General Public License
  21    along with this program; if not, write to the Free Software
  22    Foundation, Inc., 59 Temple Place - Suite 330,
  23    Boston, MA 02111-1307, USA.  */
  24
  25 #include "defs.h"
  26
  27 /* This file is only useful if BREAKPOINT is set.  If not, we punt.  */
  28
  29 #include "symtab.h"
  30 #include "breakpoint.h"
  31 #include "inferior.h"
  32 #include "target.h"
  33
  34
  35 /* Use the program counter to determine the contents and size
  36    of a breakpoint instruction.  If no target-dependent macro
  37    BREAKPOINT_FROM_PC has been defined to implement this function,
  38    assume that the breakpoint doesn't depend on the PC, and
  39    use the values of the BIG_BREAKPOINT and LITTLE_BREAKPOINT macros.
  40    Return a pointer to a string of bytes that encode a breakpoint
  41    instruction, stores the length of the string to *lenptr,
  42    and optionally adjust the pc to point to the correct memory location
  43    for inserting the breakpoint.  */
  44
  45 const unsigned char *
  46 memory_breakpoint_from_pc (CORE_ADDR *pcptr, int *lenptr)
  47 {
  48   /* {BIG_,LITTLE_}BREAKPOINT is the sequence of bytes we insert for a
  49      breakpoint.  On some machines, breakpoints are handled by the
  50      target environment and we don't have to worry about them here.  */
  51 #ifdef BIG_BREAKPOINT
  52   if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
  53     {
  54       static unsigned char big_break_insn[] = BIG_BREAKPOINT;
  55       *lenptr = sizeof (big_break_insn);
  56       return big_break_insn;
  57     }
  58 #endif
  59 #ifdef LITTLE_BREAKPOINT
  60   if (TARGET_BYTE_ORDER != BFD_ENDIAN_BIG)
  61     {
  62       static unsigned char little_break_insn[] = LITTLE_BREAKPOINT;
  63       *lenptr = sizeof (little_break_insn);
  64       return little_break_insn;
  65     }
  66 #endif
  67 #ifdef BREAKPOINT
  68   {
  69     static unsigned char break_insn[] = BREAKPOINT;
  70     *lenptr = sizeof (break_insn);
  71     return break_insn;
  72   }
  73 #endif
  74   *lenptr = 0;
  75   return NULL;
  76 }
  77
  78
  79 /* Insert a breakpoint on targets that don't have any better breakpoint
  80    support.  We read the contents of the target location and stash it,
  81    then overwrite it with a breakpoint instruction.  ADDR is the target
  82    location in the target machine.  CONTENTS_CACHE is a pointer to
  83    memory allocated for saving the target contents.  It is guaranteed
  84    by the caller to be long enough to save BREAKPOINT_LEN bytes (this
  85    is accomplished via BREAKPOINT_MAX).  */
  86
  87 int
  88 default_memory_insert_breakpoint (CORE_ADDR addr, char *contents_cache)
  89 {
  90   int val;
  91   const unsigned char *bp;
  92   int bplen;
  93
  94   /* Determine appropriate breakpoint contents and size for this address.  */
  95   bp = BREAKPOINT_FROM_PC (&addr, &bplen);
  96   if (bp == NULL)
  97     error ("Software breakpoints not implemented for this target.");
  98
  99   /* Save the memory contents.  */
 100   val = target_read_memory (addr, contents_cache, bplen);
 101
 102   /* Write the breakpoint.  */
 103   if (val == 0)
 104     val = target_write_memory (addr, (char *) bp, bplen);
 105
 106   return val;
 107 }
 108
 109
 110 int
 111 default_memory_remove_breakpoint (CORE_ADDR addr, char *contents_cache)
 112 {
 113   const unsigned char *bp;
 114   int bplen;
 115
 116   /* Determine appropriate breakpoint contents and size for this address.  */
 117   bp = BREAKPOINT_FROM_PC (&addr, &bplen);
 118   if (bp == NULL)
 119     error ("Software breakpoints not implemented for this target.");
 120
 121   return target_write_memory (addr, contents_cache, bplen);
 122 }
 123
 124
 125 int
 126 memory_insert_breakpoint (CORE_ADDR addr, char *contents_cache)
 127 {
 128   return MEMORY_INSERT_BREAKPOINT(addr, contents_cache);
 129 }
 130
 131 int
 132 memory_remove_breakpoint (CORE_ADDR addr, char *contents_cache)
 133 {
 134   return MEMORY_REMOVE_BREAKPOINT(addr, contents_cache);
 135 }