gdb/mem-break.c

   1 /* Simulate breakpoints by patching locations in the target system, for GDB.
   2    Copyright 1990, 1991, 1995 Free Software Foundation, Inc.
   3    Contributed by Cygnus Support.  Written by John Gilmore.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 59 Temple Place - Suite 330,
  20    Boston, MA 02111-1307, USA.  */
  21
  22 #include "defs.h"
  23
  24 /* This file is only useful if BREAKPOINT is set.  If not, we punt.  */
  25
  26 #include "symtab.h"
  27 #include "breakpoint.h"
  28 #include "inferior.h"
  29 #include "target.h"
  30
  31
  32 /* Use the program counter to determine the contents and size
  33    of a breakpoint instruction.  If no target-dependent macro
  34    BREAKPOINT_FROM_PC has been defined to implement this function,
  35    assume that the breakpoint doesn't depend on the PC, and
  36    use the values of the BIG_BREAKPOINT and LITTLE_BREAKPOINT macros.
  37    Return a pointer to a string of bytes that encode a breakpoint
  38    instruction, stores the length of the string to *lenptr,
  39    and optionally adjust the pc to point to the correct memory location
  40    for inserting the breakpoint.  */
  41
  42 unsigned char *
  43 memory_breakpoint_from_pc (pcptr, lenptr)
  44      CORE_ADDR *pcptr;
  45      int *lenptr;
  46 {
  47   /* {BIG_,LITTLE_}BREAKPOINT is the sequence of bytes we insert for a
  48      breakpoint.  On some machines, breakpoints are handled by the
  49      target environment and we don't have to worry about them here.  */
  50 #ifdef BIG_BREAKPOINT
  51   if (TARGET_BYTE_ORDER == BIG_ENDIAN)
  52     {
  53       static unsigned char big_break_insn[] = BIG_BREAKPOINT;
  54       *lenptr = sizeof (big_break_insn);
  55       return big_break_insn;
  56     }
  57 #endif
  58 #ifdef LITTLE_BREAKPOINT
  59   if (TARGET_BYTE_ORDER != BIG_ENDIAN)
  60     {
  61       static unsigned char little_break_insn[] = LITTLE_BREAKPOINT;
  62       *lenptr = sizeof (little_break_insn);
  63       return little_break_insn;
  64     }
  65 #endif
  66 #ifdef BREAKPOINT
  67   {
  68     static unsigned char break_insn[] = BREAKPOINT;
  69     *lenptr = sizeof (break_insn);
  70     return break_insn;
  71   }
  72 #endif
  73   *lenptr = 0;
  74   return NULL;
  75 }
  76
  77
  78 /* Insert a breakpoint on targets that don't have any better breakpoint
  79    support.  We read the contents of the target location and stash it,
  80    then overwrite it with a breakpoint instruction.  ADDR is the target
  81    location in the target machine.  CONTENTS_CACHE is a pointer to
  82    memory allocated for saving the target contents.  It is guaranteed
  83    by the caller to be long enough to save BREAKPOINT_LEN bytes (this
  84    is accomplished via BREAKPOINT_MAX).  */
  85
  86 int
  87 default_memory_insert_breakpoint (addr, contents_cache)
  88      CORE_ADDR addr;
  89      char *contents_cache;
  90 {
  91   int val;
  92   unsigned char *bp;
  93   int bplen;
  94
  95   /* Determine appropriate breakpoint contents and size for this address.  */
  96   bp = BREAKPOINT_FROM_PC (&addr, &bplen);
  97   if (bp == NULL)
  98     error ("Software breakpoints not implemented for this target.");
  99
 100   /* Save the memory contents.  */
 101   val = target_read_memory (addr, contents_cache, bplen);
 102
 103   /* Write the breakpoint.  */
 104   if (val == 0)
 105     val = target_write_memory (addr, (char *) bp, bplen);
 106
 107   return val;
 108 }
 109
 110
 111 int
 112 default_memory_remove_breakpoint (addr, contents_cache)
 113      CORE_ADDR addr;
 114      char *contents_cache;
 115 {
 116   unsigned char *bp;
 117   int bplen;
 118
 119   /* Determine appropriate breakpoint contents and size for this address.  */
 120   bp = BREAKPOINT_FROM_PC (&addr, &bplen);
 121   if (bp == NULL)
 122     error ("Software breakpoints not implemented for this target.");
 123
 124   return target_write_memory (addr, contents_cache, bplen);
 125 }
 126
 127
 128 #if !defined(MEMORY_INSERT_BREAKPOINT)
 129 #define MEMORY_INSERT_BREAKPOINT(addr, contents_cache) \
 130   default_memory_insert_breakpoint(addr, contents_cache)
 131 #endif
 132 int
 133 memory_insert_breakpoint (addr, contents_cache)
 134      CORE_ADDR addr;
 135      char *contents_cache;
 136 {
 137   return MEMORY_INSERT_BREAKPOINT(addr, contents_cache);
 138 }
 139
 140 #if !defined(MEMORY_REMOVE_BREAKPOINT)
 141 #define MEMORY_REMOVE_BREAKPOINT(addr, contents_cache) \
 142   default_memory_remove_breakpoint(addr, contents_cache)
 143 #endif
 144 int
 145 memory_remove_breakpoint (addr, contents_cache)
 146      CORE_ADDR addr;
 147      char *contents_cache;
 148 {
 149   return MEMORY_REMOVE_BREAKPOINT(addr, contents_cache);
 150 }