gdb/mem-break.c

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