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 (CORE_ADDR *pcptr, int *lenptr)
  44 {
  45   /* {BIG_,LITTLE_}BREAKPOINT is the sequence of bytes we insert for a
  46      breakpoint.  On some machines, breakpoints are handled by the
  47      target environment and we don't have to worry about them here.  */
  48 #ifdef BIG_BREAKPOINT
  49   if (TARGET_BYTE_ORDER == BIG_ENDIAN)
  50     {
  51       static unsigned char big_break_insn[] = BIG_BREAKPOINT;
  52       *lenptr = sizeof (big_break_insn);
  53       return big_break_insn;
  54     }
  55 #endif
  56 #ifdef LITTLE_BREAKPOINT
  57   if (TARGET_BYTE_ORDER != BIG_ENDIAN)
  58     {
  59       static unsigned char little_break_insn[] = LITTLE_BREAKPOINT;
  60       *lenptr = sizeof (little_break_insn);
  61       return little_break_insn;
  62     }
  63 #endif
  64 #ifdef BREAKPOINT
  65   {
  66     static unsigned char break_insn[] = BREAKPOINT;
  67     *lenptr = sizeof (break_insn);
  68     return break_insn;
  69   }
  70 #endif
  71   *lenptr = 0;
  72   return NULL;
  73 }
  74
  75
  76 /* Insert a breakpoint on targets that don't have any better breakpoint
  77    support.  We read the contents of the target location and stash it,
  78    then overwrite it with a breakpoint instruction.  ADDR is the target
  79    location in the target machine.  CONTENTS_CACHE is a pointer to
  80    memory allocated for saving the target contents.  It is guaranteed
  81    by the caller to be long enough to save BREAKPOINT_LEN bytes (this
  82    is accomplished via BREAKPOINT_MAX).  */
  83
  84 int
  85 default_memory_insert_breakpoint (CORE_ADDR addr, char *contents_cache)
  86 {
  87   int val;
  88   unsigned char *bp;
  89   int bplen;
  90
  91   /* Determine appropriate breakpoint contents and size for this address.  */
  92   bp = BREAKPOINT_FROM_PC (&addr, &bplen);
  93   if (bp == NULL)
  94     error ("Software breakpoints not implemented for this target.");
  95
  96   /* Save the memory contents.  */
  97   val = target_read_memory (addr, contents_cache, bplen);
  98
  99   /* Write the breakpoint.  */
 100   if (val == 0)
 101     val = target_write_memory (addr, (char *) bp, bplen);
 102
 103   return val;
 104 }
 105
 106
 107 int
 108 default_memory_remove_breakpoint (CORE_ADDR addr, char *contents_cache)
 109 {
 110   unsigned char *bp;
 111   int bplen;
 112
 113   /* Determine appropriate breakpoint contents and size for this address.  */
 114   bp = BREAKPOINT_FROM_PC (&addr, &bplen);
 115   if (bp == NULL)
 116     error ("Software breakpoints not implemented for this target.");
 117
 118   return target_write_memory (addr, contents_cache, bplen);
 119 }
 120
 121
 122 int
 123 memory_insert_breakpoint (CORE_ADDR addr, char *contents_cache)
 124 {
 125   return MEMORY_INSERT_BREAKPOINT(addr, contents_cache);
 126 }
 127
 128 int
 129 memory_remove_breakpoint (CORE_ADDR addr, char *contents_cache)
 130 {
 131   return MEMORY_REMOVE_BREAKPOINT(addr, contents_cache);
 132 }