Merge GDB 7.5.1

gdb/mem-break.c

 /* Simulate breakpoints by patching locations in the target system, for GDB.
 
    Copyright (C) 1990-1993, 1995, 1997-2000, 2002, 2007-2012 Free
    Software Foundation, Inc.
 
    Contributed by Cygnus Support.  Written by John Gilmore.
 
    This file is part of GDB.
 
    This program is free software; you can redistribute it and/or modify
@@ skipping 11 matching lines @@
 
 #include "defs.h"
 
 /* This file is only useful if BREAKPOINT_FROM_PC is set.  If not, we
    punt.  */
 
 #include "symtab.h"
 #include "breakpoint.h"
 #include "inferior.h"
 #include "target.h"
+#include "gdb_string.h"
 
 
 /* Insert a breakpoint on targets that don't have any better
    breakpoint support.  We read the contents of the target location
    and stash it, then overwrite it with a breakpoint instruction.
    BP_TGT->placed_address is the target location in the target
    machine.  BP_TGT->shadow_contents is some memory allocated for
    saving the target contents.  It is guaranteed by the caller to be
    long enough to save BREAKPOINT_LEN bytes (this is accomplished via
    BREAKPOINT_MAX).  */
 
 int
 default_memory_insert_breakpoint (struct gdbarch *gdbarch,
                                   struct bp_target_info *bp_tgt)
 {
   int val;
   const unsigned char *bp;
+  gdb_byte *readbuf;
 
   /* Determine appropriate breakpoint contents and size for this address.  */
   bp = gdbarch_breakpoint_from_pc
        (gdbarch, &bp_tgt->placed_address, &bp_tgt->placed_size);
   if (bp == NULL)
     error (_("Software breakpoints not implemented for this target."));
 
-  /* Save the memory contents.  */
+  /* Save the memory contents in the shadow_contents buffer and then
+     write the breakpoint instruction.  */
   bp_tgt->shadow_len = bp_tgt->placed_size;
-  val = target_read_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
+  readbuf = alloca (bp_tgt->placed_size);
+  val = target_read_memory (bp_tgt->placed_address, readbuf,
                             bp_tgt->placed_size);
-
-  /* Write the breakpoint.  */
   if (val == 0)
-    val = target_write_raw_memory (bp_tgt->placed_address, bp,
-                                   bp_tgt->placed_size);
+    {
+      memcpy (bp_tgt->shadow_contents, readbuf, bp_tgt->placed_size);
+      val = target_write_raw_memory (bp_tgt->placed_address, bp,
+                                     bp_tgt->placed_size);
+    }
 
   return val;
 }
 
 
 int
 default_memory_remove_breakpoint (struct gdbarch *gdbarch,
                                   struct bp_target_info *bp_tgt)
 {
   return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
                                   bp_tgt->placed_size);
 }
 
 
 int
 memory_insert_breakpoint (struct gdbarch *gdbarch,
                           struct bp_target_info *bp_tgt)
 {
   return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt);
 }
 
 int
 memory_remove_breakpoint (struct gdbarch *gdbarch,
                           struct bp_target_info *bp_tgt)
 {
   return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt);
 }