Index: breakpoint.c
===================================================================
RCS file: /cvs/src/src/gdb/breakpoint.c,v
retrieving revision 1.484
diff -p -r1.484 breakpoint.c
*** breakpoint.c	19 Apr 2010 00:48:43 -0000	1.484
--- breakpoint.c	24 Apr 2010 00:51:15 -0000
*************** static int prev_breakpoint_count;
*** 416,421 ****
--- 416,430 ----
  
  static int tracepoint_count;
  
+ /* This is true if we want to send the original program code that will
+    be overwritten by a tracepoint.  This can happen with JIT code that
+    changes the program code between tracepoint definition and trace
+    run.  We default to 1 so that tracepoint definition at startup does
+    record the original code, and expect targets that don't want this
+    in their tracepoint definitions to turn it off.  */
+ 
+ int check_original_contents = 1;
+ 
  static struct cmd_list_element *breakpoint_set_cmdlist;
  static struct cmd_list_element *breakpoint_show_cmdlist;
  static struct cmd_list_element *save_cmdlist;
*************** set_raw_breakpoint (struct gdbarch *gdba
*** 5481,5486 ****
--- 5490,5498 ----
    struct breakpoint *b = set_raw_breakpoint_without_location (gdbarch, bptype);
    CORE_ADDR adjusted_address;
    struct gdbarch *loc_gdbarch;
+   int orig_len = 0;
+   gdb_byte orig[BREAKPOINT_MAX];
+   int err;
  
    loc_gdbarch = get_sal_arch (sal);
    if (!loc_gdbarch)
*************** set_raw_breakpoint (struct gdbarch *gdba
*** 5497,5502 ****
--- 5509,5523 ----
       location that's only been partially initialized.  */
    adjusted_address = adjust_breakpoint_address (loc_gdbarch, sal.pc, b->type);
  
+   if (check_original_contents)
+     {
+       orig_len = (b->type == bp_fast_tracepoint ? 5 : 1);  /* x86-only */
+       err = target_read_memory (adjusted_address, orig, orig_len);
+       /* If we can't read memory, just give up on this feature.  */
+       if (err)
+ 	orig_len = 0;
+     }
+ 
    b->loc = allocate_bp_location (b);
    b->loc->gdbarch = loc_gdbarch;
    b->loc->requested_address = sal.pc;
*************** set_raw_breakpoint (struct gdbarch *gdba
*** 5516,5521 ****
--- 5537,5549 ----
  
    set_breakpoint_location_function (b->loc);
  
+   /* Save the bytes that we are expecting to replace.  */
+   if (check_original_contents && orig_len)
+     {
+       b->loc->orig_len = orig_len;
+       memcpy (b->loc->orig_contents, orig, orig_len);
+     }
+ 
    breakpoints_changed ();
  
    return b;
*************** add_location_to_breakpoint (struct break
*** 6793,6798 ****
--- 6821,6838 ----
    loc->section = sal->section;
  
    set_breakpoint_location_function (loc);
+ 
+   /* Maybe try to collect bytes at the location.  */
+   if (check_original_contents)
+     {
+       int err;
+       loc->orig_len = (b->type == bp_fast_tracepoint ? 5 : 1); /* x86-only */
+       err = target_read_memory (loc->address, loc->orig_contents,
+ 				loc->orig_len);
+       if (err)
+ 	loc->orig_len = 0;
+     }
+ 
    return loc;
  }
  
Index: breakpoint.h
===================================================================
RCS file: /cvs/src/src/gdb/breakpoint.h,v
retrieving revision 1.118
diff -p -r1.118 breakpoint.h
*** breakpoint.h	19 Apr 2010 00:48:43 -0000	1.118
--- breakpoint.h	24 Apr 2010 00:51:16 -0000
*************** struct bp_location
*** 331,336 ****
--- 331,344 ----
       This variable keeps a number of events still to go, when
       it becomes 0 this location is retired.  */
    int events_till_retirement;
+ 
+   /* For targets that have JITs that can change code between definition
+      time and execution time (for either breakpoints or tracepoints),
+      this is a copy of memory at the time the breakpoint was defined.  */
+   gdb_byte orig_contents[BREAKPOINT_MAX];
+ 
+   /* This is the number of bytes in orig_contents.  */
+   int orig_len;
  };
  
  /* This structure is a collection of function pointers that, if available,
Index: remote.c
===================================================================
RCS file: /cvs/src/src/gdb/remote.c,v
retrieving revision 1.402
diff -p -r1.402 remote.c
*** remote.c	16 Apr 2010 07:49:35 -0000	1.402
--- remote.c	24 Apr 2010 00:51:16 -0000
*************** enum {
*** 1153,1158 ****
--- 1153,1159 ----
    PACKET_bc,
    PACKET_bs,
    PACKET_TracepointSource,
+   PACKET_CheckOriginalContents,
    PACKET_MAX
  };
  
*************** remote_start_remote (struct ui_out *uiou
*** 2956,2961 ****
--- 2957,2965 ----
       which later probes to skip.  */
    remote_query_supported ();
  
+   /* Only do the original contents check if the target wants it.  */
+   check_original_contents = (remote_protocol_packets[PACKET_CheckOriginalContents].support == PACKET_ENABLE);
+ 
    /* Next, we possibly activate noack mode.
  
       If the QStartNoAckMode packet configuration is set to AUTO,
*************** static struct protocol_feature remote_pr
*** 3462,3467 ****
--- 3466,3473 ----
      PACKET_bs },
    { "TracepointSource", PACKET_DISABLE, remote_supported_packet,
      PACKET_TracepointSource },
+   { "CheckOriginalContents", PACKET_DISABLE, remote_supported_packet,
+     PACKET_CheckOriginalContents },
  };
  
  static char *remote_support_xml;
*************** remote_download_tracepoint (struct break
*** 9476,9481 ****
--- 9482,9492 ----
  	  else
  	    warning (_("Target does not support conditional tracepoints, ignoring tp %d cond"), t->number);
  	}
+       if (check_original_contents && loc->orig_len > 0)
+ 	{
+ 	  sprintf (buf + strlen (buf), ":W%x,", loc->orig_len);
+ 	  bin2hex (loc->orig_contents, buf + strlen (buf), loc->orig_len);
+ 	}
  
    if (t->commands || *default_collect)
  	strcat (buf, "-");
*************** Show the maximum size of the address (in
*** 10415,10426 ****
--- 10426,10441 ----
  
    add_packet_config_cmd (&remote_protocol_packets[PACKET_ConditionalTracepoints],
  			 "ConditionalTracepoints", "conditional-tracepoints", 0);
+ 
    add_packet_config_cmd (&remote_protocol_packets[PACKET_FastTracepoints],
  			 "FastTracepoints", "fast-tracepoints", 0);
  
    add_packet_config_cmd (&remote_protocol_packets[PACKET_TracepointSource],
  			 "TracepointSource", "TracepointSource", 0);
  
+   add_packet_config_cmd (&remote_protocol_packets[PACKET_CheckOriginalContents],
+ 			 "CheckOriginalContents", "CheckOriginalContents", 0);
+ 
    /* Keep the old ``set remote Z-packet ...'' working.  Each individual
       Z sub-packet has its own set and show commands, but users may
       have sets to this variable in their .gdbinit files (or in their
Index: tracepoint.h
===================================================================
RCS file: /cvs/src/src/gdb/tracepoint.h,v
retrieving revision 1.35
diff -p -r1.35 tracepoint.h
*** tracepoint.h	9 Apr 2010 03:00:58 -0000	1.35
--- tracepoint.h	24 Apr 2010 00:51:16 -0000
*************** extern void tfind_1 (enum trace_find_typ
*** 215,218 ****
--- 215,220 ----
  
  extern void trace_save (const char *filename, int target_does_save);
  
+ extern int check_original_contents;
+ 
  #endif	/* TRACEPOINT_H */
Index: doc/gdb.texinfo
===================================================================
RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
retrieving revision 1.713
diff -p -r1.713 gdb.texinfo
*** doc/gdb.texinfo	23 Apr 2010 16:20:10 -0000	1.713
--- doc/gdb.texinfo	24 Apr 2010 00:51:17 -0000
*************** These are the currently defined stub fea
*** 31278,31283 ****
--- 31278,31288 ----
  @tab @samp{-}
  @tab No
  
+ @item @samp{CheckOriginalContents}
+ @tab No
+ @tab @samp{-}
+ @tab No
+ 
  @end multitable
  
  These are the currently defined stub features, in more detail:
*************** The remote stub accepts and implements t
*** 31375,31380 ****
--- 31380,31394 ----
  The remote stub understands the @samp{QTDPsrc} packet that supplies
  the source form of tracepoint definitions.
  
+ @item CheckOriginalContents
+ If @value{GDBN} adds an optional @samp{W} field to tracepoint
+ definition packets, the target will check that the current program
+ code matches the supplied value of the field; if they do not match, it
+ will reply with an error and cancel the trace run.  This is useful in
+ cases where a JIT or other dynamic code-changing mechanism may
+ invalidate the tracepoint definition between the time of its
+ definition and the tstart command.
+ 
  @end table
  
  @item qSymbol::
*************** tracepoints (@pxref{Tracepoints}).
*** 31734,31740 ****
  
  @table @samp
  
! @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
  Create a new tracepoint, number @var{n}, at @var{addr}.  If @var{ena}
  is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
  the tracepoint is disabled.  @var{step} is the tracepoint's step
--- 31748,31754 ----
  
  @table @samp
  
! @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}:@var{options}@r{]}@r{[}-@r{]}
  Create a new tracepoint, number @var{n}, at @var{addr}.  If @var{ena}
  is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
  the tracepoint is disabled.  @var{step} is the tracepoint's step
*************** encodings as described below.  If the tr
*** 31748,31753 ****
--- 31762,31790 ----
  further @samp{QTDP} packets will follow to specify this tracepoint's
  actions.
  
+ Additional optional fields @var{options} may be supplied.  They are
+ colon-separated, and distinguished by a letter.
+ 
+ @table @samp
+ 
+ @item F@var{n}
+ The tracepoint is to be a fast tracepoint, and @var{n} bytes of
+ program code (typically the length of one instruction replaced by the
+ tracepoint) are to be copied elsewhere.
+ 
+ @item W@var{n},@var{bytes}
+ The bytes in the hex-encoded sequence @var{bytes} (length @var{n}, a
+ hexadecimal number) are the original program bytes present at the
+ tracepoint address.  This is useful for checking that a JIT or other
+ dynamic loading mechanism has not silently invalidated the tracepoint.
+ 
+ @item X@var{n},@var{bytes}
+ Defines a tracepoint condition, which consists of a hexadecimal
+ length, followed by a comma and hex-encoded bytes, in a manner similar
+ to action encodings as described below.
+ 
+ @end table
+ 
  Replies:
  @table @samp
  @item OK