Re: PATCH : allow to set length of hw watchpoints (e.g. for Valgrind gdbserver)

["Philippe Waroquiers" <philippe dot waroquiers at skynet dot be>]

Thanks for the quick review.
Find below a new version of the patch (also in attachment).

> If this is accepted, I think this is NEWS worthy.
Added a paragraph to describe this. 

> I think we should tell explicitly that the limit is in bytes.  (Btw,
> why the corresponding data types are `int' and not `ssize_t'?)
Added 'in bytes' in the doc and in the on-line command description.
Note that I have kept 'int' as all other similar variables are int, and an int
will be large enough for any reasonable watchpoint.

> Also, I think we also document the "show" counterpart of each "set"
> command.
Done.

2011-05-14  Philippe Waroquiers <philippe.waroquiers@skynet.be>
* remote.c (remote_region_ok_for_hw_watchpoint): New function.
(remote_hw_watchpoint_length_limit): New variable.
(_initialize_remote) add set,show cmds for this new variable.
gdb.texinfo: document these new commands.
NEWS: document the change.

Index: gdb/NEWS
===================================================================
RCS file: /cvs/src/src/gdb/NEWS,v
retrieving revision 1.441
diff -c -p -r1.441 NEWS
*** gdb/NEWS 13 May 2011 22:36:06 -0000 1.441
--- gdb/NEWS 15 May 2011 19:51:54 -0000
***************
*** 3,8 ****
--- 3,18 ----
 
 *** Changes since GDB 7.3
 
+ * GDB has two new commands: "set remote hardware-watchpoint-length-limit"
+   and "show remote hardware-watchpoint-length-limit". These allows to
+   set or show the maximum length limit (in bytes) of a remote
+   target hardware watchpoint.
+ 
+   This allows e.g. to use "unlimited" hardware watchpoints with the
+   gdbserver integrated in Valgrind version >= 3.7.0. Such Valgrind
+   watchpoints are slower than real hardware watchpoints but are
+   significantly faster than gdb software watchpoints.
+ 
 * libthread-db-search-path now supports two special values: $sdir and $pdir.
   $sdir specifies the default system locations of shared libraries.
   $pdir specifies the directory where the libpthread used by the application
Index: gdb/remote.c
===================================================================
RCS file: /cvs/src/src/gdb/remote.c,v
retrieving revision 1.446
diff -c -p -r1.446 remote.c
*** gdb/remote.c 12 May 2011 12:09:16 -0000 1.446
--- gdb/remote.c 15 May 2011 19:52:00 -0000
*************** remote_remove_watchpoint (CORE_ADDR addr
*** 7756,7764 ****
--- 7756,7778 ----
 
 
 int remote_hw_watchpoint_limit = -1;
+ int remote_hw_watchpoint_length_limit = -1;
 int remote_hw_breakpoint_limit = -1;
 
 static int
+ remote_region_ok_for_hw_watchpoint (CORE_ADDR addr, int len)
+ {
+   if (remote_hw_watchpoint_length_limit == 0)
+     return 0;
+   else if (remote_hw_watchpoint_length_limit < 0)
+     return 1;
+   else if (len <= remote_hw_watchpoint_length_limit)
+     return 1;
+   else
+     return 0;
+ }
+ 
+ static int
 remote_check_watch_resources (int type, int cnt, int ot)
 {
   if (type == bp_hardware_breakpoint)
*************** Specify the serial device it is connecte
*** 10326,10331 ****
--- 10340,10347 ----
   remote_ops.to_can_use_hw_breakpoint = remote_check_watch_resources;
   remote_ops.to_insert_hw_breakpoint = remote_insert_hw_breakpoint;
   remote_ops.to_remove_hw_breakpoint = remote_remove_hw_breakpoint;
+   remote_ops.to_region_ok_for_hw_watchpoint
+      = remote_region_ok_for_hw_watchpoint;
   remote_ops.to_insert_watchpoint = remote_insert_watchpoint;
   remote_ops.to_remove_watchpoint = remote_remove_watchpoint;
   remote_ops.to_kill = remote_kill;
*************** Specify a negative limit for unlimited."
*** 10735,10740 ****
--- 10751,10765 ----
         number of target hardware
         watchpoints is %s.  */
        &remote_set_cmdlist, &remote_show_cmdlist);
+   add_setshow_zinteger_cmd ("hardware-watchpoint-length-limit", no_class,
+        &remote_hw_watchpoint_length_limit, _("\
+ Set the maximum length (in bytes) of a target hardware watchpoint."), _("\
+ Show the maximum length (in bytes) of a target hardware watchpoint."), _("\
+ Specify a negative limit for unlimited."),
+        NULL, NULL, /* FIXME: i18n: The maximum
+                                            length (in bytes) of a target
+                                            hardware watchpoint is %s.  */
+        &remote_set_cmdlist, &remote_show_cmdlist);
   add_setshow_zinteger_cmd ("hardware-breakpoint-limit", no_class,
        &remote_hw_breakpoint_limit, _("\
 Set the maximum number of target hardware breakpoints."), _("\
Index: gdb/doc/gdb.texinfo
===================================================================
RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
retrieving revision 1.838
diff -c -p -r1.838 gdb.texinfo
*** gdb/doc/gdb.texinfo 13 May 2011 22:36:07 -0000 1.838
--- gdb/doc/gdb.texinfo 15 May 2011 19:52:25 -0000
*************** responses.
*** 16578,16583 ****
--- 16578,16595 ----
 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
 watchpoints.  A limit of -1, the default, is treated as unlimited.
 
+ @cindex limit hardware watchpoints length
+ @cindex remote target, limit watchpoints length
+ @anchor{set remote hardware-watchpoint-length-limit}
+ @item set remote hardware-watchpoint-length-limit @var{limit}
+ Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
+ a remote hardware watchpoint.  A limit of -1, the default, is treated
+ as unlimited.
+ 
+ @item show remote hardware-watchpoint-length-limit
+ Show the current limit (in bytes) of the maximum length of
+ a remote hardware watchpoint.
+ 
 @item set remote exec-file @var{filename}
 @itemx show remote exec-file
 @anchor{set remote exec-file}

Attachment: set-length-limit-3.desc.txt
Description: Text document