[PATCH V3 3/9] New commands `enable probe' and `disable probe'.

This patch adds the above-mentioned commands to the generic probe
abstraction implemented in probe.[ch].  The effects associated to
enabling or disabling a probe depend on the type of probe being
handled, and is triggered by invoking two back-end hooks in
`probe_ops'.

In case some particular probe type does not support the notion of
enabling and/or disabling, the corresponding fields on `probe_ops' can
be initialized to NULL.  This is the case of SystemTap probes.

gdb/ChangeLog:

  2014-10-28  Jose E. Marchesi  <[email protected]>

    	* stap-probe.c (stap_probe_ops): Add NULLs in the static
    	stap_probe_ops for `enable_probe' and `disable_probe'.
    	* probe.c (enable_probes_command): New function.
    	(disable_probes_command): Likewise.
    	(_initialize_probe): Define the cli commands `enable probe' and
    	`disable probe'.
    	(parse_probe_linespec): New function.
    	(info_probes_for_ops): Use parse_probe_linespec.
    	* probe.h (probe_ops): New hooks `enable_probe' and
    	`disable_probe'.

gdb/doc/ChangeLog:

  2014-10-28  Jose E. Marchesi  <[email protected]>

  	* gdb.texinfo (Static Probe Points): Cover the `enable probe' and
	  `disable probe' commands.
---
 gdb/ChangeLog       |   13 +++++
 gdb/doc/ChangeLog   |    5 ++
 gdb/doc/gdb.texinfo |   29 ++++++++++
 gdb/probe.c         |  161 ++++++++++++++++++++++++++++++++++++++++++++-------
 gdb/probe.h         |   12 ++++
 gdb/stap-probe.c    |    2 +
 6 files changed, 202 insertions(+), 20 deletions(-)

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 15c2908..cfdc506 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -4976,6 +4976,35 @@ given, all object files are considered.
 List the available static probes, from all types.
 @end table
 
+@cindex enabling and disabling probes
+Some probe points can be enabled and/or disabled.  The effect of
+enabling or disabling a probe depends on the type of probe being
+handled.  @code{SystemTap} probes cannot be disabled.
+
+You can enable (or disable) one or more probes using the following
+commands, with optional arguments:
+
+@table @code
+@kindex enable probes
+@item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
+If given, @var{provider} is a regular expression used to match against
+provider names when selecting which probes to enable.  If omitted,
+all probes from all providers are enabled.
+
+If given, @var{name} is a regular expression to match against probe
+names when selecting which probes to enable.  If omitted, probe names
+are not considered when deciding whether to enable them.
+
+If given, @var{objfile} is a regular expression used to select which
+object files (executable or shared libraries) to examine.  If not
+given, all object files are considered.
+
+@kindex disable probes
+@item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
+See the @code{enable probes} command above for a description of the
+optional arguments accepted by this command.
+@end table
+
 @vindex $_probe_arg@r{, convenience variable}
 A probe may specify up to twelve arguments.  These are available at the
 point at which the probe is defined---that is, when the current PC is
diff --git a/gdb/probe.c b/gdb/probe.c
index 102c2e1..b96c8ac 100644
--- a/gdb/probe.c
+++ b/gdb/probe.c
@@ -423,18 +423,18 @@ print_ui_out_not_applicables (const struct probe_ops *pops)
   VEC (info_probe_column_s) *headings = NULL;
   info_probe_column_s *column;
   int ix;
-  
+
   if (pops->gen_info_probes_table_header == NULL)
     return;
 
   c = make_cleanup (VEC_cleanup (info_probe_column_s), &headings);
   pops->gen_info_probes_table_header (&headings);
-  
+
   for (ix = 0;
        VEC_iterate (info_probe_column_s, headings, ix, column);
        ++ix)
     ui_out_field_string (current_uiout, column->field_name, _("n/a"));
-  
+
   do_cleanups (c);
 }
 
@@ -527,6 +527,24 @@ exists_probe_with_pops (VEC (bound_probe_s) *probes,
   return 0;
 }
 
+/* Helper function that parses a probe linespec of the form [PROVIDER
+   [PROBE [OBJNAME]]] from the provided string STR.  */
+
+static void
+parse_probe_linespec (const char *str, char **provider,
+		      char **probe_name, char **objname)
+{
+  *probe_name = *objname = NULL;
+
+  *provider = extract_arg_const (&str);
+  if (*provider != NULL)
+    {
+      *probe_name = extract_arg_const (&str);
+      if (*probe_name != NULL)
+	*objname = extract_arg_const (&str);
+    }
+}
+
 /* See comment in probe.h.  */
 
 void
@@ -546,26 +564,14 @@ info_probes_for_ops (const char *arg, int from_tty,
   struct bound_probe *probe;
   struct gdbarch *gdbarch = get_current_arch ();
 
-  /* Do we have a `provider:probe:objfile' style of linespec?  */
-  provider = extract_arg_const (&arg);
-  if (provider)
-    {
-      make_cleanup (xfree, provider);
-
-      probe_name = extract_arg_const (&arg);
-      if (probe_name)
-	{
-	  make_cleanup (xfree, probe_name);
-
-	  objname = extract_arg_const (&arg);
-	  if (objname)
-	    make_cleanup (xfree, objname);
-	}
-    }
+  parse_probe_linespec (arg, &provider, &probe_name, &objname);
+  make_cleanup (xfree, provider);
+  make_cleanup (xfree, probe_name);
+  make_cleanup (xfree, objname);
 
   probes = collect_probes (objname, provider, probe_name, pops);
   make_cleanup (VEC_cleanup (probe_p), &probes);
-  
+
   if (pops == NULL)
     {
       const struct probe_ops *po;
@@ -689,6 +695,98 @@ info_probes_command (char *arg, int from_tty)
   info_probes_for_ops (arg, from_tty, NULL);
 }
 
+/* Implementation of the `enable probes' command.  */
+
+static void
+enable_probes_command (char *arg, int from_tty)
+{
+  char *provider, *probe_name = NULL, *objname = NULL;
+  struct cleanup *cleanup = make_cleanup (null_cleanup, NULL);
+  VEC (bound_probe_s) *probes;
+  struct bound_probe *probe;
+  int i;
+
+  parse_probe_linespec ((const char *) arg, &provider, &probe_name, &objname);
+  make_cleanup (xfree, provider);
+  make_cleanup (xfree, probe_name);
+  make_cleanup (xfree, objname);
+
+  probes = collect_probes (objname, provider, probe_name, NULL);
+  if (VEC_empty (bound_probe_s, probes))
+    {
+      ui_out_message (current_uiout, 0, _("No probes matched.\n"));
+      do_cleanups (cleanup);
+      return;
+    }
+
+  /* Enable the selected probes, provided their backends support the
+     notion of enabling a probe.  */
+  for (i = 0; VEC_iterate (bound_probe_s, probes, i, probe); ++i)
+    {
+      const struct probe_ops *pops = probe->probe->pops;
+
+      if (pops->enable_probe != NULL)
+	{
+	  pops->enable_probe (probe->probe);
+	  ui_out_message (current_uiout, 0,
+			  _("Probe %s:%s enabled.\n"),
+			  probe->probe->provider, probe->probe->name);
+	}
+      else
+	ui_out_message (current_uiout, 0,
+			_("Probe %s:%s cannot be enabled.\n"),
+			probe->probe->provider, probe->probe->name);
+    }
+
+  do_cleanups (cleanup);
+}
+
+/* Implementation of the `disable probes' command.  */
+
+static void
+disable_probes_command (char *arg, int from_tty)
+{
+  char *provider, *probe_name = NULL, *objname = NULL;
+  struct cleanup *cleanup = make_cleanup (null_cleanup, NULL);
+  VEC (bound_probe_s) *probes;
+  struct bound_probe *probe;
+  int i;
+
+  parse_probe_linespec ((const char *) arg, &provider, &probe_name, &objname);
+  make_cleanup (xfree, provider);
+  make_cleanup (xfree, probe_name);
+  make_cleanup (xfree, objname);
+
+  probes = collect_probes (objname, provider, probe_name, NULL /* pops */);
+  if (VEC_empty (bound_probe_s, probes))
+    {
+      ui_out_message (current_uiout, 0, _("No probes matched.\n"));
+      do_cleanups (cleanup);
+      return;
+    }
+
+  /* Disable the selected probes, provided their backends support the
+     notion of enabling a probe.  */
+  for (i = 0; VEC_iterate (bound_probe_s, probes, i, probe); ++i)
+    {
+      const struct probe_ops *pops = probe->probe->pops;
+
+      if (pops->disable_probe != NULL)
+	{
+	  pops->disable_probe (probe->probe);
+	  ui_out_message (current_uiout, 0,
+			  _("Probe %s:%s disabled.\n"),
+			  probe->probe->provider, probe->probe->name);
+	}
+      else
+	ui_out_message (current_uiout, 0,
+			_("Probe %s:%s cannot be disabled.\n"),
+			probe->probe->provider, probe->probe->name);
+    }
+
+  do_cleanups (cleanup);
+}
+
 /* See comments in probe.h.  */
 
 CORE_ADDR
@@ -950,4 +1048,27 @@ _initialize_probe (void)
 	   _("\
 Show information about all type of probes."),
 	   info_probes_cmdlist_get ());
+
+  add_cmd ("probes", class_breakpoint, enable_probes_command, _("\
+Enable probes.\n\
+Usage: enable probes [PROVIDER [NAME [OBJECT]]]\n\
+Each argument is a regular expression, used to select probes.\n\
+PROVIDER matches probe provider names.\n\
+NAME matches the probe names.\n\
+OBJECT matches the executable or shared library name.\n\
+If you do not specify any argument then the command will enable\n\
+all defined probes."),
+	   &enablelist);
+
+  add_cmd ("probes", class_breakpoint, disable_probes_command, _("\
+Disable probes.\n\
+Usage: disable probes [PROVIDER [NAME [OBJECT]]]\n\
+Each argument is a regular expression, used to select probes.\n\
+PROVIDER matches probe provider names.\n\
+NAME matches the probe names.\n\
+OBJECT matches the executable or shared library name.\n\
+If you do not specify any argument then the command will disable\n\
+all defined probes."),
+	   &disablelist);
+
 }
diff --git a/gdb/probe.h b/gdb/probe.h
index 66c8c53..c244a21 100644
--- a/gdb/probe.h
+++ b/gdb/probe.h
@@ -138,6 +138,18 @@ struct probe_ops
 
     void (*gen_info_probes_table_values) (struct probe *probe,
 					  VEC (const_char_ptr) **values);
+
+    /* Enable a probe.  The semantics of "enabling" a probe depend on
+       the specific backend and the field can be NULL in case enabling
+       probes is not supported.  */
+
+    void (*enable_probe) (struct probe *probe);
+
+    /* Disable a probe.  The semantics of "disabling" a probe depend
+       on the specific backend and the field can be NULL in case
+       disabling probes is not supported.  */
+
+    void (*disable_probe) (struct probe *probe);
   };
 
 /* Definition of a vector of probe_ops.  */
diff --git a/gdb/stap-probe.c b/gdb/stap-probe.c
index ed4ce69..8366ce2 100644
--- a/gdb/stap-probe.c
+++ b/gdb/stap-probe.c
@@ -1684,6 +1684,8 @@ static const struct probe_ops stap_probe_ops =
   stap_type_name,
   stap_gen_info_probes_table_header,
   stap_gen_info_probes_table_values,
+  NULL,  /* enable_probe  */
+  NULL   /* disable_probe  */
 };
 
 /* Implementation of the `info probes stap' command.  */
-- 
1.7.10.4