perf probe: Show accessible local variables

Add -V (--vars) option for listing accessible local variables at given probe
point. This will help finding which local variables are available for event
arguments.

e.g.)
 # perf probe -V call_timer_fn:23
 Available variables at call_timer_fn:23
         @<run_timer_softirq+345>
                 function_type*  fn
                 int     preempt_count
                 long unsigned int       data
                 struct list_head        work_list
                 struct list_head*       head
                 struct timer_list*      timer
                 struct tvec_base*       base

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20101021101323.3542.40282.stgit@ltc236.sdl.hitachi.co.jp>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

6 files changed, 480 insertions, 105 deletions

diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt
index 27d52dae5a4..72f5d9e2143 100644
--- a/tools/perf/Documentation/perf-probe.txt
+++ b/tools/perf/Documentation/perf-probe.txt
@@ -17,6 +17,8 @@ or
 'perf probe' --list
 or
 'perf probe' --line='FUNC[:RLN[+NUM|:RLN2]]|SRC:ALN[+NUM|:ALN2]'
+or
+'perf probe' --vars='PROBEPOINT'
 
 DESCRIPTION
 -----------
@@ -57,6 +59,11 @@ OPTIONS
         Show source code lines which can be probed. This needs an argument
         which specifies a range of the source code. (see LINE SYNTAX for detail)
 
+-V::
+--vars=::
+        Show available local variables at given probe point. The argument
+        syntax is same as PROBE SYNTAX, but NO ARGs.
+
 -f::
 --force::
         Forcibly add events with existing name.
diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
index 199d5e19554..91bb6cf4e02 100644
--- a/tools/perf/builtin-probe.c
+++ b/tools/perf/builtin-probe.c
@@ -50,6 +50,8 @@ static struct {
         bool list_events;
         bool force_add;
         bool show_lines;
+        bool show_vars;
+        bool mod_events;
         int nevents;
         struct perf_probe_event events[MAX_PROBES];
         struct strlist *dellist;
@@ -57,7 +59,6 @@ static struct {
         int max_probe_points;
 } params;
 
-
 /* Parse an event definition. Note that any error must die. */
 static int parse_probe_event(const char *str)
 {
@@ -92,6 +93,7 @@ static int parse_probe_event_argv(int argc, const char **argv)
         len = 0;
         for (i = 0; i < argc; i++)
                 len += sprintf(&buf[len], "%s ", argv[i]);
+        params.mod_events = true;
         ret = parse_probe_event(buf);
         free(buf);
         return ret;
@@ -100,9 +102,10 @@ static int parse_probe_event_argv(int argc, const char **argv)
 static int opt_add_probe_event(const struct option *opt __used,
                               const char *str, int unset __used)
 {
-        if (str)
+        if (str) {
+                params.mod_events = true;
                 return parse_probe_event(str);
-        else
+        } else
                 return 0;
 }
 
@@ -110,6 +113,7 @@ static int opt_del_probe_event(const struct option *opt __used,
                                const char *str, int unset __used)
 {
         if (str) {
+                params.mod_events = true;
                 if (!params.dellist)
                         params.dellist = strlist__new(true, NULL);
                 strlist__add(params.dellist, str);
@@ -130,6 +134,25 @@ static int opt_show_lines(const struct option *opt __used,
 
         return ret;
 }
+
+static int opt_show_vars(const struct option *opt __used,
+                         const char *str, int unset __used)
+{
+        struct perf_probe_event *pev = &params.events[params.nevents];
+        int ret;
+
+        if (!str)
+                return 0;
+
+        ret = parse_probe_event(str);
+        if (!ret && pev->nargs != 0) {
+                pr_err("  Error: '--vars' doesn't accept arguments.\n");
+                return -EINVAL;
+        }
+        params.show_vars = true;
+
+        return ret;
+}
 #endif
 
 static const char * const probe_usage[] = {
@@ -139,6 +162,7 @@ static const char * const probe_usage[] = {
         "perf probe --list",
 #ifdef DWARF_SUPPORT
         "perf probe --line 'LINEDESC'",
+        "perf probe --vars 'PROBEPOINT'",
 #endif
         NULL
 };
@@ -180,6 +204,9 @@ static const struct option options[] = {
         OPT_CALLBACK('L', "line", NULL,
                      "FUNC[:RLN[+NUM|-RLN2]]|SRC:ALN[+NUM|-ALN2]",
                      "Show source code lines.", opt_show_lines),
+        OPT_CALLBACK('V', "vars", NULL,
+                     "FUNC[@SRC][+OFF|%return|:RL|;PT]|SRC:AL|SRC;PT",
+                     "Show accessible variables on PROBEDEF", opt_show_vars),
         OPT_STRING('k', "vmlinux", &symbol_conf.vmlinux_name,
                    "file", "vmlinux pathname"),
         OPT_STRING('s', "source", &symbol_conf.source_prefix,
@@ -217,7 +244,7 @@ int cmd_probe(int argc, const char **argv, const char *prefix __used)
                 usage_with_options(probe_usage, options);
 
         if (params.list_events) {
-                if (params.nevents != 0 || params.dellist) {
+                if (params.mod_events) {
                         pr_err("  Error: Don't use --list with --add/--del.\n");
                         usage_with_options(probe_usage, options);
                 }
@@ -225,6 +252,10 @@ int cmd_probe(int argc, const char **argv, const char *prefix __used)
                         pr_err("  Error: Don't use --list with --line.\n");
                         usage_with_options(probe_usage, options);
                 }
+                if (params.show_vars) {
+                        pr_err(" Error: Don't use --list with --vars.\n");
+                        usage_with_options(probe_usage, options);
+                }
                 ret = show_perf_probe_events();
                 if (ret < 0)
                         pr_err("  Error: Failed to show event list. (%d)\n",
@@ -234,9 +265,13 @@ int cmd_probe(int argc, const char **argv, const char *prefix __used)
 
 #ifdef DWARF_SUPPORT
         if (params.show_lines) {
-                if (params.nevents != 0 || params.dellist) {
-                        pr_warning("  Error: Don't use --line with"
-                                   " --add/--del.\n");
+                if (params.mod_events) {
+                        pr_err("  Error: Don't use --line with"
+                               " --add/--del.\n");
+                        usage_with_options(probe_usage, options);
+                }
+                if (params.show_vars) {
+                        pr_err(" Error: Don't use --line with --vars.\n");
                         usage_with_options(probe_usage, options);
                 }
 
@@ -245,6 +280,18 @@ int cmd_probe(int argc, const char **argv, const char *prefix __used)
                         pr_err("  Error: Failed to show lines. (%d)\n", ret);
                 return ret;
         }
+        if (params.show_vars) {
+                if (params.mod_events) {