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>

1 files changed, 72 insertions, 0 deletions

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index fcc16e4349df..288ebe8279d2 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -378,6 +378,72 @@ end:
         return ret;
 }
 
+static int show_available_vars_at(int fd, struct perf_probe_event *pev,
+                                  int max_vls)
+{
+        char *buf;
+        int ret, i;
+        struct str_node *node;
+        struct variable_list *vls = NULL, *vl;
+
+        buf = synthesize_perf_probe_point(&pev->point);
+        if (!buf)
+                return -EINVAL;
+        pr_debug("Searching variables at %s\n", buf);
+
+        ret = find_available_vars_at(fd, pev, &vls, max_vls);
+        if (ret > 0) {
+                /* Some variables were found */
+                fprintf(stdout, "Available variables at %s\n", buf);
+                for (i = 0; i < ret; i++) {
+                        vl = &vls[i];
+                        /*
+                         * A probe point might be converted to
+                         * several trace points.
+                         */
+                        fprintf(stdout, "\t@<%s+%lu>\n", vl->point.symbol,
+                                vl->point.offset);
+                        free(vl->point.symbol);
+                        if (vl->vars) {
+                                strlist__for_each(node, vl->vars)
+                                        fprintf(stdout, "\t\t%s\n", node->s);
+                                strlist__delete(vl->vars);
+                        } else
+                                fprintf(stdout, "(No variables)\n");
+                }
+                free(vls);
+        } else
+                pr_err("Failed to find variables at %s (%d)\n", buf, ret);
+
+        free(buf);
+        return ret;
+}
+
+/* Show available variables on given probe point */
+int show_available_vars(struct perf_probe_event *pevs, int npevs,
+                        int max_vls)
+{
+        int i, fd, ret = 0;
+
+        ret = init_vmlinux();
+        if (ret < 0)
+                return ret;
+
+        fd = open_vmlinux();
+        if (fd < 0) {
+                pr_warning("Failed to open debuginfo file.\n");
+                return fd;
+        }
+
+        setup_pager();
+
+        for (i = 0; i < npevs && ret >= 0; i++)
+                ret = show_available_vars_at(fd, &pevs[i], max_vls);
+
+        close(fd);
+        return ret;
+}
+
 #else   /* !DWARF_SUPPORT */
 
 static int kprobe_convert_to_perf_probe(struct probe_trace_point *tp,
@@ -409,6 +475,12 @@ int show_line_range(struct line_range *lr __unused)
         return -ENOSYS;
 }
 
+int show_available_vars(struct perf_probe_event *pevs __unused,
+                        int npevs __unused, int max_probe_points __unused)
+{
+        pr_warning("Debuginfo-analysis is not supported.\n");
+        return -ENOSYS;
+}
 #endif
 
 int parse_line_range_desc(const char *arg, struct line_range *lr)