perf probe: Warn if given uprobe event accesses memory on older kernel
authorMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Sat, 28 Feb 2015 02:53:29 +0000 (11:53 +0900)
committerArnaldo Carvalho de Melo <acme@redhat.com>
Mon, 2 Mar 2015 15:27:43 +0000 (12:27 -0300)
Warn if given uprobe event accesses memory on older kernel.

Until 3.14, uprobe event only supports accessing registers so this warns
to upgrade kernel if uprobe-event returns -EINVAL and an argument of the
event accesses memory ($stack, @+offset, and +|-offs() symtax).

With this patch (on 3.10.0-123.13.2.el7.x86_64);
  -----
  # ./perf probe -x ./perf warn_uprobe_event_compat stack=-0\(%sp\)
  Added new event:
  Failed to write event: Invalid argument
  Please upgrade your kernel to at least 3.14 to have access to feature -0(%sp)
    Error: Failed to add events.
  -----

Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20150228025329.32106.70581.stgit@localhost.localdomain
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
tools/perf/util/probe-event.c

index 7c0e765..1c570c2 100644 (file)
@@ -2199,6 +2199,27 @@ static int get_new_event_name(char *buf, size_t len, const char *base,
        return ret;
 }
 
+/* Warn if the current kernel's uprobe implementation is old */
+static void warn_uprobe_event_compat(struct probe_trace_event *tev)
+{
+       int i;
+       char *buf = synthesize_probe_trace_command(tev);
+
+       /* Old uprobe event doesn't support memory dereference */
+       if (!tev->uprobes || tev->nargs == 0 || !buf)
+               goto out;
+
+       for (i = 0; i < tev->nargs; i++)
+               if (strglobmatch(tev->args[i].value, "[$@+-]*")) {
+                       pr_warning("Please upgrade your kernel to at least "
+                                  "3.14 to have access to feature %s\n",
+                                  tev->args[i].value);
+                       break;
+               }
+out:
+       free(buf);
+}
+
 static int __add_probe_trace_events(struct perf_probe_event *pev,
                                     struct probe_trace_event *tevs,
                                     int ntevs, bool allow_suffix)
@@ -2295,6 +2316,8 @@ static int __add_probe_trace_events(struct perf_probe_event *pev,
                 */
                allow_suffix = true;
        }
+       if (ret == -EINVAL && pev->uprobes)
+               warn_uprobe_event_compat(tev);
 
        /* Note that it is possible to skip all events because of blacklist */
        if (ret >= 0 && tev->event) {