tracing: Add hist trigger 'execname' modifier

Allow users to have common_pid field values displayed as program names
in the output by appending '.execname' to a common_pid field name:

   # echo hist:keys=common_pid.execname ... \
              [ if filter] > event/trigger

Link: http://lkml.kernel.org/r/e172e81f10f5b8d1f08450e3763c850f39fbf698.1457029949.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 34459eb0c844013851c619b71a75e20eeb6f0e24..58a8bee50c6ed1542b47aeeb135e7f7bf654a3b0 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3857,7 +3857,8 @@ static const char readme_msg[] =
        "\t    following modifiers to the field name, as applicable:\n\n"
        "\t            .hex        display a number as a hex value\n"
        "\t            .sym        display an address as a symbol\n"
-       "\t            .sym-offset display an address as a symbol and offset\n\n"
+       "\t            .sym-offset display an address as a symbol and offset\n"
+       "\t            .execname   display a common_pid as a program name\n\n"
        "\t    The 'pause' parameter can be used to pause an existing hist\n"
        "\t    trigger or to start a hist trigger but not log any events\n"
        "\t    until told to do so.  'continue' can be used to start or\n"

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 808cc06cdb615385dc8dbc900f4b3d632313e080..227e6c21b1eb5c23eff8325ed2049c3b98dde58a 100644 (file)
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -83,6 +83,7 @@ enum hist_field_flags {
        HIST_FIELD_FL_HEX               = 8,
        HIST_FIELD_FL_SYM               = 16,
        HIST_FIELD_FL_SYM_OFFSET        = 32,
+       HIST_FIELD_FL_EXECNAME          = 64,
 };
 
 struct hist_trigger_attrs {
@@ -232,6 +233,73 @@ static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)
        return ERR_PTR(ret);
 }
 
+static inline void save_comm(char *comm, struct task_struct *task)
+{
+       if (!task->pid) {
+               strcpy(comm, "<idle>");
+               return;
+       }
+
+       if (WARN_ON_ONCE(task->pid < 0)) {
+               strcpy(comm, "<XXX>");
+               return;
+       }
+
+       memcpy(comm, task->comm, TASK_COMM_LEN);
+}
+
+static void hist_trigger_elt_comm_free(struct tracing_map_elt *elt)
+{
+       kfree((char *)elt->private_data);
+}
+
+static int hist_trigger_elt_comm_alloc(struct tracing_map_elt *elt)
+{
+       struct hist_trigger_data *hist_data = elt->map->private_data;
+       struct hist_field *key_field;
+       unsigned int i;
+
+       for_each_hist_key_field(i, hist_data) {
+               key_field = hist_data->fields[i];
+
+               if (key_field->flags & HIST_FIELD_FL_EXECNAME) {
+                       unsigned int size = TASK_COMM_LEN + 1;
+
+                       elt->private_data = kzalloc(size, GFP_KERNEL);
+                       if (!elt->private_data)
+                               return -ENOMEM;
+                       break;
+               }
+       }
+
+       return 0;
+}
+
+static void hist_trigger_elt_comm_copy(struct tracing_map_elt *to,
+                                      struct tracing_map_elt *from)
+{
+       char *comm_from = from->private_data;
+       char *comm_to = to->private_data;
+
+       if (comm_from)
+               memcpy(comm_to, comm_from, TASK_COMM_LEN + 1);
+}
+
+static void hist_trigger_elt_comm_init(struct tracing_map_elt *elt)
+{
+       char *comm = elt->private_data;
+
+       if (comm)
+               save_comm(comm, current);
+}
+
+static const struct tracing_map_ops hist_trigger_elt_comm_ops = {
+       .elt_alloc      = hist_trigger_elt_comm_alloc,
+       .elt_copy       = hist_trigger_elt_comm_copy,
+       .elt_free       = hist_trigger_elt_comm_free,
+       .elt_init       = hist_trigger_elt_comm_init,
+};
+
 static void destroy_hist_field(struct hist_field *hist_field)
 {
        kfree(hist_field);
@@ -403,6 +471,9 @@ static int create_key_field(struct hist_trigger_data *hist_data,
                        flags |= HIST_FIELD_FL_SYM;
                else if (strcmp(field_str, "sym-offset") == 0)
                        flags |= HIST_FIELD_FL_SYM_OFFSET;
+               else if ((strcmp(field_str, "execname") == 0) &&
+                        (strcmp(field_name, "common_pid") == 0))
+                       flags |= HIST_FIELD_FL_EXECNAME;
                else {
                        ret = -EINVAL;
                        goto out;
@@ -624,11 +695,27 @@ static int create_tracing_map_fields(struct hist_trigger_data *hist_data)
        return 0;
 }
 
+static bool need_tracing_map_ops(struct hist_trigger_data *hist_data)
+{
+       struct hist_field *key_field;
+       unsigned int i;
+
+       for_each_hist_key_field(i, hist_data) {
+               key_field = hist_data->fields[i];
+
+               if (key_field->flags & HIST_FIELD_FL_EXECNAME)
+                       return true;
+       }
+
+       return false;
+}
+
 static struct hist_trigger_data *
 create_hist_data(unsigned int map_bits,
                 struct hist_trigger_attrs *attrs,
                 struct trace_event_file *file)
 {
+       const struct tracing_map_ops *map_ops = NULL;
        struct hist_trigger_data *hist_data;
        int ret = 0;
 
@@ -646,8 +733,11 @@ create_hist_data(unsigned int map_bits,
        if (ret)
                goto free;
 
+       if (need_tracing_map_ops(hist_data))
+               map_ops = &hist_trigger_elt_comm_ops;
+
        hist_data->map = tracing_map_create(map_bits, hist_data->key_size,
-                                           NULL, hist_data);
+                                           map_ops, hist_data);
        if (IS_ERR(hist_data->map)) {
                ret = PTR_ERR(hist_data->map);
                hist_data->map = NULL;
@@ -758,6 +848,12 @@ hist_trigger_entry_print(struct seq_file *m,
                        sprint_symbol(str, uval);
                        seq_printf(m, "%s: [%llx] %-55s",
                                   key_field->field->name, uval, str);
+               } else if (key_field->flags & HIST_FIELD_FL_EXECNAME) {
+                       char *comm = elt->private_data;
+
+                       uval = *(u64 *)(key + key_field->offset);
+                       seq_printf(m, "%s: %-16s[%10llu]",
+                                  key_field->field->name, comm, uval);
                } else if (key_field->flags & HIST_FIELD_FL_STRING) {
                        seq_printf(m, "%s: %-50s", key_field->field->name,
                                   (char *)(key + key_field->offset));
@@ -877,6 +973,8 @@ static const char *get_hist_field_flags(struct hist_field *hist_field)
                flags_str = "sym";
        else if (hist_field->flags & HIST_FIELD_FL_SYM_OFFSET)
                flags_str = "sym-offset";
+       else if (hist_field->flags & HIST_FIELD_FL_EXECNAME)
+               flags_str = "execname";
 
        return flags_str;
 }