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    Subject[PATCH v16 10/23] tracing: Add hist trigger 'execname' modifier
    Date
    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

    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>
    ---
    kernel/trace/trace.c | 3 +-
    kernel/trace/trace_events_hist.c | 100 ++++++++++++++++++++++++++++++++++++++-
    2 files changed, 101 insertions(+), 2 deletions(-)

    diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
    index 202220c..bfcbfee 100644
    --- a/kernel/trace/trace.c
    +++ b/kernel/trace/trace.c
    @@ -3848,7 +3848,8 @@ 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 808cc06..227e6c2 100644
    --- 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;
    }
    --
    1.9.3
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