tools lib traceevent: Add direct access to dynamic arrays

Jiri Olsa was writing a plugin for the cfg80211_tx_mlme_mgmt trace
event, and was not able to get the implemented function working.
The event's print fmt looks like:

   "netdev:%s(%d), ftype:0x%.2x", REC->name, REC->ifindex,
            __le16_to_cpup((__le16 *)__get_dynamic_array(frame))

As there's no helper function for __le16_to_cpup(), Jiri was creating one
with a plugin. But unfortunately, it would not work even though he set
up the plugin correctly.

The problem is that the function parameters do not handle the helper
function "__get_dynamic_array()", and that passes in a NULL pointer.

Adding PRINT_DYNAMIC_ARRAY direct support to eval_num_arg() allows the
use of __get_dynamic_array() in function parameters.

Reported-by: Jiri Olsa <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
Tested-by: Jiri Olsa <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index 8f450adaa9c27107d6ecc42bed6b5702833babe9..0362d575de7d185752b2a23a53845236c71510f6 100644 (file)
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -3435,6 +3435,19 @@ eval_num_arg(void *data, int size, struct event_format *event, struct print_arg
                        goto out_warning_op;
                }
                break;
+       case PRINT_DYNAMIC_ARRAY:
+               /* Without [], we pass the address to the dynamic data */
+               offset = pevent_read_number(pevent,
+                                           data + arg->dynarray.field->offset,
+                                           arg->dynarray.field->size);
+               /*
+                * The actual length of the dynamic array is stored
+                * in the top half of the field, and the offset
+                * is in the bottom half of the 32 bit field.
+                */
+               offset &= 0xffff;
+               val = (unsigned long long)(data + offset);
+               break;
        default: /* not sure what to do there */
                return 0;
        }