Thanks Jérémie. It worked out fine by using the bt_ctf_get_index() function. As for now, I ignored the warning " [warning] Extracting String".
Regards, Salman -- Salman Rafiq Geschäftsfeld Industrial Communication Fraunhofer-Institut für Eingebettete Systeme und Kommunikationstechnik ESK Hansastraße 32 | 80686 München Telefon, Fax: +49 89 547088-356 | +49 89 547088-221 E-Mail: [email protected] Internet: http://www.esk.fraunhofer.de http://www.twitter.com/FraunhoferESK -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jérémie Galarneau Sent: Donnerstag, 7. November 2013 22:41 To: Salman Rafiq Cc: Mathieu Desnoyers; Julien Desfossez; [email protected] Subject: Re: Reading CTF trace using Babeltrace API On Wed, Oct 23, 2013 at 10:50 AM, Salman Rafiq <[email protected]> wrote: > Hello again :) > > While reading Kernel trace events (system calls), I came across an issue > related to reading the field 'args' inside 'sys_unknown' system call event. > > Below is the information I get using public babeltrace API's for the event > field type. > Ctf_type_id = 8 (CTF_TYPE_ARRAY) > > > But when I try to read the value for the field using the following API > char * bt_ctf_get_char_array(const struct bt_definition *field); > > I receive null value. Also it gives me warning that I am instead extracting a > String. > [warning] Extracting String > > Also, I am unable to read the value using the following API. > char *bt_ctf_get_string(const struct bt_definition *field); > You should be using the bt_ctf_get_index() function to access the individual elements of _args. Let me know how that works out. As for the "Extracting string" message, it can indeed be misleading... Jérémie > > below is the sample event recorded: > [00002934900435406801] (+0.000009630) sys_unknown: { cpu_id = 3 }, { > id = 277, args = [ [0] = 22, [1] = 0, [2] = 4096, [3] = 2, [4] = 4096, > [5] = 5 ] } > > AND the event definition: > event { > name = sys_unknown; > id = 2; > stream_id = 0; > fields := struct { > integer { size = 32; align = 8; signed = 0; encoding = none; > base = 10; } _id > integer { size = 64; align = 8; signed = 0; encoding = none; > base = 10; } _args[6]; > }; > }; > > > Any suggestion related to that will be very helpful. > Thanks! > > Best Regards, > Salman > -- > Salman Rafiq > Geschäftsfeld Industrial Communication Fraunhofer-Institut für > Eingebettete Systeme und Kommunikationstechnik ESK > > Hansastraße 32 | 80686 München > Telefon, Fax: +49 89 547088-356 | +49 89 547088-221 > E-Mail: [email protected] > > Internet: > http://www.esk.fraunhofer.de > http://www.twitter.com/FraunhoferESK > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] > On Behalf Of Jérémie Galarneau > Sent: Mittwoch, 9. Oktober 2013 01:50 > To: Mathieu Desnoyers > Cc: Salman Rafiq; Julien Desfossez; [email protected] > Subject: Re: Reading CTF trace using Babeltrace API > > On Tue, Oct 8, 2013 at 7:14 PM, Mathieu Desnoyers > <[email protected]> wrote: >> ----- Original Message ----- >>> From: "Jérémie Galarneau" <[email protected]> >>> To: "Salman Rafiq" <[email protected]> >>> Cc: [email protected], [email protected], "Mathieu >>> Desnoyers" <[email protected]> >>> Sent: Tuesday, October 8, 2013 2:52:38 PM >>> Subject: Re: Reading CTF trace using Babeltrace API >> [...] >>> >>> The problem is that the "id" fields in both struct >>> event_header_compact and event_header_large acts as a variant's tag >>> enumeration. >>> >>> For instance, if we take a look at the event_header_compact >>> structure, >>> >>> struct event_header_compact { >>> enum : uint5_t { compact = 0 ... 30, extended = 31 } id; >>> variant <id> { >>> struct { >>> uint27_clock_monotonic_t timestamp; >>> } compact; >>> struct { >>> uint32_t id; >>> uint64_clock_monotonic_t timestamp; >>> } extended; >>> } v; >>> } align(8); >>> >>> The "enum id" field will indicate the event's id if it has a value >>> of [0, 30]. It also indicates that the "compact" structure is >>> selected in the variant that follows. If id == 31, the "extended" >>> structure is selected, which means that you should retrieve the "id" >>> field's value from that structure. >>> >>> Since code is worth a thousand words, here's a more complete code >>> sample to read the id fields. >>> >>> while ((ctf_event = bt_ctf_iter_read_event(iter))) { >>> uint64_t event_id = 0; >>> const struct bt_definition *stream_event_header_scope = >>> bt_ctf_get_top_level_scope( >>> ctf_event, BT_STREAM_EVENT_HEADER); >>> const struct bt_definition *id_definition = >>> bt_ctf_get_field(ctf_event, stream_event_header_scope, >>> "id"); >>> const struct bt_definition *v_definition = >>> bt_ctf_get_field(ctf_event, stream_event_header_scope, >>> "v"); >>> >>> /* "id may be an enum, get the underlying integer if it's the case >>> */ >>> if (id_definition && >>> bt_ctf_field_type(bt_ctf_get_decl_from_def(id_definition)) == >>> CTF_TYPE_ENUM) { >>> id_definition = bt_ctf_get_enum_int(id_definition); >>> } >>> >>> /* Check if there is a "v" field and if it contains an "id" field */ >>> if (v_definition && >>> bt_ctf_field_type(bt_ctf_get_decl_from_def(v_definition)) == >>> CTF_TYPE_STRUCT) { >>> struct bt_definition const * const *list = NULL; >>> unsigned int count = 0; >>> unsigned int i; >>> >>> ret = bt_ctf_get_field_list(ctf_event, v_definition, >>> &list, &count); >>> if (ret) { >>> goto end; >>> } >>> >>> for (i = 0; i < count; i++) { >>> const char *name = >>> bt_ctf_field_name(list[i]); >>> >>> if (strcmp("id", name) == 0) { >>> id_definition = list[i]; >>> break; >>> } >>> } >> >> Instead of doing this bt_ctf_get_field_list() and iteration, can't we simply >> use bt_ctf_get_field() to try getting the struct bt_definition ? > > Right. I was under the impression the bt_ctf_get_field() would only work on > scopes, but it's not the case. > > Thanks! > Jérémie > >> >> Thanks, >> >> Mathieu >> >>> } >>> >>> if (id_definition && >>> bt_ctf_field_type(bt_ctf_get_decl_from_def(id_definition)) == >>> CTF_TYPE_INTEGER) { >>> event_id = bt_ctf_get_uint64(id_definition); >>> } >>> >>> printf("id = %" PRIu64 "\n", event_id); } >>> >>> Regards, >>> Jérémie >>> >>> > Thanks a lot! >>> > >>> > Regards, >>> > Salman >>> > >>> > -- >>> > Salman Rafiq >>> > Geschäftsfeld Industrial Communication Fraunhofer-Institut für >>> > Eingebettete Systeme und Kommunikationstechnik ESK >>> > >>> > Hansastraße 32 | 80686 München >>> > Telefon, Fax: +49 89 547088-356 | +49 89 547088-221 >>> > E-Mail: [email protected] >>> > >>> > Internet: >>> > http://www.esk.fraunhofer.de >>> > http://www.twitter.com/FraunhoferESK >>> > >>> > >>> > -----Original Message----- >>> > From: [email protected] >>> > [mailto:[email protected]] On Behalf Of Jérémie >>> > Galarneau >>> > Sent: Mittwoch, 2. Oktober 2013 20:25 >>> > To: Salman Rafiq >>> > Cc: [email protected]; [email protected]; Mathieu >>> > Desnoyers >>> > Subject: Re: Reading CTF trace using Babeltrace API >>> > >>> > On Wed, Oct 2, 2013 at 12:55 PM, Salman Rafiq >>> > <[email protected]> wrote: >>> >> Dear LTTngers, >>> >> >>> >> I would like to ask few questions related to the API's for >>> >> reading CTF traces. >>> >> >>> >> 1. Is there any way to read CTF metadata independently, like we >>> >> have certain API's to read the events. >>> >> >>> > >>> > Not from the public API, unfortunately. >>> > >>> >> 2. There are certain scopes defined in ctf/events.h like: >>> >> BT_TRACE_PACKET_HEADER = 0, >>> >> BT_STREAM_PACKET_CONTEXT = 1, >>> >> BT_STREAM_EVENT_HEADER = 2, >>> >> BT_STREAM_EVENT_CONTEXT = 3, >>> >> BT_EVENT_CONTEXT = 4, >>> >> BT_EVENT_FIELDS = 5, >>> >> >>> >> I could not figure out the way to ready the fields 'id' and >>> >> 'stream_id', for a particular event while iterating through the trace. >>> >> Though I can ready the event name using an API and fields using >>> >> BT_EVENT_FIELDS as a scope. >>> >> For e.g. consider the >>> >> >>> >> event { >>> >> name = sched_migrate_task; >>> >> id = 1; >>> >> stream_id = 0; >>> >> fields := struct { >>> >> integer { size = 8; align = 8; signed = 1; encoding = >>> >> UTF8; base = 10; } _comm[16]; >>> >> integer { size = 32; align = 8; signed = 1; encoding = >>> >> none; base = 10; } _tid; >>> >> integer { size = 32; align = 8; signed = 1; encoding = >>> >> none; base = 10; } _prio; >>> >> integer { size = 32; align = 8; signed = 1; encoding = >>> >> none; base = 10; } _orig_cpu; >>> >> integer { size = 32; align = 8; signed = 1; encoding = >>> >> none; base = 10; } _dest_cpu; >>> >> }; >>> >> }; >>> >> >>> > >>> > The "id" field is part of the BT_STREAM_EVENT_HEADER scope, while >>> > the "stream_id" field is part of the BT_TRACE_PACKET_HEADER scope. >>> > >>> > The code below is adapted from converter/babeltrace.c's >>> > convert_trace() loop to print both values. >>> > >>> > while ((ctf_event = bt_ctf_iter_read_event(iter))) { >>> > >>> > const struct bt_definition *stream_event_header_scope = >>> > bt_ctf_get_top_level_scope( >>> > ctf_event, BT_STREAM_EVENT_HEADER); >>> > const struct bt_definition *id_field = >>> > bt_ctf_get_field( >>> > ctf_event, stream_event_header_scope, >>> > "id"); >>> > >>> > printf("id = %" PRIu64 "\n", bt_ctf_get_uint64(id_field)); >>> > >>> > const struct bt_definition *packet_header_scope = >>> > bt_ctf_get_top_level_scope( >>> > ctf_event, BT_TRACE_PACKET_HEADER); >>> > const struct bt_definition *stream_id_field = >>> > bt_ctf_get_field( >>> > ctf_event, packet_header_scope, >>> > "stream_id"); >>> > >>> > printf("stream_id = %" PRIu64 "\n", bt_ctf_get_uint64( >>> > stream_id_field)); [...] } >>> > >>> > Regards, >>> > Jérémie >>> > >>> >> >>> >> Any help or suggestion related to this issue will be really appreciated. >>> >> Thanks! >>> >> >>> >> Regards, >>> >> Salman >>> >> >>> >> -- >>> >> Salman Rafiq >>> >> Geschäftsfeld Industrial Communication Fraunhofer-Institut für >>> >> Eingebettete Systeme und Kommunikationstechnik ESK >>> >> >>> >> Hansastraße 32 | 80686 München >>> >> Telefon, Fax: +49 89 547088-356 | +49 89 547088-221 >>> >> E-Mail: [email protected] >>> >> >>> >> Internet: >>> >> http://www.esk.fraunhofer.de >>> >> http://www.twitter.com/FraunhoferESK >>> >> >>> > >>> > >>> > >>> > -- >>> > Jérémie Galarneau >>> > EfficiOS Inc. >>> > http://www.efficios.com >>> >>> >>> >>> -- >>> Jérémie Galarneau >>> EfficiOS Inc. >>> http://www.efficios.com >>> >> >> -- >> Mathieu Desnoyers >> EfficiOS Inc. >> http://www.efficios.com > > > > -- > Jérémie Galarneau > EfficiOS Inc. > http://www.efficios.com -- Jérémie Galarneau EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
