From mboxrd@z Thu Jan 1 00:00:00 1970 From: jeremie.galarneau@efficios.com (=?ISO-8859-1?Q?J=E9r=E9mie_Galarneau?=) Date: Thu, 7 Nov 2013 16:40:30 -0500 Subject: [lttng-dev] Reading CTF trace using Babeltrace API In-Reply-To: References: <439534666.36114.1381274066505.JavaMail.zimbra@efficios.com> Message-ID: On Wed, Oct 23, 2013 at 10:50 AM, Salman Rafiq 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... J?r?mie > > 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 > Gesch?ftsfeld Industrial Communication > Fraunhofer-Institut f?r Eingebettete Systeme und Kommunikationstechnik ESK > > Hansastra?e 32 | 80686 M?nchen > Telefon, Fax: +49 89 547088-356 | +49 89 547088-221 > E-Mail: salman.rafiq at esk.fraunhofer.de > > Internet: > http://www.esk.fraunhofer.de > http://www.twitter.com/FraunhoferESK > > > -----Original Message----- > From: jeremie.galarneau@gmail.com [mailto:jeremie.galarneau@gmail.com] On Behalf Of J?r?mie Galarneau > Sent: Mittwoch, 9. Oktober 2013 01:50 > To: Mathieu Desnoyers > Cc: Salman Rafiq; Julien Desfossez; lttng-dev at lists.lttng.org > Subject: Re: Reading CTF trace using Babeltrace API > > On Tue, Oct 8, 2013 at 7:14 PM, Mathieu Desnoyers wrote: >> ----- Original Message ----- >>> From: "J?r?mie Galarneau" >>> To: "Salman Rafiq" >>> Cc: jdesfossez at efficios.com, lttng-dev at lists.lttng.org, "Mathieu >>> Desnoyers" >>> 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 { >>> 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! > J?r?mie > >> >> 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, >>> J?r?mie >>> >>> > Thanks a lot! >>> > >>> > Regards, >>> > Salman >>> > >>> > -- >>> > Salman Rafiq >>> > Gesch?ftsfeld Industrial Communication Fraunhofer-Institut f?r >>> > Eingebettete Systeme und Kommunikationstechnik ESK >>> > >>> > Hansastra?e 32 | 80686 M?nchen >>> > Telefon, Fax: +49 89 547088-356 | +49 89 547088-221 >>> > E-Mail: salman.rafiq at esk.fraunhofer.de >>> > >>> > Internet: >>> > http://www.esk.fraunhofer.de >>> > http://www.twitter.com/FraunhoferESK >>> > >>> > >>> > -----Original Message----- >>> > From: jeremie.galarneau@gmail.com >>> > [mailto:jeremie.galarneau at gmail.com] On Behalf Of J?r?mie Galarneau >>> > Sent: Mittwoch, 2. Oktober 2013 20:25 >>> > To: Salman Rafiq >>> > Cc: jdesfossez at efficios.com; lttng-dev at lists.lttng.org; Mathieu >>> > Desnoyers >>> > Subject: Re: Reading CTF trace using Babeltrace API >>> > >>> > On Wed, Oct 2, 2013 at 12:55 PM, Salman Rafiq >>> > 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, >>> > J?r?mie >>> > >>> >> >>> >> Any help or suggestion related to this issue will be really appreciated. >>> >> Thanks! >>> >> >>> >> Regards, >>> >> Salman >>> >> >>> >> -- >>> >> Salman Rafiq >>> >> Gesch?ftsfeld Industrial Communication Fraunhofer-Institut f?r >>> >> Eingebettete Systeme und Kommunikationstechnik ESK >>> >> >>> >> Hansastra?e 32 | 80686 M?nchen >>> >> Telefon, Fax: +49 89 547088-356 | +49 89 547088-221 >>> >> E-Mail: salman.rafiq at esk.fraunhofer.de >>> >> >>> >> Internet: >>> >> http://www.esk.fraunhofer.de >>> >> http://www.twitter.com/FraunhoferESK >>> >> >>> > >>> > >>> > >>> > -- >>> > J?r?mie Galarneau >>> > EfficiOS Inc. >>> > http://www.efficios.com >>> >>> >>> >>> -- >>> J?r?mie Galarneau >>> EfficiOS Inc. >>> http://www.efficios.com >>> >> >> -- >> Mathieu Desnoyers >> EfficiOS Inc. >> http://www.efficios.com > > > > -- > J?r?mie Galarneau > EfficiOS Inc. > http://www.efficios.com -- J?r?mie Galarneau EfficiOS Inc. http://www.efficios.com