From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751746AbaIXQMh (ORCPT ); Wed, 24 Sep 2014 12:12:37 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.231]:3479 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750940AbaIXQMg (ORCPT ); Wed, 24 Sep 2014 12:12:36 -0400 Date: Wed, 24 Sep 2014 12:12:34 -0400 From: Steven Rostedt To: Josef Bacik Cc: Subject: Re: [PATCH] trace-cmd: add helper to read kernel_stack functions Message-ID: <20140924121234.066bd249@gandalf.local.home> In-Reply-To: <1411574609-12129-1-git-send-email-jbacik@fb.com> References: <1411574609-12129-1-git-send-email-jbacik@fb.com> X-Mailer: Claws Mail 3.10.1 (GTK+ 2.24.24; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.142:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 24 Sep 2014 12:03:29 -0400 Josef Bacik wrote: > The way the ftrace kernel_stack event is handled doesn't work right with the > normal event reading stuff in python. The raw buffer read stuff expects the > size of the event to be non-zero, but in the case of kernel_stack the caller > array is 0 and we are given a size field > > field:int size; offset:8; size:4; signed:1; > field:unsigned long caller; offset:16; size:0; signed:0; > > This screws up python becuase it uses the size field to indicate how much of the > memory buffer is there to read, which in this case is 0. This makes it > impossible to actually read the caller array from python. So add a new c > binding to specially read the addr array and go ahead and look up the function > names for the addr and return those strings. With this I can now pull the > function names for a kernel_stack event from the python library. Thanks, No need to add "Thanks" to a change log ;-) Will this still work if we convert the kernel_stack to be the same as the other dynamic_arrays? I'm assuming so, as there doesn't seem to be anything here that looks specific to the kernel_stack event, and we wouldn't want to break the other events. I just want to make sure you are testing both formats. Thanks, -- Steve > > Signed-off-by: Josef Bacik > --- > ctracecmd.i | 24 ++++++++++++++++++++++++ > tracecmd.py | 11 +++++++++++ > 2 files changed, 35 insertions(+) > > diff --git a/ctracecmd.i b/ctracecmd.i > index 3970803..c175254 100644 > --- a/ctracecmd.i > +++ b/ctracecmd.i > @@ -49,6 +49,30 @@ void py_pevent_register_event_handler(struct pevent *pevent, int id, > python_callback, pyfunc); > } > > +static PyObject *py_field_get_addr_string(struct pevent *pevent, > + struct pevent_record *record, > + struct format_field *field, > + int long_size, int index) > +{ > + void *data = record->data; > + const char *func = NULL; > + off_t offset = field->offset + (index * long_size); > + unsigned long addr; > + > + if (offset + long_size > record->size) { > + PyErr_SetString(PyExc_IndexError, > + "Index is beyond beyond the range"); > + return NULL; > + } > + > + addr = pevent_read_number(pevent, data + offset, long_size); > + func = pevent_find_function(pevent, addr); > + if (!func) > + return NULL; > + > + return PyString_FromStringAndSize(func, strlen(func)); > +} > + > static PyObject *py_field_get_data(struct format_field *f, struct pevent_record *r) > { > if (!strncmp(f->type, "__data_loc ", 11)) { > diff --git a/tracecmd.py b/tracecmd.py > index cdd619b..a43d788 100644 > --- a/tracecmd.py > +++ b/tracecmd.py > @@ -117,6 +117,13 @@ class Event(object, DictMixin): > return None > return py_field_get_str(f, self._record) > > + def addr_field_index(self, name, long_size, index): > + f = pevent_find_any_field(self._format, name) > + if f is None: > + return None > + return py_field_get_addr_string(self._pevent, self._record, f, > + long_size, index) > + > class TraceSeq(object): > def __init__(self, trace_seq): > self._trace_seq = trace_seq > @@ -192,6 +199,10 @@ class Trace(object): > def cpus(self): > return tracecmd_cpus(self._handle) > > + @cached_property > + def long_size(self): > + return tracecmd_long_size(self._handle) > + > def read_event(self, cpu): > rec = tracecmd_read_data(self._handle, cpu) > if rec: