lttng-context-ppid.c

   1 /*
   2  * lttng-context-ppid.c
   3  *
   4  * LTTng PPID context.
   5  *
   6  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; only
  11  * version 2.1 of the License.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include <linux/module.h>
  24 #include <linux/slab.h>
  25 #include <linux/sched.h>
  26 #include <linux/syscalls.h>
  27 #include "lttng-events.h"
  28 #include "wrapper/ringbuffer/frontend_types.h"
  29 #include "wrapper/vmalloc.h"
  30 #include "lttng-tracer.h"
  31
  32 static
  33 size_t ppid_get_size(size_t offset)
  34 {
  35         size_t size = 0;
  36
  37         size += lib_ring_buffer_align(offset, lttng_alignof(pid_t));
  38         size += sizeof(pid_t);
  39         return size;
  40 }
  41
  42 static
  43 void ppid_record(struct lttng_ctx_field *field,
  44                  struct lib_ring_buffer_ctx *ctx,
  45                  struct lttng_channel *chan)
  46 {
  47         pid_t ppid;
  48
  49         /*
  50          * TODO: when we eventually add RCU subsystem instrumentation,
  51          * taking the rcu read lock here will trigger RCU tracing
  52          * recursively. We should modify the kernel synchronization so
  53          * it synchronizes both for RCU and RCU sched, and rely on
  54          * rcu_read_lock_sched_notrace.
  55          */
  56         rcu_read_lock();
  57         ppid = task_tgid_nr(current->real_parent);
  58         rcu_read_unlock();
  59         lib_ring_buffer_align_ctx(ctx, lttng_alignof(ppid));
  60         chan->ops->event_write(ctx, &ppid, sizeof(ppid));
  61 }
  62
  63 static
  64 void ppid_get_value(struct lttng_ctx_field *field,
  65                 union lttng_ctx_value *value)
  66 {
  67         pid_t ppid;
  68
  69         /*
  70          * TODO: when we eventually add RCU subsystem instrumentation,
  71          * taking the rcu read lock here will trigger RCU tracing
  72          * recursively. We should modify the kernel synchronization so
  73          * it synchronizes both for RCU and RCU sched, and rely on
  74          * rcu_read_lock_sched_notrace.
  75          */
  76         rcu_read_lock();
  77         ppid = task_tgid_nr(current->real_parent);
  78         rcu_read_unlock();
  79         value->s64 = ppid;
  80 }
  81
  82 int lttng_add_ppid_to_ctx(struct lttng_ctx **ctx)
  83 {
  84         struct lttng_ctx_field *field;
  85
  86         field = lttng_append_context(ctx);
  87         if (!field)
  88                 return -ENOMEM;
  89         if (lttng_find_context(*ctx, "ppid")) {
  90                 lttng_remove_context_field(ctx, field);
  91                 return -EEXIST;
  92         }
  93         field->event_field.name = "ppid";
  94         field->event_field.type.atype = atype_integer;
  95         field->event_field.type.u.basic.integer.size = sizeof(pid_t) * CHAR_BIT;
  96         field->event_field.type.u.basic.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
  97         field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(pid_t);
  98         field->event_field.type.u.basic.integer.reverse_byte_order = 0;
  99         field->event_field.type.u.basic.integer.base = 10;
 100         field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
 101         field->get_size = ppid_get_size;
 102         field->record = ppid_record;
 103         field->get_value = ppid_get_value;
 104         lttng_context_update(*ctx);
 105         wrapper_vmalloc_sync_all();
 106         return 0;
 107 }
 108 EXPORT_SYMBOL_GPL(lttng_add_ppid_to_ctx);