lttng-context-vppid.c

   1 /*
   2  * lttng-context-vppid.c
   3  *
   4  * LTTng vPPID 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 vppid_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 vppid_record(struct lttng_ctx_field *field,
  44                   struct lib_ring_buffer_ctx *ctx,
  45                   struct lttng_channel *chan)
  46 {
  47         struct task_struct *parent;
  48         pid_t vppid;
  49
  50         /*
  51          * current nsproxy can be NULL when scheduled out of exit. pid_vnr uses
  52          * the current thread nsproxy to perform the lookup.
  53          */
  54
  55         /*
  56          * TODO: when we eventually add RCU subsystem instrumentation,
  57          * taking the rcu read lock here will trigger RCU tracing
  58          * recursively. We should modify the kernel synchronization so
  59          * it synchronizes both for RCU and RCU sched, and rely on
  60          * rcu_read_lock_sched_notrace.
  61          */
  62
  63         rcu_read_lock();
  64         parent = rcu_dereference(current->real_parent);
  65         if (!current->nsproxy)
  66                 vppid = 0;
  67         else
  68                 vppid = task_tgid_vnr(parent);
  69         rcu_read_unlock();
  70         lib_ring_buffer_align_ctx(ctx, lttng_alignof(vppid));
  71         chan->ops->event_write(ctx, &vppid, sizeof(vppid));
  72 }
  73
  74 static
  75 void vppid_get_value(struct lttng_ctx_field *field,
  76                 struct lttng_probe_ctx *lttng_probe_ctx,
  77                 union lttng_ctx_value *value)
  78 {
  79         struct task_struct *parent;
  80         pid_t vppid;
  81
  82         /*
  83          * current nsproxy can be NULL when scheduled out of exit. pid_vnr uses
  84          * the current thread nsproxy to perform the lookup.
  85          */
  86
  87         /*
  88          * TODO: when we eventually add RCU subsystem instrumentation,
  89          * taking the rcu read lock here will trigger RCU tracing
  90          * recursively. We should modify the kernel synchronization so
  91          * it synchronizes both for RCU and RCU sched, and rely on
  92          * rcu_read_lock_sched_notrace.
  93          */
  94
  95         rcu_read_lock();
  96         parent = rcu_dereference(current->real_parent);
  97         if (!current->nsproxy)
  98                 vppid = 0;
  99         else
 100                 vppid = task_tgid_vnr(parent);
 101         rcu_read_unlock();
 102         value->s64 = vppid;
 103 }
 104
 105 int lttng_add_vppid_to_ctx(struct lttng_ctx **ctx)
 106 {
 107         struct lttng_ctx_field *field;
 108
 109         field = lttng_append_context(ctx);
 110         if (!field)
 111                 return -ENOMEM;
 112         if (lttng_find_context(*ctx, "vppid")) {
 113                 lttng_remove_context_field(ctx, field);
 114                 return -EEXIST;
 115         }
 116         field->event_field.name = "vppid";
 117         field->event_field.type.atype = atype_integer;
 118         field->event_field.type.u.basic.integer.size = sizeof(pid_t) * CHAR_BIT;
 119         field->event_field.type.u.basic.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
 120         field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(pid_t);
 121         field->event_field.type.u.basic.integer.reverse_byte_order = 0;
 122         field->event_field.type.u.basic.integer.base = 10;
 123         field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
 124         field->get_size = vppid_get_size;
 125         field->record = vppid_record;
 126         field->get_value = vppid_get_value;
 127         lttng_context_update(*ctx);
 128         wrapper_vmalloc_sync_all();
 129         return 0;
 130 }
 131 EXPORT_SYMBOL_GPL(lttng_add_vppid_to_ctx);