lttng-context-vppid.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-vppid.c
   4  *
   5  * LTTng vPPID context.
   6  *
   7  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/slab.h>
  12 #include <linux/sched.h>
  13 #include <linux/syscalls.h>
  14 #include <lttng/lttng-events.h>
  15 #include <ringbuffer/frontend_types.h>
  16 #include <lttng/lttng-tracer.h>
  17
  18 static
  19 size_t vppid_get_size(size_t offset)
  20 {
  21         size_t size = 0;
  22
  23         size += lib_ring_buffer_align(offset, lttng_alignof(pid_t));
  24         size += sizeof(pid_t);
  25         return size;
  26 }
  27
  28 static
  29 void vppid_record(struct lttng_ctx_field *field,
  30                   struct lib_ring_buffer_ctx *ctx,
  31                   struct lttng_channel *chan)
  32 {
  33         struct task_struct *parent;
  34         pid_t vppid;
  35
  36         /*
  37          * current nsproxy can be NULL when scheduled out of exit. pid_vnr uses
  38          * the current thread nsproxy to perform the lookup.
  39          */
  40
  41         /*
  42          * TODO: when we eventually add RCU subsystem instrumentation,
  43          * taking the rcu read lock here will trigger RCU tracing
  44          * recursively. We should modify the kernel synchronization so
  45          * it synchronizes both for RCU and RCU sched, and rely on
  46          * rcu_read_lock_sched_notrace.
  47          */
  48
  49         rcu_read_lock();
  50         parent = rcu_dereference(current->real_parent);
  51         if (!current->nsproxy)
  52                 vppid = 0;
  53         else
  54                 vppid = task_tgid_vnr(parent);
  55         rcu_read_unlock();
  56         lib_ring_buffer_align_ctx(ctx, lttng_alignof(vppid));
  57         chan->ops->event_write(ctx, &vppid, sizeof(vppid));
  58 }
  59
  60 static
  61 void vppid_get_value(struct lttng_ctx_field *field,
  62                 struct lttng_probe_ctx *lttng_probe_ctx,
  63                 union lttng_ctx_value *value)
  64 {
  65         struct task_struct *parent;
  66         pid_t vppid;
  67
  68         /*
  69          * current nsproxy can be NULL when scheduled out of exit. pid_vnr uses
  70          * the current thread nsproxy to perform the lookup.
  71          */
  72
  73         /*
  74          * TODO: when we eventually add RCU subsystem instrumentation,
  75          * taking the rcu read lock here will trigger RCU tracing
  76          * recursively. We should modify the kernel synchronization so
  77          * it synchronizes both for RCU and RCU sched, and rely on
  78          * rcu_read_lock_sched_notrace.
  79          */
  80
  81         rcu_read_lock();
  82         parent = rcu_dereference(current->real_parent);
  83         if (!current->nsproxy)
  84                 vppid = 0;
  85         else
  86                 vppid = task_tgid_vnr(parent);
  87         rcu_read_unlock();
  88         value->s64 = vppid;
  89 }
  90
  91 int lttng_add_vppid_to_ctx(struct lttng_ctx **ctx)
  92 {
  93         struct lttng_ctx_field *field;
  94
  95         field = lttng_append_context(ctx);
  96         if (!field)
  97                 return -ENOMEM;
  98         if (lttng_find_context(*ctx, "vppid")) {
  99                 lttng_remove_context_field(ctx, field);
 100                 return -EEXIST;
 101         }
 102         field->event_field.name = "vppid";
 103         field->event_field.type.atype = atype_integer;
 104         field->event_field.type.u.integer.size = sizeof(pid_t) * CHAR_BIT;
 105         field->event_field.type.u.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
 106         field->event_field.type.u.integer.signedness = lttng_is_signed_type(pid_t);
 107         field->event_field.type.u.integer.reverse_byte_order = 0;
 108         field->event_field.type.u.integer.base = 10;
 109         field->event_field.type.u.integer.encoding = lttng_encode_none;
 110         field->get_size = vppid_get_size;
 111         field->record = vppid_record;
 112         field->get_value = vppid_get_value;
 113         lttng_context_update(*ctx);
 114         return 0;
 115 }
 116 EXPORT_SYMBOL_GPL(lttng_add_vppid_to_ctx);