lttng-context-vppid.c

   1 /* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1)
   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-events.h>
  15 #include <wrapper/ringbuffer/frontend_types.h>
  16 #include <wrapper/vmalloc.h>
  17 #include <lttng-tracer.h>
  18
  19 static
  20 size_t vppid_get_size(size_t offset)
  21 {
  22         size_t size = 0;
  23
  24         size += lib_ring_buffer_align(offset, lttng_alignof(pid_t));
  25         size += sizeof(pid_t);
  26         return size;
  27 }
  28
  29 static
  30 void vppid_record(struct lttng_ctx_field *field,
  31                   struct lib_ring_buffer_ctx *ctx,
  32                   struct lttng_channel *chan)
  33 {
  34         struct task_struct *parent;
  35         pid_t vppid;
  36
  37         /*
  38          * current nsproxy can be NULL when scheduled out of exit. pid_vnr uses
  39          * the current thread nsproxy to perform the lookup.
  40          */
  41
  42         /*
  43          * TODO: when we eventually add RCU subsystem instrumentation,
  44          * taking the rcu read lock here will trigger RCU tracing
  45          * recursively. We should modify the kernel synchronization so
  46          * it synchronizes both for RCU and RCU sched, and rely on
  47          * rcu_read_lock_sched_notrace.
  48          */
  49
  50         rcu_read_lock();
  51         parent = rcu_dereference(current->real_parent);
  52         if (!current->nsproxy)
  53                 vppid = 0;
  54         else
  55                 vppid = task_tgid_vnr(parent);
  56         rcu_read_unlock();
  57         lib_ring_buffer_align_ctx(ctx, lttng_alignof(vppid));
  58         chan->ops->event_write(ctx, &vppid, sizeof(vppid));
  59 }
  60
  61 static
  62 void vppid_get_value(struct lttng_ctx_field *field,
  63                 struct lttng_probe_ctx *lttng_probe_ctx,
  64                 union lttng_ctx_value *value)
  65 {
  66         struct task_struct *parent;
  67         pid_t vppid;
  68
  69         /*
  70          * current nsproxy can be NULL when scheduled out of exit. pid_vnr uses
  71          * the current thread nsproxy to perform the lookup.
  72          */
  73
  74         /*
  75          * TODO: when we eventually add RCU subsystem instrumentation,
  76          * taking the rcu read lock here will trigger RCU tracing
  77          * recursively. We should modify the kernel synchronization so
  78          * it synchronizes both for RCU and RCU sched, and rely on
  79          * rcu_read_lock_sched_notrace.
  80          */
  81
  82         rcu_read_lock();
  83         parent = rcu_dereference(current->real_parent);
  84         if (!current->nsproxy)
  85                 vppid = 0;
  86         else
  87                 vppid = task_tgid_vnr(parent);
  88         rcu_read_unlock();
  89         value->s64 = vppid;
  90 }
  91
  92 int lttng_add_vppid_to_ctx(struct lttng_ctx **ctx)
  93 {
  94         struct lttng_ctx_field *field;
  95
  96         field = lttng_append_context(ctx);
  97         if (!field)
  98                 return -ENOMEM;
  99         if (lttng_find_context(*ctx, "vppid")) {
 100                 lttng_remove_context_field(ctx, field);
 101                 return -EEXIST;
 102         }
 103         field->event_field.name = "vppid";
 104         field->event_field.type.atype = atype_integer;
 105         field->event_field.type.u.basic.integer.size = sizeof(pid_t) * CHAR_BIT;
 106         field->event_field.type.u.basic.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
 107         field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(pid_t);
 108         field->event_field.type.u.basic.integer.reverse_byte_order = 0;
 109         field->event_field.type.u.basic.integer.base = 10;
 110         field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
 111         field->get_size = vppid_get_size;
 112         field->record = vppid_record;
 113         field->get_value = vppid_get_value;
 114         lttng_context_update(*ctx);
 115         wrapper_vmalloc_sync_all();
 116         return 0;
 117 }
 118 EXPORT_SYMBOL_GPL(lttng_add_vppid_to_ctx);