src/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/events.h>
  15 #include <lttng/events-internal.h>
  16 #include <ringbuffer/frontend_types.h>
  17 #include <wrapper/vmalloc.h>
  18 #include <lttng/tracer.h>
  19
  20 static
  21 size_t vppid_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset)
  22 {
  23         size_t size = 0;
  24
  25         size += lib_ring_buffer_align(offset, lttng_alignof(pid_t));
  26         size += sizeof(pid_t);
  27         return size;
  28 }
  29
  30 static
  31 void vppid_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx,
  32                   struct lttng_kernel_ring_buffer_ctx *ctx,
  33                   struct lttng_kernel_channel_buffer *chan)
  34 {
  35         struct task_struct *parent;
  36         pid_t vppid;
  37
  38         /*
  39          * current nsproxy can be NULL when scheduled out of exit. pid_vnr uses
  40          * the current thread nsproxy to perform the lookup.
  41          */
  42
  43         /*
  44          * TODO: when we eventually add RCU subsystem instrumentation,
  45          * taking the rcu read lock here will trigger RCU tracing
  46          * recursively. We should modify the kernel synchronization so
  47          * it synchronizes both for RCU and RCU sched, and rely on
  48          * rcu_read_lock_sched_notrace.
  49          */
  50
  51         rcu_read_lock();
  52         parent = rcu_dereference(current->real_parent);
  53         if (!current->nsproxy)
  54                 vppid = 0;
  55         else
  56                 vppid = task_tgid_vnr(parent);
  57         rcu_read_unlock();
  58         lib_ring_buffer_align_ctx(ctx, lttng_alignof(vppid));
  59         chan->ops->event_write(ctx, &vppid, sizeof(vppid));
  60 }
  61
  62 static
  63 void vppid_get_value(void *priv,
  64                 struct lttng_kernel_probe_ctx *lttng_probe_ctx,
  65                 struct lttng_ctx_value *value)
  66 {
  67         struct task_struct *parent;
  68         pid_t vppid;
  69
  70         /*
  71          * current nsproxy can be NULL when scheduled out of exit. pid_vnr uses
  72          * the current thread nsproxy to perform the lookup.
  73          */
  74
  75         /*
  76          * TODO: when we eventually add RCU subsystem instrumentation,
  77          * taking the rcu read lock here will trigger RCU tracing
  78          * recursively. We should modify the kernel synchronization so
  79          * it synchronizes both for RCU and RCU sched, and rely on
  80          * rcu_read_lock_sched_notrace.
  81          */
  82
  83         rcu_read_lock();
  84         parent = rcu_dereference(current->real_parent);
  85         if (!current->nsproxy)
  86                 vppid = 0;
  87         else
  88                 vppid = task_tgid_vnr(parent);
  89         rcu_read_unlock();
  90         value->u.s64 = vppid;
  91 }
  92
  93 static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
  94         lttng_kernel_static_event_field("vppid",
  95                 lttng_kernel_static_type_integer_from_type(pid_t, __BYTE_ORDER, 10),
  96                 false, false, false),
  97         vppid_get_size,
  98         vppid_record,
  99         vppid_get_value,
 100         NULL, NULL);
 101
 102 int lttng_add_vppid_to_ctx(struct lttng_kernel_ctx **ctx)
 103 {
 104         int ret;
 105
 106         if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
 107                 return -EEXIST;
 108         ret = lttng_kernel_context_append(ctx, ctx_field);
 109         wrapper_vmalloc_sync_mappings();
 110         return ret;
 111 }
 112 EXPORT_SYMBOL_GPL(lttng_add_vppid_to_ctx);