lttng-context-cgroup-ns.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-cgroup-ns.c
   4  *
   5  * LTTng cgroup namespace context.
   6  *
   7  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *               2019 Michael Jeanson <mjeanson@efficios.com>
   9  *
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/slab.h>
  14 #include <linux/sched.h>
  15 #include <linux/cgroup.h>
  16 #include <lttng/lttng-events.h>
  17 #include <ringbuffer/frontend_types.h>
  18 #include <lttng/lttng-tracer.h>
  19
  20 #if defined(CONFIG_CGROUPS)
  21
  22 static
  23 size_t cgroup_ns_get_size(size_t offset)
  24 {
  25         size_t size = 0;
  26
  27         size += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
  28         size += sizeof(unsigned int);
  29         return size;
  30 }
  31
  32 static
  33 void cgroup_ns_record(struct lttng_ctx_field *field,
  34                  struct lib_ring_buffer_ctx *ctx,
  35                  struct lttng_channel *chan)
  36 {
  37         unsigned int cgroup_ns_inum = 0;
  38
  39         /*
  40          * nsproxy can be NULL when scheduled out of exit.
  41          *
  42          * As documented in 'linux/nsproxy.h' namespaces access rules, no
  43          * precautions should be taken when accessing the current task's
  44          * namespaces, just dereference the pointers.
  45          */
  46         if (current->nsproxy)
  47                 cgroup_ns_inum = current->nsproxy->cgroup_ns->ns.inum;
  48
  49         lib_ring_buffer_align_ctx(ctx, lttng_alignof(cgroup_ns_inum));
  50         chan->ops->event_write(ctx, &cgroup_ns_inum, sizeof(cgroup_ns_inum));
  51 }
  52
  53 static
  54 void cgroup_ns_get_value(struct lttng_ctx_field *field,
  55                 struct lttng_probe_ctx *lttng_probe_ctx,
  56                 union lttng_ctx_value *value)
  57 {
  58         unsigned int cgroup_ns_inum = 0;
  59
  60         /*
  61          * nsproxy can be NULL when scheduled out of exit.
  62          *
  63          * As documented in 'linux/nsproxy.h' namespaces access rules, no
  64          * precautions should be taken when accessing the current task's
  65          * namespaces, just dereference the pointers.
  66          */
  67         if (current->nsproxy)
  68                 cgroup_ns_inum = current->nsproxy->cgroup_ns->ns.inum;
  69
  70         value->s64 = cgroup_ns_inum;
  71 }
  72
  73 int lttng_add_cgroup_ns_to_ctx(struct lttng_ctx **ctx)
  74 {
  75         struct lttng_ctx_field *field;
  76
  77         field = lttng_append_context(ctx);
  78         if (!field)
  79                 return -ENOMEM;
  80         if (lttng_find_context(*ctx, "cgroup_ns")) {
  81                 lttng_remove_context_field(ctx, field);
  82                 return -EEXIST;
  83         }
  84         field->event_field.name = "cgroup_ns";
  85         field->event_field.type.atype = atype_integer;
  86         field->event_field.type.u.integer.size = sizeof(unsigned int) * CHAR_BIT;
  87         field->event_field.type.u.integer.alignment = lttng_alignof(unsigned int) * CHAR_BIT;
  88         field->event_field.type.u.integer.signedness = lttng_is_signed_type(unsigned int);
  89         field->event_field.type.u.integer.reverse_byte_order = 0;
  90         field->event_field.type.u.integer.base = 10;
  91         field->event_field.type.u.integer.encoding = lttng_encode_none;
  92         field->get_size = cgroup_ns_get_size;
  93         field->record = cgroup_ns_record;
  94         field->get_value = cgroup_ns_get_value;
  95         lttng_context_update(*ctx);
  96         return 0;
  97 }
  98 EXPORT_SYMBOL_GPL(lttng_add_cgroup_ns_to_ctx);
  99
 100 #endif