src/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/events.h>
  17 #include <lttng/events-internal.h>
  18 #include <ringbuffer/frontend_types.h>
  19 #include <wrapper/vmalloc.h>
  20 #include <wrapper/namespace.h>
  21 #include <lttng/tracer.h>
  22
  23 #if defined(CONFIG_CGROUPS) && \
  24         ((LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(4,6,0)) || \
  25          LTTNG_UBUNTU_KERNEL_RANGE(4,4,0,0, 4,5,0,0))
  26
  27 static
  28 size_t cgroup_ns_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset)
  29 {
  30         size_t size = 0;
  31
  32         size += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
  33         size += sizeof(unsigned int);
  34         return size;
  35 }
  36
  37 static
  38 void cgroup_ns_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx,
  39                  struct lttng_kernel_ring_buffer_ctx *ctx,
  40                  struct lttng_kernel_channel_buffer *chan)
  41 {
  42         unsigned int cgroup_ns_inum = 0;
  43
  44         /*
  45          * nsproxy can be NULL when scheduled out of exit.
  46          *
  47          * As documented in 'linux/nsproxy.h' namespaces access rules, no
  48          * precautions should be taken when accessing the current task's
  49          * namespaces, just dereference the pointers.
  50          */
  51         if (current->nsproxy)
  52                 cgroup_ns_inum = current->nsproxy->cgroup_ns->lttng_ns_inum;
  53
  54         chan->ops->event_write(ctx, &cgroup_ns_inum, sizeof(cgroup_ns_inum), lttng_alignof(cgroup_ns_inum));
  55 }
  56
  57 static
  58 void cgroup_ns_get_value(void *priv,
  59                 struct lttng_kernel_probe_ctx *lttng_probe_ctx,
  60                 struct lttng_ctx_value *value)
  61 {
  62         unsigned int cgroup_ns_inum = 0;
  63
  64         /*
  65          * nsproxy can be NULL when scheduled out of exit.
  66          *
  67          * As documented in 'linux/nsproxy.h' namespaces access rules, no
  68          * precautions should be taken when accessing the current task's
  69          * namespaces, just dereference the pointers.
  70          */
  71         if (current->nsproxy)
  72                 cgroup_ns_inum = current->nsproxy->cgroup_ns->lttng_ns_inum;
  73
  74         value->u.s64 = cgroup_ns_inum;
  75 }
  76
  77 static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
  78         lttng_kernel_static_event_field("cgroup_ns",
  79                 lttng_kernel_static_type_integer_from_type(unsigned int, __BYTE_ORDER, 10),
  80                 false, false, false),
  81         cgroup_ns_get_size,
  82         cgroup_ns_record,
  83         cgroup_ns_get_value,
  84         NULL, NULL);
  85
  86 int lttng_add_cgroup_ns_to_ctx(struct lttng_kernel_ctx **ctx)
  87 {
  88         int ret;
  89
  90         if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
  91                 return -EEXIST;
  92         ret = lttng_kernel_context_append(ctx, ctx_field);
  93         wrapper_vmalloc_sync_mappings();
  94         return ret;
  95 }
  96 EXPORT_SYMBOL_GPL(lttng_add_cgroup_ns_to_ctx);
  97
  98 #endif