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 <ringbuffer/frontend_types.h>
  18 #include <wrapper/vmalloc.h>
  19 #include <wrapper/namespace.h>
  20 #include <lttng/tracer.h>
  21
  22 #if defined(CONFIG_CGROUPS) && \
  23         ((LINUX_VERSION_CODE >= KERNEL_VERSION(4,6,0)) || \
  24          LTTNG_UBUNTU_KERNEL_RANGE(4,4,0,0, 4,5,0,0))
  25
  26 static
  27 size_t cgroup_ns_get_size(size_t offset)
  28 {
  29         size_t size = 0;
  30
  31         size += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
  32         size += sizeof(unsigned int);
  33         return size;
  34 }
  35
  36 static
  37 void cgroup_ns_record(struct lttng_ctx_field *field,
  38                  struct lib_ring_buffer_ctx *ctx,
  39                  struct lttng_channel *chan)
  40 {
  41         unsigned int cgroup_ns_inum = 0;
  42
  43         /*
  44          * nsproxy can be NULL when scheduled out of exit.
  45          *
  46          * As documented in 'linux/nsproxy.h' namespaces access rules, no
  47          * precautions should be taken when accessing the current task's
  48          * namespaces, just dereference the pointers.
  49          */
  50         if (current->nsproxy)
  51                 cgroup_ns_inum = current->nsproxy->cgroup_ns->lttng_ns_inum;
  52
  53         lib_ring_buffer_align_ctx(ctx, lttng_alignof(cgroup_ns_inum));
  54         chan->ops->event_write(ctx, &cgroup_ns_inum, sizeof(cgroup_ns_inum));
  55 }
  56
  57 static
  58 void cgroup_ns_get_value(struct lttng_ctx_field *field,
  59                 struct lttng_probe_ctx *lttng_probe_ctx,
  60                 union 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->s64 = cgroup_ns_inum;
  75 }
  76
  77 int lttng_add_cgroup_ns_to_ctx(struct lttng_ctx **ctx)
  78 {
  79         struct lttng_ctx_field *field;
  80
  81         field = lttng_append_context(ctx);
  82         if (!field)
  83                 return -ENOMEM;
  84         if (lttng_find_context(*ctx, "cgroup_ns")) {
  85                 lttng_remove_context_field(ctx, field);
  86                 return -EEXIST;
  87         }
  88         field->event_field.name = "cgroup_ns";
  89         field->event_field.type.atype = atype_integer;
  90         field->event_field.type.u.integer.size = sizeof(unsigned int) * CHAR_BIT;
  91         field->event_field.type.u.integer.alignment = lttng_alignof(unsigned int) * CHAR_BIT;
  92         field->event_field.type.u.integer.signedness = lttng_is_signed_type(unsigned int);
  93         field->event_field.type.u.integer.reverse_byte_order = 0;
  94         field->event_field.type.u.integer.base = 10;
  95         field->event_field.type.u.integer.encoding = lttng_encode_none;
  96         field->get_size = cgroup_ns_get_size;
  97         field->record = cgroup_ns_record;
  98         field->get_value = cgroup_ns_get_value;
  99         lttng_context_update(*ctx);
 100         wrapper_vmalloc_sync_mappings();
 101         return 0;
 102 }
 103 EXPORT_SYMBOL_GPL(lttng_add_cgroup_ns_to_ctx);
 104
 105 #endif