src/lttng-context-uts-ns.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-uts-ns.c
   4  *
   5  * LTTng uts 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/utsname.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 <lttng/tracer.h>
  21
  22 #if defined(CONFIG_UTS_NS) && \
  23         (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(3,8,0))
  24
  25 static
  26 size_t uts_ns_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset)
  27 {
  28         size_t size = 0;
  29
  30         size += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
  31         size += sizeof(unsigned int);
  32         return size;
  33 }
  34
  35 static
  36 void uts_ns_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx,
  37                  struct lttng_kernel_ring_buffer_ctx *ctx,
  38                  struct lttng_kernel_channel_buffer *chan)
  39 {
  40         unsigned int uts_ns_inum = 0;
  41
  42         /*
  43          * nsproxy can be NULL when scheduled out of exit.
  44          *
  45          * As documented in 'linux/nsproxy.h' namespaces access rules, no
  46          * precautions should be taken when accessing the current task's
  47          * namespaces, just dereference the pointers.
  48          */
  49         if (current->nsproxy)
  50                 uts_ns_inum = current->nsproxy->uts_ns->ns.inum;
  51
  52         chan->ops->event_write(ctx, &uts_ns_inum, sizeof(uts_ns_inum), lttng_alignof(uts_ns_inum));
  53 }
  54
  55 static
  56 void uts_ns_get_value(void *priv,
  57                 struct lttng_kernel_probe_ctx *lttng_probe_ctx,
  58                 struct lttng_ctx_value *value)
  59 {
  60         unsigned int uts_ns_inum = 0;
  61
  62         /*
  63          * nsproxy can be NULL when scheduled out of exit.
  64          *
  65          * As documented in 'linux/nsproxy.h' namespaces access rules, no
  66          * precautions should be taken when accessing the current task's
  67          * namespaces, just dereference the pointers.
  68          */
  69         if (current->nsproxy)
  70                 uts_ns_inum = current->nsproxy->uts_ns->ns.inum;
  71
  72         value->u.s64 = uts_ns_inum;
  73 }
  74
  75 static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
  76         lttng_kernel_static_event_field("uts_ns",
  77                 lttng_kernel_static_type_integer_from_type(unsigned int, __BYTE_ORDER, 10),
  78                 false, false),
  79         uts_ns_get_size,
  80         uts_ns_record,
  81         uts_ns_get_value,
  82         NULL, NULL);
  83
  84 int lttng_add_uts_ns_to_ctx(struct lttng_kernel_ctx **ctx)
  85 {
  86         int ret;
  87
  88         if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
  89                 return -EEXIST;
  90         ret = lttng_kernel_context_append(ctx, ctx_field);
  91         wrapper_vmalloc_sync_mappings();
  92         return ret;
  93 }
  94 EXPORT_SYMBOL_GPL(lttng_add_uts_ns_to_ctx);
  95
  96 #endif