lttng-context-mnt-ns.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-mnt-ns.c
   4  *
   5  * LTTng mount 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 <lttng/lttng-events.h>
  16 #include <linux/nsproxy.h>
  17 #include <ringbuffer/frontend_types.h>
  18 #include <lttng/lttng-tracer.h>
  19
  20 #if !defined(LTTNG_MNT_NS_MISSING_HEADER)
  21
  22 #include <../fs/mount.h>
  23
  24 static
  25 size_t mnt_ns_get_size(size_t offset)
  26 {
  27         size_t size = 0;
  28
  29         size += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
  30         size += sizeof(unsigned int);
  31         return size;
  32 }
  33
  34 static
  35 void mnt_ns_record(struct lttng_ctx_field *field,
  36                  struct lib_ring_buffer_ctx *ctx,
  37                  struct lttng_channel *chan)
  38 {
  39         unsigned int mnt_ns_inum = 0;
  40
  41         /*
  42          * nsproxy can be NULL when scheduled out of exit.
  43          *
  44          * As documented in 'linux/nsproxy.h' namespaces access rules, no
  45          * precautions should be taken when accessing the current task's
  46          * namespaces, just dereference the pointers.
  47          */
  48         if (current->nsproxy)
  49                 mnt_ns_inum = current->nsproxy->mnt_ns->ns.inum;
  50
  51         lib_ring_buffer_align_ctx(ctx, lttng_alignof(mnt_ns_inum));
  52         chan->ops->event_write(ctx, &mnt_ns_inum, sizeof(mnt_ns_inum));
  53 }
  54
  55 static
  56 void mnt_ns_get_value(struct lttng_ctx_field *field,
  57                 struct lttng_probe_ctx *lttng_probe_ctx,
  58                 union lttng_ctx_value *value)
  59 {
  60         unsigned int mnt_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                 mnt_ns_inum = current->nsproxy->mnt_ns->ns.inum;
  71
  72         value->s64 = mnt_ns_inum;
  73 }
  74
  75 int lttng_add_mnt_ns_to_ctx(struct lttng_ctx **ctx)
  76 {
  77         struct lttng_ctx_field *field;
  78
  79         field = lttng_append_context(ctx);
  80         if (!field)
  81                 return -ENOMEM;
  82         if (lttng_find_context(*ctx, "mnt_ns")) {
  83                 lttng_remove_context_field(ctx, field);
  84                 return -EEXIST;
  85         }
  86         field->event_field.name = "mnt_ns";
  87         field->event_field.type.atype = atype_integer;
  88         field->event_field.type.u.integer.size = sizeof(unsigned int) * CHAR_BIT;
  89         field->event_field.type.u.integer.alignment = lttng_alignof(unsigned int) * CHAR_BIT;
  90         field->event_field.type.u.integer.signedness = lttng_is_signed_type(unsigned int);
  91         field->event_field.type.u.integer.reverse_byte_order = 0;
  92         field->event_field.type.u.integer.base = 10;
  93         field->event_field.type.u.integer.encoding = lttng_encode_none;
  94         field->get_size = mnt_ns_get_size;
  95         field->record = mnt_ns_record;
  96         field->get_value = mnt_ns_get_value;
  97         lttng_context_update(*ctx);
  98         return 0;
  99 }
 100 EXPORT_SYMBOL_GPL(lttng_add_mnt_ns_to_ctx);
 101
 102 #endif