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-events.h>
  16 #include <linux/nsproxy.h>
  17 #include <wrapper/ringbuffer/frontend_types.h>
  18 #include <lttng-tracer.h>
  19
  20 #if !defined(LTTNG_MNT_NS_MISSING_HEADER) && \
  21         (LINUX_VERSION_CODE >= KERNEL_VERSION(3,8,0))
  22
  23 #include <../fs/mount.h>
  24
  25 static
  26 size_t mnt_ns_get_size(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 mnt_ns_record(struct lttng_ctx_field *field,
  37                  struct lib_ring_buffer_ctx *ctx,
  38                  struct lttng_channel *chan)
  39 {
  40         unsigned int mnt_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                 mnt_ns_inum = current->nsproxy->mnt_ns->ns.inum;
  51
  52         lib_ring_buffer_align_ctx(ctx, lttng_alignof(mnt_ns_inum));
  53         chan->ops->event_write(ctx, &mnt_ns_inum, sizeof(mnt_ns_inum));
  54 }
  55
  56 static
  57 void mnt_ns_get_value(struct lttng_ctx_field *field,
  58                 struct lttng_probe_ctx *lttng_probe_ctx,
  59                 union lttng_ctx_value *value)
  60 {
  61         unsigned int mnt_ns_inum = 0;
  62
  63         /*
  64          * nsproxy can be NULL when scheduled out of exit.
  65          *
  66          * As documented in 'linux/nsproxy.h' namespaces access rules, no
  67          * precautions should be taken when accessing the current task's
  68          * namespaces, just dereference the pointers.
  69          */
  70         if (current->nsproxy)
  71                 mnt_ns_inum = current->nsproxy->mnt_ns->ns.inum;
  72
  73         value->s64 = mnt_ns_inum;
  74 }
  75
  76 int lttng_add_mnt_ns_to_ctx(struct lttng_ctx **ctx)
  77 {
  78         struct lttng_ctx_field *field;
  79
  80         field = lttng_append_context(ctx);
  81         if (!field)
  82                 return -ENOMEM;
  83         if (lttng_find_context(*ctx, "mnt_ns")) {
  84                 lttng_remove_context_field(ctx, field);
  85                 return -EEXIST;
  86         }
  87         field->event_field.name = "mnt_ns";
  88         field->event_field.type.atype = atype_integer;
  89         field->event_field.type.u.integer.size = sizeof(unsigned int) * CHAR_BIT;
  90         field->event_field.type.u.integer.alignment = lttng_alignof(unsigned int) * CHAR_BIT;
  91         field->event_field.type.u.integer.signedness = lttng_is_signed_type(unsigned int);
  92         field->event_field.type.u.integer.reverse_byte_order = 0;
  93         field->event_field.type.u.integer.base = 10;
  94         field->event_field.type.u.integer.encoding = lttng_encode_none;
  95         field->get_size = mnt_ns_get_size;
  96         field->record = mnt_ns_record;
  97         field->get_value = mnt_ns_get_value;
  98         lttng_context_update(*ctx);
  99         return 0;
 100 }
 101 EXPORT_SYMBOL_GPL(lttng_add_mnt_ns_to_ctx);
 102
 103 #endif