lttng-context-mnt-ns.c

   1 /* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1)
   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 <wrapper/vmalloc.h>
  19 #include <wrapper/namespace.h>
  20 #include <lttng-tracer.h>
  21
  22 #if !defined(LTTNG_MNT_NS_MISSING_HEADER) && \
  23         (LINUX_VERSION_CODE >= KERNEL_VERSION(3,8,0))
  24
  25 #include <../fs/mount.h>
  26
  27 static
  28 size_t mnt_ns_get_size(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 mnt_ns_record(struct lttng_ctx_field *field,
  39                  struct lib_ring_buffer_ctx *ctx,
  40                  struct lttng_channel *chan)
  41 {
  42         unsigned int mnt_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                 mnt_ns_inum = current->nsproxy->mnt_ns->lttng_ns_inum;
  53
  54         lib_ring_buffer_align_ctx(ctx, lttng_alignof(mnt_ns_inum));
  55         chan->ops->event_write(ctx, &mnt_ns_inum, sizeof(mnt_ns_inum));
  56 }
  57
  58 static
  59 void mnt_ns_get_value(struct lttng_ctx_field *field,
  60                 struct lttng_probe_ctx *lttng_probe_ctx,
  61                 union lttng_ctx_value *value)
  62 {
  63         unsigned int mnt_ns_inum = 0;
  64
  65         /*
  66          * nsproxy can be NULL when scheduled out of exit.
  67          *
  68          * As documented in 'linux/nsproxy.h' namespaces access rules, no
  69          * precautions should be taken when accessing the current task's
  70          * namespaces, just dereference the pointers.
  71          */
  72         if (current->nsproxy)
  73                 mnt_ns_inum = current->nsproxy->mnt_ns->lttng_ns_inum;
  74
  75         value->s64 = mnt_ns_inum;
  76 }
  77
  78 int lttng_add_mnt_ns_to_ctx(struct lttng_ctx **ctx)
  79 {
  80         struct lttng_ctx_field *field;
  81
  82         field = lttng_append_context(ctx);
  83         if (!field)
  84                 return -ENOMEM;
  85         if (lttng_find_context(*ctx, "mnt_ns")) {
  86                 lttng_remove_context_field(ctx, field);
  87                 return -EEXIST;
  88         }
  89         field->event_field.name = "mnt_ns";
  90         field->event_field.type.atype = atype_integer;
  91         field->event_field.type.u.basic.integer.size = sizeof(unsigned int) * CHAR_BIT;
  92         field->event_field.type.u.basic.integer.alignment = lttng_alignof(unsigned int) * CHAR_BIT;
  93         field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(unsigned int);
  94         field->event_field.type.u.basic.integer.reverse_byte_order = 0;
  95         field->event_field.type.u.basic.integer.base = 10;
  96         field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
  97         field->get_size = mnt_ns_get_size;
  98         field->record = mnt_ns_record;
  99         field->get_value = mnt_ns_get_value;
 100         lttng_context_update(*ctx);
 101         wrapper_vmalloc_sync_all();
 102         return 0;
 103 }
 104 EXPORT_SYMBOL_GPL(lttng_add_mnt_ns_to_ctx);
 105
 106 #endif