src/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 <lttng/events-internal.h>
  17 #include <linux/nsproxy.h>
  18 #include <ringbuffer/frontend_types.h>
  19 #include <wrapper/vmalloc.h>
  20 #include <wrapper/namespace.h>
  21 #include <lttng/tracer.h>
  22
  23 #if !defined(LTTNG_MNT_NS_MISSING_HEADER) && \
  24         (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(3,8,0))
  25
  26 #include <../fs/mount.h>
  27
  28 static
  29 size_t mnt_ns_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset)
  30 {
  31         size_t size = 0;
  32
  33         size += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
  34         size += sizeof(unsigned int);
  35         return size;
  36 }
  37
  38 static
  39 void mnt_ns_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx,
  40                  struct lttng_kernel_ring_buffer_ctx *ctx,
  41                  struct lttng_kernel_channel_buffer *chan)
  42 {
  43         unsigned int mnt_ns_inum = 0;
  44
  45         /*
  46          * nsproxy can be NULL when scheduled out of exit.
  47          *
  48          * As documented in 'linux/nsproxy.h' namespaces access rules, no
  49          * precautions should be taken when accessing the current task's
  50          * namespaces, just dereference the pointers.
  51          */
  52         if (current->nsproxy)
  53                 mnt_ns_inum = current->nsproxy->mnt_ns->lttng_ns_inum;
  54
  55         lib_ring_buffer_align_ctx(ctx, lttng_alignof(mnt_ns_inum));
  56         chan->ops->event_write(ctx, &mnt_ns_inum, sizeof(mnt_ns_inum));
  57 }
  58
  59 static
  60 void mnt_ns_get_value(void *priv,
  61                 struct lttng_kernel_probe_ctx *lttng_probe_ctx,
  62                 struct lttng_ctx_value *value)
  63 {
  64         unsigned int mnt_ns_inum = 0;
  65
  66         /*
  67          * nsproxy can be NULL when scheduled out of exit.
  68          *
  69          * As documented in 'linux/nsproxy.h' namespaces access rules, no
  70          * precautions should be taken when accessing the current task's
  71          * namespaces, just dereference the pointers.
  72          */
  73         if (current->nsproxy)
  74                 mnt_ns_inum = current->nsproxy->mnt_ns->lttng_ns_inum;
  75
  76         value->u.s64 = mnt_ns_inum;
  77 }
  78
  79 static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
  80         lttng_kernel_static_event_field("mnt_ns",
  81                 lttng_kernel_static_type_integer_from_type(unsigned int, __BYTE_ORDER, 10),
  82                 false, false, false),
  83         mnt_ns_get_size,
  84         mnt_ns_record,
  85         mnt_ns_get_value,
  86         NULL, NULL);
  87
  88 int lttng_add_mnt_ns_to_ctx(struct lttng_kernel_ctx **ctx)
  89 {
  90         int ret;
  91
  92         if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
  93                 return -EEXIST;
  94         ret = lttng_kernel_context_append(ctx, ctx_field);
  95         wrapper_vmalloc_sync_mappings();
  96         return ret;
  97 }
  98 EXPORT_SYMBOL_GPL(lttng_add_mnt_ns_to_ctx);
  99
 100 #endif