src/lttng-context-vuid.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-vuid.c
   4  *
   5  * LTTng namespaced real user ID 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/sched.h>
  14 #include <linux/user_namespace.h>
  15
  16 #include <lttng/events.h>
  17 #include <lttng/events-internal.h>
  18 #include <lttng/tracer.h>
  19 #include <ringbuffer/frontend_types.h>
  20 #include <wrapper/vmalloc.h>
  21
  22 static
  23 size_t vuid_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset)
  24 {
  25         size_t size = 0;
  26
  27         size += lib_ring_buffer_align(offset, lttng_alignof(uid_t));
  28         size += sizeof(uid_t);
  29         return size;
  30 }
  31
  32 static
  33 void vuid_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx,
  34                  struct lttng_kernel_ring_buffer_ctx *ctx,
  35                  struct lttng_kernel_channel_buffer *chan)
  36 {
  37         uid_t vuid;
  38
  39         vuid = from_kuid_munged(current_user_ns(), current_uid());
  40         chan->ops->event_write(ctx, &vuid, sizeof(vuid), lttng_alignof(vuid));
  41 }
  42
  43 static
  44 void vuid_get_value(void *priv,
  45                 struct lttng_kernel_probe_ctx *lttng_probe_ctx,
  46                 struct lttng_ctx_value *value)
  47 {
  48         value->u.s64 = from_kuid_munged(current_user_ns(), current_uid());
  49 }
  50
  51 static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
  52         lttng_kernel_static_event_field("vuid",
  53                 lttng_kernel_static_type_integer_from_type(uid_t, __BYTE_ORDER, 10),
  54                 false, false),
  55         vuid_get_size,
  56         vuid_record,
  57         vuid_get_value,
  58         NULL, NULL);
  59
  60 int lttng_add_vuid_to_ctx(struct lttng_kernel_ctx **ctx)
  61 {
  62         int ret;
  63
  64         if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
  65                 return -EEXIST;
  66         ret = lttng_kernel_context_append(ctx, ctx_field);
  67         wrapper_vmalloc_sync_mappings();
  68         return ret;
  69 }
  70 EXPORT_SYMBOL_GPL(lttng_add_vuid_to_ctx);