src/lttng-context-veuid.c

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