src/lttng-context-vsgid.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-vsgid.c
   4  *
   5  * LTTng namespaced saved set-group-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 vsgid_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset)
  23 {
  24         size_t size = 0;
  25
  26         size += lib_ring_buffer_align(offset, lttng_alignof(gid_t));
  27         size += sizeof(gid_t);
  28         return size;
  29 }
  30
  31 static
  32 void vsgid_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx,
  33                  struct lttng_kernel_ring_buffer_ctx *ctx,
  34                  struct lttng_kernel_channel_buffer *chan)
  35 {
  36         gid_t vsgid;
  37
  38         vsgid = lttng_current_vsgid();
  39         chan->ops->event_write(ctx, &vsgid, sizeof(vsgid), lttng_alignof(vsgid));
  40 }
  41
  42 static
  43 void vsgid_get_value(void *priv,
  44                 struct lttng_kernel_probe_ctx *lttng_probe_ctx,
  45                 struct lttng_ctx_value *value)
  46 {
  47         value->u.s64 = lttng_current_vsgid();
  48 }
  49
  50 static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
  51         lttng_kernel_static_event_field("vsgid",
  52                 lttng_kernel_static_type_integer_from_type(gid_t, __BYTE_ORDER, 10),
  53                 false, false, false),
  54         vsgid_get_size,
  55         vsgid_record,
  56         vsgid_get_value,
  57         NULL, NULL);
  58
  59 int lttng_add_vsgid_to_ctx(struct lttng_kernel_ctx **ctx)
  60 {
  61         int ret;
  62
  63         if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
  64                 return -EEXIST;
  65         ret = lttng_kernel_context_append(ctx, ctx_field);
  66         wrapper_vmalloc_sync_mappings();
  67         return ret;
  68 }
  69 EXPORT_SYMBOL_GPL(lttng_add_vsgid_to_ctx);