src/lttng-context-suid.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-suid.c
   4  *
   5  * LTTng saved set-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/tracer.h>
  16 #include <ringbuffer/frontend_types.h>
  17 #include <wrapper/vmalloc.h>
  18 #include <wrapper/user_namespace.h>
  19
  20 static
  21 size_t suid_get_size(size_t offset)
  22 {
  23         size_t size = 0;
  24
  25         size += lib_ring_buffer_align(offset, lttng_alignof(uid_t));
  26         size += sizeof(uid_t);
  27         return size;
  28 }
  29
  30 static
  31 void suid_record(struct lttng_ctx_field *field,
  32                  struct lib_ring_buffer_ctx *ctx,
  33                  struct lttng_channel *chan)
  34 {
  35         uid_t suid;
  36
  37         suid = lttng_current_suid();
  38         lib_ring_buffer_align_ctx(ctx, lttng_alignof(suid));
  39         chan->ops->event_write(ctx, &suid, sizeof(suid));
  40 }
  41
  42 static
  43 void suid_get_value(struct lttng_ctx_field *field,
  44                 struct lttng_probe_ctx *lttng_probe_ctx,
  45                 union lttng_ctx_value *value)
  46 {
  47         value->s64 = lttng_current_suid();
  48 }
  49
  50 int lttng_add_suid_to_ctx(struct lttng_ctx **ctx)
  51 {
  52         struct lttng_ctx_field *field;
  53
  54         field = lttng_append_context(ctx);
  55         if (!field)
  56                 return -ENOMEM;
  57         if (lttng_find_context(*ctx, "suid")) {
  58                 lttng_remove_context_field(ctx, field);
  59                 return -EEXIST;
  60         }
  61         field->event_field.name = "suid";
  62         field->event_field.type.atype = atype_integer;
  63         field->event_field.type.u.integer.size = sizeof(uid_t) * CHAR_BIT;
  64         field->event_field.type.u.integer.alignment = lttng_alignof(uid_t) * CHAR_BIT;
  65         field->event_field.type.u.integer.signedness = lttng_is_signed_type(uid_t);
  66         field->event_field.type.u.integer.reverse_byte_order = 0;
  67         field->event_field.type.u.integer.base = 10;
  68         field->event_field.type.u.integer.encoding = lttng_encode_none;
  69         field->get_size = suid_get_size;
  70         field->record = suid_record;
  71         field->get_value = suid_get_value;
  72         lttng_context_update(*ctx);
  73         wrapper_vmalloc_sync_mappings();
  74         return 0;
  75 }
  76 EXPORT_SYMBOL_GPL(lttng_add_suid_to_ctx);