src/lttng-context-migratable.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-migratable.c
   4  *
   5  * LTTng migratable context.
   6  *
   7  * Copyright (C) 2009-2015 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/slab.h>
  12 #include <linux/sched.h>
  13 #include <linux/irqflags.h>
  14 #include <lttng/events.h>
  15 #include <ringbuffer/frontend_types.h>
  16 #include <wrapper/vmalloc.h>
  17 #include <lttng/tracer.h>
  18
  19 static
  20 size_t migratable_get_size(size_t offset)
  21 {
  22         size_t size = 0;
  23
  24         size += lib_ring_buffer_align(offset, lttng_alignof(uint8_t));
  25         size += sizeof(uint8_t);
  26         return size;
  27 }
  28
  29 static
  30 void migratable_record(struct lttng_ctx_field *field,
  31                 struct lib_ring_buffer_ctx *ctx,
  32                 struct lttng_channel *chan)
  33 {
  34         uint8_t migratable = !current->migrate_disable;
  35
  36         lib_ring_buffer_align_ctx(ctx, lttng_alignof(migratable));
  37         chan->ops->event_write(ctx, &migratable, sizeof(migratable));
  38 }
  39
  40 static
  41 void migratable_get_value(struct lttng_ctx_field *field,
  42                 struct lttng_probe_ctx *lttng_probe_ctx,
  43                 union lttng_ctx_value *value)
  44 {
  45         value->s64 = !current->migrate_disable;
  46 }
  47
  48 int lttng_add_migratable_to_ctx(struct lttng_ctx **ctx)
  49 {
  50         struct lttng_ctx_field *field;
  51
  52         field = lttng_append_context(ctx);
  53         if (!field)
  54                 return -ENOMEM;
  55         if (lttng_find_context(*ctx, "migratable")) {
  56                 lttng_remove_context_field(ctx, field);
  57                 return -EEXIST;
  58         }
  59         field->event_field.name = "migratable";
  60         field->event_field.type.atype = atype_integer;
  61         field->event_field.type.u.integer.size = sizeof(uint8_t) * CHAR_BIT;
  62         field->event_field.type.u.integer.alignment = lttng_alignof(uint8_t) * CHAR_BIT;
  63         field->event_field.type.u.integer.signedness = lttng_is_signed_type(uint8_t);
  64         field->event_field.type.u.integer.reverse_byte_order = 0;
  65         field->event_field.type.u.integer.base = 10;
  66         field->event_field.type.u.integer.encoding = lttng_encode_none;
  67         field->get_size = migratable_get_size;
  68         field->record = migratable_record;
  69         field->get_value = migratable_get_value;
  70         lttng_context_update(*ctx);
  71         wrapper_vmalloc_sync_mappings();
  72         return 0;
  73 }
  74 EXPORT_SYMBOL_GPL(lttng_add_migratable_to_ctx);