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 <lttng/events-internal.h>
  16 #include <ringbuffer/frontend_types.h>
  17 #include <wrapper/vmalloc.h>
  18 #include <lttng/tracer.h>
  19
  20 static
  21 size_t migratable_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset)
  22 {
  23         size_t size = 0;
  24
  25         size += lib_ring_buffer_align(offset, lttng_alignof(uint8_t));
  26         size += sizeof(uint8_t);
  27         return size;
  28 }
  29
  30 static
  31 void migratable_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx,
  32                 struct lttng_kernel_ring_buffer_ctx *ctx,
  33                 struct lttng_channel *chan)
  34 {
  35         uint8_t migratable = !current->migrate_disable;
  36
  37         lib_ring_buffer_align_ctx(ctx, lttng_alignof(migratable));
  38         chan->ops->event_write(ctx, &migratable, sizeof(migratable));
  39 }
  40
  41 static
  42 void migratable_get_value(void *priv,
  43                 struct lttng_kernel_probe_ctx *lttng_probe_ctx,
  44                 struct lttng_ctx_value *value)
  45 {
  46         value->u.s64 = !current->migrate_disable;
  47 }
  48
  49 static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
  50         lttng_kernel_static_event_field("migratable",
  51                 lttng_kernel_static_type_integer_from_type(uint8_t, __BYTE_ORDER, 10),
  52                 false, false, false),
  53         migratable_get_size,
  54         migratable_record,
  55         migratable_get_value,
  56         NULL, NULL);
  57
  58 int lttng_add_migratable_to_ctx(struct lttng_kernel_ctx **ctx)
  59 {
  60         int ret;
  61
  62         if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
  63                 return -EEXIST;
  64         ret = lttng_kernel_context_append(ctx, ctx_field);
  65         wrapper_vmalloc_sync_mappings();
  66         return ret;
  67 }
  68 EXPORT_SYMBOL_GPL(lttng_add_migratable_to_ctx);