src/lttng-context-prio.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-prio.c
   4  *
   5  * LTTng priority context.
   6  *
   7  * Copyright (C) 2009-2012 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 <lttng/events.h>
  14 #include <lttng/events-internal.h>
  15 #include <ringbuffer/frontend_types.h>
  16 #include <wrapper/vmalloc.h>
  17 #include <wrapper/kallsyms.h>
  18 #include <lttng/tracer.h>
  19
  20 static
  21 int (*wrapper_task_prio_sym)(struct task_struct *t);
  22
  23 int wrapper_task_prio_init(void)
  24 {
  25         wrapper_task_prio_sym = (void *) kallsyms_lookup_funcptr("task_prio");
  26         if (!wrapper_task_prio_sym) {
  27                 printk(KERN_WARNING "LTTng: task_prio symbol lookup failed.\n");
  28                 return -EINVAL;
  29         }
  30         return 0;
  31 }
  32
  33 /*
  34  * Canary function to check for 'task_prio()' at compile time.
  35  *
  36  * From 'include/linux/sched.h':
  37  *
  38  *   extern int task_prio(const struct task_struct *p);
  39  */
  40 __attribute__((unused)) static
  41 int __canary__task_prio(const struct task_struct *p)
  42 {
  43         return task_prio(p);
  44 }
  45
  46 static
  47 size_t prio_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset)
  48 {
  49         size_t size = 0;
  50
  51         size += lib_ring_buffer_align(offset, lttng_alignof(int));
  52         size += sizeof(int);
  53         return size;
  54 }
  55
  56 static
  57 void prio_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx,
  58                 struct lttng_kernel_ring_buffer_ctx *ctx,
  59                 struct lttng_kernel_channel_buffer *chan)
  60 {
  61         int prio;
  62
  63         prio = wrapper_task_prio_sym(current);
  64         lib_ring_buffer_align_ctx(ctx, lttng_alignof(prio));
  65         chan->ops->event_write(ctx, &prio, sizeof(prio));
  66 }
  67
  68 static
  69 void prio_get_value(void *priv,
  70                 struct lttng_kernel_probe_ctx *lttng_probe_ctx,
  71                 struct lttng_ctx_value *value)
  72 {
  73         value->u.s64 = wrapper_task_prio_sym(current);
  74 }
  75
  76 static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
  77         lttng_kernel_static_event_field("prio",
  78                 lttng_kernel_static_type_integer_from_type(int, __BYTE_ORDER, 10),
  79                 false, false, false),
  80         prio_get_size,
  81         prio_record,
  82         prio_get_value,
  83         NULL, NULL);
  84
  85 int lttng_add_prio_to_ctx(struct lttng_kernel_ctx **ctx)
  86 {
  87         int ret;
  88
  89         if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
  90                 return -EEXIST;
  91         ret = lttng_kernel_context_append(ctx, ctx_field);
  92         wrapper_vmalloc_sync_mappings();
  93         return ret;
  94 }
  95 EXPORT_SYMBOL_GPL(lttng_add_prio_to_ctx);