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 <ringbuffer/frontend_types.h>
  15 #include <wrapper/vmalloc.h>
  16 #include <wrapper/kallsyms.h>
  17 #include <lttng/tracer.h>
  18
  19 static
  20 int (*wrapper_task_prio_sym)(struct task_struct *t);
  21
  22 int wrapper_task_prio_init(void)
  23 {
  24         wrapper_task_prio_sym = (void *) kallsyms_lookup_funcptr("task_prio");
  25         if (!wrapper_task_prio_sym) {
  26                 printk(KERN_WARNING "LTTng: task_prio symbol lookup failed.\n");
  27                 return -EINVAL;
  28         }
  29         return 0;
  30 }
  31
  32 /*
  33  * Canary function to check for 'task_prio()' at compile time.
  34  *
  35  * From 'include/linux/sched.h':
  36  *
  37  *   extern int task_prio(const struct task_struct *p);
  38  */
  39 __attribute__((unused)) static
  40 int __canary__task_prio(const struct task_struct *p)
  41 {
  42         return task_prio(p);
  43 }
  44
  45 static
  46 size_t prio_get_size(size_t offset)
  47 {
  48         size_t size = 0;
  49
  50         size += lib_ring_buffer_align(offset, lttng_alignof(int));
  51         size += sizeof(int);
  52         return size;
  53 }
  54
  55 static
  56 void prio_record(struct lttng_ctx_field *field,
  57                 struct lib_ring_buffer_ctx *ctx,
  58                 struct lttng_channel *chan)
  59 {
  60         int prio;
  61
  62         prio = wrapper_task_prio_sym(current);
  63         lib_ring_buffer_align_ctx(ctx, lttng_alignof(prio));
  64         chan->ops->event_write(ctx, &prio, sizeof(prio));
  65 }
  66
  67 static
  68 void prio_get_value(struct lttng_ctx_field *field,
  69                 struct lttng_probe_ctx *lttng_probe_ctx,
  70                 union lttng_ctx_value *value)
  71 {
  72         value->s64 = wrapper_task_prio_sym(current);
  73 }
  74
  75 int lttng_add_prio_to_ctx(struct lttng_ctx **ctx)
  76 {
  77         struct lttng_ctx_field *field;
  78         int ret;
  79
  80         if (!wrapper_task_prio_sym) {
  81                 ret = wrapper_task_prio_init();
  82                 if (ret)
  83                         return ret;
  84         }
  85
  86         field = lttng_append_context(ctx);
  87         if (!field)
  88                 return -ENOMEM;
  89         if (lttng_find_context(*ctx, "prio")) {
  90                 lttng_remove_context_field(ctx, field);
  91                 return -EEXIST;
  92         }
  93         field->event_field.name = "prio";
  94         field->event_field.type.atype = atype_integer;
  95         field->event_field.type.u.integer.size = sizeof(int) * CHAR_BIT;
  96         field->event_field.type.u.integer.alignment = lttng_alignof(int) * CHAR_BIT;
  97         field->event_field.type.u.integer.signedness = lttng_is_signed_type(int);
  98         field->event_field.type.u.integer.reverse_byte_order = 0;
  99         field->event_field.type.u.integer.base = 10;
 100         field->event_field.type.u.integer.encoding = lttng_encode_none;
 101         field->get_size = prio_get_size;
 102         field->record = prio_record;
 103         field->get_value = prio_get_value;
 104         lttng_context_update(*ctx);
 105         wrapper_vmalloc_sync_mappings();
 106         return 0;
 107 }
 108 EXPORT_SYMBOL_GPL(lttng_add_prio_to_ctx);