lttng-context-ppid.c

   1 /* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1)
   2  *
   3  * lttng-context-ppid.c
   4  *
   5  * LTTng PPID 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 <linux/syscalls.h>
  14 #include <lttng-events.h>
  15 #include <wrapper/ringbuffer/frontend_types.h>
  16 #include <wrapper/vmalloc.h>
  17 #include <lttng-tracer.h>
  18
  19 static
  20 size_t ppid_get_size(size_t offset)
  21 {
  22         size_t size = 0;
  23
  24         size += lib_ring_buffer_align(offset, lttng_alignof(pid_t));
  25         size += sizeof(pid_t);
  26         return size;
  27 }
  28
  29 static
  30 void ppid_record(struct lttng_ctx_field *field,
  31                  struct lib_ring_buffer_ctx *ctx,
  32                  struct lttng_channel *chan)
  33 {
  34         pid_t ppid;
  35
  36         /*
  37          * TODO: when we eventually add RCU subsystem instrumentation,
  38          * taking the rcu read lock here will trigger RCU tracing
  39          * recursively. We should modify the kernel synchronization so
  40          * it synchronizes both for RCU and RCU sched, and rely on
  41          * rcu_read_lock_sched_notrace.
  42          */
  43         rcu_read_lock();
  44         ppid = task_tgid_nr(current->real_parent);
  45         rcu_read_unlock();
  46         lib_ring_buffer_align_ctx(ctx, lttng_alignof(ppid));
  47         chan->ops->event_write(ctx, &ppid, sizeof(ppid));
  48 }
  49
  50 static
  51 void ppid_get_value(struct lttng_ctx_field *field,
  52                 struct lttng_probe_ctx *lttng_probe_ctx,
  53                 union lttng_ctx_value *value)
  54 {
  55         pid_t ppid;
  56
  57         /*
  58          * TODO: when we eventually add RCU subsystem instrumentation,
  59          * taking the rcu read lock here will trigger RCU tracing
  60          * recursively. We should modify the kernel synchronization so
  61          * it synchronizes both for RCU and RCU sched, and rely on
  62          * rcu_read_lock_sched_notrace.
  63          */
  64         rcu_read_lock();
  65         ppid = task_tgid_nr(current->real_parent);
  66         rcu_read_unlock();
  67         value->s64 = ppid;
  68 }
  69
  70 int lttng_add_ppid_to_ctx(struct lttng_ctx **ctx)
  71 {
  72         struct lttng_ctx_field *field;
  73
  74         field = lttng_append_context(ctx);
  75         if (!field)
  76                 return -ENOMEM;
  77         if (lttng_find_context(*ctx, "ppid")) {
  78                 lttng_remove_context_field(ctx, field);
  79                 return -EEXIST;
  80         }
  81         field->event_field.name = "ppid";
  82         field->event_field.type.atype = atype_integer;
  83         field->event_field.type.u.basic.integer.size = sizeof(pid_t) * CHAR_BIT;
  84         field->event_field.type.u.basic.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
  85         field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(pid_t);
  86         field->event_field.type.u.basic.integer.reverse_byte_order = 0;
  87         field->event_field.type.u.basic.integer.base = 10;
  88         field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
  89         field->get_size = ppid_get_size;
  90         field->record = ppid_record;
  91         field->get_value = ppid_get_value;
  92         lttng_context_update(*ctx);
  93         wrapper_vmalloc_sync_all();
  94         return 0;
  95 }
  96 EXPORT_SYMBOL_GPL(lttng_add_ppid_to_ctx);