lttng-context-ppid.c

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