Rename "comm" context to "procname"

[lttng-modules.git] / lttng-context-procname.c

diff --git a/lttng-context-procname.c b/lttng-context-procname.c
new file mode 100644 (file)
index 0000000..c6bc646
--- /dev/null
+++ b/lttng-context-procname.c
@@ -0,0 +1,72 @@
+/*
+ * (C) Copyright       2009-2011 -
+ *             Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * LTTng procname context.
+ *
+ * Dual LGPL v2.1/GPL v2 license.
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include "ltt-events.h"
+#include "wrapper/ringbuffer/frontend_types.h"
+#include "wrapper/vmalloc.h"
+#include "ltt-tracer.h"
+
+static
+size_t procname_get_size(size_t offset)
+{
+       size_t size = 0;
+
+       size += sizeof(current->comm);
+       return size;
+}
+
+/*
+ * Racy read of procname. We simply copy its whole array size.
+ * Races with /proc/<task>/procname write only.
+ * Otherwise having to take a mutex for each event is cumbersome and
+ * could lead to crash in IRQ context and deadlock of the lockdep tracer.
+ */
+static
+void procname_record(struct lttng_ctx_field *field,
+                struct lib_ring_buffer_ctx *ctx,
+                struct ltt_channel *chan)
+{
+       chan->ops->event_write(ctx, current->comm, sizeof(current->comm));
+}
+
+int lttng_add_procname_to_ctx(struct lttng_ctx **ctx)
+{
+       struct lttng_ctx_field *field;
+
+       field = lttng_append_context(ctx);
+       if (!field)
+               return -ENOMEM;
+       if (lttng_find_context(*ctx, "procname")) {
+               lttng_remove_context_field(ctx, field);
+               return -EEXIST;
+       }
+       field->event_field.name = "procname";
+       field->event_field.type.atype = atype_array;
+       field->event_field.type.u.array.elem_type.atype = atype_integer;
+       field->event_field.type.u.array.elem_type.u.basic.integer.size = sizeof(char) * CHAR_BIT;
+       field->event_field.type.u.array.elem_type.u.basic.integer.alignment = ltt_alignof(char) * CHAR_BIT;
+       field->event_field.type.u.array.elem_type.u.basic.integer.signedness = is_signed_type(char);
+       field->event_field.type.u.array.elem_type.u.basic.integer.reverse_byte_order = 0;
+       field->event_field.type.u.array.elem_type.u.basic.integer.base = 10;
+       field->event_field.type.u.array.elem_type.u.basic.integer.encoding = lttng_encode_UTF8;
+       field->event_field.type.u.array.length = sizeof(current->comm);
+
+       field->get_size = procname_get_size;
+       field->record = procname_record;
+       wrapper_vmalloc_sync_all();
+       return 0;
+}
+EXPORT_SYMBOL_GPL(lttng_add_procname_to_ctx);
+
+MODULE_LICENSE("GPL and additional rights");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("Linux Trace Toolkit Perf Support");