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authorChunyan Zhang <zhang.chunyan@linaro.org>2016-11-21 15:57:18 +0800
committerSteven Rostedt <rostedt@goodmis.org>2016-11-22 17:40:00 -0500
commit478409dd683db76cbcfe7bf8332a37f01deb0a2d (patch)
treeaceb894271a28bea11df6930c6ca7227ea5c6c03 /kernel/trace
parent153aae5f996d4cb3e8a64990b6b09cde4a1529b0 (diff)
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tracing: Add hook to function tracing for other subsystems to use
Currently Function traces can be only exported to the ring buffer. This adds a trace_export concept which can process traces and export them to a registered destination as an addition to the current one that outputs to Ftrace - i.e. ring buffer. In this way, if we want function traces to be sent to other destinations rather than only to the ring buffer, we just need to register a new trace_export and implement its own .write() function for writing traces to storage. With this patch, only function tracing (trace type is TRACE_FN) is supported. Link: http://lkml.kernel.org/r/1479715043-6534-2-git-send-email-zhang.chunyan@linaro.org Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/trace.c129
1 files changed, 128 insertions, 1 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 57069e7f369c..edccdff8a36d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -40,6 +40,7 @@
#include <linux/poll.h>
#include <linux/nmi.h>
#include <linux/fs.h>
+#include <linux/trace.h>
#include <linux/sched/rt.h>
#include "trace.h"
@@ -2128,6 +2129,129 @@ void trace_buffer_unlock_commit_regs(struct trace_array *tr,
ftrace_trace_userstack(buffer, flags, pc);
}
+static void
+trace_process_export(struct trace_export *export,
+ struct ring_buffer_event *event)
+{
+ struct trace_entry *entry;
+ unsigned int size = 0;
+
+ entry = ring_buffer_event_data(event);
+ size = ring_buffer_event_length(event);
+ export->write(entry, size);
+}
+
+static DEFINE_MUTEX(ftrace_export_lock);
+
+static struct trace_export __rcu *ftrace_exports_list __read_mostly;
+
+static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled);
+
+static inline void ftrace_exports_enable(void)
+{
+ static_branch_enable(&ftrace_exports_enabled);
+}
+
+static inline void ftrace_exports_disable(void)
+{
+ static_branch_disable(&ftrace_exports_enabled);
+}
+
+void ftrace_exports(struct ring_buffer_event *event)
+{
+ struct trace_export *export;
+
+ preempt_disable_notrace();
+
+ export = rcu_dereference_raw_notrace(ftrace_exports_list);
+ while (export) {
+ trace_process_export(export, event);
+ export = rcu_dereference_raw_notrace(export->next);
+ }
+
+ preempt_enable_notrace();
+}
+
+static inline void
+add_trace_export(struct trace_export **list, struct trace_export *export)
+{
+ rcu_assign_pointer(export->next, *list);
+ /*
+ * We are entering export into the list but another
+ * CPU might be walking that list. We need to make sure
+ * the export->next pointer is valid before another CPU sees
+ * the export pointer included into the list.
+ */
+ rcu_assign_pointer(*list, export);
+}
+
+static inline int
+rm_trace_export(struct trace_export **list, struct trace_export *export)
+{
+ struct trace_export **p;
+
+ for (p = list; *p != NULL; p = &(*p)->next)
+ if (*p == export)
+ break;
+
+ if (*p != export)
+ return -1;
+
+ rcu_assign_pointer(*p, (*p)->next);
+
+ return 0;
+}
+
+static inline void
+add_ftrace_export(struct trace_export **list, struct trace_export *export)
+{
+ if (*list == NULL)
+ ftrace_exports_enable();
+
+ add_trace_export(list, export);
+}
+
+static inline int
+rm_ftrace_export(struct trace_export **list, struct trace_export *export)
+{
+ int ret;
+
+ ret = rm_trace_export(list, export);
+ if (*list == NULL)
+ ftrace_exports_disable();
+
+ return ret;
+}
+
+int register_ftrace_export(struct trace_export *export)
+{
+ if (WARN_ON_ONCE(!export->write))
+ return -1;
+
+ mutex_lock(&ftrace_export_lock);
+
+ add_ftrace_export(&ftrace_exports_list, export);
+
+ mutex_unlock(&ftrace_export_lock);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(register_ftrace_export);
+
+int unregister_ftrace_export(struct trace_export *export)
+{
+ int ret;
+
+ mutex_lock(&ftrace_export_lock);
+
+ ret = rm_ftrace_export(&ftrace_exports_list, export);
+
+ mutex_unlock(&ftrace_export_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(unregister_ftrace_export);
+
void
trace_function(struct trace_array *tr,
unsigned long ip, unsigned long parent_ip, unsigned long flags,
@@ -2146,8 +2270,11 @@ trace_function(struct trace_array *tr,
entry->ip = ip;
entry->parent_ip = parent_ip;
- if (!call_filter_check_discard(call, entry, buffer, event))
+ if (!call_filter_check_discard(call, entry, buffer, event)) {
+ if (static_branch_unlikely(&ftrace_exports_enabled))
+ ftrace_exports(event);
__buffer_unlock_commit(buffer, event);
+ }
}
#ifdef CONFIG_STACKTRACE