new file mode 100644
@@ -0,0 +1,28 @@
+#ifndef _LINUX_TRACE_H
+#define _LINUX_TRACE_H
+
+#ifdef CONFIG_TRACING
+/*
+ * The trace export - an export of Ftrace output. The trace_export
+ * can process traces and export them to a registered destination as
+ * an addition to the current only output of Ftrace - i.e. ring buffer.
+ *
+ * If you want traces to be sent to some other place rather than ring
+ * buffer only, just need to register a new trace_export and implement
+ * its own .write() function for writing traces to the storage.
+ *
+ * next - pointer to the next trace_export
+ * write - copy traces which have been delt with ->commit() to
+ * the destination
+ */
+struct trace_export {
+ struct trace_export __rcu *next;
+ void (*write)(const void *, unsigned int);
+};
+
+int register_ftrace_export(struct trace_export *export);
+int unregister_ftrace_export(struct trace_export *export);
+
+#endif /* CONFIG_TRACING */
+
+#endif /* _LINUX_TRACE_H */
@@ -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
Currently Function traces can be only exported to ring buffer, this patch added trace_export concept which can process traces and export them to a registered destination as an addition to the current only one output of Ftrace - i.e. ring buffer. In this way, if we want Function traces to be sent to other destination rather than ring buffer only, 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 trace (trace type is TRACE_FN) is supported. Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org> --- include/linux/trace.h | 28 +++++++++++ kernel/trace/trace.c | 129 +++++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 156 insertions(+), 1 deletion(-) create mode 100644 include/linux/trace.h