ftrace: add readpos to struct trace_seq; add trace_seq_to_user()

Refactor code from tracing_read_pipe() and create trace_seq_to_user().
Moved trace_seq_reset() call before iter->trace->read() call so that
when all leftover data is returned, trace_seq is reset automatically.

Signed-off-by: Pekka Paalanen <pq@iki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 3 insertions, 0 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index ee53d706066f..8845033ab49d 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -155,6 +155,7 @@ struct tracer {
 struct trace_seq {
         unsigned char           buffer[PAGE_SIZE];
         unsigned int            len;
+        unsigned int            readpos;
 };
 
 /*
@@ -301,6 +302,8 @@ extern int trace_selftest_startup_sched_switch(struct tracer *trace,
 
 extern void *head_page(struct trace_array_cpu *data);
 extern int trace_seq_printf(struct trace_seq *s, const char *fmt, ...);
+extern ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf,
+                                 size_t cnt);
 extern long ns2usecs(cycle_t nsec);
 
 extern unsigned long trace_flags;