tracing: Add trace_puts() for even faster trace_printk() tracing

The trace_printk() is extremely fast and is very handy as it can be
used in any context (including NMIs!). But it still requires scanning
the fmt string for parsing the args. Even the trace_bprintk() requires
a scan to know what args will be saved, although it doesn't copy the
format string itself.

Several times trace_printk() has no args, and wastes cpu cycles scanning
the fmt string.

Adding trace_puts() allows the developer to use an even faster
tracing method that only saves the pointer to the string in the
ring buffer without doing any format parsing at all. This will
help remove even more of the "Heisenbug" effect, when debugging.

Also fixed up the F_printk()s for the ftrace internal bprint and print events.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 75 insertions, 0 deletions

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 2edc7220d017..19f48e7edc39 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -37,6 +37,22 @@ int trace_print_seq(struct seq_file *m, struct trace_seq *s)
         return ret;
 }
 
+enum print_line_t trace_print_bputs_msg_only(struct trace_iterator *iter)
+{
+        struct trace_seq *s = &iter->seq;
+        struct trace_entry *entry = iter->ent;
+        struct bputs_entry *field;
+        int ret;
+
+        trace_assign_type(field, entry);
+
+        ret = trace_seq_puts(s, field->str);
+        if (!ret)
+                return TRACE_TYPE_PARTIAL_LINE;
+
+        return TRACE_TYPE_HANDLED;
+}
+
 enum print_line_t trace_print_bprintk_msg_only(struct trace_iterator *iter)
 {
         struct trace_seq *s = &iter->seq;
@@ -1244,6 +1260,64 @@ static struct trace_event trace_user_stack_event = {
         .funcs          = &trace_user_stack_funcs,
 };
 
+/* TRACE_BPUTS */
+static enum print_line_t
+trace_bputs_print(struct trace_iterator *iter, int flags,
+                   struct trace_event *event)
+{
+        struct trace_entry *entry = iter->ent;
+        struct trace_seq *s = &iter->seq;
+        struct bputs_entry *field;
+
+        trace_assign_type(field, entry);
+
+        if (!seq_print_ip_sym(s, field->ip, flags))
+                goto partial;
+
+        if (!trace_seq_puts(s, ": "))
+                goto partial;
+
+        if (!trace_seq_puts(s, field->str))
+                goto partial;
+
+        return TRACE_TYPE_HANDLED;
+
+ partial:
+        return TRACE_TYPE_PARTIAL_LINE;
+}
+
+
+static enum print_line_t
+trace_bputs_raw(struct trace_iterator *iter, int flags,
+                struct trace_event *event)
+{
+        struct bputs_entry *field;
+        struct trace_seq *s = &iter->seq;
+
+        trace_assign_type(field, iter->ent);
+
+        if (!trace_seq_printf(s, ": %lx : ", field->ip))
+                goto partial;
+
+        if (!trace_seq_puts(s, field->str))
+                goto partial;
+
+        return TRACE_TYPE_HANDLED;
+
+ partial:
+        return TRACE_TYPE_PARTIAL_LINE;
+}
+
+static struct trace_event_functions trace_bputs_funcs = {
+        .trace          = trace_bputs_print,
+        .raw            = trace_bputs_raw,
+};
+
+static struct trace_event trace_bputs_event = {
+        .type           = TRACE_BPUTS,
+        .funcs          = &trace_bputs_funcs,
+};
+
 /* TRACE_BPRINT */
 static enum print_line_t
 trace_bprint_print(struct trace_iterator *iter, int flags,
@@ -1356,6 +1430,7 @@ static struct trace_event *events[] __initdata = {
         &trace_wake_event,
         &trace_stack_event,
         &trace_user_stack_event,
+        &trace_bputs_event,
         &trace_bprint_event,
         &trace_print_event,
         NULL