tracing: Add trigger file for trace_markers tracefs/ftrace/print

Allow writing to the trace_markers file initiate triggers defined in
tracefs/ftrace/print/trigger file. This will allow of user space to trigger
the same type of triggers (including histograms) that the trace events use.

Had to create a ftrace_event_register() function that will become the
trace_marker print event's reg() function. This is required because of how
triggers are enabled:

  event_trigger_write() {
    event_trigger_regex_write() {
      trigger_process_regex() {
        for p in trigger_commands {
          p->func(); /* trigger_snapshot_cmd->func */
            event_trigger_callback() {
              cmd_ops->reg() /* register_trigger() */ {
                trace_event_trigger_enable_disable() {
                  trace_event_enable_disable() {
                    call->class->reg();

Without the reg() function, the trigger code will call a NULL pointer and
crash the system.

Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Karim Yaghmour <karim.yaghmour@opersys.com>
Cc: Brendan Gregg <bgregg@netflix.com>
Suggested-by: Joel Fernandes <joelaf@google.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d5000cb..e69820f 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6074,6 +6074,7 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
 {
        struct trace_array *tr = filp->private_data;
        struct ring_buffer_event *event;
+       enum event_trigger_type tt = ETT_NONE;
        struct ring_buffer *buffer;
        struct print_entry *entry;
        unsigned long irq_flags;
@@ -6122,6 +6123,12 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
                written = cnt;
        len = cnt;
 
+       if (tr->trace_marker_file && !list_empty(&tr->trace_marker_file->triggers)) {
+               /* do not add \n before testing triggers, but add \0 */
+               entry->buf[cnt] = '\0';
+               tt = event_triggers_call(tr->trace_marker_file, entry, event);
+       }
+
        if (entry->buf[cnt - 1] != '\n') {
                entry->buf[cnt] = '\n';
                entry->buf[cnt + 1] = '\0';
@@ -6130,6 +6137,9 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
 
        __buffer_unlock_commit(buffer, event);
 
+       if (tt)
+               event_triggers_post_call(tr->trace_marker_file, tt);
+
        if (written > 0)
                *fpos += written;
 
@@ -7896,6 +7906,7 @@ static __init void create_trace_instances(struct dentry *d_tracer)
 static void
 init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
 {
+       struct trace_event_file *file;
        int cpu;
 
        trace_create_file("available_tracers", 0444, d_tracer,
@@ -7928,6 +7939,12 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
        trace_create_file("trace_marker", 0220, d_tracer,
                          tr, &tracing_mark_fops);
 
+       file = __find_event_file(tr, "ftrace", "print");
+       if (file && file->dir)
+               trace_create_file("trigger", 0644, file->dir, file,
+                                 &event_trigger_fops);
+       tr->trace_marker_file = file;
+
        trace_create_file("trace_marker_raw", 0220, d_tracer,
                          tr, &tracing_mark_raw_fops);
 

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index d0319cb..630c5a2 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -259,6 +259,7 @@ struct trace_array {
        struct trace_options    *topts;
        struct list_head        systems;
        struct list_head        events;
+       struct trace_event_file *trace_marker_file;
        cpumask_var_t           tracing_cpumask; /* only trace on set CPUs */
        int                     ref;
 #ifdef CONFIG_FUNCTION_TRACER

diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index e3a658b..1d67464 100644 (file)
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -230,7 +230,7 @@ FTRACE_ENTRY(bprint, bprint_entry,
        FILTER_OTHER
 );
 
-FTRACE_ENTRY(print, print_entry,
+FTRACE_ENTRY_REG(print, print_entry,
 
        TRACE_PRINT,
 
@@ -242,7 +242,9 @@ FTRACE_ENTRY(print, print_entry,
        F_printk("%ps: %s",
                 (void *)__entry->ip, __entry->buf),
 
-       FILTER_OTHER
+       FILTER_OTHER,
+
+       ftrace_event_register
 );
 
 FTRACE_ENTRY(raw_data, raw_data_entry,

diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c
index d842f1e..45630a7 100644 (file)
--- a/kernel/trace/trace_export.c
+++ b/kernel/trace/trace_export.c
@@ -14,6 +14,13 @@
 
 #include "trace_output.h"
 
+/* Stub function for events with triggers */
+static int ftrace_event_register(struct trace_event_call *call,
+                                enum trace_reg type, void *data)
+{
+       return 0;
+}
+
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM   ftrace