From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
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@xxxxxxxxxxxxxxx>
Cc: Clark Williams <williams@xxxxxxxxxx>
Cc: Karim Yaghmour <karim.yaghmour@xxxxxxxxxxx>
Cc: Brendan Gregg <bgregg@xxxxxxxxxxx>
Suggested-by: Joel Fernandes <joelaf@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
kernel/trace/trace.c | 17 +++++++++++++++++
kernel/trace/trace.h | 1 +
kernel/trace/trace_entries.h | 6 ++++--
kernel/trace/trace_export.c | 7 +++++++
4 files changed, 29 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e0d6ffb76985..f11b89fa5049 100644
--- 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 2414fd72dedd..c7fa58d31a84 100644
--- 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 e3a658bac10f..1d67464ed95e 100644
--- 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 d842f1eadfe5..45630a76ed3a 100644
--- 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
--
2.17.0
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