tracing: Ignore mmiotrace from kernel commandline

The mmiotrace tracer cannot be enabled with ftrace=mmiotrace in kernel
commandline. With this patch, noboot is added to the tracer struct,
and when system boot with a tracer that has noboot=true, it will print
out a warning message and continue booting.

Link: http://lkml.kernel.org/r/1505111195-31942-1-git-send-email-zsun@redhat.com
Signed-off-by: Ziqian SUN (Zamir) <zsun@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a7fb136..d3ca35f 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5364,6 +5364,13 @@ static int tracing_set_tracer(struct trace_array *tr, const char *buf)
        if (t == tr->current_trace)
                goto out;
 
+       /* Some tracers won't work on kernel command line */
+       if (system_state < SYSTEM_RUNNING && t->noboot) {
+               pr_warn("Tracer '%s' is not allowed on command line, ignored\n",
+                       t->name);
+               goto out;
+       }
+
        /* Some tracers are only allowed for the top level buffer */
        if (!trace_ok_for_array(t, tr)) {
                ret = -EINVAL;

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index fb5d54d..652c682 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -444,6 +444,8 @@ struct tracer {
 #ifdef CONFIG_TRACER_MAX_TRACE
        bool                    use_max_tr;
 #endif
+       /* True if tracer cannot be enabled in kernel param */
+       bool                    noboot;
 };
 
 

diff --git a/kernel/trace/trace_mmiotrace.c b/kernel/trace/trace_mmiotrace.c
index cd7480d..dca78fc 100644 (file)
--- a/kernel/trace/trace_mmiotrace.c
+++ b/kernel/trace/trace_mmiotrace.c
@@ -282,6 +282,7 @@ static struct tracer mmio_tracer __read_mostly =
        .close          = mmio_close,
        .read           = mmio_read,
        .print_line     = mmio_print_line,
+       .noboot         = true,
 };
 
 __init static int init_mmio_trace(void)