tracing: Let tracing_snapshot() be used by modules but not NMI

Add EXPORT_SYMBOL_GPL() to let the tracing_snapshot() functions be
called from modules.

Also add a test to see if the snapshot was called from NMI context
and just warn in the tracing buffer if so, and return.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d372c6504c99..5c53e4092269 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -442,6 +442,12 @@ void tracing_snapshot(void)
         struct tracer *tracer = tr->current_trace;
         unsigned long flags;
 
+        if (in_nmi()) {
+                internal_trace_puts("*** SNAPSHOT CALLED FROM NMI CONTEXT ***\n");
+                internal_trace_puts("*** snapshot is being ignored        ***\n");
+                return;
+        }
+
         if (!tr->allocated_snapshot) {
                 internal_trace_puts("*** SNAPSHOT NOT ALLOCATED ***\n");
                 internal_trace_puts("*** stopping trace here!   ***\n");
@@ -460,6 +466,7 @@ void tracing_snapshot(void)
         update_max_tr(tr, current, smp_processor_id());
         local_irq_restore(flags);
 }
+EXPORT_SYMBOL_GPL(tracing_snapshot);
 
 static int resize_buffer_duplicate_size(struct trace_buffer *trace_buf,
                                         struct trace_buffer *size_buf, int cpu_id);
@@ -493,16 +500,19 @@ void tracing_snapshot_alloc(void)
 
         tracing_snapshot();
 }
+EXPORT_SYMBOL_GPL(tracing_snapshot_alloc);
 #else
 void tracing_snapshot(void)
 {
         WARN_ONCE(1, "Snapshot feature not enabled, but internal snapshot used");
 }
+EXPORT_SYMBOL_GPL(tracing_snapshot);
 void tracing_snapshot_alloc(void)
 {
         /* Give warning */
         tracing_snapshot();
 }
+EXPORT_SYMBOL_GPL(tracing_snapshot_alloc);
 #endif /* CONFIG_TRACER_SNAPSHOT */
 
 /**