Author: Alan Ding <alanding@google.com>
Date:   Fri Mar 19 12:43:00 2021 -0700

    ureadahead: Allow disable debug tracing
    
    Adds command line option: --no-debug-tracing (off by default).
    Provide flag to disable tracing with tracing/events/fs/* and start them
    in init instead since such events can be never allowed while enforcing
    SELinux on debugfs_tracing_debug security context for non-init process.
    
    There is no functional effect if option is not used.

diff --git a/src/trace.c b/src/trace.c
index dd1c585..854a570 100644
--- a/src/trace.c
+++ b/src/trace.c
@@ -122,7 +122,8 @@ trace (int daemonise,
        const char *filename_to_replace,
        const char *pack_file,
        const char *path_prefix_filter,
-       const PathPrefixOption *path_prefix)
+       const PathPrefixOption *path_prefix,
+       int debug_tracing)
 {
 	int                 dfd;
 	FILE                *fp;
@@ -182,21 +183,23 @@ trace (int daemonise,
 		num_cpus = 1;
 
 	/* Enable tracing of open() syscalls */
-	if (set_value (dfd, "events/fs/do_sys_open/enable",
-		       TRUE, &old_sys_open_enabled) < 0)
-		goto error;
- 	if (set_value (dfd, "events/fs/open_exec/enable",
-		       TRUE, &old_open_exec_enabled) < 0)
-		goto error;
- 	if (set_value (dfd, "events/fs/uselib/enable",
-		       TRUE, &old_uselib_enabled) < 0) {
-		NihError *err;
+	if (debug_tracing) {
+		if (set_value (dfd, "events/fs/do_sys_open/enable",
+			       TRUE, &old_sys_open_enabled) < 0)
+			goto error;
+ 		if (set_value (dfd, "events/fs/open_exec/enable",
+			       TRUE, &old_open_exec_enabled) < 0)
+			goto error;
+ 		if (set_value (dfd, "events/fs/uselib/enable",
+			       TRUE, &old_uselib_enabled) < 0) {
+			NihError *err;
 
-		err = nih_error_get ();
-		nih_debug ("Missing uselib tracing: %s", err->message);
-		nih_free (err);
+			err = nih_error_get ();
+			nih_debug ("Missing uselib tracing: %s", err->message);
+			nih_free (err);
 
-		old_uselib_enabled = -1;
+			old_uselib_enabled = -1;
+		}
 	}
 	if (set_value (dfd, "buffer_size_kb", 8192/num_cpus, &old_buffer_size_kb) < 0)
 		goto error;
@@ -240,16 +243,18 @@ trace (int daemonise,
 	if (set_value (dfd, "tracing_on",
 		       old_tracing_enabled, NULL) < 0)
 		goto error;
-	if (old_uselib_enabled >= 0)
-		if (set_value (dfd, "events/fs/uselib/enable",
-			       old_uselib_enabled, NULL) < 0)
+	if (debug_tracing) {
+		if (old_uselib_enabled >= 0)
+			if (set_value (dfd, "events/fs/uselib/enable",
+				       old_uselib_enabled, NULL) < 0)
+				goto error;
+		if (set_value (dfd, "events/fs/open_exec/enable",
+			       old_open_exec_enabled, NULL) < 0)
 			goto error;
-	if (set_value (dfd, "events/fs/open_exec/enable",
-		       old_open_exec_enabled, NULL) < 0)
-		goto error;
-	if (set_value (dfd, "events/fs/do_sys_open/enable",
-		       old_sys_open_enabled, NULL) < 0)
-		goto error;
+		if (set_value (dfd, "events/fs/do_sys_open/enable",
+			       old_sys_open_enabled, NULL) < 0)
+			goto error;
+	}
 
 	/* Be nicer */
 	if (nice (15))
diff --git a/src/trace.h b/src/trace.h
index 16af782..f809cc6 100644
--- a/src/trace.h
+++ b/src/trace.h
@@ -37,7 +37,8 @@ int trace (int daemonise, int timeout,
            const char *filename_to_replace,
            const char *pack_file,  /* May be null */
            const char *path_prefix_filter,  /* May be null */
-           const PathPrefixOption *path_prefix);
+           const PathPrefixOption *path_prefix,
+           int debug_tracing);
 
 NIH_END_EXTERN
 
diff --git a/src/ureadahead.c b/src/ureadahead.c
index 066bfff..d1bf5a1 100644
--- a/src/ureadahead.c
+++ b/src/ureadahead.c
@@ -110,6 +110,14 @@ static char *pack_file = NULL;
  */
 static char *path_prefix_filter = NULL;
 
+/**
+ * no_debug_tracing:
+ *
+ * Provide flag to disable tracing with tracing/events/fs/* and start them in
+ * init instead since such events can be never allowed while enforcing SELinux.
+ */
+static int no_debug_tracing = FALSE;
+
 static int
 path_prefix_option (NihOption  *option,
                     const char *arg)
@@ -211,6 +219,8 @@ static NihOption options[] = {
 	  NULL, "PREFIX_FILTER", &path_prefix_filter, dup_string_handler },
 	{ 0, "pack-file", N_("Path of the pack file to use"),
 	  NULL, "PACK_FILE", &pack_file, dup_string_handler },
+	{ 0, "no-debug-tracing", N_("do not enable debug tracing events"),
+	  NULL, NULL, &no_debug_tracing, NULL },
 
 	NIH_OPTION_LAST
 };
@@ -301,7 +311,7 @@ main (int   argc,
 
 	/* Trace to generate new pack files */
 	if (trace (daemonise, timeout, filename, pack_file,
-		   path_prefix_filter, &path_prefix) < 0) {
+		   path_prefix_filter, &path_prefix, (no_debug_tracing == FALSE)) < 0) {
 		NihError *err;
 
 		err = nih_error_get ();