Commit cbd965bd authored Jul 03, 2019 by Steven Rostedt (VMware)

ftrace/selftests: Return the skip code when tracing directory not configured in kernel

If the kernel is not configured with ftrace enabled, the ftracetest
selftests should return the error code of "4" as that is the kselftests
"skip" code, and not "1" which means an error.

To determine if ftrace is enabled, first the newer "tracefs" is searched for
in /proc/mounts. If it is not found, then "debugfs" is searched for (as old
kernels do not have tracefs). If that is not found, an attempt to mount the
tracefs or debugfs is performed. This is done by seeing first if the
/sys/kernel/tracing directory exists. If it does than tracefs is configured
in the kernel and an attempt to mount it is performed.

If /sys/kernel/tracing does not exist, then /sys/kernel/debug is tested to
see if that directory exists. If it does, then an attempt to mount debugfs
on that directory is performed. If it does not exist, then debugfs is not
configured in the running kernel and the test exits with the skip code.

If either mount fails, then a normal error is returned as they do exist in
the kernel but something went wrong to mount them.

This changes the test to always try the tracefs file system first as it has
been in the kernel for some time now and it is better to test it if it is
available instead of always testing debugfs.

Link: http://lkml.kernel.org/r/20190702062358.7330-1-po-hsu.lin@canonical.com

Reported-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

parent 715fa2fd

tools/testing/selftests/ftrace/ftracetest

+32 −6

Original line number	Diff line number	Diff line
		@@ -23,9 +23,15 @@ echo " If <dir> is -, all logs output in console only"
		exit $1
		}

		# default error
		err_ret=1

		# kselftest skip code is 4
		err_skip=4

		errexit() { # message
		echo "Error: $1" 1>&2
		exit 1
		exit $err_ret
		}

		# Ensuring user privilege
		@@ -116,11 +122,31 @@ parse_opts() { # opts
		}

		# Parameters
		TRACING_DIR=`grep tracefs /proc/mounts \| cut -f2 -d' ' \| head -1`
		if [ -z "$TRACING_DIR" ]; then
		DEBUGFS_DIR=`grep debugfs /proc/mounts \| cut -f2 -d' ' \| head -1`
		if [ -z "$DEBUGFS_DIR" ]; then
		TRACING_DIR=`grep tracefs /proc/mounts \| cut -f2 -d' ' \| head -1`
		# If tracefs exists, then so does /sys/kernel/tracing
		if [ -d "/sys/kernel/tracing" ]; then
		mount -t tracefs nodev /sys/kernel/tracing \|\|
		errexit "Failed to mount /sys/kernel/tracing"
		TRACING_DIR="/sys/kernel/tracing"
		# If debugfs exists, then so does /sys/kernel/debug
		elif [ -d "/sys/kernel/debug" ]; then
		mount -t debugfs nodev /sys/kernel/debug \|\|
		errexit "Failed to mount /sys/kernel/debug"
		TRACING_DIR="/sys/kernel/debug/tracing"
		else
		TRACING_DIR=$DEBUGFS_DIR/tracing
		err_ret=$err_skip
		errexit "debugfs and tracefs are not configured in this kernel"
		fi
		else
		TRACING_DIR="$DEBUGFS_DIR/tracing"
		fi
		fi
		if [ ! -d "$TRACING_DIR" ]; then
		err_ret=$err_skip
		errexit "ftrace is not configured in this kernel"
		fi

		TOP_DIR=`absdir $0`