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SubjectRe: [PATCH 1/2] ftrace/selftests: Return the skip code when tracing directory not configured in kernel
On Wed, 03 Jul 2019 15:50:00 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
>
> 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>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
> tools/testing/selftests/ftrace/ftracetest | 38 +++++++++++++++++++----
> 1 file changed, 32 insertions(+), 6 deletions(-)
>
> diff --git a/tools/testing/selftests/ftrace/ftracetest b/tools/testing/selftests/ftrace/ftracetest
> index 136387422b00..edf5ea35d2a7 100755
> --- a/tools/testing/selftests/ftrace/ftracetest
> +++ b/tools/testing/selftests/ftrace/ftracetest
> @@ -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 $err_ret
> }
>
> # Ensuring user privilege
> @@ -116,11 +122,31 @@ parse_opts() { # opts
> }
>
> # Parameters
> -DEBUGFS_DIR=`grep debugfs /proc/mounts | cut -f2 -d' ' | head -1`
> -if [ -z "$DEBUGFS_DIR" ]; then
> - TRACING_DIR=`grep tracefs /proc/mounts | cut -f2 -d' ' | head -1`
> -else
> - TRACING_DIR=$DEBUGFS_DIR/tracing
> +TRACING_DIR=`grep tracefs /proc/mounts | cut -f2 -d' ' | head -1`
> +if [ -z "$TRACING_DIR" ]; then
> + DEBUGFS_DIR=`grep debugfs /proc/mounts | cut -f2 -d' ' | head -1`
> + if [ -z "$DEBUGFS_DIR" ]; then
> + # If tracefs exists, then so does /sys/kernel/tracing

Ah, indeed. the mount point also may not exist on older kernel.

OK, this looks good to me.

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

Thank you!

> + 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
> + 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`
> --
> 2.20.1
>
>


--
Masami Hiramatsu <mhiramat@kernel.org>

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