linux-kernel - Re: [PATCH v2 1/2] selftests: livepatch: add new ftrace helpers functions

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Message-ID: <Z+GmGfcdEceUzTQc@redhat.com>
Date: Mon, 24 Mar 2025 14:36:09 -0400
From: Joe Lawrence <joe.lawrence@...hat.com>
To: Filipe Xavier <felipeaggger@...il.com>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>, Jiri Kosina <jikos@...nel.org>,
	Miroslav Benes <mbenes@...e.cz>, Petr Mladek <pmladek@...e.com>,
	Shuah Khan <shuah@...nel.org>,
	Marcos Paulo de Souza <mpdesouza@...e.com>,
	live-patching@...r.kernel.org, linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org, felipe_life@...e.com
Subject: Re: [PATCH v2 1/2] selftests: livepatch: add new ftrace helpers
 functions

On Tue, Mar 18, 2025 at 06:20:35PM -0300, Filipe Xavier wrote:
> [ ... snip ... ]
> 
> +	if [[ -n "$FTRACE_FILTER" ]]; then
> +		echo "$FTRACE_FILTER" \
> +			| sed -e "/#### all functions enabled ####/d"
> +			> "$SYSFS_TRACING_DIR/set_ftrace_filter"
> +	fi
  
Also, this may be more stylistic than a functional nit (I don't know for
sure), but shellcheck [1] seemed confused about these lines:

   In tools/testing/selftests/livepatch/functions.sh line 90:
                          > "$SYSFS_TRACING_DIR/set_ftrace_filter"
                          ^-- SC2188 (warning): This redirection doesn't have a command. Move to its command (or use 'true' as no-op).

I wasn't going to comment on these until I saw shellcheck note them, but
I thought shell script convention was typically to end the line with the
redirection/pipe then escape the end of line like:

  commands | commands > \
      tee output.txt

There are a few existing examples of this pattern if you grep the
functions.sh file for '\\$'.

That said, I'm far from certain whether which order is better than the
other.  The only reason for bringing it up is that shellcheck warns on
this patch's usage.

[1] https://www.shellcheck.net/

-- Joe