linux-kernel - Re: [PATCH 2/2] selftests: firmware: add CONFIG_FW_LOADER_USER_HELPER

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Date:   Thu, 29 Nov 2018 18:31:15 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Dan Rue <dan.rue@...aro.org>, Shuah Khan <shuah@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>,
        linux-kselftest@...r.kernel.org,
        Brendan Higgins <brendanhiggins@...gle.com>
Subject: Re: [PATCH 2/2] selftests: firmware: add
 CONFIG_FW_LOADER_USER_HELPER_FALLBACK to config

On Mon, Nov 26, 2018 at 09:12:16PM -0600, Dan Rue wrote:
> CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y is required for fw_fallback.sh.
> Without it, fw_fallback.sh fails with 'usermode helper disabled so
> ignoring test'. Enable the config in selftest so that it gets built by
> default.
> 
> Signed-off-by: Dan Rue <dan.rue@...aro.org>
> ---
>  tools/testing/selftests/firmware/config | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/tools/testing/selftests/firmware/config b/tools/testing/selftests/firmware/config
> index bf634dda0720..913a25a4a32b 100644
> --- a/tools/testing/selftests/firmware/config
> +++ b/tools/testing/selftests/firmware/config
> @@ -1,5 +1,6 @@
>  CONFIG_TEST_FIRMWARE=y
>  CONFIG_FW_LOADER=y
>  CONFIG_FW_LOADER_USER_HELPER=y
> +CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y
>  CONFIG_IKCONFIG=y
>  CONFIG_IKCONFIG_PROC=y

NACK -- the point of the changes was to *allow* us to mimic such
configuration through a proc sysctl knob.

You aren forcing CONFIG_FW_LOADER_USER_HELPER_FALLBACK but just having
CONFIG_FW_LOADER_USER_HELPER suffices to emulate the_FALLBACK
functionality.

The issue here seems to be that *all* tests fail once a configuration is
found which is not suitable a tests. With the shiny new proc sysctls we
can test all 3 kernel configurations in one shot. Since we test 3
different kernel configurations naturally some of these won't have the
features needed, so that failure should be treated as non-fatal to allow
the chain of other tests to continue.

This issue was a regression due to commit a6a9be9270c87 ("selftests:
firmware: return Kselftest Skip code for skipped tests") by Shuah for
the verify_reqs(). We need to treat this as a non-fatal / don't skip
return value.

The following would fix this chaining issue:

diff --git a/tools/testing/selftests/firmware/fw_lib.sh b/tools/testing/selftests/firmware/fw_lib.sh
index 6c5f1b2ffb74..1cbb12e284a6 100755
--- a/tools/testing/selftests/firmware/fw_lib.sh
+++ b/tools/testing/selftests/firmware/fw_lib.sh
@@ -91,7 +91,7 @@ verify_reqs()
 	if [ "$TEST_REQS_FW_SYSFS_FALLBACK" = "yes" ]; then
 		if [ ! "$HAS_FW_LOADER_USER_HELPER" = "yes" ]; then
 			echo "usermode helper disabled so ignoring test"
-			exit $ksft_skip
+			exit 0
 		fi
 	fi
 }

However its not clear to me if instead we want some new special return
value for selftests so that the framework can detect an that an error
is non-fatal, and can continue. This is a tricky situation given the
script, existing upstream kernel module, are aware of such emulation
hacks via sysctl, but knowledge of this is not obvious to selftests.

Shuah, how do you suggest we handle this corner case? If you are OK
with the above hunk for now I can send a fix for it. In either case
this commit was added on v4.18, so the fix would be a stable fix.

  Luis