linux-kernel - Re: [PATCH v4 1/3] kbuild: allow symbol whitelisting with TRIM_UNUSED

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Message-ID: <20200217142322.GA183353@google.com>
Date:   Mon, 17 Feb 2020 14:23:22 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     masahiroy@...nel.org, nico@...xnic.net
Cc:     linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        maennich@...gle.com, kernel-team@...roid.com, jeyu@...nel.org,
        hch@...radead.org
Subject: Re: [PATCH v4 1/3] kbuild: allow symbol whitelisting with
 TRIM_UNUSED_KSYMS

On Wednesday 12 Feb 2020 at 20:21:38 (+0000), Quentin Perret wrote:
> diff --git a/scripts/adjust_autoksyms.sh b/scripts/adjust_autoksyms.sh
> index a904bf1f5e67..93f4d10e66e6 100755
> --- a/scripts/adjust_autoksyms.sh
> +++ b/scripts/adjust_autoksyms.sh
> @@ -38,6 +38,10 @@ esac
>  # We need access to CONFIG_ symbols
>  . include/config/auto.conf
>  
> +# Use 'eval' to expand the whitelist path and check if it is relative
> +eval ksym_wl="${CONFIG_UNUSED_KSYMS_WHITELIST:-/dev/null}"
> +[ "${ksym_wl:0:1}" = "/" ] || ksym_wl="$abs_srctree/$ksym_wl"

Our internal CI just informed me that this is *still* not quite POSIX
compliant ... I believe that the following should (finally) solve this
issue:

  [ "${ksym_wl}" != "${ksym_wl#/}" ] || ksym_wl="$abs_srctree/$ksym_wl"

The above seems to work with bash, zsh, dash, posh and, IIUC, complies
with https://pubs.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html.
I'll try other shells and stare at the doc some more, but if there is a
preferred pattern in the kernel I'm happy to change it.

Thanks,
Quentin