linux-kernel - Re: [PATCH v2] kbuild: allow symbol whitelisting with TRIM_UNUSED

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Message-ID: <20200131174055.GA8425@google.com>
Date:   Fri, 31 Jan 2020 17:40:55 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     Matthias Maennich <maennich@...gle.com>
Cc:     masahiroy@...nel.org, nico@...xnic.net,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        kernel-team@...roid.com, jeyu@...nel.org
Subject: Re: [PATCH v2] kbuild: allow symbol whitelisting with
 TRIM_UNUSED_KSYMS

On Friday 31 Jan 2020 at 13:15:08 (+0000), 'Matthias Maennich' via kernel-team wrote:
> On Wed, Jan 29, 2020 at 06:15:41PM +0000, Quentin Perret wrote:
> > diff --git a/scripts/adjust_autoksyms.sh b/scripts/adjust_autoksyms.sh
> > index a904bf1f5e67..8e1b7f70e800 100755
> > --- a/scripts/adjust_autoksyms.sh
> > +++ b/scripts/adjust_autoksyms.sh
> > @@ -48,6 +48,7 @@ cat > "$new_ksyms_file" << EOT
> > EOT
> > sed 's/ko$/mod/' modules.order |
> > xargs -n1 sed -n -e '2{s/ /\n/g;/^$/!p;}' -- |
> > +cat - "${CONFIG_UNUSED_KSYMS_WHITELIST:-/dev/null}" |
> 
> This handles absolute paths very well. I wonder whether we can make this
> more useful for folks that want to maintain such a whitelist in their
> copy of the tree. Lets say, I have in my sources
> arch/x86/configs/x86_64_symbol_whitelist and in my config I have
> CONFIG_UNUSED_KSYMS_WHITELIST="arch/x86/configs/x86_64_symbol_whitelist".
> 
> If I see it correctly, UNUSED_KSYMS_WHITELIST is currently either an
> absolute path or a relative path to the current build directory. I would
> prefer if relative paths would be relative to the source directory to
> support the above use case. (Note, that scenario above works if I build
> directly in the sources, but fails if I build O=/somewhere/else.)

Right, that is an interesting use case. I suppose something like the
below should work (with appropriate documentation of the config option).

---8<---
diff --git a/scripts/adjust_autoksyms.sh b/scripts/adjust_autoksyms.sh
index 8e1b7f70e800..d37803fd75ce 100755
--- a/scripts/adjust_autoksyms.sh
+++ b/scripts/adjust_autoksyms.sh
@@ -38,6 +38,12 @@ esac
 # We need access to CONFIG_ symbols
 . include/config/auto.conf
 
+ksym_wl="${CONFIG_UNUSED_KSYMS_WHITELIST:-/dev/null}"
+# If the path is relative, it must be relative to the source tree
+if [ "$ksym_wl" == "${ksym_wl#/}" ]; then
+       ksym_wl="$abs_srctree/$ksym_wl"
+fi
+
 # Generate a new ksym list file with symbols needed by the current
 # set of modules.
 cat > "$new_ksyms_file" << EOT
@@ -48,7 +54,7 @@ cat > "$new_ksyms_file" << EOT
 EOT
 sed 's/ko$/mod/' modules.order |
 xargs -n1 sed -n -e '2{s/ /\n/g;/^$/!p;}' -- |
-cat - "${CONFIG_UNUSED_KSYMS_WHITELIST:-/dev/null}" |
+cat - "$ksym_wl" |
 sort -u |
 sed -e 's/\(.*\)/#define __KSYM_\1 1/' >> "$new_ksyms_file"
--->8---

Thoughts ?

Thanks,
Quentin