Re: [PATCH v2] kbuild: fix UNUSED_KSYMS_WHITELIST for Clang LTO
From: Sedat Dilek
Date: Fri Feb 26 2021 - 04:29:06 EST
On Fri, Feb 26, 2021 at 7:26 AM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote:
>
>
Commit fbe078d397b4 ("kbuild: lto: add a default list of used symbols")
>
does not work as expected if the .config file has already specified
>
CONFIG_UNUSED_KSYMS_WHITELIST="my/own/white/list" before enabling
>
CONFIG_LTO_CLANG.
>
>
So, the user-supplied whitelist and LTO-specific white list must be
>
independent of each other.
>
>
I refactored the shell script so CONFIG_MODVERSIONS and CONFIG_CLANG_LTO
>
handle whitelists in the same way.
>
>
Fixes: fbe078d397b4 ("kbuild: lto: add a default list of used symbols")
>
Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
>
---
>
>
Changes in v2:
>
- Rebase on top of Arnd's patch:
>
https://lore.kernel.org/lkml/20210225143456.3829513-1-arnd@xxxxxxxxxx/
>
>
init/Kconfig | 1 -
>
scripts/gen_autoksyms.sh | 35 ++++++++++++++++++++++++---------
>
scripts/lto-used-symbollist.txt | 6 ------
People who want to use their own "white-listed" (allow-listed)
symbollist-file can do that via
CONFIG_UNUSED_KSYMS_WHITELIST="my/own/white/list".
Correct?
Why do you delete the default "scripts/lto-used-symbollist.txt" file
and remove the default in the appropriate Kconfig for people who want
to enable Clang-(Thin)LTO?
These people should now use
CONFIG_UNUSED_KSYMS_WHITELIST="scripts/lto-used-symbollist.txt"?
But again - the file was deleted with your patch.
Do I miss something?
- Sedat -
>
3 files changed, 26 insertions(+), 16 deletions(-)
>
delete mode 100644 scripts/lto-used-symbollist.txt
>
>
diff --git a/init/Kconfig b/init/Kconfig
>
index 719871f8727c..64c32300d1b4 100644
>
--- a/init/Kconfig
>
+++ b/init/Kconfig
>
@@ -2283,7 +2283,6 @@ config TRIM_UNUSED_KSYMS
>
config UNUSED_KSYMS_WHITELIST
>
string "Whitelist of symbols to keep in ksymtab"
>
depends on TRIM_UNUSED_KSYMS
>
- default "scripts/lto-used-symbollist.txt" if LTO_CLANG
>
help
>
By default, all unused exported symbols will be un-exported from the
>
build when TRIM_UNUSED_KSYMS is selected.
>
diff --git a/scripts/gen_autoksyms.sh b/scripts/gen_autoksyms.sh
>
index d54dfba15bf2..da320151e7c3 100755
>
--- a/scripts/gen_autoksyms.sh
>
+++ b/scripts/gen_autoksyms.sh
>
@@ -19,7 +19,26 @@ esac
>
# We need access to CONFIG_ symbols
>
. include/config/auto.conf
>
>
-ksym_wl=/dev/null
>
+needed_symbols=
>
+
>
+# Special case for modversions (see modpost.c)
>
+if [ -n "$CONFIG_MODVERSIONS" ]; then
>
+ needed_symbols="$needed_symbols module_layout"
>
+fi
>
+
>
+# With CONFIG_LTO_CLANG, LLVM bitcode has not yet been compiled into a binary
>
+# when the .mod files are generated, which means they don't yet contain
>
+# references to certain symbols that will be present in the final binaries.
>
+if [ -n "$CONFIG_LTO_CLANG" ]; then
>
+ # intrinsic functions
>
+ needed_symbols="$needed_symbols memcpy memmove memset"
>
+ # ftrace
>
+ needed_symbols="$needed_symbols _mcount"
>
+ # stack protector symbols
>
+ needed_symbols="$needed_symbols __stack_chk_fail __stack_chk_guard"
>
+fi
>
+
>
+ksym_wl=
>
if [ -n "$CONFIG_UNUSED_KSYMS_WHITELIST" ]; then
>
# Use 'eval' to expand the whitelist path and check if it is relative
>
eval ksym_wl="$CONFIG_UNUSED_KSYMS_WHITELIST"
>
@@ -40,16 +59,14 @@ cat > "$output_file" << EOT
>
EOT
>
>
[ -f modules.order ] && modlist=modules.order || modlist=/dev/null
>
-sed 's/ko$/mod/' $modlist |
>
-xargs -n1 sed -n -e '2{s/ /\n/g;/^$/!p;}' -- |
>
-cat - "$ksym_wl" |
>
+
>
+{
>
+ sed 's/ko$/mod/' $modlist | xargs -n1 sed -n -e '2p'
>
+ echo "$needed_symbols"
>
+ [ -n "$ksym_wl" ] && cat "$ksym_wl"
>
+} | sed -e 's/ /\n/g' | sed -n -e '/^$/!p' |
>
# Remove the dot prefix for ppc64; symbol names with a dot (.) hold entry
>
# point addresses.
>
sed -e 's/^\.//' |
>
sort -u |
>
sed -e 's/\(.*\)/#define __KSYM_1円 1/' >> "$output_file"
>
-
>
-# Special case for modversions (see modpost.c)
>
-if [ -n "$CONFIG_MODVERSIONS" ]; then
>
- echo "#define __KSYM_module_layout 1" >> "$output_file"
>
-fi
>
diff --git a/scripts/lto-used-symbollist.txt b/scripts/lto-used-symbollist.txt
>
deleted file mode 100644
>
index 406ada65e926..000000000000
>
--- a/scripts/lto-used-symbollist.txt
>
+++ /dev/null
>
@@ -1,6 +0,0 @@
>
-memcpy
>
-memmove
>
-memset
>
-_mcount
>
-__stack_chk_fail
>
-__stack_chk_guard
>
--
>
2.27.0
>
>
--
>
You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
>
To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@xxxxxxxxxxxxxxxx.
>
To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20210226062548.3334081-1-masahiroy%40kernel.org.