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kbuild: fix UNUSED_KSYMS_WHITELIST for Clang LTO

Commit fbe078d397 ("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: fbe078d397 ("kbuild: lto: add a default list of used symbols")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
master
Masahiro Yamada 2 months ago
parent
commit
a6aaeb8411
3 changed files with 26 additions and 16 deletions
  1. +0
    -1
      init/Kconfig
  2. +26
    -9
      scripts/gen_autoksyms.sh
  3. +0
    -6
      scripts/lto-used-symbollist.txt

+ 0
- 1
init/Kconfig View File

@ -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.


+ 26
- 9
scripts/gen_autoksyms.sh View File

@ -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 1/' >> "$output_file"
# Special case for modversions (see modpost.c)
if [ -n "$CONFIG_MODVERSIONS" ]; then
echo "#define __KSYM_module_layout 1" >> "$output_file"
fi

+ 0
- 6
scripts/lto-used-symbollist.txt View File

@ -1,6 +0,0 @@
memcpy
memmove
memset
_mcount
__stack_chk_fail
__stack_chk_guard

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