diff mbox series

[v2] kbuild: fix UNUSED_KSYMS_WHITELIST for Clang LTO

Message ID 20210226062548.3334081-1-masahiroy@kernel.org (mailing list archive)
State New, archived
Headers show
Series [v2] kbuild: fix UNUSED_KSYMS_WHITELIST for Clang LTO | expand

Commit Message

Masahiro Yamada Feb. 26, 2021, 6:25 a.m. UTC 
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@kernel.org>
---

Changes in v2:
  - Rebase on top of Arnd's patch:
    https://lore.kernel.org/lkml/20210225143456.3829513-1-arnd@kernel.org/

 init/Kconfig                    |  1 -
 scripts/gen_autoksyms.sh        | 35 ++++++++++++++++++++++++---------
 scripts/lto-used-symbollist.txt |  6 ------
 3 files changed, 26 insertions(+), 16 deletions(-)
 delete mode 100644 scripts/lto-used-symbollist.txt

Comments

Sedat Dilek Feb. 26, 2021, 9:25 a.m. UTC | #1 
On Fri, Feb 26, 2021 at 7:26 AM Masahiro Yamada <masahiroy@kernel.org> 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@kernel.org>
> ---
>
> Changes in v2:
>   - Rebase on top of Arnd's patch:
>     https://lore.kernel.org/lkml/20210225143456.3829513-1-arnd@kernel.org/
>
>  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 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
>
> --
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Masahiro Yamada Feb. 27, 2021, 6:54 a.m. UTC | #2 
On Fri, Feb 26, 2021 at 6:26 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
>
> On Fri, Feb 26, 2021 at 7:26 AM Masahiro Yamada <masahiroy@kernel.org> 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@kernel.org>
> > ---
> >
> > Changes in v2:
> >   - Rebase on top of Arnd's patch:
> >     https://lore.kernel.org/lkml/20210225143456.3829513-1-arnd@kernel.org/
> >
> >  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?

I think so.

I moved those symbols to scripts/gen_autoksyms.sh
Sedat Dilek Feb. 27, 2021, 7:08 a.m. UTC | #3 
On Sat, Feb 27, 2021 at 7:55 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Fri, Feb 26, 2021 at 6:26 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
> >
> > On Fri, Feb 26, 2021 at 7:26 AM Masahiro Yamada <masahiroy@kernel.org> 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@kernel.org>
> > > ---
> > >
> > > Changes in v2:
> > >   - Rebase on top of Arnd's patch:
> > >     https://lore.kernel.org/lkml/20210225143456.3829513-1-arnd@kernel.org/
> > >
> > >  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?
>
> I think so.
>
> I moved those symbols to scripts/gen_autoksyms.sh
>

OK, I have overseen hat.

- Sedat -
Sedat Dilek Feb. 27, 2021, 8:05 p.m. UTC | #4 
On Sat, Feb 27, 2021 at 8:08 AM Sedat Dilek <sedat.dilek@gmail.com> wrote:
>
> On Sat, Feb 27, 2021 at 7:55 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >
> > On Fri, Feb 26, 2021 at 6:26 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
> > >
> > > On Fri, Feb 26, 2021 at 7:26 AM Masahiro Yamada <masahiroy@kernel.org> 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@kernel.org>

Tested-by: Sedat Dilek <sedat.dilek@gmail.com>

- Sedat -

> > > > ---
> > > >
> > > > Changes in v2:
> > > >   - Rebase on top of Arnd's patch:
> > > >     https://lore.kernel.org/lkml/20210225143456.3829513-1-arnd@kernel.org/
> > > >
> > > >  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?
> >
> > I think so.
> >
> > I moved those symbols to scripts/gen_autoksyms.sh
> >
>
> OK, I have overseen hat.
>
> - Sedat -
diff mbox series

Patch

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 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