Re: [PATCH v2] kbuild: check uniqueness of module names

[Alexander Kapshuk]

On Fri, May 17, 2019 at 8:33 AM Masahiro Yamada
<yamada.masahiro@xxxxxxxxxxxxx> wrote:
>
> In the recent build test of linux-next, Stephen saw a build error
> caused by a broken .tmp_versions/*.mod file:
>
>   https://lkml.org/lkml/2019/5/13/991
>
> drivers/net/phy/asix.ko and drivers/net/usb/asix.ko have the same
> basename, and there is a race in generating .tmp_versions/asix.mod
>
> Kbuild has not checked this before, and it suddenly shows up with
> obscure error message when this kind of race occurs.
>
> Non-unique module names cause various sort of problems, but it is
> not trivial to catch them by eyes.
>
> Hence, this script.
>
> It checks not only real modules, but also built-in modules (i.e.
> controlled by tristate CONFIG option, but currently compiled with =y).
> Non-unique names for built-in modules also cause problems because
> /sys/modules/ would fall over.
>
> I tested allmodconfig on the latest kernel, and it detected the
> following:
>
> warning: same basename if the following are built as modules:
>   drivers/regulator/88pm800.ko
>   drivers/mfd/88pm800.ko
> warning: same basename if the following are built as modules:
>   drivers/gpu/drm/bridge/adv7511/adv7511.ko
>   drivers/media/i2c/adv7511.ko
> warning: same basename if the following are built as modules:
>   drivers/net/phy/asix.ko
>   drivers/net/usb/asix.ko
> warning: same basename if the following are built as modules:
>   fs/coda/coda.ko
>   drivers/media/platform/coda/coda.ko
> warning: same basename if the following are built as modules:
>   drivers/net/phy/realtek.ko
>   drivers/net/dsa/realtek.ko
>
> Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
>
> Changes in v2:
>  - redirect messages to stderr
>  - use '--' after 'basename -a'
>  - use '-r' for xargs to cope with empty modules.order/modules.builtin
>
>  Makefile                 |  1 +
>  scripts/modules-check.sh | 20 ++++++++++++++++++++
>  2 files changed, 21 insertions(+)
>  create mode 100755 scripts/modules-check.sh
>
> diff --git a/Makefile b/Makefile
> index a61a95b6b38f..30792fec7a12 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1290,6 +1290,7 @@ modules: $(vmlinux-dirs) $(if $(KBUILD_BUILTIN),vmlinux) modules.builtin
>         $(Q)$(AWK) '!x[$$0]++' $(vmlinux-dirs:%=$(objtree)/%/modules.order) > $(objtree)/modules.order
>         @$(kecho) '  Building modules, stage 2.';
>         $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
> +       $(Q)$(CONFIG_SHELL) $(srctree)/scripts/modules-check.sh
>
>  modules.builtin: $(vmlinux-dirs:%=%/modules.builtin)
>         $(Q)$(AWK) '!x[$$0]++' $^ > $(objtree)/modules.builtin
> diff --git a/scripts/modules-check.sh b/scripts/modules-check.sh
> new file mode 100755
> index 000000000000..c875f6eab01e
> --- /dev/null
> +++ b/scripts/modules-check.sh
> @@ -0,0 +1,20 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0
> +
> +set -e
> +
> +# Check uniqueness of module names
> +check_same_name_modules()
> +{
> +       same_name_modules=$(cat modules.order modules.builtin | \
> +                               xargs -r basename -a -- | sort | uniq -d)
> +
> +       for m in $same_name_modules
> +       do
> +               echo "warning: same basename if the following are built as modules:" >&2
> +               grep -h -e "/$m" modules.order modules.builtin | \
> +                                               sed 's:^kernel/:  :' >&2
> +       done
> +}
> +
> +check_same_name_modules
> --
> 2.17.1
>

The 'xargs' '-r' flag is a GNU extension.
If POSIX compliance is important here, the use of 'cat', 'xargs' and
'basename' may be substituted with that of 'sed' to initialise
same_name_modules:
sed 's!.*/!!' modules.order modules.builtin | sort | uniq -d

'Sed' may also be used on its own in the 'for' loop instead of as part
of a pipeline along with 'grep' to generate the desired output:
sed '/\/'$m'/!d;s:^kernel/:  :' modules.order modules.builtin

Just a suggestion.