[Linux-kernel-mentees] [PATCH] kbuild: doc: describe proper script invocation

[Masahiro Yamada]

On Thu, Oct 1, 2020 at 4:57 PM Lukas Bulwahn <lukas.bulwahn at gmail.com> wrote:
>
> During an investigation to fix up the execute bits of scripts in the kernel
> repository, Andrew Morton and Kees Cook pointed out that the execute bit
> should not matter, and that build scripts cannot rely on that. Kees could
> not point to any documentation, though.
>
> Masahiro Yamada explained the convention of setting execute bits to make it
> easier for manual script invocation.
>
> Provide some basic documentation how the build shall invoke scripts, such
> that the execute bits do not matter, and acknowledge that execute bits
> are useful nonetheless.
>
> This serves as reference for further clean-up patches in the future.
>
> Link: https://lore.kernel.org/lkml/20200830174409.c24c3f67addcce0cea9a9d4c@linux-foundation.org/
> Link: https://lore.kernel.org/lkml/202008271102.FEB906C88@keescook/
> Link: https://lore.kernel.org/linux-kbuild/CAK7LNAQdrvMkDA6ApDJCGr+5db8SiPo=G+p8EiOvnnGvEN80gA@mail.gmail.com/
>
> Suggested-by: Andrew Morton <akpm at linux-foundation.org>
> Suggested-by: Kees Cook <keescook at chromium.org>
> Signed-off-by: Lukas Bulwahn <lukas.bulwahn at gmail.com>


Applied to linux-kbuild.
Thanks.


> ---
> RFC v1 -> RFC v2:
> explain why execute bits are still convenient.
>
> Kees, Andrew, please ack.
>
> Masahiro-san, I have taken your feedback into account. Please pick this small
> documentation update into your kbuild tree.
>
> Ujjwal Kumar, a potential future mentee, will follow up with further fixes to
> the build scripts.
>
>  Documentation/kbuild/makefiles.rst | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
> index 58d513a0fa95..bd3e1baf58be 100644
> --- a/Documentation/kbuild/makefiles.rst
> +++ b/Documentation/kbuild/makefiles.rst
> @@ -21,6 +21,7 @@ This document describes the Linux kernel Makefiles.
>            --- 3.10 Special Rules
>            --- 3.11 $(CC) support functions
>            --- 3.12 $(LD) support functions
> +          --- 3.13 Script Invocation
>
>         === 4 Host Program support
>            --- 4.1 Simple Host Program
> @@ -605,6 +606,25 @@ more details, with real examples.
>                 #Makefile
>                 LDFLAGS_vmlinux += $(call ld-option, -X)
>
> +3.13 Script invocation
> +----------------------
> +
> +       Make rules may invoke scripts to build the kernel. The rules shall
> +       always provide the appropriate interpreter to execute the script. They
> +       shall not rely on the execute bits being set, and shall not invoke the
> +       script directly. For the convenience of manual script invocation, such
> +       as invoking ./scripts/checkpatch.pl, it is recommended to set execute
> +       bits on the scripts nonetheless.
> +
> +       Kbuild provides variables $(CONFIG_SHELL), $(AWK), $(PERL),
> +       $(PYTHON) and $(PYTHON3) to refer to interpreters for the respective
> +       scripts.
> +
> +       Example::
> +
> +               #Makefile
> +               cmd_depmod = $(CONFIG_SHELL) $(srctree)/scripts/depmod.sh $(DEPMOD) \
> +                            $(KERNELRELEASE)
>
>  4 Host Program support
>  ======================
> --
> 2.17.1
>


-- 
Best Regards
Masahiro Yamada