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kbuild: doc: describe proper script invocation

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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.

Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ujjwal Kumar <ujjwalkumar0501@gmail.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
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/
Link: https://lkml.kernel.org/r/20201001075723.24246-1-lukas.bulwahn@gmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Lukas Bulwahn 2020-10-13 16:48:05 -07:00 committed by Linus Torvalds
parent 4d6fb34acb
commit eb38f37c3c
1 changed files with 20 additions and 0 deletions
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20
Documentation/kbuild/makefiles.rst
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@ -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
======================