lkml.org 
[lkml]   [2022]   [Aug]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[RFC PATCH 3/3] kbuild: use bash as the default shell for Make and Kconfig
Date
GNU Make uses /bin/sh by default for running recipe lines and $(shell ),
and so does Kconfig for $(shell,...).

We are sometimes hit by subtle portability issues like [1] because the
code was only tested on systems where /bin/sh is a symlink to bash.

One way is to continue whack-a-mole game as somebody will eventually
notice that the code is not working on their build environments.

Another is a big hammer approach; force bash in the build system so that
it works in the same way for everyone. In fact, there exists such a
guideline that permits only Bash as the shell scripting language. [2]
The kbuild test robot also specifies SHELL=/bin/bash to eliminate the
shell portability issue.

This commit changes the shell for Make and Kconfig to bash. As the GNU
Make manual [3] says, the 'SHELL' is never set from the environment.
You cannot do 'export SHELL:=/bin/bash' to propagate it to sub-makes.
Instead, use MAKEOVERRIDES to make SHELL:=/bin/bash globally effective.

[1]: https://lore.kernel.org/all/20220804190320.262510-1-alexandre.belloni@bootlin.com/
[2]: https://google.github.io/styleguide/shellguide.html
[3]: https://www.gnu.org/software/make/manual/html_node/Choosing-the-Shell.html

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

Makefile | 7 +++++++
scripts/Kconfig.include | 3 +++
2 files changed, 10 insertions(+)

diff --git a/Makefile b/Makefile
index f09673b6c11d..cc01987560b3 100644
--- a/Makefile
+++ b/Makefile
@@ -36,6 +36,13 @@ __all:

ifneq ($(sub_make_done),1)

+# Use /bin/bash for repices and $(shell ) invocations.
+SHELL := /bin/bash
+
+# Unlike the other variables, the 'SHELL' is never set from the environment.
+# Use MAKEOVERRIDES to pass 'SHELL' down to sub-makes.
+MAKEOVERRIDES += SHELL=$(SHELL)
+
# Do not use make's built-in rules and variables
# (this increases performance and avoids hard-to-debug behaviour)
MAKEFLAGS += -rR
diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index a0ccceb22cf8..d37b864ba1f2 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -1,6 +1,9 @@
# SPDX-License-Identifier: GPL-2.0-only
# Kconfig helper macros

+# Use /bin/bash to evaluate $(shell,) functions
+SHELL := /bin/bash
+
# Convenient variables
comma := ,
quote := "
--
2.34.1
\
 
 \ /
  Last update: 2022-08-19 08:59    [W:2.520 / U:0.140 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site