[PATCH v4 02/31] kbuild: remove CONFIG_CROSS_COMPILE support

Masahiro Yamada
2018-05-17T06:18:50Z

Kbuild provides a couple of ways to specify CROSS_COMPILE:

[1] Command line
[2] Environment
[3] arch/*/Makefile (only some architectures)
[4] CONFIG_CROSS_COMPILE

[4] is problematic for the compiler capability tests in Kconfig.
CONFIG_CROSS_COMPILE allows users to change the compiler prefix from
'make menuconfig', etc. It means, the compiler options would have
to be all re-calculated everytime CONFIG_CROSS_COMPILE is changed.

To avoid complexity and performance issues, I'd like to evaluate
the shell commands statically, i.e. only parsing Kconfig files.

I guess the majority is [1] or [2]. Currently, there are only
5 defconfig files that specify CONFIG_CROSS_COMPILE.
arch/arm/configs/lpc18xx_defconfig
arch/hexagon/configs/comet_defconfig
arch/nds32/configs/defconfig
arch/openrisc/configs/or1ksim_defconfig
arch/openrisc/configs/simple_smp_defconfig

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---

Changes in v4: None
Changes in v3: None
Changes in v2: None

Makefile | 3 ---
init/Kconfig | 9 ---------
2 files changed, 12 deletions(-)

diff --git a/Makefile b/Makefile
index e78f73f..01b2211 100644
--- a/Makefile
+++ b/Makefile
@@ -316,12 +316,9 @@ SUBARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
# CROSS_COMPILE can be set on the command line
# make CROSS_COMPILE=ia64-linux-
# Alternatively CROSS_COMPILE can be set in the environment.
-# A third alternative is to store a setting in .config so that plain
-# "make" in the configured kernel build directory always uses that.
# Default value for CROSS_COMPILE is not to prefix executables
# Note: Some architectures assign CROSS_COMPILE in their arch/*/Makefile
ARCH ?= $(SUBARCH)
-CROSS_COMPILE ?= $(CONFIG_CROSS_COMPILE:"%"=%)

# Architecture as present in compile.h
UTS_MACHINE := $(ARCH)
diff --git a/init/Kconfig b/init/Kconfig
index f013afc..4537962 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -54,15 +54,6 @@ config INIT_ENV_ARG_LIMIT
Maximum of each of the number of arguments and environment
variables passed to init from the kernel command line.

-
-config CROSS_COMPILE
- string "Cross-compiler tool prefix"
- help
- Same as running 'make CROSS_COMPILE=prefix-' but stored for
- default make runs in this kernel build directory. You don't
- need to set this unless you want the configured kernel build
- directory to select the cross-compiler automatically.
-
config COMPILE_TEST
bool "Compile also drivers which will not load"
depends on !UML
--
2.7.4