path: root/Kconfig
diff options
authorMasahiro Yamada <>2018-05-28 12:21:40 +0300
committerMasahiro Yamada <>2018-05-28 21:28:58 +0300
commit104daea149c45cc84842ce77a9bd6436d19f3dd8 (patch)
tree7f0aaa24e9fa03154a74b2bd7bcb93f24d678ea4 /Kconfig
parentf1089c92da791034af73478159626007cba7f092 (diff)
kconfig: reference environment variables directly and remove 'option env='
To get access to environment variables, Kconfig needs to define a symbol using "option env=" syntax. It is tedious to add a symbol entry for each environment variable given that we need to define much more such as 'CC', 'AS', 'srctree' etc. to evaluate the compiler capability in Kconfig. Adding '$' for symbol references is grammatically inconsistent. Looking at the code, the symbols prefixed with 'S' are expanded by: - conf_expand_value() This is used to expand 'arch/$ARCH/defconfig' and 'defconfig_list' - sym_expand_string_value() This is used to expand strings in 'source' and 'mainmenu' All of them are fixed values independent of user configuration. So, they can be changed into the direct expansion instead of symbols. This change makes the code much cleaner. The bounce symbols 'SRCARCH', 'ARCH', 'SUBARCH', 'KERNELVERSION' are gone. sym_init() hard-coding 'UNAME_RELEASE' is also gone. 'UNAME_RELEASE' should be replaced with an environment variable. ARCH_DEFCONFIG is a normal symbol, so it should be simply referenced without '$' prefix. The new syntax is addicted by Make. The variable reference needs parentheses, like $(FOO), but you can omit them for single-letter variables, like $F. Yet, in Makefiles, people tend to use the parenthetical form for consistency / clarification. At this moment, only the environment variable is supported, but I will extend the concept of 'variable' later on. The variables are expanded in the lexer so we can simplify the token handling on the parser side. For example, the following code works. [Example code] config MY_TOOLCHAIN_LIST string default "My tools: CC=$(CC), AS=$(AS), CPP=$(CPP)" [Result] $ make -s alldefconfig && tail -n 1 .config CONFIG_MY_TOOLCHAIN_LIST="My tools: CC=gcc, AS=as, CPP=gcc -E" Signed-off-by: Masahiro Yamada <> Reviewed-by: Kees Cook <>
Diffstat (limited to 'Kconfig')
1 files changed, 2 insertions, 6 deletions
diff --git a/Kconfig b/Kconfig
index 8c4c1cb0f9cd..4af1b42ef62e 100644
--- a/Kconfig
+++ b/Kconfig
@@ -3,10 +3,6 @@
# For a description of the syntax of this configuration file,
# see Documentation/kbuild/kconfig-language.txt.
-mainmenu "Linux/$ARCH $KERNELVERSION Kernel Configuration"
+mainmenu "Linux/$(ARCH) $(KERNELVERSION) Kernel Configuration"
-config SRCARCH
- string
- option env="SRCARCH"
-source "arch/$SRCARCH/Kconfig"
+source "arch/$(SRCARCH)/Kconfig"