On Thu, Dec 09, 2021 at 08:45:30AM +0100, Arnd Bergmann wrote: > On Thu, Dec 9, 2021 at 6:07 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > > > tl;dr: is there a way to force a config default to "off" under > > all*config builds, but still leave it configurable? (i.e. not "depends > > on !COMPILE_TEST") > > > > I'm trying to understand a Kconfig behavior with regard to > > COMPILE_TEST. I'm able to use an "all*config" target, followed by specific > > additional config changes (e.g. turning off KCOV), but I can't enable > > things like DEBUG_INFO because of their "depends on !COMPILE_TEST". > > Whenever I want to examine debug info from all*config build I need to > > patch lib/Kconfig.debug to remove the depends. I was hoping I could, > > instead do: > > This would be a minor hassle for my randconfig testing because I really > want to have DEBUG_INFO disabled when building randconfigs in order > to keep down compile times. I could however just force DEBUG_INFO=n > the same way as forcing COMPILE_TEST=y at the moment. Right, yes, I want the default for DEBUG_INFO to be off for the COMPILE_TEST=y case (for savings on speed, storage, etc), but I want to be _able_ to turn it on when I'm doing whole-build binary comparisons or pahole archaeology. :) > > > I then thought I could use: > > > > default !COMPILE_TEST > > > > since this works: > > > > config WERROR > > bool "Compile the kernel with warnings as errors" > > default COMPILE_TEST > > > > but I think the above is a no-op: it's the same as not having > > "default COMPILE_TEST" when doing an all*config build: it'll be enabled > > not because of COMPILE_TEST but because of the all*config pass. > > Correct. One trick that works here is to use a 'choice' statement, as those > still honor the 'default' value even for allmodconfig -- Kconfig has no > idea which one of them is the 'all' version. > > > How can I make DEBUG_INFO configurable, but default off under > > all*config? > > I'd try generalizing the "DWARF version" choice to offer 'none' as a > default, like > > choice > prompt "Debug information" > default DEBUG_INFO_NONE if COMPILE_TEST > default DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT if DEBUG_KERNEL > > config DEBUG_INFO_NONE > bool "Turn off all debug information" > > config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT > bool "Rely on the toolchain's implicit default DWARF version" > > config DEBUG_INFO_DWARF4 > bool "Generate DWARF Version 4 debuginfo" > > config DEBUG_INFO_DWARF5 > bool "Generate DWARF Version 5 debuginfo" > depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || > (AS_IS_GNU && AS_VERSION >= 23502))) > depends on !DEBUG_INFO_BTF > > endchoice Ooooh! Yes, that's excellent. I will give that a try. Thanks! -Kees -- Kees Cook
