| Message ID | 202112082057.C993DC6881@keescook (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | question about all*config and COMPILE_TEST | expand |
On Thu, Dec 9, 2021 at 6:07 AM Kees Cook <keescook@chromium.org> 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. > 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 Arnd
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@chromium.org> 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
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 0e2de4b375f3..e8533ffc92c3 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -212,7 +212,8 @@ menu "Compile-time checks and compiler options" config DEBUG_INFO bool "Compile the kernel with debug info" - depends on DEBUG_KERNEL && !COMPILE_TEST + depends on DEBUG_KERNEL + default n if COMPILE_TEST help If you say Y here the resulting kernel image will include debugging info resulting in a larger kernel image.
Hi, 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: Which would turn this off when COMPILE_TEST was enabled, but I assume it doesn't work because an all*config target turns everything on first, and therefore this "default" gets ignored since DEBUG_INFO already has a value set. 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. How can I make DEBUG_INFO configurable, but default off under all*config? Thanks!