Messages in this thread | | | From | Kees Cook <> | Date | Wed, 10 Apr 2019 15:04:24 -0700 | Subject | Re: [PATCH v1] init: Do not select DEBUG_KERNEL by default |
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On Wed, Apr 10, 2019 at 2:54 PM Sinan Kaya <Okaya@kernel.org> wrote: > > On 4/10/2019 5:45 PM, Kees Cook wrote: > > On Wed, Apr 10, 2019 at 2:26 PM Sinan Kaya <okaya@kernel.org> wrote: > >> > >> We can't seem to have a kernel with CONFIG_EXPERT set but > >> CONFIG_DEBUG_KERNEL unset these days. > >> > >> While some of the features under the CONFIG_EXPERT require > >> CONFIG_DEBUG_KERNEL, it doesn't apply for all features. > >> > >> The meaning of CONFIG_EXPERT and CONFIG_DEBUG_KERNEL has been > >> mixed here. > > > > I don't agree: the point of EXPERT is to show _everything_, which > > means DEBUG_KERNEL should be selected to show those options as well. I > > think this is fine as-is. What is the problem you want to solve? > > > > I think of it as low (nothing selected) medium (DEBUG_KERNEL) and high > > (EXPERT and DEBUG_KERNEL). So EXPERT enables DEBUG_KERNEL too. > > > > Sure, let's see if there is a better option. > > I don't want any of the debug features in my kernel but still > need all the expert features. My kernel is considered a production > kernel. I don't really want to ship all the good debug enables.
Production kernels enable it. e.g. Ubuntu: $ grep '\bCONFIG_DEBUG_KERNEL\b' /boot/config-$(uname -r) CONFIG_DEBUG_KERNEL=y
> On the other hand, I need the features under CONFIG_EXPERT to have > a functional system. > > Let's take "multiple users" as an example. > > What's the point of having a kernel without multiple users? :) > > I don't see the relationship between CONFIG_DEBUG and CONFIG_EXPERT > as none of the features except KALLSYMS depend on it. If there was > a compile time dependency, I'd say move it to the things that need > it as this patch suggests.
CONFIG_DEBUG_KERNEL mainly only enables the visibility of various other options. I can only find two instances of it controlling a "default", and one is overridden by CONFIG_SMP on alpha. :)
$ git grep -B2 'default.*DEBUG_KERNEL' arch/alpha/Kconfig.debug-config MATHEMU arch/alpha/Kconfig.debug- tristate "Kernel FP software completion" if DEBUG_KERNEL && !SMP arch/alpha/Kconfig.debug: default y if !DEBUG_KERNEL || SMP -- kernel/trace/Kconfig-menuconfig FTRACE kernel/trace/Kconfig- bool "Tracers" kernel/trace/Kconfig: default y if DEBUG_KERNEL
What do you see enabled that CONFIG_DEBUG_KERNEL enables that you don't want?
-- Kees Cook
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