Option CONFIG_DEBUG_SET_MODULE_RONX not working for kernel 3.10

[Paul Bolle]

On Thu, 2014-08-14 at 09:38 -0400, Valdis Kletnieks wrote:
> On Thu, 14 Aug 2014 16:46:22 +0530, Chetan Nanda said:
> > I am trying to enable 'CONFIG_DEBUG_SET_MODULE_RONX' config option on
> > 3.10 kernel (for ARM arch) via writing  CONFIG_DEBUG_SET_MODULE_RONX=y
> > at the end of
> > board specific config file.
> >
> > But .config generated after kernel build do not have this option enabled.
> >
> > Do I need to enable any other option also before enabling this one?
> 
> Go into 'make menuconfig', Enter a '/'.  In the textbox, enter a substring
> of the symbol (I entered 'MODULE_RONX').
> 
> At least on x86_64, this shows me:
> 
>   x Symbol: DEBUG_SET_MODULE_RONX [=y]                                                                                                  x
>   x Type  : boolean                                                                                                                     x
>   x Prompt: Set loadable kernel module data as NX and text as RO                                                                        x
>   x   Location:                                                                                                                         x
>   x (1) -> Kernel hacking                                                                                                               x
>   x   Defined at arch/x86/Kconfig.debug:112                                                                                             x
>   x   Depends on: MODULES [=y]
> 
> Perhaps it's different on ARM - seems pretty silly to enable MODULE_RONX
> if your kernel doesn't have CONFIG_MODULES=y in the build.

DEBUG_SET_MODULE_RONX was added for ARM in v3.14:
$ git grep -nw DEBUG_SET_MODULE_RONX v3.13
v3.13:arch/s390/Kconfig.debug:32:config DEBUG_SET_MODULE_RONX
v3.13:arch/x86/Kconfig.debug:103:config DEBUG_SET_MODULE_RONX
$ git grep -nw DEBUG_SET_MODULE_RONX v3.14
v3.14:arch/arm/Kconfig.debug:1198:config DEBUG_SET_MODULE_RONX
v3.14:arch/s390/Kconfig.debug:32:config DEBUG_SET_MODULE_RONX
v3.14:arch/x86/Kconfig.debug:103:config DEBUG_SET_MODULE_RONX

See commit dca9aa92fc7c ("ARM: add DEBUG_SET_MODULE_RONX option to
Kconfig"). So using that Kconfig symbol in v3.10 is pointless (for ARM).

> But in general, you should *NOT* simply edit the config file, because
> that does *not* do any checking of select/depend as you make the change.
> 
> Then when you actually make the kernel, it *will* re-drive the select/depend
> logic, and convert the provided .config to a self-consistent form.

And, as Chetan noticed, it will also drop Kconfig symbols that are
unknown for that build (as, in this case, DEBUG_SET_MODULE_RONX).

> Of course,
> there is zero guarantee that the self-consistent form corresponds to your
> intentions....


Paul Bolle