On 09/08/17 00:30, Jason A. Donenfeld wrote:
> For (1) and (2), though, what do you think of the warning I've added
> to Gentoo? That's what I meant by asking for thoughts on "this
> pattern" -- the whole thing with comparing running kernel and
> compiled-for-kernel and comparing loaded-module-version and
> compiled-module-version.
> 

Ah, righty. From my admittedly limited experience that seems fine - for
example, from the Debian/Ubuntu virtualbox-dkms package
(vboxdrv/Makefile, #192):

>  # kernel base directory
>  ifndef KERN_DIR
>   # build for the current kernel, version check
>   KERN_DIR := /lib/modules/$(shell uname -r)/build
>   ifneq ($(shell if test -d $(KERN_DIR); then echo yes; fi),yes)
>    KERN_DIR := /usr/src/linux
>    ifneq ($(shell if test -d $(KERN_DIR); then echo yes; fi),yes)
>     $(error Error: unable to find the sources of your current Linux kernel. \
> 	           Specify KERN_DIR=<directory> and run Make again)
>    endif
>    $(warning Warning: using /usr/src/linux as the source directory of your \
>                       Linux kernel. If this is not correct, specify \
> 		      KERN_DIR=<directory> and run Make again.)
>   endif
>  else
>   ifneq ($(shell if test -d $(KERN_DIR); then echo yes; fi),yes)
>    $(error Error: KERN_DIR does not point to a directory)
>   endif
>  endif