Several improvements
* Drop the detection of EFI through kallsyms. This detection is no
longer useful since commit 2c0c4c9fd1 ("Using CONFIG_EFI instead of
user defined HAS_EFI (#1036)") replaced `HAS_EFI` with `CONFIG_EFI`.
* Use `...-objs-y` and `...-objs-$(CONFIG_...)` logic to choose which
`cpu.asm` file is being built. This is something that other modules do
in Linux kernel source.
* Introduce `quiet_cmd_...` and `cmd_...` definition in order to use the
build system of the kernel to compile `cpu.asm` with NASM. This should
prevent issues like the one mentioned in 2210002bab ("Fixed build
error on latest Ubuntu") from happening again. Moreover this makes the
custom clean command `rm -f ${asm-path}/cpu.o` no longer necessary.
* Remove variables which become unused after these changes. Now, all
that `Makefile` needs is a kernel directory, specified with `KSRC`.
This change has been tested on a test system running Ubuntu 20.10 and on
GitHub Actions workers running Ubuntu 16.04, 18.04 and 20.04 on Linux
5.4.0-1040-azure. It has also been compile-tested on many other Linux
distributions using a work-in-progress GitHub Actions configuration
(https://github.com/fishilico/chipsec/actions/runs/661200380).
It was previously possible to build Chipsec kernel module for a different Linux
kernel than the running one, and ff4a273 broke that possibility.
Bring that back just by giving a way to override the KSRC variable when calling
the Makefile.
Fix issue #1122
drivers/linux/Makefile:
* Replaced KERNEL_SRC_DIR variable with KSRC.
* Added KSRC variable which should enable successful DKMS compilation,
as opposed to bailing out with "Unable to find the Linux source tree."
This patch has been tested on Black Arch.
Nathaniel Mitchell