On Tue, 13 Oct 2020 at 18:46, Mimi Zohar [off-list ref] wrote:

[Cc'ing linuxppc-dev@lists.ozlabs.org]

On Tue, 2020-10-13 at 10:18 +0200, Ard Biesheuvel wrote:

quoted

Chester reports that it is necessary to introduce a new way to pass
the EFI secure boot status between the EFI stub and the core kernel
on ARM systems. The usual way of obtaining this information is by
checking the SecureBoot and SetupMode EFI variables, but this can
only be done after the EFI variable workqueue is created, which
occurs in a subsys_initcall(), whereas arch_ima_get_secureboot()
is called much earlier by the IMA framework.

However, the IMA framework itself is started as a late_initcall,
and the only reason the call to arch_ima_get_secureboot() occurs
so early is because it happens in the context of a __setup()
callback that parses the ima_appraise= command line parameter.

So let's refactor this code a little bit, by using a core_param()
callback to capture the command line argument, and deferring any
reasoning based on its contents to the IMA init routine.

Cc: Chester Lin <redacted>
Cc: Mimi Zohar <zohar@linux.ibm.com>
Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Link: https://lore.kernel.org/linux-arm-kernel/20200904072905.25332-2-clin@suse.com/ (local)
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
v2: rebase onto series 'integrity: improve user feedback for invalid bootparams'

Thanks, Ard.  Based on my initial, limited testing on Power, it looks
good, but I'm hesistant to include it in the integrity 5.10 pull
request without it having been in linux-next and some additional
testing.  It's now queued in the next-integrity-testing branch awaiting
some tags.

Thanks. No rush as far as I am concerned, although I suppose Chester
may want to rebase his arm64 IMA enablement series on this.

Suggestion: can we take the get_sb_mode() code from ima_arch.c in
arch/x86, and generalize it for all EFI architectures? That way, we
can enable 32-bit ARM and RISC-V seamlessly once someone gets around
to enabling IMA on those platforms. In fact, get_sb_mode() itself
should probably be factored out into a generic helper for use outside
of IMA as well (Xen/x86 has code that does roughly the same already)