Current proposed secureboot implementation disables kexec/kdump because
it can allow unsigned kernel to run on a secureboot platform. Intial
idea was to sign /sbin/kexec binary and let that binary do the kernel
signature verification. I had posted RFC patches for this apparoach
here.
https://lkml.org/lkml/2013/9/10/560
Later we had discussion at Plumbers and most of the people thought
that signing and trusting /sbin/kexec is becoming complex. So a
better idea might be let kernel do the signature verification of
new kernel being loaded. This calls for implementing a new system call
and moving lot of user space code in kernel.
kexec_load() system call allows loading a kexec/kdump kernel and jump
to that kernel at right time. Though a lot of processing is done in
user space which prepares a list of segments/buffers to be loaded and
kexec_load() works on that list of segments. It does not know what's
contained in those segments.
Now a new system call kexec_file_load() is implemented which takes
kernel fd and initrd fd as parameters. Now kernel should be able
to verify signature of newly loaded kernel.
This is an early RFC patchset. I have not done signature handling
part yet. This is more of a minimal patch to show how new system
call and functionality will look like. Right now it can only handle
bzImage with 64bit entry point on x86_64. No EFI, no x86_32 or any
other architecture. Rest of the things can be added slowly as need
arises. In first iteration, I have tried to address most common use case
for us.
Any feedback is welcome.