Protect BBL data, not just text

h/t @michaeljclark

Protect M-mode memory from S-mode

bbl: boot payload in machine mode when --enable-boot-machine is passed

Properly license all nontrivial files

RISC-V: Support separate firmware and kernel payload

Support for separate firmware and kernel payload is added
by updating BBL to read optional preloaded kernel address
attributes from device-tree using a similar mechanism to
that used to pass init ramdisk addresses to linux kernel.

chosen {
riscv,kernel-start = <0x00000000 0x80200000>;
riscv,kernel-end = <0x00000000 0x80590634>;
};

These attributes are added by QEMU and read by BBL when combining
-bios <firmware-image> and -kernel <kernel-image> options. e.g.

$ qemu-system-riscv64 -machine virt -bios bbl -kernel vmlinux

With this change, bbl can be compiled without --with-payload
and the dummy payload alignment is altered to make the memory
footprint of the firmware-only bbl smaller. The dummy payload
message is updated to indicate the alternative load method.

This load method could also be supported by a first stage boot
loader that reads seperate firmware and kernel from SPI flash.
The main advantage of this new mechanism is that it eases kernel
development by avoiding the riscv-pk packaging step after kernel
builds, makes building per repository artefacts for CI simpler,
and mimics bootloaders on other platforms that can load a kernel
image file directly. Ultimately BBL should use an SPI driver to
load the kernel image however this mechanism supports use cases
such such as QEMU's -bios, -kernel and -initrd options following
examples from other platforms that pass kernel entry to firmware
via device-tree.

Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Alistair Francis <Alistair.Francis@wdc.com>
Signed-off-by: Michael Clark <mjc@sifive.com>

Remove the platform interface

We now automatically detect everything that the platform interface used
to be used for, so it's now obsolete!

Detect harts that can't boot Linux instead of hard-coding them

This checks to see if a hart can't boot Linux by looking for a
compatible "mmu-type" field. If the hart can't boot Linux, then bbl
masks it off.

The DTB argument to boot_other_hart shouldn't be used in BBL

I screwed up refactoring bbl.

Add the '--enable-print-device-tree' argument

I'm trying to debug some device tree problems while booting Linux and
figured it would be really nice to have access to the device tree while
trying to debug these problems. I think this might be useful for lots
of people, so I went ahead and cleaned up the code enough that it should
actaully work in most cases.

Move DISABLED_HART_MASK to the platform

Some platforms can't boot Linux on all the harts. This commit allows
platforms to define the set of harts that should be prevented from
booting past BBL. This is essentially just a new mechanism for defining
the DISABLED_HART_MASK.

Rename HART_MASK to DISABLED_HART_MASK to clarify polarity

bbl: prevent named cores from booting

fdt: redact clint, plic, and debug hardware

bbl: copy dtb after the kernel

SBI: a0+a1 hold hartid+dtb pointer between boot loader stages

Don't block for acks on console writes

Clean up boot loader for physical address loading

WIP towards ECALL interface for SBI

Incorporate sptbr/sfence.vma changes

avoid non-standard predefined macros

Udpate to new PTE format

Move DRAM to high addresses

Refactor pk, bbl, machine into separate libraries

Yuck.