Machine privilege level was specially designed to use in vendor's
firmware or bootloader. We have implemented operation in machine
mode in FreeBSD as part of understanding RISC-V ISA, but it is time
to remove it.
We now use BBL (Berkeley Boot Loader) -- standard RISC-V firmware,
which provides operation in machine mode for us.
We now use standard SBI calls to machine mode, instead of handmade
'syscalls'.
o Remove HTIF bus.
HTIF bus is now legacy and no longer exists in RISC-V specification.
HTIF code still exists in Spike simulator, but BBL do not provide
raw interface to it.
Memory disk is only choice for now to have multiuser booted in Spike,
until Spike has implemented more devices (e.g. Virtio, etc).
Sponsored by: DARPA, AFRL
Sponsored by: HEIF5
The linker script CONSTRUCTORS keyword is only meaningful "when linking
object file formats which do not support arbitrary sections, such as
ECOFF and XCOFF"[1] and is ignored for other object file formats.
LLVM's lld does not yet accept (and ignore) CONSTRUCTORS, so just remove
CONSTRUCTORS from the linker scripts as it has no effect.
[1] https://sourceware.org/binutils/docs/ld/Output-Section-Keywords.html
Reviewed by: kib
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D7343
This is the final step required allowing to compile and to run RISC-V
kernel and userland from HEAD.
RISC-V is a completely open ISA that is freely available to academia
and industry.
Thanks to all the people involved! Special thanks to Andrew Turner,
David Chisnall, Ed Maste, Konstantin Belousov, John Baldwin and
Arun Thomas for their help.
Thanks to Robert Watson for organizing this project.
This project sponsored by UK Higher Education Innovation Fund (HEIF5) and
DARPA CTSRD project at the University of Cambridge Computer Laboratory.
FreeBSD/RISC-V project home: https://wiki.freebsd.org/riscv
Reviewed by: andrew, emaste, kib
Relnotes: Yes
Sponsored by: DARPA, AFRL
Sponsored by: HEIF5
Differential Revision: https://reviews.freebsd.org/D4982
