Import busybear-linux build script

.gitignore

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+*~
+build/
+archives/
+busybear.bin

Makefile

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+all: busybear.bin
+
+clean:
+	rm -fr build busybear.bin
+
+distclean: clean
+	rm -fr archives
+
+busybear.bin: scripts/build.sh scripts/image.sh
+	sh scripts/build.sh
+	sudo -E sh scripts/image.sh
+
+archive:
+	tar --exclude build --exclude archives --exclude busybear.bin \
+	    -C .. -cjf ../busybear-linux.tar.bz2 busybear-linux

README.md

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+# busybear-linux
+
+busybear-linux is a tiny RISC-V Linux root filesystem image that targets
+the `virt` board in riscv-qemu. As the name suggests, busybear-linux is
+a riscv-linux root image comprised of busybox and dropbear.
+
+The root image is intended to demonstrate virtio-net and virtio-block in
+riscv-qemu and features a dropbear ssh server which allows out-of-the-box
+ssh access to a RISC-V virtual machine.
+
+See the [releases](https://github.com/michaeljclark/busybear-linux/releases)
+for pre-built kernel and filesystem images.
+
+## Dependencies
+
+- [riscv-gnu-toolchain](https://github.com/riscv/riscv-gnu-toolchain) (RISC-V Linux toolchain)
+- [busybox](https://busybox.net/) (downloaded automatically)
+- [dropbear](https://matt.ucc.asn.au/dropbear/dropbear.html) (downloaded automatically)
+- sudo, curl, openssl and rsync
+
+## Features
+
+- `ntpd` for time configuration
+- `klog` for kernel logging
+- `syslog` for system logging
+- `dropbear` for ssh access
+- `busybox` with almost everything enabled
+
+## Configuration
+
+- `conf` contains the linux image build configuration
+  - `conf/linux.config` contains the linux-kernel configuration
+  - `conf/busybox.config` contains the busybox configuration
+  - `conf/busybear.config` contains the image build configuration
+    - `ROOT_PASSWORD=busybear`
+    - `IMAGE_FILE=busybear.bin`
+- `etc` contains the linux guest system configuration
+  - `etc/network/interfaces` (guest 192.168.100.2, router 192.168.100.1)
+  - `etc/resolv.conf` (nameserver 8.8.8.8, nameserver 8.8.4.4)
+  - `etc/ntp.conf` (server 0.pool.ntp.org, server 1.pool.ntp.org)
+  - `etc/passwd`, `etc/shadow`, `etc/group` and `etc/hosts`
+
+The default config assumes bridged networking with `192.168.100.1`
+on the host and `192.168.100.2` in the guest.
+
+## Build
+
+The build process downloads busybox and dropbear, compiles them and prepares
+a root filesystem image to the file `busybear.bin`. The build script needs
+to be run in Linux, even if preparing a root filesystem image for macOS.
+
+### busybear-linux
+
+```
+git clone https://github.com/michaeljclark/busybear-linux.git
+cd busybear-linux
+make
+```
+
+### QEMU
+
+```
+git clone https://github.com/riscv/riscv-qemu.git
+cd riscv-qemu
+./configure --target-list=riscv64-softmmu,riscv32-softmmu
+make
+```
+
+### riscv-linux
+
+```
+git clone https://github.com/riscv/riscv-linux.git
+cd riscv-linux
+git checkout riscv-linux-4.14
+cp ../busybear-linux/conf/linux.config .config
+make ARCH=riscv olddefconfig
+make ARCH=riscv vmlinux
+```
+
+### bbl
+
+```
+git clone https://github.com/riscv/riscv-pk.git
+cd riscv-pk
+mkdir build
+cd build
+../configure \
+    --enable-logo \
+    --host=riscv64-unknown-elf \
+    --with-payload=../../riscv-linux/vmlinux
+make
+```
+
+## Running
+
+busybear requires the riscv-qemu `virt` board with virtio-block
+and virtio-net devices.
+
+The following command starts busybear-linux.
+
+```
+sudo qemu-system-riscv64 -nographic -machine virt -kernel bbl \
+  -drive file=busybear.bin,format=raw,id=hd0 \
+  -device virtio-blk-device,drive=hd0 \
+  -netdev type=tap,script=./ifup,downscript=./ifdown,id=net0 \
+  -device virtio-net-device,netdev=net0
+```
+
+After booting the virtual machine you should be able to ssh into it.
+
+```
+$ ssh [email protected]
+The authenticity of host '192.168.100.2 (192.168.100.2)' can't be established.
+ECDSA key fingerprint is 3f:4b:69:59:01:c8:b2:9c:fb:52:a5:d4:21:c9:3c:1b.
+Are you sure you want to continue connecting (yes/no)? yes
+Warning: Permanently added '192.168.100.2' (ECDSA) to the list of known hosts.
+[email protected]'s password: 
+    ____                   ____                     __    _                 
+   / __ )__  _________  __/ __ )___  ____ ______   / /   (_)___  __  ___  __
+  / __  / / / / ___/ / / / __  / _ \/ __ `/ ___/  / /   / / __ \/ / / / |/_/
+ / /_/ / /_/ (__  ) /_/ / /_/ /  __/ /_/ / /     / /___/ / / / / /_/ />  <  
+/_____/\__,_/____/\__, /_____/\___/\__,_/_/     /_____/_/_/ /_/\__,_/_/|_|  
+                 /____/                                                     
+root@ucbvax:~# uname -a
+Linux ucbvax 4.14.0-00030-gc2d852cb2f3d #56 Thu Dec 14 10:12:10 NZDT 2017 riscv64 GNU/Linux
+root@ucbvax:~# cat /proc/interrupts 
+           CPU0       
+  1:        107  riscv,plic0,c000000  10  ttyS0
+  7:        115  riscv,plic0,c000000   7  virtio1
+  8:        135  riscv,plic0,c000000   8  virtio0
+root@ucbvax:~# 
+```
+
+Note: the disk image is stateful and needs to be shutdown cleanly.
+
+```
+root@ucbvax:~# halt
+```
+
+## macOS bridged networking
+
+These steps show how to setup tuntap bridged networking on macOS:
+
+### install tuntap
+
+Note: the tuntap driver installation requires authorization in the
+macOS Security and Privacy section of System Preferences.
+
+```
+brew tap caskroom/cask
+brew install caskroom/cask/tuntap
+```
+
+### create bridge
+
+```
+sudo ifconfig bridge1 create
+sudo ifconfig bridge1 192.168.100.1/24
+```
+
+### ifup script
+
+```
+#!/bin/bash
+ifconfig bridge1 addm $1
+```
+
+### ifdown script
+
+```
+#!/bin/bash
+ifconfig bridge1 deletem $1
+```
+
+### pfctl.rules (packet filter rules)
+
+```
+nat on en0 from { 192.168.100.0/24 } to any -> (en0)
+pass from {lo0, 192.168.100.0/24} to any keep state
+```
+
+### NAT forwarding (guest access to the Internet)
+
+```
+sudo sysctl -w net.inet.ip.forwarding=1
+sudo pfctl -e
+sudo pfctl -F all
+sudo pfctl -f pfctl.rules 
+```
+
+## linux configuration
+
+The following is a minimal linux-kernel `.config` that can be used with
+`make ARCH=riscv olddefconfig`.
+
+```
+CONFIG_HZ_100=y
+CONFIG_PCI=y
+CONFIG_CROSS_COMPILE="riscv64-unknown-elf-"
+CONFIG_DEFAULT_HOSTNAME="ucbvax"
+CONFIG_PARTITION_ADVANCED=y
+CONFIG_NET=y
+CONFIG_UNIX=y
+CONFIG_INET=y
+CONFIG_DEVTMPFS=y
+CONFIG_DEVTMPFS_MOUNT=y
+CONFIG_VIRTIO_BLK=y
+CONFIG_NETDEVICES=y
+CONFIG_VIRTIO_NET=y
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+CONFIG_SERIAL_OF_PLATFORM=y
+CONFIG_VIRT_DRIVERS=y
+CONFIG_VIRTIO_MMIO=y
+CONFIG_EXT4_FS=y
+CONFIG_TMPFS=y
+CONFIG_CMDLINE_BOOL=y
+CONFIG_CMDLINE="root=/dev/vda ro"
+CONFIG_PRINTK_TIME=y
+```

bin/ldd

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+#!/bin/sh
+LD_TRACE_LOADED_OBJECTS=1 $*

conf/busybear.config

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+BUSYBOX_VERSION=1.27.2
+DROPBEAR_VERSION=2017.75
+COMPILER_PREFIX=riscv64-unknown-linux-gnu
+IMAGE_FILE=busybear.bin
+IMAGE_SIZE=64
+ROOT_PASSWORD=busybear