目的

FPGAでLinuxのブートシミュレーションがしたい。
Linuxブート動作を電子回路のレイヤーで覗いてみたい。
（Verilog HDLシミュレータで信号シミュレーションが出来るのか？はまだ未確認）

LiteXとは？

FPGA Linux simulationなどのキーワードでぐぐっていたら見つかった。
どうやらこれを使うとFPGA上にLinuxが動くSoC（System On Chip）回路を作ってくれて、さらにLinuxイメージのロードもしてシミュレーションやら、実機にダウンロードして動作させる事が出来る素晴らしい取り組み。

これが本家（かな？）
https://github.com/enjoy-digital/litex

今回スクリプト構築の参考にしたサイトはこちら
https://github.com/litex-hub/linux-on-litex-vexriscv

実験環境

ホストOS：　Ubuntu 20.04
ホストCPU：　INTEL
ホストメモリ：　32GB
ホストDISK：　512GB

スクリプトのポイント

・参考にした記事のGNU toolchainインストール手順は使ってるデータが古かったのでそこだけ別のサイトを参考にした。
https://github.com/litex-hub/linux-on-litex-vexriscv

・GNU toolchainビルドの時の以下で（自分の環境では）長い時間止まるので「何かおかしい？」と思ったが、そんな時は別ウィンドウで「watch -n 1 df」を実行し、少しづつだけど何かダウンロードされている事を見て、自分を安心させる。

INFO : (riscv-gnu-toolchain) make linux                      -------
cd /root/riscv/linux_on_riscv_arty_a7-100t/riscv-gnu-toolchain && \
flock `git rev-parse --git-dir`/config git submodule init /root/riscv/linux_on_riscv_arty_a7-100t/riscv-gnu-toolchain/gcc/ && \
flock `git rev-parse --git-dir`/config git submodule update /root/riscv/linux_on_riscv_arty_a7-100t/riscv-gnu-toolchain/gcc/
Submodule 'gcc' (https://gcc.gnu.org/git/gcc.git) registered for path 'gcc'
Cloning into '/root/riscv/linux_on_riscv_arty_a7-100t/riscv-gnu-toolchain/gcc'...

・Digilent社Arty A7 100Tボードはそこそこ高額でお財布がイタイが、別のボードを選んで余計なデバッグをしなくて済むように、そこはガマンした。もっと安い35Tの方でも問題ないと思われるが未確認。

事前準備

・別記事で書いたスクリプトを参考に、Vivado 2019.1をインストールしておく。
　⇒　LiteXを記事の通り動かすには実行には、Vivado HLx Editionsが必要だった。
　　　2015.1とかのバージョンだとVivado（無印）なのでLiteXコマンドでエラーになった模様。
　　　Artix-7をサポートしてるバージョンとして2019.1を選択。

LiteX環境構築スクリプト

#!/bin/bash

  # https://github.com/litex-hub/linux-on-litex-vexriscv

  echo "INFO : add it to PATH      in /etc/bash.bashrc : /root/.sdkman/contrib/completion/bash     --------------------------------"; export PATH=/root/.sdkman/contrib/completion/bash:$PATH
  echo "INFO : add it to PATH      in /etc/bash.bashrc : /root/.sdkman/candidates/java/current/bin --------------------------------"; export PATH=/root/.sdkman/candidates/java/current/bin:$PATH
  echo "INFO : add it to PATH      in /etc/bash.bashrc : /opt/riscv/bin                            --------------------------------"; export PATH=/opt/riscv/bin:$PATH

  echo "INFO : source /tools/Xilinx/Vivado/2019.1/settings64.sh                                    --------------------------------"; source /tools/Xilinx/Vivado/2019.1/settings64.sh


DIR_BASE=/root/riscv/linux_on_riscv_arty_a7-100t
DIR_PJ=$DIR_BASE/linux-on-litex-vexriscv
  echo "INFO : apt -y update   -----------------------------------------"; apt -y update
  echo "INFO : apt -y upgrade  -----------------------------------------"; apt -y upgrade
  echo "INFO : (Prerequisites) mkdir $DIR_BASE  ------------------------"; mkdir -p $DIR_BASE

  echo "INFO : (riscv-gnu-toolchain) cd    $DIR_BASE  ----------------------"; cd       $DIR_BASE
  echo "INFO : (riscv-gnu-toolchain) install autoconf        ---------------"; apt-get -y install autoconf
  echo "INFO : (riscv-gnu-toolchain) install automake        ---------------"; apt-get -y install automake
  echo "INFO : (riscv-gnu-toolchain) install autotools-dev   ---------------"; apt-get -y install autotools-dev
  echo "INFO : (riscv-gnu-toolchain) install curl            ---------------"; apt-get -y install curl
  echo "INFO : (riscv-gnu-toolchain) install python3         ---------------"; apt-get -y install python3
  echo "INFO : (riscv-gnu-toolchain) install python3-pip     ---------------"; apt-get -y install python3-pip
  echo "INFO : (riscv-gnu-toolchain) install libmpc-dev      ---------------"; apt-get -y install libmpc-dev
  echo "INFO : (riscv-gnu-toolchain) install libmpfr-dev     ---------------"; apt-get -y install libmpfr-dev
  echo "INFO : (riscv-gnu-toolchain) install libgmp-dev      ---------------"; apt-get -y install libgmp-dev
  echo "INFO : (riscv-gnu-toolchain) install gawk            ---------------"; apt-get -y install gawk
  echo "INFO : (riscv-gnu-toolchain) install build-essential ---------------"; apt-get -y install build-essential
  echo "INFO : (riscv-gnu-toolchain) install bison           ---------------"; apt-get -y install bison
  echo "INFO : (riscv-gnu-toolchain) install flex            ---------------"; apt-get -y install flex
  echo "INFO : (riscv-gnu-toolchain) install texinfo         ---------------"; apt-get -y install texinfo
  echo "INFO : (riscv-gnu-toolchain) install gperf           ---------------"; apt-get -y install gperf
  echo "INFO : (riscv-gnu-toolchain) install libtool         ---------------"; apt-get -y install libtool
  echo "INFO : (riscv-gnu-toolchain) install patchutils      ---------------"; apt-get -y install patchutils
  echo "INFO : (riscv-gnu-toolchain) install bc              ---------------"; apt-get -y install bc
  echo "INFO : (riscv-gnu-toolchain) install zlib1g-dev      ---------------"; apt-get -y install zlib1g-dev
  echo "INFO : (riscv-gnu-toolchain) install libexpat-dev    ---------------"; apt-get -y install libexpat-dev
  echo "INFO : (riscv-gnu-toolchain) install ninja-build     ---------------"; apt-get -y install ninja-build
  echo "INFO : (riscv-gnu-toolchain) install git             ---------------"; apt-get -y install git
  echo "INFO : (riscv-gnu-toolchain) install cmake           ---------------"; apt-get -y install cmake
  echo "INFO : (riscv-gnu-toolchain) install libglib2.0-dev  ---------------"; apt-get -y install libglib2.0-dev
  # https://stackoverflow.com/questions/72987674/git-pull-error-rpc-failed-curl-16-error-in-the-http2-framing-layer-fatal-exp
  echo "INFO : (riscv-gnu-toolchain) git config for make linux error -------"; git config --global http.version HTTP/1.1
  echo "INFO : (riscv-gnu-toolchain) git clone riscv-gnu-toolchain ---------"; git clone https://github.com/riscv/riscv-gnu-toolchain
  echo "INFO : (riscv-gnu-toolchain) cd riscv-gnu-toolchain/         -------"; cd riscv-gnu-toolchain/
  echo "INFO : (riscv-gnu-toolchain) ./configure --prefix=/opt/riscv -------"; ./configure --prefix=/opt/riscv
  echo "INFO : (riscv-gnu-toolchain) make linux                      -------"; export GIT_SSL_NO_VERIFY=1; make linux

  echo "INFO : (Prerequisites) cd    $DIR_BASE  ------------------------"; cd       $DIR_BASE
  echo "INFO : (Prerequisites) install build-essential -----------------"; apt -y install build-essential
  echo "INFO : (Prerequisites) install device-tree-compiler ------------"; apt -y install device-tree-compiler wget git python3-setuptools
  echo "INFO : (Prerequisites) install wget                  -----------"; apt -y install wget
  echo "INFO : (Prerequisites) install git                   -----------"; apt -y install git
  echo "INFO : (Prerequisites) install python3-setuptools    -----------"; apt -y install python3-setuptools
  echo "INFO : (Prerequisites) git clone linux-on-litex-vexriscv -------"; git clone https://github.com/litex-hub/linux-on-litex-vexriscv

  echo "INFO : (Pre-built Bitstreams and Linux/OpenSBI images) cd linux-on-litex-vexriscv/images -------"; cd $DIR_PJ/images
  echo "INFO : (Pre-built Bitstreams and Linux/OpenSBI images) wget linux + opensbi              -------"; wget https://github.com/litex-hub/linux-on-litex-vexriscv/files/8331338/linux_2022_03_23.zip
  echo "INFO : (Pre-built Bitstreams and Linux/OpenSBI images) unzip opensbi_2020_12_15.zip      -------"; unzip -o linux_2022_03_23.zip

  echo "INFO : (Installing LiteX) cd $DIR_BASE     ---------------------"; cd $DIR_BASE
  echo "INFO : (Installing LiteX) wget  litex_setup.py           -------"; wget https://raw.githubusercontent.com/enjoy-digital/litex/master/litex_setup.py
  echo "INFO : (Installing LiteX) chmod litex_setup.py           -------"; chmod +x litex_setup.py
  echo "INFO : (Installing LiteX) install python3-pip            -------"; apt-get -y install python3-pip
  echo "INFO : (Installing LiteX) litex_setup.py init install    -------"; ./litex_setup.py --init --install --user

  echo "INFO : (Installing Verilator) install verilator      ------------------------------"; apt -y install verilator
  echo "INFO : (Installing Verilator) install libevent-dev   ------------------------------"; apt -y install libevent-dev
  echo "INFO : (Installing Verilator) install libjson-c-dev  ------------------------------"; apt -y install libjson-c-dev
  
  echo "INFO : cd $DIR_BASE ---------------------------------------------------------------"; cd $DIR_BASE
  echo "INFO : (Installing OpenOCD) install libtool           -----------------------------"; apt -y install libtool
  echo "INFO : (Installing OpenOCD) install automake          -----------------------------"; apt -y install automake
  echo "INFO : (Installing OpenOCD) install pkg-config        -----------------------------"; apt -y install pkg-config
  echo "INFO : (Installing OpenOCD) install libusb-1.0-0-dev  -----------------------------"; apt -y install libusb-1.0-0-dev
  echo "INFO : (Installing OpenOCD) git clone openocd.git     -----------------------------"; git clone https://github.com/ntfreak/openocd.git
  echo "INFO : (Installing OpenOCD) cd openocd                -----------------------------"; cd openocd
  echo "INFO : (Installing OpenOCD) ./bootstrap               -----------------------------"; ./bootstrap
  echo "INFO : (Installing OpenOCD) ./configure --enable-ftdi -----------------------------"; ./configure --enable-ftdi
  echo "INFO : (Installing OpenOCD) make                      -----------------------------"; make
  echo "INFO : (Installing OpenOCD) make install              -----------------------------"; make install

  echo "INFO : cd $DIR_BASE ---------------------------------------------------------------"; cd $DIR_BASE
  echo "INFO : (sbt for sim.py) tee /etc/apt/sources.list.d/sbt.list     ------------------"; echo "deb https://repo.scala-sbt.org/scalasbt/debian all main" | sudo tee /etc/apt/sources.list.d/sbt.list
  echo "INFO : (sbt for sim.py) tee /etc/apt/sources.list.d/sbt_old.list ------------------"; echo "deb https://repo.scala-sbt.org/scalasbt/debian /"        | sudo tee /etc/apt/sources.list.d/sbt_old.list
  echo "INFO : (sbt for sim.py) curl keyserver.ubuntu.com/pks & apt-key add  --------------"; curl -sL "https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x2EE0EA64E40A89B84B2DF73499E82A75642AC823" | sudo apt-key add
  echo "INFO : (sbt for sim.py) update       ----------------------------------------------"; apt-get -y update
  echo "INFO : (sbt for sim.py) install sbt  ----------------------------------------------"; apt-get -y install sbt

  echo "INFO : cd $DIR_BASE ---------------------------------------------------------------"; cd $DIR_BASE
  echo "INFO : (java by sdkman for sim.py) install sdkman  --------------------------------"; curl -s "https://get.sdkman.io" | bash
  echo "INFO : (java by sdkman for sim.py) chmod 744 sdk   --------------------------------"; chmod 744 /root/.sdkman/contrib/completion/bash/sdk
  echo "INFO : (java by sdkman for sim.py) source sdkman-init.sh --------------------------"; source /root/.sdkman/bin/sdkman-init.sh
  echo "INFO : (java by sdkman for sim.py) install java    --------------------------------"; sdk install java $(sdk list java | grep -o "\b8\.[0-9]*\.[0-9]*\-tem" | head -1)

  echo "INFO : (meson for sim.py) upgrade pip      ----------------------------------------"; python3 -m pip install --upgrade pip
  echo "INFO : (meson for sim.py) install meson    ----------------------------------------"; pip3 install meson

  echo "INFO : cd $DIR_PJ                                              --------------------"; cd $DIR_PJ
  # to prevent from following error.
  # [error] [launcher] error during sbt launcher: java.lang.OutOfMemoryError: GC overhead limit exceeded
  # https://support.snyk.io/hc/en-us/articles/360003143417-Out-of-Memory-Error-when-testing-Scala-sbt-project
  echo "INFO : (Build the FPGA bitstream)          SBT limit setting   --------------------"; export SBT_OPTS="-Xms1024M -Xmx4G -Xss2M -XX:MaxMetaspaceSize=2G"
  echo "INFO : (Build the FPGA bitstream)          build bitstream     --------------------"; ./make.py --board=arty --variant=a7-100 --cpu-count=1 --build
  echo "INFO : (Running the LiteX simulation)      sim.py              --------------------"; ./sim.py

# Arty A7ボードをPCとUSBケーブルで接続してるなら、以下も実行可能。
# echo "INFO : (Load the FPGA bitstream)           load  bitstream     --------------------"; ./make.py --board=arty --variant=a7-100 --cpu-count=1 --load
# echo "INFO : (Load the Linux images over Serial) load linux via uart --------------------"; python3 litex_term.py --images=images/boot.json /dev/ttyUSB1

スクリプト実行ログ

最後に実行したsim.pyの方のログ。

：
[clocker] sys_clk: freq_hz=1000000, phase_deg=0

        __   _ __      _  __
       / /  (_) /____ | |/_/
      / /__/ / __/ -_)>  <
     /____/_/\__/\__/_/|_|
   Build your hardware, easily!

 (c) Copyright 2012-2023 Enjoy-Digital
 (c) Copyright 2007-2015 M-Labs

 BIOS built on Oct 15 2023 14:02:35
 BIOS CRC passed (0aaad8a5)

 LiteX git sha1: e499dd84

--=============== SoC ==================--
CPU:            VexRiscv SMP-LINUX @ 100MHz
BUS:            WISHBONE 32-bit @ 4GiB
CSR:            32-bit data
ROM:            64.0KiB
SRAM:           8.0KiB
SDRAM:          64.0MiB 32-bit @ 100MT/s (CL-2 CWL-2)
MAIN-RAM:       64.0MiB

--========== Initialization ============--
Initializing SDRAM @0x40000000...
Switching SDRAM to software control.
Switching SDRAM to hardware control.

--============== Boot ==================--
Booting from serial...
Press Q or ESC to abort boot completely.
sL5DdSMmkekro
Timeout
Executing booted program at 0x40f00000

--============= Liftoff! ===============--

OpenSBI v0.8-1-gecf7701
   ____                    _____ ____ _____
  / __ \                  / ____|  _ \_   _|
 | |  | |_ __   ___ _ __ | (___ | |_) || |
 | |  | | '_ \ / _ \ '_ \ \___ \|  _ < | |
 | |__| | |_) |  __/ | | |____) | |_) || |_
  \____/| .__/ \___|_| |_|_____/|____/_____|
        | |
        |_|

Platform Name       : LiteX / VexRiscv-SMP
Platform Features   : timer,mfdeleg
Platform HART Count : 8
Boot HART ID        : 0
Boot HART ISA       : rv32imas
BOOT HART Features  : pmp,scounteren,mcounteren,time
BOOT HART PMP Count : 16
Firmware Base       : 0x40f00000
Firmware Size       : 124 KB
Runtime SBI Version : 0.2

MIDELEG : 0x00000222
MEDELEG : 0x0000b109
[    0.000000] Linux version 5.14.0 (florent@panda) (riscv32-buildroot-linux-gnu-gcc.br_real (Buildroot 2021.08-381-g279167ee8d) 10.3.0, GNU ld (GNU Binutils) 2.36.1) #1 SMP Tue Sep 21 12:57:31 CEST 2021
[    0.000000] earlycon: liteuart0 at I/O port 0x0 (options '')
[    0.000000] Malformed early option 'console'
[    0.000000] earlycon: liteuart0 at MMIO 0xf0001000 (options '')
[    0.000000] printk: bootconsole [liteuart0] enabled
[    0.000000] Zone ranges:
[    0.000000]   Normal   [mem 0x0000000040000000-0x0000000043ffffff]
[    0.000000] Movable zone start for each node
[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x0000000040000000-0x0000000043ffffff]
[    0.000000] Initmem setup node 0 [mem 0x0000000040000000-0x0000000043ffffff]
[    0.000000] SBI specification v0.2 detected
[    0.000000] SBI implementation ID=0x1 Version=0x8
[    0.000000] SBI TIME extension detected
[    0.000000] SBI IPI extension detected
[    0.000000] SBI RFENCE extension detected
[    0.000000] SBI v0.2 HSM extension detected
[    0.000000] riscv: ISA extensions aimp
[    0.000000] riscv: ELF capabilities aim
[    0.000000] percpu: Embedded 8 pages/cpu s11340 r0 d21428 u32768
[    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: 16256
[    0.000000] Kernel command line: console=liteuart earlycon=liteuart,0xf0001000 rootwait root=/dev/ram0
[    0.000000] Dentry cache hash table entries: 8192 (order: 3, 32768 bytes, linear)
[    0.000000] Inode-cache hash table entries: 4096 (order: 2, 16384 bytes, linear)
[    0.000000] Sorting __ex_table...
[    0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
[    0.000000] Memory: 48648K/65536K available (5685K kernel code, 572K rwdata, 883K rodata, 209K init, 221K bss, 16888K reserved, 0K cma-reserved)
[    0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[    0.000000] rcu: Hierarchical RCU implementation.
[    0.000000] rcu:     RCU restricting CPUs from NR_CPUS=8 to nr_cpu_ids=1.
[    0.000000] rcu: RCU calculated value of scheduler-enlistment delay is 25 jiffies.
[    0.000000] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=1
[    0.000000] NR_IRQS: 64, nr_irqs: 64, preallocated irqs: 0
[    0.000000] riscv-intc: 32 local interrupts mapped
[    0.000000] plic: interrupt-controller@f0c00000: mapped 32 interrupts with 1 handlers for 2 contexts.
[    0.000000] random: get_random_bytes called from start_kernel+0x4ac/0x63c with crng_init=0
[    0.000000] riscv_timer_init_dt: Registering clocksource cpuid [0] hartid [0]
[    0.000000] clocksource: riscv_clocksource: mask: 0xffffffffffffffff max_cycles: 0x171024e7e0, max_idle_ns: 440795205315 ns
[    0.000017] sched_clock: 64 bits at 100MHz, resolution 10ns, wraps every 4398046511100ns
[    0.002154] Console: colour dummy device 80x25
[    0.003085] Calibrating delay loop (skipped), value calculated using timer frequency.. 200.00 BogoMIPS (lpj=400000)
[    0.004624] pid_max: default: 32768 minimum: 301
[    0.008050] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
[    0.009087] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
[    0.029602] ASID allocator using 9 bits (512 entries)
[    0.032202] rcu: Hierarchical SRCU implementation.
[    0.037667] smp: Bringing up secondary CPUs ...
[    0.038228] smp: Brought up 1 node, 1 CPU
[    0.043635] devtmpfs: initialized
[    0.066964] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
[    0.068287] futex hash table entries: 256 (order: 2, 16384 bytes, linear)
[    0.075961] NET: Registered PF_NETLINK/PF_ROUTE protocol family
[    0.219089] pps_core: LinuxPPS API ver. 1 registered
[    0.219624] pps_core: Software ver. 5.3.6 - Copyright 2005-2007 Rodolfo Giometti <giometti@linux.it>
[    0.221051] PTP clock support registered
[    0.224211] FPGA manager framework
[    0.237389] clocksource: Switched to clocksource riscv_clocksource
[    0.388115] NET: Registered PF_INET protocol family
[    0.390255] IP idents hash table entries: 2048 (order: 2, 16384 bytes, linear)
[    0.397785] tcp_listen_portaddr_hash hash table entries: 512 (order: 0, 6144 bytes, linear)
[    0.399109] TCP established hash table entries: 1024 (order: 0, 4096 bytes, linear)
[    0.400341] TCP bind hash table entries: 1024 (order: 1, 8192 bytes, linear)
[    0.401563] TCP: Hash tables configured (established 1024 bind 1024)
[    0.402993] UDP hash table entries: 256 (order: 1, 8192 bytes, linear)
[    0.404087] UDP-Lite hash table entries: 256 (order: 1, 8192 bytes, linear)
[    0.421832] Unpacking initramfs...
[    0.457634] workingset: timestamp_bits=30 max_order=14 bucket_order=0
[    0.666444] io scheduler mq-deadline registered
[    0.667037] io scheduler kyber registered
[    0.918171] LiteX SoC Controller driver initialized
[    4.166205] Freeing initrd memory: 8192K
[    4.659111] f0001000.serial: ttyLXU0 at MMIO 0x0 (irq = 0, base_baud = 0) is a liteuart
[    4.660393] printk: console [liteuart0] enabled
[    4.660393] printk: console [liteuart0] enabled
[    4.661316] printk: bootconsole [liteuart0] disabled
[    4.661316] printk: bootconsole [liteuart0] disabled
[    4.682040] i2c_dev: i2c /dev entries driver
[    4.719192] NET: Registered PF_INET6 protocol family
[    4.732729] Segment Routing with IPv6
[    4.733825] In-situ OAM (IOAM) with IPv6
[    4.735364] sit: IPv6, IPv4 and MPLS over IPv4 tunneling driver
[    4.748263] NET: Registered PF_PACKET protocol family
[    4.759811] Freeing unused kernel image (initmem) memory: 204K
[    4.760589] Kernel memory protection not selected by kernel config.
[    4.761872] Run /init as init process
Starting syslogd: OK
Starting klogd: OK
Running sysctl: OK
Saving random seed: [    6.829806] random: dd: uninitialized urandom read (512 bytes read)
OK
Starting network: OK

Welcome to Buildroot
buildroot login: root　※　ここでrootと入力してENTER（シミュレーションなのでだいぶ遅い）
                   __   _
                  / /  (_)__  __ ____ __
                 / /__/ / _ \/ // /\ \ /
                /____/_/_//_/\_,_//_\_\
                      / _ \/ _ \
   __   _ __      _  _\___/_//_/         ___  _
  / /  (_) /____ | |/_/__| | / /____ __ / _ \(_)__ _____  __
 / /__/ / __/ -_)>  </___/ |/ / -_) \ // , _/ (_-</ __/ |/ /
/____/_/\__/\__/_/|_|____|___/\__/_\_\/_/|_/_/___/\__/|___/
                  / __/  |/  / _ \
                 _\ \/ /|_/ / ___/
                /___/_/  /_/_/
  32-bit RISC-V Linux running on LiteX / VexRiscv-SMP.

login[70]: root login on 'console'
root@buildroot:~# pwd　※　試しにpwdコマンド実行したら効いた
/root
root@buildroot:~#

これでVivadoを事前にインストールしておけば、スクリプト一発でLiteXがお試し出来た。