WSL 安装 gem5
先执行 git config 命令配置好代理，然后执行
git clone https://gem5.googlesource.com/public/gem5
cd gem5
scons build/X86/gem5.opt -j 12这里 -j 后的内容代表同时执行的工作数，即使是单核处理器，SCons -Q 命令也会默认指定 -j 2。如果指定 -j 1，需要花费数小时时间才能构建完成，但如果用满 CPU，只需一个多小时就可以构建完成。对于 6 核 12 线程（逻辑处理器），一般指定 -j 6 及以上就可以用满 CPU。
显示
scons: Reading SConscript files ...
You're missing the gem5 style or commit message hook. These hooks help
to ensure that your code follows gem5's style rules on git commit.
This script will now install the hook in your .git/hooks/ directory.
Press enter to continue, or ctrl-c to abort:
回车。Windows 是无法安装 gem5 的，回车会出现
Error updating git pre-commit hook
OSError: [WinError 1314] 客户端没有所需的特权。: '..\\..\\util\\git-pre-commit.py' -> 'F:\\Documents\\GitHub\\ECE4700J_SU2022\\Lab6\\gem5\\.git\\hooks\\pre-commit':
File "F:\Documents\GitHub\ECE4700J_SU2022\Lab6\gem5\SConstruct", line 177:
main = Environment(tools=[
File "E:\Program_Files\Python310\lib\site-packages\SCons\Environment.py", line 1010:
apply_tools(self, tools, toolpath)
File "E:\Program_Files\Python310\lib\site-packages\SCons\Environment.py", line 116:
_ = env.Tool(tool)
File "E:\Program_Files\Python310\lib\site-packages\SCons\Environment.py", line 1879:
tool(self)
File "E:\Program_Files\Python310\lib\site-packages\SCons\Tool\__init__.py", line 273:
self.generate(env, *args, **kw)
File "F:\Documents\GitHub\ECE4700J_SU2022\Lab6\gem5\site_scons\site_tools\git.py", line 120:
install_style_hooks(env)
File "F:\Documents\GitHub\ECE4700J_SU2022\Lab6\gem5\site_scons\site_tools\git.py", line 115:
hook_install("pre-commit", git_style_script)
File "F:\Documents\GitHub\ECE4700J_SU2022\Lab6\gem5\site_scons\site_tools\git.py", line 94:
os.symlink(script_path, hook.get_abspath())
以管理员身份运行 PowerShell 执行 scons 命令，在上述回车后会显示
TypeError: 'NoneType' object is not callable:
File "F:\Documents\GitHub\ECE4700J_SU2022\Lab6\gem5\SConstruct", line 182:
main.Tool(SCons.Tool.FindTool(['gcc', 'clang'], main))
File "E:\Program_Files\Python310\lib\site-packages\SCons\Environment.py", line 1879:
tool(self)
显示 scons 并未找到 gcc 或 clang（可参考十年前的 mailinglist archive：problems when compiling (narkive.com)）。该检查位于 SConstruct 文件的第 182~183 行：
main.Tool(SCons.Tool.FindTool(['gcc', 'clang'], main))
main.Tool(SCons.Tool.FindTool(['g++', 'clang++'], main))如果使用虚拟机打开，应将 gem5 克隆到虚拟机磁盘内，而不要使用挂载在 /mnt/hgfs 的克隆，否则会在上述回车后报错
FileNotFoundError: [Errno 2] No such file or directory: "/mnt/hgfs/Documents/Senior/ECE4700J,Computer Architecture/Lab #6/gem5/fatal: unsafe repository ('/mnt/hgfs/Documents/Senior/ECE4700J,Computer Architecture/Lab #6/gem5' is owned by someone else)\nTo add an exception for this directory, call:\n\n\tgit config --global --add safe.directory '/mnt/hgfs/Documents/Senior/ECE4700J,Computer Architecture/Lab #6/gem5'/hooks":
File "/mnt/hgfs/Documents/Senior/ECE4700J,Computer Architecture/Lab #6/gem5/SConstruct", line 177:
main = Environment(tools=[
File "/home/ayka-tsuzuki/.local/lib/python3.10/site-packages/SCons/Environment.py", line 1010:
apply_tools(self, tools, toolpath)
File "/home/ayka-tsuzuki/.local/lib/python3.10/site-packages/SCons/Environment.py", line 116:
_ = env.Tool(tool)
File "/home/ayka-tsuzuki/.local/lib/python3.10/site-packages/SCons/Environment.py", line 1879:
tool(self)
File "/home/ayka-tsuzuki/.local/lib/python3.10/site-packages/SCons/Tool/__init__.py", line 273:
self.generate(env, *args, **kw)
File "/mnt/hgfs/Documents/Senior/ECE4700J,Computer Architecture/Lab #6/gem5/site_scons/site_tools/git.py", line 120:
install_style_hooks(env)
File "/mnt/hgfs/Documents/Senior/ECE4700J,Computer Architecture/Lab #6/gem5/site_scons/site_tools/git.py", line 115:
hook_install("pre-commit", git_style_script)
File "/mnt/hgfs/Documents/Senior/ECE4700J,Computer Architecture/Lab #6/gem5/site_scons/site_tools/git.py", line 78:
os.mkdir(git_hooks.get_abspath())
我们在这里用 WSL 安装，打开 WSL Ubuntu（注意，zsh 打开 gem5 目录会卡住不动，所以应全程使用 bash），cd 到克隆文件夹下执行 scons 命令，在上述回车后即可成功开始安装：
然而，构建在 [VER TAGS] -> X86/sim/tags.cc 出错误停止，报错：
[VER TAGS] -> X86/sim/tags.cc
/usr/bin/env: ‘python3\r’: No such file or directory
scons: *** [build/X86/sim/tags.cc] Error 127
scons: building terminated because of errors.
*** Summary of Warnings ***
Warning: You can get a 12% performance improvement by installing tcmalloc (libgoogle-perftools-dev package on Ubuntu or
RedHat).
Warning: Deprecated namespaces are not supported by this compiler.
Please make sure to check the mailing list for deprecation announcements.
Warning: Couldn't find HDF5 C++ libraries. Disabling HDF5 support.
Warning: While checking protoc version: [Errno 2] No such file or directory: 'protoc'
Warning: Protocol buffer compiler (protoc) not found.
Please install protobuf-compiler for tracing support.
研究 gem5 源码，报错位置在 src/SConscript 的第 644-647 行：
tags = \
env.Command('sim/tags.cc', None,
MakeAction('util/cpt_upgrader.py --get-cc-file > $TARGET',
Transform("VER TAGS")))这里的 env 是主目录的 SConstruct 文件中第 720 行
exports=['env', 'gem5py_env']导出让所有子目录下的 SConscript 文件可以直接使用的，而 env 是在第 366 行
env = main.Clone()从 main 克隆而来的，且中间的修改没有关键影响，而 main 是第 177-180 行
main = Environment(tools=[
'default', 'git', TempFileSpawn, EnvDefaults, MakeActionTool,
ConfigFile, AddLocalRPATH, SwitchingHeaders, TagImpliesTool, Blob
])定义的，且中间的修改没有关键影响，这里 python 实际上就是 'default' 引入的。通过学习 SCons，可编写以下最小可工作样例 SConstruct 文件：
env = Environment()
tags = env.Command('sim/tags.cc', None, 'util/cpt_upgrader.py --get-cc-file > $TARGET')其中，Environment() 与 Environment(tools=['default']) 等价，env.Command 的第 3 个参数 action 等价于 SCons.Script.Action('util/cpt_upgrader.py --get-cc-file > $TARGET')，然后在命令行执行 scons 命令，输出：
scons: Reading SConscript files ...
scons: done reading SConscript files.
scons: Building targets ...
util/cpt_upgrader.py --get-cc-file > sim/tags.cc
/usr/bin/env: 'python3\r': No such file or directory
scons: *** [sim/tags.cc] Error 127
查看 util/cpt_upgrader.py，直接执行
python util/cpt_upgrader.py --get-cc-file可生成一段代码重定向到 $TARGET 也就是 sim/tags.cc 中：
// this file is auto-generated by util/cpt_upgrader.py
#include
#include
namespace gem5
{
std::set version_tags = {
"arm-ccregs",
"arm-contextidr-el2",
"arm-gem5-gic-ext",
"arm-gicv2-banked-regs",
"arm-hdlcd-upgrade",
"arm-miscreg-teehbr",
"arm-sve",
"arm-sysreg-mapping-ns",
"armv8",
"cpu-pid",
"dvfs-perflevel",
"etherswitch",
"globals-to-root",
"ide-dma-abort",
"isa-is-simobject",
"memory-per-range",
"mempool-sections",
"mempool-to-seworkload",
"multiple-event-queues",
"process-fdmap-rename",
"remove-arm-cpsr-mode-miscreg",
"ruby-block-size-bytes",
"smt-interrupts",
"x86-add-tlb",
};
} // namespace gem5 通过研究 SCons 源码知道，可以切换到工作目录下进入 Python，直接在 Python 命令行输入
import SCons.Platform
SCons.Platform.Platform().name
import SCons.Environment
SCons.Environment.Environment()._dict检查 Platform 为 'posix'，Environment 一个键为 'BUILDERS'、子键有 'Program'、'SharedLibrary' 等的大字典，其中子键 'ENV' 的值为 {"PATH": "/usr/local/bin:/opt/bin:/bin:/usr/bin:/snap/bin"}。然后参考 SCons/EnvironmentTests.py 中的 test_Command 函数执行
act = 'util/cpt_upgrader.py --get-cc-file > $TARGET'
env = SCons.Environment.Environment()
t = env.Command('sim/tags.cc', None, act)[0]
t.build()同样可以复现错误：
util/cpt_upgrader.py --get-cc-file > sim/tags.cc
sh: 1: cannot create sim/tags.cc: Directory nonexistent
Traceback (most recent call last):
File "", line 1, in
File "/mnt/f/Documents/GitHub/scons/SCons/Node/__init__.py", line 755, in build
self.get_executor()(self, **kw)
File "/mnt/f/Documents/GitHub/scons/SCons/Executor.py", line 384, in __call__
return _do_execute_map[self._do_execute](self, target, kw)
File "/mnt/f/Documents/GitHub/scons/SCons/Executor.py", line 120, in execute_action_list
raise status # TODO pylint E0702: raising int not allowed
SCons.Errors.BuildError: Error 2
这里的 t 是 SCons.Node.FS.Entry object 或 SCons.Node.FS.File object，其所在的列表只有 t 一个元素；t.builder 是 SCons.Builder.BuilderBase object；str(t) 为 'sim/tags.cc'。这里的函数调用链为 SCons.Environment.Base.Command -> SCons.Builder.BuilderBase.__call__ -> SCons.Builder.BuilderBase._execute -> SCons.Node.Node.build-> SCons.Node.Node.get_executor -> Scons.Executor.Executor._call__ -> Scons.Executor.Executor._do_execute_map -> Scons.Executor.execute_action_list。这里为了复现
env = obj.get_build_env()
kw = obj.get_kw(kw)
args = ([], [], env)
status = act(*args, **kw)的行为，可在 Python 命令行中继续执行
args = ([], [], env)
act_obj = t.get_executor().get_action_list()[0]
kw = t.get_executor().get_kw()
act_obj(*args, **kw)可以直接复现错误。这里的 env 和 t.get_executor().get_build_env()、t.get_executor()._memo['get_build_env'] 是一样的。我们还可以执行
SCons.Debug.track_instances = True重新执行 act_obj，会给出 SCons.Erros.BuildError 的具体信息：
BuildError(None, 'Error 127', 127, 2, None, None,
, ['util/cpt_upgrader.py', '--get-cc-file', '>', '"sim/tags.cc"'], (None, None, None))
这里 act_obj 为 SCons.Action.CommandAction object，kw 为字典，键为 'executor'，值为 SCons.Executor.Executor object，env 为 SCons.Environment.Base object。CommandAction 类继承自 _ActionAction 类，其 __call__ 函数调用子类的 execute 函数。env['SHELL'] 、env['SPAWN'] 和 env['ESCAPE'] 对于 posix 系统而言都定义在 SCons/Platform/posix.py 中，分别是 'sh'、subprocess_spawn -> subprocess_spawn -> exec_subprocess -> subprocess.Popen 和 escape。对于 ENV 变量而言，_resolve_shell_env 函数中 shell_gen = env.get('SHELL_ENV_GENERATORS') 为空，ENV = get_default_ENV(env) 也就是 env['ENV']。因此，SCons 实际执行的命令就是直接执行
sh -c util/cpt_upgrader.py --get-cc-file > sim/tags.cc而不手动指定 Python 编译器。因为 util/cpt_upgrader.py 的第一行的 shebang 是
#!/usr/bin/env python3所以在 WSL 中直接执行上述命令时注意到文件行尾序列为 CRLF 而非 LF，因此才导致错误读入 \r，注意到在 PowerShell 中克隆 gem5 源码时，执行
git config --list其中有一条配置：core.autocrlf=true，所以才导致 git clone 时自动将行尾序列从 LF 转换到 CRLF，可参考 linux - Git replacing LF with CRLF - Stack Overflow 修改，也可参考 How do I convert all files in a folder to a different line ending? (on Windows) - Super User 和 Recursively Change Line Endings (Windows) (github.com) 执行
sudo apt install dos2unix
find gem5 -type f -exec dos2unix {} \;递归地转换 gem5 文件夹下的所有文件：
完成后，重新执行构建命令即可成功：
执行
pip install pydot
build/X86/gem5.opt configs/learning_gem5/part1/simple.py
测试成功。