下面开始介绍如何把环境弄好，以X86架构下的FS模式为例，在Ubuntu14.04 LTS环境下。
建议全程用root身份。
1.进入gem5目录下，编译X86架构
root@ubuntu14:/home/zzh/gem5# scons build/X86/gem5.opt
2.下载X86架构对应的全系统文件，也就是disk
wget http://www.m5sim.org/dist/current/x86/x86-system.tar.bz2
3.下载alpha对应的全系统文件，这是因为后面会用到里面解压出来的一个文件。
wget http://www.m5sim.org/dist/current/m5_system_2.0b3.tar.bz2
4.gem5目录下新建个文件夹fs-image，进入该目录，解压x86-system.tar.gz
root@ubuntu14:/home/zzh/gem5# mkdir fs-image
root@ubuntu14:/home/zzh/gem5# cd fs-image
root@ubuntu14:/home/zzh/gem5/fs-image# tar -xjf x86-system.tar.bz2
5.我第三步下载的alpha对应的全系统文件——m5_system_2.0b3放在Download目录下，将其解压，并将disks目录下的Linux-bigswap2.img放到x86-system解压后的disks目录下。
root@ubuntu14:/home/zzh/gem5/fs-image# cp /home/zzh/Downloads/m5_system_2.0b3/disks/linux-bigswap2.img disks/
6.修改.bashrc文件，添加下面的环境变量
root@ubuntu14:~# ls -a
. .. .bash_history .bashrc .profile .viminfo
root@ubuntu14:~# vim .bashrc
export M5_PATH=$M5_PATH:/home/zzh/gem5/fs-image/
7.使环境变量生效
root@ubuntu14:~# source .bashrc
8.进入gem5目录下，启动X86架构的FS模式
root@ubuntu14:~# cd /home/zzh/gem5
root@ubuntu14:/home/zzh/gem5# build/X86/gem5.opt configs/example/fs.py
9.报了下面的错误：
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/home/zzh/gem5/src/python/m5/main.py", line 400, in main
exec filecode in scope
File "configs/example/fs.py", line 341, in <module>
test_sys = build_test_system(np)
File "configs/example/fs.py", line 96, in build_test_system
options.ruby, cmdline=cmdline)
File "/home/zzh/gem5/configs/common/FSConfig.py", line 620, in makeLinuxX86System
makeX86System(mem_mode, numCPUs, mdesc, self, Ruby)
File "/home/zzh/gem5/configs/common/FSConfig.py", line 545, in makeX86System
disk0.childImage(mdesc.disk())
File "/home/zzh/gem5/configs/common/Benchmarks.py", line 60, in disk
return env.get('LINUX_IMAGE', disk('x86root.img'))
File "/home/zzh/gem5/configs/common/SysPaths.py", line 44, in disk
system()
File "/home/zzh/gem5/configs/common/SysPaths.py", line 69, in system
raise IOError, "Can't find a path to system files."
IOError: Can't find a path to system files.
错误：Can’t find a path to system files.
解决办法：修改gem5目录下的configs/common/SysPath.py，将目录改成你现在的目录
except KeyError:
path = [ '/dist/m5/system', '/n/poolfs/z/dist/m5/system' ]
except KeyError:
path = [ '/dist/m5/system', '/home/zzh/gem5/fs-image' ]
10.重新启动，报了第二个错
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/home/zzh/gem5/src/python/m5/main.py", line 400, in main
exec filecode in scope
File "configs/example/fs.py", line 341, in <module>
test_sys = build_test_system(np)
File "configs/example/fs.py", line 96, in build_test_system
options.ruby, cmdline=cmdline)
File "/home/zzh/gem5/configs/common/FSConfig.py", line 620, in makeLinuxX86System
makeX86System(mem_mode, numCPUs, mdesc, self, Ruby)
File "/home/zzh/gem5/configs/common/FSConfig.py", line 545, in makeX86System
disk0.childImage(mdesc.disk())
File "/home/zzh/gem5/configs/common/Benchmarks.py", line 60, in disk
return env.get('LINUX_IMAGE', disk('x86root.img'))
File "/home/zzh/gem5/configs/common/SysPaths.py", line 45, in disk
return searchpath(disk.path, filename)
File "/home/zzh/gem5/configs/common/SysPaths.py", line 41, in searchpath
raise IOError, "Can't find file '%s' on path." % filename
IOError: Can't find file 'x86root.img' on path.
错误：Can’t find file ‘x86root.img’ on path.
解决办法：修改Benchmarks.py文件，将x86root.img改为linux-x86.img
zzh@ubuntu14:~/gem5/configs/common$ vim Benchmarks.py
elif buildEnv['TARGET_ISA'] == 'x86':
return env.get('LINUX_IMAGE', disk('x86root.img'))
elif buildEnv['TARGET_ISA'] == 'x86':
return env.get('LINUX_IMAGE', disk('linux-x86.img'))
11.重新启动，命令行可以指定kernel和使用的disk-image，报下面的错误：Error opening /home/zzh/gem5/fs-image/disks/linux-bigswap2.img
zzh@ubuntu14:~/gem5$ build/X86/gem5.opt configs/example/fs.py --kernel=x86_64-vmlinux-2.6.22.9 --disk-image=linux-x86.img
info: kernel located at: /home/zzh/gem5/fs-image/binaries/x86_64-vmlinux-2.6.22.9
Listening for com_1 connection on port 3456
0: rtc: Real-time clock set to Sun Jan 1 00:00:00 2012
panic: Error opening /home/zzh/gem5/fs-image/disks/linux-bigswap2.img
查了查权限。
要sudo权限，上面那个启动命令。
zzh@ubuntu14:~/gem5$ sudo build/X86/gem5.opt configs/example/fs.py --kernel=x86_64-vmlinux-2.6.22.9 --disk-image=linux-x86.img
没问题了，会出现下面的输出：
12.打开另一个终端，用于连接FS模拟的全系统。这里使用的是m5term，先编译安装这个工具，在gem5的目录下有。
zzh@ubuntu14:~/gem5$ cd util/term/
zzh@ubuntu14:~/gem5/util/term$ make
cc -o m5term term.c
zzh@ubuntu14:~/gem5/util/term$ sudo make install
[sudo] password for zzh:
install -o root -m 555 m5term /usr/local/bin
13.用如下命令连接，注意3456是个端口，是在上图里出现的端口3456，默认情况下启动的第一个端口都是这个，再接着开启第二个就会是3457。
zzh@ubuntu14:~/gem5/util/term$ sudo ./m5term 127.0.0.1 3456
然后就会有如下输出。到最后就显示已经连上了，已经是进入了模拟的系统里。【这个地方，很神奇，一般第一次连接的时候很快就进去了，但是之后就大概要花个几分钟。】
==== m5 slave terminal: Terminal 0 ====
Linux version 2.6.22.9 (blackga@nacho) (gcc version 4.1.2 (Gentoo 4.1.2)) #2 Mon Oct 8 13:13:00 PDT 2007
Command line: earlyprintk=ttyS0 console=ttyS0 lpj=7999923 root=/dev/hda1
BIOS-provided physical RAM map:
BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
BIOS-e820: 000000000009fc00 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 0000000020000000 (usable)
BIOS-e820: 0000000020000000 - 00000000c0000000 (reserved)
BIOS-e820: 00000000ffff0000 - 0000000100000000 (reserved)
end_pfn_map = 1048576
kernel direct mapping tables up to 100000000 @ 8000-d000
DMI 2.5 present.
Zone PFN ranges:
DMA 0 -> 4096
DMA32 4096 -> 1048576
Normal 1048576 -> 1048576
early_node_map[2] active PFN ranges
0: 0 -> 159
0: 256 -> 131072
Intel MultiProcessor Specification v1.4
MPTABLE: OEM ID: MPTABLE: Product ID: MPTABLE: APIC at: 0xFEE00000
Processor #0 (Bootup-CPU)
I/O APIC #1 at 0xFEC00000.
Setting APIC routing to flat
Processors: 1
swsusp: Registered nosave memory region: 000000000009f000 - 00000000000a0000
swsusp: Registered nosave memory region: 00000000000a0000 - 0000000000100000
Allocating PCI resources starting at c4000000 (gap: c0000000:3fff0000)
Built 1 zonelists. Total pages: 127570
Kernel command line: earlyprintk=ttyS0 console=ttyS0 lpj=7999923 root=/dev/hda1
Initializing CPU#0
PID hash table entries: 2048 (order: 11, 16384 bytes)
time.c: Detected 1999.998 MHz processor.
Console: colour dummy device 80x25
console handover: boot [earlyser0] -> real [ttyS0]
Dentry cache hash table entries: 65536 (order: 7, 524288 bytes)
Inode-cache hash table entries: 32768 (order: 6, 262144 bytes)
Checking aperture...
Memory: 509248k/524288k available (3742k kernel code, 14444k reserved, 1874k data, 232k init)
Calibrating delay loop (skipped)... 3999.96 BogoMIPS preset
Mount-cache hash table entries: 256
CPU: L1 I Cache: 64K (64 bytes/line), D cache 64K (64 bytes/line)
CPU: L2 Cache: 1024K (64 bytes/line)
using mwait in idle threads.
CPU: Fake M5 x86_64 CPU stepping 01
ACPI: Core revision 20070126
ACPI Exception (tbxface-0618): AE_NO_ACPI_TABLES, While loading namespace from ACPI tables [20070126]
ACPI: Unable to load the System Description Tables
Using local APIC timer interrupts.
result 7812510
Detected 7.812 MHz APIC timer.
NET: Registered protocol family 16
PCI: Using configuration type 1
ACPI: Interpreter disabled.
Linux Plug and Play Support v0.97 (c) Adam Belay
pnp: PnP ACPI: disabled
SCSI subsystem initialized
usbcore: registered new interface driver usbfs
usbcore: registered new interface driver hub
usbcore: registered new device driver usb
PCI: Probing PCI hardware
PCI->APIC IRQ transform: 0000:00:04.0[A] -> IRQ 16
PCI-GART: No AMD northbridge found.
NET: Registered protocol family 2
Time: tsc clocksource has been installed.
IP route cache hash table entries: 16384 (order: 5, 131072 bytes)
TCP established hash table entries: 65536 (order: 8, 1048576 bytes)
TCP bind hash table entries: 65536 (order: 7, 524288 bytes)
TCP: Hash tables configured (established 65536 bind 65536)
TCP reno registered
Total HugeTLB memory allocated, 0
Installing knfsd (copyright (C) 1996 okir@monad.swb.de).
io scheduler noop registered
io scheduler deadline registered
io scheduler cfq registered (default)
Real Time Clock Driver v1.12ac
Linux agpgart interface v0.102 (c) Dave Jones
Serial: 8250/16550 driver $Revision: 1.90 $ 4 ports, IRQ sharing disabled
serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 8250
floppy0: no floppy controllers found
RAMDISK driver initialized: 16 RAM disks of 4096K size 1024 blocksize
loop: module loaded
Intel(R) PRO/1000 Network Driver - version 7.3.20-k2
Copyright (c) 1999-2006 Intel Corporation.
e100: Intel(R) PRO/100 Network Driver, 3.5.17-k4-NAPI
e100: Copyright(c) 1999-2006 Intel Corporation
forcedeth.c: Reverse Engineered nForce ethernet driver. Version 0.60.
tun: Universal TUN/TAP device driver, 1.6
tun: (C) 1999-2004 Max Krasnyansky <maxk@qualcomm.com>
netconsole: not configured, aborting
Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2
ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
PIIX4: IDE controller at PCI slot 0000:00:04.0
PCI: Enabling device 0000:00:04.0 (0000 -> 0001)
PIIX4: chipset revision 0
PIIX4: not 100% native mode: will probe irqs later
ide0: BM-DMA at 0x1000-0x1007, BIOS settings: hda:DMA, hdb:DMA
ide1: BM-DMA at 0x1008-0x100f, BIOS settings: hdc:DMA, hdd:DMA
hda: M5 IDE Disk, ATA DISK drive
hdb: M5 IDE Disk, ATA DISK drive
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
hda: max request size: 128KiB
hda: 1048320 sectors (536 MB), CHS=1040/16/63, UDMA(33)
hda: hda1
hdb: max request size: 128KiB
hdb: 4177920 sectors (2139 MB), CHS=4144/16/63, UDMA(33)
hdb: unknown partition table
megaraid cmm: 2.20.2.7 (Release Date: Sun Jul 16 00:01:03 EST 2006)
megaraid: 2.20.5.1 (Release Date: Thu Nov 16 15:32:35 EST 2006)
megasas: 00.00.03.10-rc5 Thu May 17 10:09:32 PDT 2007
Fusion MPT base driver 3.04.04
Copyright (c) 1999-2007 LSI Logic Corporation
Fusion MPT SPI Host driver 3.04.04
Fusion MPT SAS Host driver 3.04.04
ieee1394: raw1394: /dev/raw1394 device initialized
USB Universal Host Controller Interface driver v3.0
usbcore: registered new interface driver usblp
drivers/usb/class/usblp.c: v0.13: USB Printer Device Class driver
Initializing USB Mass Storage driver...
usbcore: registered new interface driver usb-storage
USB Mass Storage support registered.
PNP: No PS/2 controller found. Probing ports directly.
serio: i8042 KBD port at 0x60,0x64 irq 1
serio: i8042 AUX port at 0x60,0x64 irq 12
mice: PS/2 mouse device common for all mice
input: AT Translated Set 2 keyboard as /class/input/input0
device-mapper: ioctl: 4.11.0-ioctl (2006-10-12) initialised: dm-devel@redhat.com
input: PS/2 Generic Mouse as /class/input/input1
usbcore: registered new interface driver usbhid
drivers/hid/usbhid/hid-core.c: v2.6:USB HID core driver
oprofile: using timer interrupt.
TCP cubic registered
NET: Registered protocol family 1
NET: Registered protocol family 10
IPv6 over IPv4 tunneling driver
NET: Registered protocol family 17
EXT2-fs warning: mounting unchecked fs, running e2fsck is recommended
VFS: Mounted root (ext2 filesystem).
Freeing unused kernel memory: 232k freed
INIT: version 2.86 booting
mounting filesystems...
loading script...
Script from M5 readfile is empty, starting bash shell...
(none) / #
好了。