陆续写些关于新书《自己动手写CPU》的博客，本篇主要是讲解 gem5运行全系统模拟

使用gem5可以启动Linux内核，称为全系统模拟，启动之后，可以通过telent连接，进行访问，但四telent有时不稳定，gem5推荐使用m5term进行连接访问，整个步骤如下：

（假设gem5文件加压缩后，位于/root/gem5/gem5-stable-50ff05095970文件夹）

（1）打开终端，进入/root/gem5/gem5-stable-50ff05095970目录，使用如下命令得到x86的二进制虚拟机

scons build/X86/gem5.opt 

（2）在http://www.m5sim.org/Download下载x86对应的全系统文件，我用的下载地址是http://www.m5sim.org/dist/current/x86/x86-system.tar.bz2

下载后，在/root/gem5/gem5-stable-50ff05095970目录下新建一个文件夹fs-image，将下载的x86-system.tar.bz2复制到该文件夹下，并解压缩。

（3）在http://www.m5sim.org/Download下载alpha对应的全系统文件，我用的下载地址是http://www.m5sim.org/dist/current/m5_system_2.0b3.tar.bz2

下载后，解压缩，将其中disks目录下的linux-bigswap2.img复制到/root/gem5/gem5-stable-50ff05095970/fs-image/x86-system/disks目录下。

（4）修改/root/.bashrc，其中添加环境变量，如下：

export M5_PATH=$M5_PATH:/root/gem5/gem5-stable-50ff05095970/fs-image/x86-system

（5）在终端中进入/root/gem5/gem5-stable-50ff05095970目录，是如如下命令可以启动x86虚拟机：

build/X86/gem5.opt configs/example/fs.py --kernel=x86_64-vmlinux-2.6.22.9 --disk-image=linux-x86.img

gem5 Simulator System.  http://gem5.org
gem5 is copyrighted software; use the --copyright option for details.

gem5 compiled Jan 26 2015 13:54:19
gem5 started Jan 26 2015 18:19:14
gem5 executing on localhost.localdomain
command line: build/X86/gem5.opt configs/example/fs.py --kernel=x86_64-vmlinux-2.6.22.9 --disk-image=linux-x86.img
Global frequency set at 1000000000000 ticks per second
info: kernel located at: /root/gem5/gem5-stable-50ff05095970/fs-image/x86-system/binaries/x86_64-vmlinux-2.6.22.9
      0: rtc: Real-time clock set to Sun Jan  1 00:00:00 2012
Listening for com_1 connection on port 3456
warn: Reading current count from inactive timer.
0: system.remote_gdb.listener: listening for remote gdb #0 on port 7000
**** REAL SIMULATION ****
info: Entering event queue @ 0.  Starting simulation...
warn: Don't know what interrupt to clear for console.
53268325000: system.pc.com_1.terminal: attach terminal 0
warn: x86 cpuid: unknown family 0x8086

接下来可以编译m5term，以便连接到上面的监听端口，m5term的源码在gem5源代码的util/term目录下，进入该目录，输入熟悉命令进行编译：

        % cd m5/util/term 
	% make
	gcc  -o m5term term.c
	% make install
	sudo install -o root -m 555 m5term /usr/local/bin

./m5term 127.0.0.1 3456

[root@localhost term]# ./m5term 127.0.0.1 3456
==== 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: 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 30000000 (gap: 20000000:dfff0000)
Built 1 zonelists.  Total pages: 127572
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: 509256k/524288k available (3742k kernel code, 14436k 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)
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-GART: No AMD northbridge found.
Time: tsc clocksource has been installed.
NET: Registered protocol family 2
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) / #

(none) / # ls
bin   dev  home  lib32  lost+found  opt   root  sys  usr
boot  etc  lib   lib64  mnt         proc  sbin  tmp  var

gem5全系统模拟