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QEMU is a FAST! processor emulator using dynamic translation to achieve good emulation speed.
QEMU has two operating modes:
As QEMU requires no host kernel driver to run, it is very safe and easy to use.
For system emulation, the following hardware targets are supported:
For user emulation, x86, PowerPC, ARM, and SPARC CPUs are supported.
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If you want to compile QEMU, please read the `README' which gives the related information. Otherwise just download the binary distribution (`qemu-XXX-i386.tar.gz') and untar it as root in `/':
su cd / tar zxvf /tmp/qemu-XXX-i386.tar.gz |
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./configure --enable-mingw32 |
Note: Currently, Wine does not seem able to launch QEMU for Win32.
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Mac OS X is currently not supported.
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The QEMU System emulator simulates a complete PC.
In order to meet specific user needs, two versions of QEMU are available:
qemu-fast
uses the host Memory Management Unit (MMU) to simulate
the x86 MMU. It is fast but has limitations because the whole 4 GB
address space cannot be used and some memory mapped peripherials
cannot be emulated accurately yet. Therefore, a specific Linux kernel
must be used (See section 3.8 Linux Kernel Compilation).
qemu
uses a software MMU. It is about two times
slower but gives a more accurate emulation.
QEMU emulates the following PC peripherials:
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Download and uncompress the linux image (`linux.img') and type:
qemu linux.img |
Linux should boot and give you a prompt.
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usage: qemu [options] [disk_image] |
disk_image is a raw hard disk image for IDE hard disk 0.
General options:
Normally, QEMU uses SDL to display the VGA output. With this option, you can totally disable graphical output so that QEMU is a simple command line application. The emulated serial port is redirected on the console. Therefore, you can still use QEMU to debug a Linux kernel with a serial console.
The SB16 emulation is disabled by default as it may give problems with Windows. You can enable it manually with this option.
Network options:
Set the mac address of the first interface (the format is aa:bb:cc:dd:ee:ff in hexa). The mac address is incremented for each new network interface.
Linux boot specific. When using this options, you can use a given Linux kernel without installing it in the disk image. It can be useful for easier testing of various kernels.
Debug options:
During the graphical emulation, you can use the following keys:
During emulation, you can use C-S (Control and Shift) to release the mouse pointer. If you are using the serial console, use C-a h to get terminal commands:
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The QEMU monitor is used to give complex commands to the QEMU emulator. You can use it to:
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The following commands are available:
fmt is a format which tells the command how to format the data. Its syntax is: `/{count}{format}{size}'
h
or w
can be specified with the i
format to
respectively select 16 or 32 bit code instruction size.
Examples:
(qemu) x/10i $eip 0x90107063: ret 0x90107064: sti 0x90107065: lea 0x0(%esi,1),%esi 0x90107069: lea 0x0(%edi,1),%edi 0x90107070: ret 0x90107071: jmp 0x90107080 0x90107073: nop 0x90107074: nop 0x90107075: nop 0x90107076: nop |
(qemu) xp/80hx 0xb8000 0x000b8000: 0x0b50 0x0b6c 0x0b65 0x0b78 0x0b38 0x0b36 0x0b2f 0x0b42 0x000b8010: 0x0b6f 0x0b63 0x0b68 0x0b73 0x0b20 0x0b56 0x0b47 0x0b41 0x000b8020: 0x0b42 0x0b69 0x0b6f 0x0b73 0x0b20 0x0b63 0x0b75 0x0b72 0x000b8030: 0x0b72 0x0b65 0x0b6e 0x0b74 0x0b2d 0x0b63 0x0b76 0x0b73 0x000b8040: 0x0b20 0x0b30 0x0b35 0x0b20 0x0b4e 0x0b6f 0x0b76 0x0b20 0x000b8050: 0x0b32 0x0b30 0x0b30 0x0b33 0x0720 0x0720 0x0720 0x0720 0x000b8060: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x000b8070: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x000b8080: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x000b8090: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 |
Print expression value. Only the format part of fmt is used.
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The monitor understands integers expressions for every integer argument. You can use register names to get the value of specifics CPU registers by prefixing them with $.
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The disk images can simply be raw images of the hard disk. You can create them with the command:
dd of=myimage bs=1024 seek=mysize count=0 |
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If you use the option `-snapshot', all disk images are considered as read only. When sectors in written, they are written in a temporary file created in `/tmp'. You can however force the write back to the raw disk images by pressing C-a s.
NOTE: The snapshot mode only works with raw disk images.
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QEMU also supports user mode Linux (http://user-mode-linux.sourceforge.net/) Copy On Write (COW) disk images. The COW disk images are much smaller than normal images as they store only modified sectors. They also permit the use of the same disk image template for many users.
To create a COW disk images, use the command:
qemu-mkcow -f myrawimage.bin mycowimage.cow |
`myrawimage.bin' is a raw image you want to use as original disk image. It will never be written to.
`mycowimage.cow' is the COW disk image which is created by
qemu-mkcow
. You can use it directly with the `-hdx'
options. You must not modify the original raw disk image if you use
COW images, as COW images only store the modified sectors from the raw
disk image. QEMU stores the original raw disk image name and its
modified time in the COW disk image so that chances of mistakes are
reduced.
If the raw disk image is not read-only, by pressing C-a s you can flush the COW disk image back into the raw disk image, as in snapshot mode.
COW disk images can also be created without a corresponding raw disk image. It is useful to have a big initial virtual disk image without using much disk space. Use:
qemu-mkcow mycowimage.cow 1024 |
to create a 1 gigabyte empty COW disk image.
NOTES:
ls -ls
command.
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QEMU simulates up to 6 networks cards (NE2000 boards). Each card can be connected to a specific host network interface.
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This is the standard way to emulate network. QEMU adds a virtual
network device on your host (called tun0
), and you can then
configure it as if it was a real ethernet card.
As an example, you can download the `linux-test-xxx.tar.gz'
archive and copy the script `qemu-ifup' in `/etc' and
configure properly sudo
so that the command ifconfig
contained in `qemu-ifup' can be executed as root. You must verify
that your host kernel supports the TUN/TAP network interfaces: the
device `/dev/net/tun' must be present.
See 3.7 Direct Linux Boot to have an example of network use with a Linux distribution.
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This is experimental (version 0.5.4). You must configure qemu
with --enable-slirp
. Then by using the option
`-user-net' or if you have no tun/tap init script, QEMU uses a
completely user mode network stack (you don't need root priviledge to
use the virtual network). The virtual network configuration is the
following:
QEMU Virtual Machine <------> Firewall/DHCP server <-----> Internet (10.0.2.x) | (10.0.2.2) | ----> DNS (10.0.2.3) |
The QEMU VM behaves as if it was behind a firewall which blocks all incoming connections. You can use a DHCP client to automatically configure the network in the QEMU VM.
In order to check that the user mode network is working, you can ping the address 10.0.2.2 and verify that you got an address in the range 10.0.2.x from the QEMU virtual DHCP server.
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This section explains how to launch a Linux kernel inside QEMU without having to make a full bootable image. It is very useful for fast Linux kernel testing. The QEMU network configuration is also explained.
sudo
so that the command ifconfig
contained in
`qemu-ifup' can be executed as root. You must verify that your host
kernel supports the TUN/TAP network interfaces: the device
`/dev/net/tun' must be present.
When network is enabled, there is a virtual network connection between the host kernel and the emulated kernel. The emulated kernel is seen from the host kernel at IP address 172.20.0.2 and the host kernel is seen from the emulated kernel at IP address 172.20.0.1.
qemu.sh
. You should have the following output:
> ./qemu.sh Connected to host network interface: tun0 Linux version 2.4.21 (bellard@voyager.localdomain) (gcc version 3.2.2 20030222 (Red Hat Linux 3.2.2-5)) #5 Tue Nov 11 18:18:53 CET 2003 BIOS-provided physical RAM map: BIOS-e801: 0000000000000000 - 000000000009f000 (usable) BIOS-e801: 0000000000100000 - 0000000002000000 (usable) 32MB LOWMEM available. On node 0 totalpages: 8192 zone(0): 4096 pages. zone(1): 4096 pages. zone(2): 0 pages. Kernel command line: root=/dev/hda sb=0x220,5,1,5 ide2=noprobe ide3=noprobe ide4=noprobe ide5=noprobe console=ttyS0 ide_setup: ide2=noprobe ide_setup: ide3=noprobe ide_setup: ide4=noprobe ide_setup: ide5=noprobe Initializing CPU#0 Detected 2399.621 MHz processor. Console: colour EGA 80x25 Calibrating delay loop... 4744.80 BogoMIPS Memory: 28872k/32768k available (1210k kernel code, 3508k reserved, 266k data, 64k init, 0k highmem) Dentry cache hash table entries: 4096 (order: 3, 32768 bytes) Inode cache hash table entries: 2048 (order: 2, 16384 bytes) Mount cache hash table entries: 512 (order: 0, 4096 bytes) Buffer-cache hash table entries: 1024 (order: 0, 4096 bytes) Page-cache hash table entries: 8192 (order: 3, 32768 bytes) CPU: Intel Pentium Pro stepping 03 Checking 'hlt' instruction... OK. POSIX conformance testing by UNIFIX Linux NET4.0 for Linux 2.4 Based upon Swansea University Computer Society NET3.039 Initializing RT netlink socket apm: BIOS not found. Starting kswapd Journalled Block Device driver loaded Detected PS/2 Mouse Port. pty: 256 Unix98 ptys configured Serial driver version 5.05c (2001-07-08) with no serial options enabled ttyS00 at 0x03f8 (irq = 4) is a 16450 ne.c:v1.10 9/23/94 Donald Becker (becker@scyld.com) Last modified Nov 1, 2000 by Paul Gortmaker NE*000 ethercard probe at 0x300: 52 54 00 12 34 56 eth0: NE2000 found at 0x300, using IRQ 9. RAMDISK driver initialized: 16 RAM disks of 4096K size 1024 blocksize Uniform Multi-Platform E-IDE driver Revision: 7.00beta4-2.4 ide: Assuming 50MHz system bus speed for PIO modes; override with idebus=xx hda: QEMU HARDDISK, ATA DISK drive ide0 at 0x1f0-0x1f7,0x3f6 on irq 14 hda: attached ide-disk driver. hda: 20480 sectors (10 MB) w/256KiB Cache, CHS=20/16/63 Partition check: hda: Soundblaster audio driver Copyright (C) by Hannu Savolainen 1993-1996 NET4: Linux TCP/IP 1.0 for NET4.0 IP Protocols: ICMP, UDP, TCP, IGMP IP: routing cache hash table of 512 buckets, 4Kbytes TCP: Hash tables configured (established 2048 bind 4096) NET4: Unix domain sockets 1.0/SMP for Linux NET4.0. EXT2-fs warning: mounting unchecked fs, running e2fsck is recommended VFS: Mounted root (ext2 filesystem). Freeing unused kernel memory: 64k freed Linux version 2.4.21 (bellard@voyager.localdomain) (gcc version 3.2.2 20030222 (Red Hat Linux 3.2.2-5)) #5 Tue Nov 11 18:18:53 CET 2003 QEMU Linux test distribution (based on Redhat 9) Type 'exit' to halt the system sh-2.05b# |
ls
for example. Type Ctrl-a h to have an help
about the keys you can type inside the virtual serial console. In
particular, use Ctrl-a x to exit QEMU and use Ctrl-a b as
the Magic SysRq key.
. /etc/linuxrc |
Then enable X11 connections on your PC from the emulated Linux:
xhost +172.20.0.2 |
You can now launch `xterm' or `xlogo' and verify that you have a real Virtual Linux system !
NOTES:
ide1=noprobe ide2=noprobe ide3=noprobe ide4=noprobe ide5=noprobe |
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You can use any linux kernel with QEMU. However, if you want to use
qemu-fast
to get maximum performances, you must use a modified
guest kernel. If you are using a 2.6 guest kernel, you can use
directly the patch `linux-2.6-qemu-fast.patch' made by Rusty
Russel available in the QEMU source archive. Otherwise, you can make the
following changes by hand to the Linux kernel:
In `include/asm/page.h', replace
#define __PAGE_OFFSET (0xc0000000) |
#define __PAGE_OFFSET (0x90000000) |
And in `arch/i386/vmlinux.lds', replace
. = 0xc0000000 + 0x100000; |
. = 0x90000000 + 0x100000; |
#define FIXADDR_TOP (0xffffX000UL) |
#define FIXADDR_TOP (0xa7ffX000UL) |
# define HZ 1000 /* Internal kernel timer frequency */ |
# define HZ 100 /* Internal kernel timer frequency */ |
The file config-2.x.x gives the configuration of the example kernels.
Just type
make bzImage |
As you would do to make a real kernel. Then you can use with QEMU exactly the same kernel as you would boot on your PC (in `arch/i386/boot/bzImage').
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QEMU has a primitive support to work with gdb, so that you can do 'Ctrl-C' while the virtual machine is running and inspect its state.
In order to use gdb, launch qemu with the '-s' option. It will wait for a gdb connection:
> qemu -s -kernel arch/i386/boot/bzImage -hda root-2.4.20.img -append "root=/dev/hda" Connected to host network interface: tun0 Waiting gdb connection on port 1234 |
Then launch gdb on the 'vmlinux' executable:
> gdb vmlinux |
In gdb, connect to QEMU:
(gdb) target remote localhost:1234 |
Then you can use gdb normally. For example, type 'c' to launch the kernel:
(gdb) c |
Here are some useful tips in order to use gdb on system code:
info reg
to display all the CPU registers.
x/10i $eip
to display the code at the PC position.
set architecture i8086
to dump 16 bit code. Then use
x/10i $cs*16+*eip
to dump the code at the PC position.
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Use the executable `qemu-system-ppc' to simulate a complete PREP PowerPC system.
QEMU emulates the following PREP peripherials:
You can read the qemu PC system emulation chapter to have more informations about QEMU usage.
More information is available at http://jocelyn.mayer.free.fr/qemu-ppc/.
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In order to launch a Linux process, QEMU needs the process executable itself and all the target (x86) dynamic libraries used by it.
qemu-i386 -L / /bin/ls |
-L /
tells that the x86 dynamic linker must be searched with a
`/' prefix.
qemu-i386 -L / qemu-i386 -L / /bin/ls |
LD_LIBRARY_PATH
is not set:
unset LD_LIBRARY_PATH |
Then you can launch the precompiled `ls' x86 executable:
qemu-i386 tests/i386/ls |
binfmt_misc
module in the
Linux kernel.
qemu-i386 /usr/local/qemu-i386/bin/qemu-i386 /usr/local/qemu-i386/bin/ls-i386 |
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qemu-i386 /usr/local/qemu-i386/bin/ls-i386 |
${HOME}/.wine
directory is saved to ${HOME}/.wine.org
.
qemu-i386 /usr/local/qemu-i386/wine/bin/wine /usr/local/qemu-i386/wine/c/Program\ Files/putty.exe |
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usage: qemu-i386 [-h] [-d] [-L path] [-s size] program [arguments...] |
Debug options:
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1. Introduction
1.1 Features2. Installation
2.1 Linux3. QEMU PC System emulator invocation
2.2 Windows
2.3 Cross compilation for Windows with Linux
2.4 Mac OS X
3.1 Introduction4. QEMU PREP PowerPC System emulator invocation
3.2 Quick Start
3.3 Invocation
3.4 QEMU Monitor
3.4.1 Commands3.5 Disk Images
3.4.2 Integer expressions
3.5.1 Raw disk images3.6 Network emulation
3.5.2 Snapshot mode
3.5.3 Copy On Write disk images
3.6.1 Using tun/tap network interface3.7 Direct Linux Boot
3.6.2 Using the user mode network stack
3.8 Linux Kernel Compilation
3.9 GDB usage
5. QEMU User space emulator invocation
5.1 Quick Start
5.2 Wine launch
5.3 Command line options
[Top] | [Contents] | [Index] | [ ? ] |
1. Introduction
2. Installation
3. QEMU PC System emulator invocation
4. QEMU PREP PowerPC System emulator invocation
5. QEMU User space emulator invocation
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where the Example assumes that the current position is at Subsubsection One-Two-Three of a document of the following structure: