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<td width=100% align=center valign=center><table border=0 width=100%><tr> |
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<td align="left" valign=center bgcolor="#d0efff"><font color="#6060e0" size="6"> |
<td align="left" valign=center bgcolor="#d0efff"><font color="#6060e0" size="6"> |
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<b>Gavare's eXperimental Emulator: </b></font> |
<b>Gavare's eXperimental Emulator:</b></font><br> |
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<font color="#000000" size="6"><b>Miscellaneous</b> |
<font color="#000000" size="6"><b>Miscellaneous</b> |
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</font></td></tr></table></td></tr></table><p> |
</font></td></tr></table></td></tr></table><p> |
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<!-- |
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$Id: misc.html,v 1.53 2005/09/04 14:00:25 debug Exp $ |
$Id: misc.html,v 1.67 2007/03/24 06:39:29 debug Exp $ |
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Copyright (C) 2003-2005 Anders Gavare. All rights reserved. |
Copyright (C) 2003-2007 Anders Gavare. All rights reserved. |
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Redistribution and use in source and binary forms, with or without |
Redistribution and use in source and binary forms, with or without |
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modification, are permitted provided that the following conditions are met: |
modification, are permitted provided that the following conditions are met: |
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<p> |
<p> |
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<ul> |
<ul> |
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<li><a href="#networking">Networking</a> |
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<li><a href="#devel">Writing operating system code, or |
<li><a href="#devel">Writing operating system code, or |
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developing firmware, using GXemul</a> |
developing firmware, using GXemul</a> |
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<li><a href="#compilercontruct">Using GXemul in compiler contruction courses</a> |
<li><a href="#compilercontruct">Using GXemul in compiler contruction courses</a> |
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<li><a href="#disk">How to start the emulator with a disk image</a> |
<li><a href="#disk">How to start the emulator with a disk image</a> |
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<li><a href="#tape_images">How to start the emulator with tape images</a> |
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<li><a href="#disk_overlays">How to use disk image overlays</a> |
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<li><a href="#filexfer">Transfering files to/from the guest OS</a> |
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<li><a href="#largeimages">How to extract large gzipped disk images</a> |
<li><a href="#largeimages">How to extract large gzipped disk images</a> |
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<li><a href="#userland">Running userland binaries</a> |
<li><a href="#userland">Running userland binaries</a> |
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<li><a href="#promdump">Using a PROM dump from a real machine</a> |
<li><a href="#promdump">Using a PROM dump from a real machine</a> |
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<p><br> |
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<a name="networking"></a> |
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<h3>Networking:</h3> |
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It is possible to let the guest OS running inside the emulator get access to |
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the Internet. If you are interested in the technical details, and the |
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reasons why networking is implemented in the emulator the way it currently |
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is implemented, you might want to read the <a href="technical.html#net"> |
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networking section in the technical documentation</a>. |
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<p> |
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The guest OS running inside the emulator uses a private IPv4 address, such |
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as 10.0.0.1, and the emulator acts as a NAT-like gateway/firewall at IPv4 |
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address 10.0.0.254. To the outside world it will seem like it is the host's |
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OS that connects to other machines on the internet, not the guest OS. |
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<p> |
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<font color="#ff0000">NOTE: This is still experimental! |
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As of 2004-07-21, ARP + ICMP + UDP + TCP are emulated well enough to let |
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NetBSD and OpenBSD install via ftp, and use the network for many normal |
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activities, but not everything works yet.</font> |
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<p><br> |
<p><br> |
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Is this a good idea? The answer is yes and no, depending on the level of |
Is this a good idea? The answer is yes and no, depending on the level of |
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detail you need in your simulations. If you are developing an operating |
detail you need in your simulations. If you are developing an operating |
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system or operating system kernel of your own, and wish to target |
system or operating system kernel of your own, then the emulator can be a |
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MIPS-like systems in general, then the answer might be yes, for |
complement to testing on real hardware. |
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experimental purposes. |
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<p>Some examples of things that <i>don't</i> work, that you should keep in |
<p>Important things to keep in mind: |
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mind: |
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<ul> |
<ul> |
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<li>Porting code to a specific machine mode, e.g. a Silicon Graphics |
<li>Porting code to a specific machine mode, e.g. a Silicon Graphics |
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machine, using GXemul, will not necessarily cause the code to |
machine, using GXemul, will not "magically" cause the code to |
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work on a real machine. Sometimes code works in GXemul which doesn't |
work on a real machine. Sometimes code works in GXemul which doesn't |
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work on real hardware, sometimes it's the other way around. |
work on real hardware, sometimes it's the other way around. |
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<li>GXemul contains bugs, and many things are not yet implemented. |
<li>GXemul contains bugs, and many things are not yet implemented. |
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<p> |
<p> |
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<li>I have only implemented devices in GXemul to the degree that |
<li><b>Very important!</b> I have only implemented devices in GXemul |
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NetBSD, OpenBSD, etc, don't complain too much. One way to say it |
to the degree that NetBSD, OpenBSD, Linux, etc don't complain too much. |
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is that the device implementations are "lazy hacks", based on the |
<p> |
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assumption that the emulated OS is already developed and bug-free. |
If you are developing a driver for a device which is emulated by |
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They are not intended to be used for development of new OS code, |
GXemul, and your driver does not seem to be working, then the |
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so if you do that, then be prepared for bugs and inconsitencies. |
probability of a bug in GXemul's implementation of the device is |
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very much higher than that of a bug in your driver. |
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<p> |
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The device implementations in GXemul are based on the assumption |
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that the emulated OS is already developed and bug-free. They are |
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not primarily intended to be used for development of new device |
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driver code in operating systems, so if you do that, then be |
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prepared for bugs and inconsitencies. |
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<p> |
<p> |
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<li>CPU details in GXemul are usually wrong. If your code depends |
<li>CPU details in GXemul are usually wrong. If your code depends |
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on, say, R10000 or MIPS64 specifics, chances are that GXemul will |
on, say, R10000 or MIPS64 specifics, chances are that GXemul will |
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not be sufficient. Again, this was done as "lazy hacks", and pretty |
not be sufficient. One example is different revisions of ISAs; |
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much assumes that the OS being emulated is already developed |
some instructions which should trigger an exception on a |
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and bug-free. |
real MIPS processor usually execute anyway in GXemul. Another |
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example is if userland code tries to access kernel memory; in some |
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cases there is protection against this, but not in all cases (to get |
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higher performance). |
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<p> |
<p> |
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<li>Caches. There is no cache emulation in GXemul right now. Caches |
<li>Caches. There is no cache emulation in GXemul right now. Caches |
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for R2000/R3000 are faked well enough to run NetBSD, Ultrix, etc |
for R2000/R3000 are faked well enough to run NetBSD, Ultrix, etc |
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<h3>Using GXemul in compiler contruction courses:</h3> |
<h3>Using GXemul in compiler contruction courses:</h3> |
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If you are learning how to write a compiler, and wish to target a |
If you are learning how to write a compiler, and wish to target a |
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realistic target platform, then MIPS (as emulated by GXemul) |
realistic target platform, then MIPS or ARM (as emulated by GXemul) |
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might be a suitable choice. |
might be suitable choices. |
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<ul> |
<ul> |
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<li><b>(+)</b> Your compiler needs to output real assembly |
<li><b>(+)</b> Your compiler needs to output real assembly |
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language code, which the assembler (eg gas, the GNU assembler) can |
language code, which the assembler (e.g. gas, the GNU assembler) can |
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then compile into object format, and then you need to link this |
then compile into object format, and then you need to link this |
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into an executable image. This is much closer to how things work |
into an executable image. This is much closer to how things work |
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in real life than running assembly language listings in a simulator |
in real life than running assembly language listings in a simulator |
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(eg SPIM). |
(e.g. SPIM). |
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<p> |
<p> |
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<li><b>(-)</b> GXemul does not simulate out-of-order |
<li><b>(-)</b> GXemul does not simulate out-of-order |
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execution, penalties related to instruction scheduling, or |
execution, penalties related to instruction scheduling, or |
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<pre> |
<pre> |
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$ <b>gxemul -e 3max -d pmax_diskimage.fs netbsd-pmax-INSTALL</b> |
$ <b>gxemul -e 3max -d pmax_diskimage.fs netbsd-pmax-INSTALL</b> |
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</pre> |
</pre> |
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<p> |
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NOTE: For some emulation modes, such as the DECstation mode, you do |
<p>NOTE: For some emulation modes, such as the DECstation mode, you do |
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<i>not</i> have to specify the name of the kernel, if the disk image is |
<i>not</i> actually have to specify the name of the kernel, if the disk |
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bootable! |
image is bootable! |
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<p> |
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It is possible to have more than one disk. For each -d argument, a disk |
<p>It is possible to have more than one disk. For each -d argument, a disk |
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image is added; the first will be SCSI target 0, the second will be target 1, and so on, |
image is added; the first will be SCSI target 0, the second will be target 1, and so on, |
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unless you specify explicitly which ID number the devices should have. |
unless you specify explicitly which ID number the devices should have. |
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<pre> |
<pre> |
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$ <b>gxemul -e 3max -d disk0.raw -d disk1.raw -d 5:disk2.raw netbsd-pmax-INSTALL</b> |
$ <b>gxemul -e 3max -d disk0.raw -d disk1.raw -d 5:disk2.raw netbsd-pmax-INSTALL</b> |
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</pre> |
</pre> |
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Note: In the example above, disk2.raw will get scsi id 5. |
Note: In the example above, disk2.raw will get scsi id 5. |
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<p> |
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If a filename has a 'c' prefix, or ends with ".iso", then it is assumed to be |
<p>If a filename has a 'c' prefix, or ends with ".iso", then it is assumed to be |
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a CDROM device (this can be overridden with a 'd' prefix, to force a read/write disk). |
a CDROM device (this can be overridden with a 'd' prefix, to force a read/write disk). |
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For example, the following command would start the emulator with two |
For example, the following command would start the emulator with two |
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CDROM images, and one harddisk image: |
CDROM images, and one harddisk image: |
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</pre> |
</pre> |
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It is probably possible to use harddisks as well this way, but I would not |
It is probably possible to use harddisks as well this way, but I would not |
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recommend it. |
recommend it. |
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<p> |
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<p><br> |
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<a name="tape_images"></a> |
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<h3>How to start the emulator with tape images:</h3> |
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Using emulated tape drives is a bit more complicated than disks, because a |
Using emulated tape drives is a bit more complicated than disks, because a |
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tape can be made up of several "files" with space in between. The solution |
tape can be made up of several "files" with space in between. The solution |
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I have choosen is to have one file in the host's file system space for each |
I have choosen is to have one file in the host's file system space for each |
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on the command line. By changing what the symbolic name points to, |
on the command line. By changing what the symbolic name points to, |
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you can "switch tapes" without quiting and restarting the emulator. |
you can "switch tapes" without quiting and restarting the emulator. |
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<p> |
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<font color="#ff0000">Note: Tape support is most likely very buggy, |
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because it has not been tested much, and has probably also suffered |
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from bit-rot by now.</font> |
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<p><br> |
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<a name="disk_overlays"></a> |
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<h3>How to use disk image overlays:</h3> |
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This is most likely best understood by an example: |
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<p><ul> |
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<li>Install e.g. <a href="guestoses.html#netbsdcatsinstall">NetBSD/cats</a>. |
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You will end up with a disk image called |
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<tt>nbsd_cats.img</tt>. |
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<p> |
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<li>Running the following command will boot straight from the disk |
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image, with no overlay images:<pre> |
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<b>gxemul -XEcats -d nbsd_cats.img netbsd.aout-GENERIC.gz</b> |
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</pre> |
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<li>You may now create an overlay file, a corresponding map file, |
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and start the emulator with the overlay image connected to |
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the same (explicit) ID as the base disk image:<pre> |
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<b>touch overlay.img overlay.img.map |
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gxemul -XEcats -d 0:nbsd_cats.img -d V0:overlay.img netbsd.aout-GENERIC.gz</b> |
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</pre> |
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<li>Any changes to the filesystem you perform when using the overlay |
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will only be written to that overlay. For example, to perform |
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a "roll back", you can do the following:<pre> |
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<b>rm -f overlay.img overlay.img.map |
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touch overlay.img overlay.img.map</b> |
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</pre> |
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and then simply start the emulator again, with the newly created |
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overlay image. |
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</ul> |
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<p>It is also possible to add multiple overlays. In that case, writes |
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always go the the <i>last</i> added overlay. |
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<p>GXemul uses Unix' way of supporting files with "holes", |
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so even if <tt>ls -l overlay.img</tt> says that the overlay is several |
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gigabytes large, <tt>du overlay.img</tt> should reveal that only the |
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blocks that have actually been written to have been stored in the |
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overlay, e.g.:<pre> |
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<b>$ ls -l |
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.. |
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-rw-r--r-- 1 debug wheel 3072319488 Mar 24 11:59 nbsd_cats.img |
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-rw-r--r-- 1 debug wheel 2465354 Mar 24 11:44 netbsd.aout-GENERIC.gz |
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-rw-r--r-- 1 debug wheel 2930841600 Mar 24 14:02 overlay.img |
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-rw-r--r-- 1 debug wheel 715538 Mar 24 14:02 overlay.img.map |
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$ du overlay.img |
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864 overlay.img |
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</b> |
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</pre> |
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<p>The .map file is simply a raw bitmap telling which blocks of the |
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overlay file that are in use. |
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<p><br> |
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<a name="filexfer"></a> |
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<h3>Transfering files to/from the guest OS:</h3> |
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If the emulated machine supports networking (see <a |
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href="networking.html#intro">this section</a> for more info), then |
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transfering files via FTP is probably easiest. |
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<p>There is another way of transfering files which works for any kind of |
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emulated machine which supports disks (either SCSI or IDE). Any file can |
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be supplied as a disk image. For example, consider the following:<pre> |
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$ <b>gxemul -XEcats -d nbsd_cats.img -d archive.tar.gz netbsd-GENERIC</b> |
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</pre> |
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This will start NetBSD/cats with <tt>nbsd_cats.img</tt> as IDE master on |
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controller 0 (wd0), and <tt>archive.tar.gz</tt> as IDE slave on controller |
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0 (wd1). From inside NetBSD, it is now possible to extract the files using |
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the following command:<pre> |
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(inside emulated NetBSD/cats) |
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# <b>tar zxvf /dev/wd1c</b> |
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</pre> |
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Don't worry if NetBSD complains about lack of disklabel; it doesn't |
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matter. On some machines, NetBSD uses <tt>wd1d</tt> instead of |
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<tt>wd1c</tt> for the entire disk. |
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There is also a minor problem: reading the end of the disk image. If you |
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experience problems untaring archives like this, then pad out the archive |
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first with some zeroes. |
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<p>Transfering files <i>out</i> from the emulated operating system to the |
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host can be done the same way. First, prepare an empty archive file:<pre> |
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$ <b>dd if=/dev/zero of=newarchive.tar bs=1024 count=1 seek=10000</b> |
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</pre>This example created a 10 MB empty file. Then, start the emulator |
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like this:<pre> |
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$ <b>gxemul -XEcats -d nbsd_cats.img -d archive.tar netbsd-GENERIC</b> |
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</pre> |
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and transfer files by creating an archive directly onto the disk image:<pre> |
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(inside emulated NetBSD/cats) |
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# <b>tar cvf /dev/wd1c filenames</b> |
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</pre> |
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where filenames are the files or directories to transfer. |
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<p><br> |
<p><br> |
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<a name="userland"></a> |
<a name="userland"></a> |
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<h3>Running userland binaries:</h3> |
<h3>Running userland binaries:</h3> |
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<font color="#ff0000">Note: This does not really work yet.</font> |
<font color="#ff0000">Note: This feature does not really work yet. |
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It is currently disabled in stable release builds of the emulator.</font> |
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<p>There is some skeleton code for running userland programs as well. This |
<p>There is some skeleton code for running userland programs as well. This |
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will not emulate any particular machine, but instead try to translate |
will not emulate any particular machine, but instead try to translate |
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<p>The graphics used in the O2 is (as far as I know) undocumented. Combining |
<p>The graphics used in the O2 is (as far as I know) undocumented. Combining |
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some traces of info from how Linux/O2 draws to the screen with some |
some traces of info from how Linux/O2 draws to the screen with some |
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reverse-engineering of my own, I've implemeneted enough of the controller to |
reverse-engineering of my own, I've implemented enough of the controller to |
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let the PROM draw rectangles and bitmaps, but not much more. The SCSI |
let the PROM draw rectangles and bitmaps, but not much more. The SCSI |
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controller is not implemented yet either. |
controller is not implemented yet either. |
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