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1  <html><head><title>GXemul documentation: Misc.</title>  <html><head><title>Gavare's eXperimental Emulator:&nbsp;&nbsp;&nbsp;Miscellaneous</title>
2  <meta name="robots" content="noarchive,nofollow,noindex"></head>  <meta name="robots" content="noarchive,nofollow,noindex"></head>
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5  <td width=100% align=center valign=center><table border=0 width=100%><tr>  <td width=100% align=center valign=center><table border=0 width=100%><tr>
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7  <b>GXemul documentation:</b></font>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  <b>Gavare's eXperimental Emulator:</b></font><br>
8  <font color="#000000" size="6"><b>Misc.</b>  <font color="#000000" size="6"><b>Miscellaneous</b>
9  </font></td></tr></table></td></tr></table><p>  </font></td></tr></table></td></tr></table><p>
10    
11  <!--  <!--
12    
13  $Id: misc.html,v 1.42 2005/06/26 08:42:26 debug Exp $  $Id: misc.html,v 1.66 2006/12/30 13:30:51 debug Exp $
14    
15  Copyright (C) 2003-2005  Anders Gavare.  All rights reserved.  Copyright (C) 2003-2007  Anders Gavare.  All rights reserved.
16    
17  Redistribution and use in source and binary forms, with or without  Redistribution and use in source and binary forms, with or without
18  modification, are permitted provided that the following conditions are met:  modification, are permitted provided that the following conditions are met:
# Line 39  SUCH DAMAGE. Line 39  SUCH DAMAGE.
39    
40  -->  -->
41    
42    
43  <a href="./">Back to the index</a>  <a href="./">Back to the index</a>
44    
45  <p><br>  <p><br>
46  <h2>Misc.</h2>  <h2>Miscellaneous</h2>
47    
48  <p>  <p>
49  <ul>  <ul>
50    <li><a href="#networking">Networking</a>    <li><a href="#devel">Writing operating system code, or
51    <li><a href="#portmips">Porting operating systems to MIPS using GXemul</a>          developing firmware, using GXemul</a>
52    <li><a href="#compilercontruct">Using GXemul in compiler contruction courses</a>    <li><a href="#compilercontruct">Using GXemul in compiler contruction courses</a>
53    <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>
54      <li><a href="#filexfer">Transfering files to/from the guest OS</a>
55    <li><a href="#largeimages">How to extract large gzipped disk images</a>    <li><a href="#largeimages">How to extract large gzipped disk images</a>
56    <li><a href="#userland">Running userland binaries</a>    <li><a href="#userland">Running userland binaries</a>
57    <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>
# Line 61  SUCH DAMAGE. Line 63  SUCH DAMAGE.
63    
64    
65    
 <p><br>  
 <a name="networking"></a>  
 <h3>Networking:</h3>  
   
 It is possible to let the guest OS running inside the emulator get access to  
 the Internet. If you are interested in the technical details, and the  
 reasons why networking is implemented in the emulator the way it currently  
 is implemented, you might want to read the <a href="technical.html#net">  
 networking section in the technical documentation</a>.  
 <p>  
 The guest OS running inside the emulator uses a private IPv4 address, such  
 as 10.0.0.1, and the emulator acts as a NAT-like gateway/firewall at IPv4  
 address 10.0.0.254. To the outside world it will seem like it is the host's  
 OS that connects to other machines on the internet, not the guest OS.  
 <p>  
 <font color="#ff0000">NOTE: This is still experimental!  
 As of 2004-07-21, ARP + ICMP + UDP + TCP are emulated well enough to let  
 NetBSD and OpenBSD install via ftp, and use the network for many normal  
 activities, but not everything works yet.</font>  
   
   
66    
67    
68    <p><br>
69    <a name="devel"></a>
70    <h3>Writing operating system code, or developing firmware, using GXemul:</h3>
71    
72    Is this a good idea?  The answer is yes and no, depending on the level of
73    detail you need in your simulations. If you are developing an operating
74    system or operating system kernel of your own, then the emulator can be a
75    complement to testing on real hardware.
76    
77  <p><br>  <p>Important things to keep in mind:
 <a name="portmips"></a>  
 <h3>Porting operating systems to MIPS using GXemul:</h3>  
78    
79  Is this a good idea?  The answer is yes and no, depending on what you are  <ul>
80  trying to port to. If you are developing an operating system or operating          <li>Porting code to a specific machine mode, e.g. a Silicon Graphics
81  system kernel of your own, and wish to target MIPS-like systems in general,          machine, using GXemul, will not "magically" cause the code to
82  then the answer might be yes, for experimental purposes.          work on a real machine. Sometimes code works in GXemul which doesn't
83            work on real hardware, sometimes it's the other way around.
84  <p>  
85  However, if you think that you can port an operating system          <p>
86  to, say, the Silicon Graphics machine mode of GXemul and hope that your          <li>GXemul contains bugs, and many things are not yet implemented.
87  operating system will run on a real SGI machine, then you will most  
88  likely fail. GXemul simply does not emulate things well enough for that to work.          <p>
89  Another example would be specific CPU details; if your code depends on,          <li><b>Very important!</b> I have only implemented devices in GXemul
90  say, R10000 specifics, chances are that GXemul will not be sufficient.          to the degree that NetBSD, OpenBSD, Linux, etc don't complain too much.
91            <p>
92  <p>          If you are developing a driver for a device which is emulated by
93  In many cases, hardware devices in GXemul are only implemented well          GXemul, and your driver does not seem to be working, then the
94  enough to fool eg. NetBSD that they are working correctly, while in          probability of a bug in GXemul's implementation of the device is
95  fact they don't work very much at all.  Please keep this in mind, if you plan          very much higher than that of a bug in your driver.
96  to use GXemul when porting your code to MIPS.          <p>
97            The device implementations in GXemul are based on the assumption
98            that the emulated OS is already developed and bug-free. They are
99            not primarily intended to be used for development of new device
100            driver code in operating systems, so if you do that, then be
101            prepared for bugs and inconsitencies.
102            <p>
103            <li>CPU details in GXemul are usually wrong. If your code depends
104            on, say, R10000 or MIPS64 specifics, chances are that GXemul will
105            not be sufficient. One example is different revisions of ISAs;
106            some instructions which should trigger an exception on a
107            real MIPS processor usually execute anyway in GXemul. Another
108            example is if userland code tries to access kernel memory; in some
109            cases there is protection against this, but not in all cases (to get
110            higher performance).
111            <p>
112            <li>Caches. There is no cache emulation in GXemul right now. Caches
113            for R2000/R3000 are faked well enough to run NetBSD, Ultrix, etc
114            in the DECstation emulation mode, but other than that, cache
115            operations are treated as nops.
116    </ul>
117    
118    <p>The bottom line is that GXemul can be useful as yet another way to test
119    your code during development, but it should not be fully relied on.
120    
121    
122    
# Line 120  to use GXemul when porting your code to Line 128  to use GXemul when porting your code to
128  <h3>Using GXemul in compiler contruction courses:</h3>  <h3>Using GXemul in compiler contruction courses:</h3>
129    
130  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
131  realistic target platform, then MIPS (as emulated by GXemul)  realistic target platform, then MIPS or ARM (as emulated by GXemul)
132  might be a suitable choice.  might be suitable choices.
133    
134  <ul>  <ul>
135    <li><b>(+)</b>&nbsp;&nbsp;Your compiler needs to output real assembly    <li><b>(+)</b>&nbsp;&nbsp;Your compiler needs to output real assembly
136          language code, which the assembler (eg gas, the GNU assembler) can          language code, which the assembler (e.g. gas, the GNU assembler) can
137          then compile into object format, and then you need to link this          then compile into object format, and then you need to link this
138          into an executable image. This is much closer to how things work          into an executable image. This is much closer to how things work
139          in real life than running assembly language listings in a simulator          in real life than running assembly language listings in a simulator
140          (eg SPIM).          (e.g. SPIM).
141    <p>    <p>
142    <li><b>(-)</b>&nbsp;&nbsp;GXemul does not simulate out-of-order    <li><b>(-)</b>&nbsp;&nbsp;GXemul does not simulate out-of-order
143          execution, penalties related to instruction scheduling, or          execution, penalties related to instruction scheduling, or
# Line 155  to get a list of possible options. Line 163  to get a list of possible options.
163  Here are some examples. If you want to run a NetBSD/pmax kernel on an  Here are some examples. If you want to run a NetBSD/pmax kernel on an
164  emulated DECstation machine, you would use a command line such as this:  emulated DECstation machine, you would use a command line such as this:
165  <pre>  <pre>
166          $ <b>gxemul -E dec -e 3max -d pmax_diskimage.fs netbsd-pmax-INSTALL</b>          $ <b>gxemul -e 3max -d pmax_diskimage.fs netbsd-pmax-INSTALL</b>
167  </pre>  </pre>
168  <p>  
169  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
170  <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
171  bootable!  image is bootable!
172  <p>  
173  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
174  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,
175  unless you specify explicitly which ID number the devices should have.  unless you specify explicitly which ID number the devices should have.
176  <pre>  <pre>
177          $ <b>gxemul -E dec -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>
178  </pre>  </pre>
179  Note: In the example above, disk2.raw will get scsi id 5.  Note: In the example above, disk2.raw will get scsi id 5.
180  <p>  
181  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
182  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).
183  For example, the following command would start the emulator with two  For example, the following command would start the emulator with two
184  CDROM images, and one harddisk image:  CDROM images, and one harddisk image:
185  <pre>  <pre>
186          $ <b>gxemul -E dec -e 3max -d image.iso -d disk0.img -d c:second_cdrom.img netbsd-pmax-INSTALL</b>          $ <b>gxemul -e 3max -d image.iso -d disk0.img -d c:second_cdrom.img netbsd-pmax-INSTALL</b>
187  </pre>  </pre>
188  Usually, the device with the lowest id becomes the boot device. To override  Usually, the device with the lowest id becomes the boot device. To override
189  this, add a 'b' prefix to one of the devices:  this, add a 'b' prefix to one of the devices:
190  <pre>  <pre>
191          $ <b>gxemul -E dec -e 3max -d rootdisk.img -d bc:install-cd.iso name_of_kernel</b>          $ <b>gxemul -e 3max -d rootdisk.img -d bc:install-cd.iso name_of_kernel</b>
192  </pre>  </pre>
193  If you have a physical CD-ROM drive on the host machine, say /dev/cd0c, you can  If you have a physical CD-ROM drive on the host machine, say /dev/cd0c, you can
194  use it as a CD-ROM directly accessible from within the emulator:  use it as a CD-ROM directly accessible from within the emulator:
195  <pre>  <pre>
196          $ <b>gxemul -E dec -e 3max -d rootdisk.img -d bc:/dev/cd0c name_of_kernel</b>          $ <b>gxemul -e 3max -d rootdisk.img -d bc:/dev/cd0c name_of_kernel</b>
197  </pre>  </pre>
198  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
199  recommend it.  recommend it.
# Line 241  you can "switch tapes" without quiting a Line 249  you can "switch tapes" without quiting a
249    
250    
251    
252    
253    
254    
255    <p><br>
256    <a name="filexfer"></a>
257    <h3>Transfering files to/from the guest OS:</h3>
258    
259    If the emulated machine supports networking (see <a
260    href="networking.html#intro">this section</a> for more info), then
261    transfering files via FTP is probably easiest.
262    
263    <p>There is another way of transfering files which works for any kind of
264    emulated machine which supports disks (either SCSI or IDE). Any file can
265    be supplied as a disk image. For example, consider the following:<pre>
266            $ <b>gxemul -XEcats -d nbsd_cats.img -d archive.tar.gz netbsd-GENERIC</b>
267    </pre>
268    This will start NetBSD/cats with <tt>nbsd_cats.img</tt> as IDE master on
269    controller 0 (wd0), and <tt>archive.tar.gz</tt> as IDE slave on controller
270    0 (wd1). From inside NetBSD, it is now possible to extract the files using
271    the following command:<pre>
272            (inside emulated NetBSD/cats)
273            # <b>tar zxvf /dev/wd1c</b>
274    </pre>
275    Don't worry if NetBSD complains about lack of disklabel; it doesn't
276    matter. On some machines, NetBSD uses <tt>wd1d</tt> instead of
277    <tt>wd1c</tt> for the entire disk.
278    There is also a minor problem: reading the end of the disk image. If you
279    experience problems untaring archives like this, then pad out the archive
280    first with some zeroes.
281    
282    <p>Transfering files <i>out</i> from the emulated operating system to the
283    host can be done the same way. First, prepare an empty archive file:<pre>
284            $ <b>dd if=/dev/zero of=newarchive.tar bs=1024 count=1 seek=10000</b>
285    </pre>This example created a 10 MB empty file. Then, start the emulator
286    like this:<pre>
287            $ <b>gxemul -XEcats -d nbsd_cats.img -d archive.tar netbsd-GENERIC</b>
288    </pre>
289    and transfer files by creating an archive directly onto the disk image:<pre>
290            (inside emulated NetBSD/cats)
291            # <b>tar cvf /dev/wd1c filenames</b>
292    </pre>
293    where filenames are the files or directories to transfer.
294    
295    
296    
297    
298    
299  <p><br>  <p><br>
300  <a name="largeimages"></a>  <a name="largeimages"></a>
301  <h3>How to extract large gzipped disk images:</h3>  <h3>How to extract large gzipped disk images:</h3>
# Line 285  count.) Line 340  count.)
340  <a name="userland"></a>  <a name="userland"></a>
341  <h3>Running userland binaries:</h3>  <h3>Running userland binaries:</h3>
342    
343  You can run (some) userland programs as well. This will not emulate any  <font color="#ff0000">Note: This feature does not really work yet.
344  particular machine, but instead try to translate syscalls from for example  It is currently disabled in stable release builds of the emulator.</font>
345  NetBSD/pmax into the host's OS' syscalls. Right now, this is just a  
346  proof-of-concept, to show that it would work; there's lots of work left to  <p>There is some skeleton code for running userland programs as well. This
347  do to make it actually run useful programs (for example dynamically linked  will not emulate any particular machine, but instead try to translate
348  programs).  syscalls from e.g. NetBSD/pmax into the host's OS' syscalls. Right now,
349    this is just a proof-of-concept, to show that it could work; there's lots
350    of work left to do to make it actually run useful programs.
351    
352  <p>  <p>
353    
# Line 321  programs). Line 378  programs).
378          tab.csbnet.se          tab.csbnet.se
379  </pre>  </pre>
380    
381    <!--
382    <p>    <p>
383    <li><b>NetBSD/powerpc:</b>    <li><b>NetBSD/powerpc:</b>
384          <br>          <br>
# Line 344  programs). Line 402  programs).
402          Hello, world!          Hello, world!
403    
404  </pre>  </pre>
405    -->
406    
407  </ul>  </ul>
408    
# Line 411  and store in a file. Let's call this fil Line 470  and store in a file. Let's call this fil
470  </pre>  </pre>
471  This binary image can now be used in the emulator:  This binary image can now be used in the emulator:
472  <pre>  <pre>
473          $ <b>gxemul -E dec -e 3min -Q -M128 -q 0xbfc00000:DECstation5000_125_promdump.bin</b>          $ <b>gxemul -e 3min -Q -M128 -q 0xbfc00000:DECstation5000_125_promdump.bin</b>
474    
475          KN02-BA V5.7e            KN02-BA V5.7e  
476          ?TFL:  3/scc/access (1:Ln1 reg-12: actual=0x00 xpctd=0x01) [KN02-BA]          ?TFL:  3/scc/access (1:Ln1 reg-12: actual=0x00 xpctd=0x01) [KN02-BA]
# Line 452  This binary image can now be used in the Line 511  This binary image can now be used in the
511           osconsole=3           osconsole=3
512          >>          >>
513  </pre>  </pre>
514  <i>(Note: at the moment, this doesn't work. I must have broken something when  
515  fixing something else, but this is what it looked like at the time.)</i>  <p><font color="#ff0000">(Note: at the moment, this doesn't work.
516  <p>  I must have broken something when fixing something else, but this
517  During bootup, the PROM complains <i>a lot</i> about hardware failures.  is what it looked like at the time.)</font>
518    
519    <p>During bootup, the PROM complains <i>a lot</i> about hardware failures.
520  That's because the emulator doesn't emulate the hardware well enough yet.  That's because the emulator doesn't emulate the hardware well enough yet.
521  <p>  
522  The command line options used are: -E dec for DECstation, -e 3min for  <p>The command line options used are: <tt>-e 3min</tt> for
523  "model 3" (5000/1xx), -Q to supress the emulator's own PROM  "DECstation 3min" (5000/1xx), <tt>-Q</tt> to supress the emulator's own PROM
524  call emulation, -M128 for 128MB RAM (because GXemul doesn't correctly  call emulation, <tt>-M128</tt> for 128MB RAM (because GXemul doesn't correctly
525  emulate memory detection well enough for the PROM to accept, so it will  emulate memory detection well enough for the PROM to accept, so it will
526  always believe there is 128MB ram anyway), and -q to supress debug messages.  always believe there is 128MB ram anyway), and <tt>-q</tt> to supress debug messages.
527  The 0xbfc00000 in front of the filename tells GXemul that it is a raw  The <tt>0xbfc00000</tt> in front of the filename tells GXemul that it is a raw
528  binary file which should be loaded at a specific virtual address.  binary file which should be loaded at a specific virtual address.
529    
530    
# Line 471  binary file which should be loaded at a Line 532  binary file which should be loaded at a
532  <h4>Dumping the PROM on a SGI O2:</h4>  <h4>Dumping the PROM on a SGI O2:</h4>
533    
534  The general ideas in this section applies to using ROM images from other  The general ideas in this section applies to using ROM images from other
535  machines as well. Besides DECstation, I've also tried this on an SGI IP32  machines as well. I have also tried this on an SGI IP32 ("O2"), in addition
536  ("O2").  to the DECstation.
537  <p>  
538  For the O2, a suitable command to dump the prom memory range is  <p>For the O2, a suitable command to dump the prom memory range is
539  <pre>  <pre>
540          &gt;&gt; <b>dump -b 0xBFC00000:0xBFC80000</b>          &gt;&gt; <b>dump -b 0xBFC00000:0xBFC80000</b>
541  </pre>  </pre>
542  Make sure you capture all the output (via serial console) into a file,  Make sure you capture all the output (via serial console) into a file,
543  and then run experiments/sgiprom_to_bin on the captured file.  and then run <tt>experiments/sgiprom_to_bin</tt> on the captured file.
 <p>  
 (2005-01-16: The emulator doesn't really emulate the IP32 well enough to  
 actually run the PROM image without using special hacks, but it might do  
 so some time in the future.)  
544    
545    <p>
546    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
547    <a href="sgi-o2-real.jpg"><img src="sgi-o2-real_small.jpg"></a>
548    &nbsp;&nbsp;&nbsp;
549    <a href="20050817-sgi-o2-success-7.png"><img src="20050817-sgi-o2-success-7_small.png"></a>
550    &nbsp;&nbsp;&nbsp;
551    <a href="20050817-sgi-o2-success-8.png"><img src="20050817-sgi-o2-success-8_small.png"></a>
552    
553    <p>The photo on the left is from the real machine. The other two are
554    screenshots of the PROM running experimentally in GXemul, using <tt>-Y2</tt>
555    framebuffer scaledown.
556    
557    <p>Normally during bootup, the IP32 PROM does a Power-On test which makes
558    sure that the caches and other things are working properly. GXemul doesn't
559    emulate all those things well enough for the tests to pass. The
560    experimental screenshots above were taken with cache detection skipped
561    manually.
562    
563    <p><font color="#ff0000">
564    In other words: don't expect this to work out-of-the-box with GXemul right
565    now. It might work once I've added correct cache emulation.</font>
566    
567    <p>The command line used to start the emulator, once correct cache
568    emulation has been implemented, would be something like <tt>gxemul -XQeo2
569    0xbfc00000:prom.bin</tt>.
570    
571    <p>The same caution applies when dealing with SGI PROMs as with
572    DECstation PROMs: GXemul doesn't really emulate the hardware, it only
573    "fakes" devices well enough to fool some things, primarily NetBSD, that
574    it is emulating a real machine. ROM code is usually a <i>lot</i> more
575    picky about the details.
576    
577    <p>The graphics used in the O2 is (as far as I know) undocumented. Combining
578    some traces of info from how Linux/O2 draws to the screen with some
579    reverse-engineering of my own, I've implemented enough of the controller to
580    let the PROM draw rectangles and bitmaps, but not much more. The SCSI
581    controller is not implemented yet either.
582    
583    
584    
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