1 |
<html> |
2 |
<head><title>GXemul documentation: Introduction</title> |
3 |
</head> |
4 |
<body bgcolor="#f8f8f8" text="#000000" link="#4040f0" vlink="#404040" alink="#ff0000"> |
5 |
<table border=0 width=100% bgcolor="#d0d0d0"><tr> |
6 |
<td width=100% align=center valign=center><table border=0 width=100%><tr> |
7 |
<td align="left" valign=center bgcolor="#d0efff"><font color="#6060e0" size="6"> |
8 |
<b>GXemul documentation:</b></font> |
9 |
<font color="#000000" size="6"><b>Introduction</b> |
10 |
</font></td></tr></table></td></tr></table><p> |
11 |
<!-- The first 10 lines are cut away by the homepage updating script. --> |
12 |
|
13 |
|
14 |
<!-- |
15 |
|
16 |
$Id: intro.html,v 1.46 2005/06/04 12:02:17 debug Exp $ |
17 |
|
18 |
Copyright (C) 2003-2005 Anders Gavare. All rights reserved. |
19 |
|
20 |
Redistribution and use in source and binary forms, with or without |
21 |
modification, are permitted provided that the following conditions are met: |
22 |
|
23 |
1. Redistributions of source code must retain the above copyright |
24 |
notice, this list of conditions and the following disclaimer. |
25 |
2. Redistributions in binary form must reproduce the above copyright |
26 |
notice, this list of conditions and the following disclaimer in the |
27 |
documentation and/or other materials provided with the distribution. |
28 |
3. The name of the author may not be used to endorse or promote products |
29 |
derived from this software without specific prior written permission. |
30 |
|
31 |
THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
32 |
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
33 |
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
34 |
ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
35 |
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
36 |
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
37 |
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
38 |
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
39 |
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
40 |
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
41 |
SUCH DAMAGE. |
42 |
|
43 |
--> |
44 |
|
45 |
<a href="./">Back to the index</a> |
46 |
|
47 |
<p><br> |
48 |
<h2>Introduction</h2> |
49 |
|
50 |
<p> |
51 |
<ul> |
52 |
<li><a href="#overview">Overview</a> |
53 |
<li><a href="#free">Is GXemul Free software?</a> |
54 |
<li><a href="#build">How to compile/build the emulator</a> |
55 |
<li><a href="#run">How to run the emulator</a> |
56 |
<li><a href="#cpus">Which CPU types does GXemul emulate?</a> |
57 |
<li><a href="#accuracy">Emulation accuracy</a> |
58 |
<li><a href="#emulmodes">Which machines does GXemul emulate?</a> |
59 |
<li><a href="#guestos">Which guest OSes are possible to run?</a> |
60 |
</ul> |
61 |
|
62 |
|
63 |
|
64 |
|
65 |
|
66 |
<p><br> |
67 |
<a name="overview"></a> |
68 |
<h3>Overview:</h3> |
69 |
|
70 |
GXemul is a machine emulator, which can be used to experiment with |
71 |
binary code for (among others) MIPS-based machines. Several emulation |
72 |
modes are available. For some emulation modes, processors and surrounding |
73 |
hardware components are emulated well enough to let unmodified operating |
74 |
systems run as if they were running on a real machine. |
75 |
|
76 |
<p> |
77 |
Devices and CPUs are not simulated with 100% accuracy. They are only |
78 |
"faked" well enough to make operating systems (eg NetBSD) run without |
79 |
complaining too much. Still, the emulator could be of interest for |
80 |
academic research and experiments, such as when learning how to write |
81 |
operating system code. |
82 |
|
83 |
<p> |
84 |
The emulator is written in C, does not depend on external libraries (except |
85 |
X11, but that is optional), and should compile and run on most Unix-like |
86 |
systems. If it doesn't, then that is a bug. |
87 |
(You do not need any MIPS compiler toolchain to build or use GXemul. |
88 |
If you need to compile MIPS binaries from sources, then of course you need |
89 |
such a toolchain, but that is completely separate from GXemul.) |
90 |
|
91 |
<p> |
92 |
The emulator contains code which tries to emulate the workings of CPUs and |
93 |
surrounding hardware found in real machines, but it does not contain any |
94 |
ROM code. You will need some form of program (in binary form) to run in |
95 |
the emulator. For many emulation modes, PROM calls are handled by the |
96 |
emulator itself, so you do not need to use any ROM image at all. |
97 |
|
98 |
<p> |
99 |
You can use pre-compiled kernels (for example NetBSD kernels, or Linux), |
100 |
or other programs that are in binary format, and in some cases even actual |
101 |
ROM images. A couple of different file formats are supported (ELF, a.out, |
102 |
ECOFF, SREC, and raw binaries). |
103 |
|
104 |
<p> |
105 |
If you do not have a kernel as a separate file, but you have a bootable |
106 |
disk image, then it is sometimes possible to boot directly from that |
107 |
image. (This works for example with DECstation emulation, or when booting |
108 |
from ISO9660 CDROM images.) |
109 |
|
110 |
|
111 |
|
112 |
|
113 |
|
114 |
|
115 |
<p><br> |
116 |
<a name="free"></a> |
117 |
<h3>Is GXemul Free software?</h3> |
118 |
|
119 |
Yes. I have released GXemul under a Free license. The code in GXemul is |
120 |
Copyrighted software, it is <i>not</i> public domain. (If this is |
121 |
confusing to you, you might want to read up on the definitions of the |
122 |
four freedoms associated with Free software, <a |
123 |
href="http://www.gnu.org/philosophy/free-sw.html">http://www.gnu.org/philosophy/free-sw.html</a>.) |
124 |
|
125 |
<p> |
126 |
The code I have written is released under a 3-clause BSD-style license |
127 |
(or "revised BSD-style" if one wants to use |
128 |
<a href="http://www.gnu.org/philosophy/bsd.html">GNU jargon</a>). |
129 |
Apart from the code I have written, some files are copied from other sources |
130 |
such as NetBSD, for example header files containing symbolic names of |
131 |
bitfields in device registers. They are also covered by similar licenses, |
132 |
but with some additional clauses. If you plan to redistribute GXemul |
133 |
(for example as a binary package), or reuse code from GXemul, |
134 |
then you should check those files for their license terms. |
135 |
|
136 |
<p> |
137 |
(The licenses usually require that the original Copyright and license |
138 |
terms are included when you make a copy or modification. The "easiest way |
139 |
out" if you plan to redistribute code from GXemul is to simply supply |
140 |
the source code. You should however check individual files for details.) |
141 |
|
142 |
|
143 |
|
144 |
|
145 |
|
146 |
<p><br> |
147 |
<a name="build"></a> |
148 |
<h3>How to compile/build the emulator:</h3> |
149 |
|
150 |
Uncompress the .tar.gz distribution file, and run |
151 |
<pre> |
152 |
$ <b>./configure</b> |
153 |
$ <b>make</b> |
154 |
</pre> |
155 |
|
156 |
<p> |
157 |
This should work on most Unix-like systems. If it doesn't, then |
158 |
mail me a bug report. |
159 |
|
160 |
<p> |
161 |
(Note for Windows users: there is a possibility that some releases |
162 |
and/or snapshots will also work with Cygwin, but I can't promise that.) |
163 |
|
164 |
<p> |
165 |
The emulator's performance is highly dependent on both runtime settings |
166 |
and on compiler settings, so you might want to experiment with different |
167 |
CC and CFLAGS environment variable values. For example, on a modern PC, |
168 |
you could try the following: |
169 |
<p> |
170 |
<pre> |
171 |
$ <b>CFLAGS="-mcpu=pentium4 -O3" ./configure</b> |
172 |
$ <b>make</b> |
173 |
</pre> |
174 |
|
175 |
<p> |
176 |
Run <b><tt>./configure --help</tt></b> to get a list of configure options. (The |
177 |
possible options differ between different releases and snapshots.) |
178 |
|
179 |
|
180 |
|
181 |
|
182 |
|
183 |
|
184 |
<p><br> |
185 |
<a name="run"></a> |
186 |
<h3>How to run the emulator:</h3> |
187 |
|
188 |
Once you have built GXemul, running it should be rather straight-forward. |
189 |
Running <tt><b>gxemul</b></tt> without arguments (or with the |
190 |
<b><tt>-h</tt></b> or <b><tt>-H</tt></b> command line options) will |
191 |
display a help message. |
192 |
|
193 |
<p> |
194 |
To get some ideas about what is possible to run in the emulator, please |
195 |
read the section about <a href="guestoses.html">installing "guest" |
196 |
operating systems</a>. If you are interested in using the emulator to |
197 |
develop code on your own, then you should also read the section about |
198 |
<a href="experiments.html#hello">Hello World</a>. |
199 |
|
200 |
<p> |
201 |
To exit the emulator, type CTRL-C to enter the |
202 |
single-step debugger, and then type <tt><b>quit</b></tt>. |
203 |
|
204 |
<p> |
205 |
If you are starting an emulation by entering settings directly on the |
206 |
command line, and you are not using the <tt><b>-x</b></tt> option, then all |
207 |
terminal input and output will go to the main controlling terminal. |
208 |
CTRL-C is used to break into the debugger, so in order to send CTRL-C to |
209 |
the running (emulated) program, you may use CTRL-B. |
210 |
(This should be a reasonable compromise to allow the emulator to be usable |
211 |
even on systems without X Windows.) |
212 |
|
213 |
<p> |
214 |
There is no way to send an actual CTRL-B to the emulated program, when |
215 |
typing in the main controlling terminal window. The solution is to either |
216 |
use <a href="configfiles.html">configuration files</a>, or use |
217 |
<tt><b>-x</b></tt>. Both these solutions cause new xterms to be opened for |
218 |
each emulated serial port that is written to. CTRL-B and CTRL-C both have |
219 |
their original meaning in those xterm windows. |
220 |
|
221 |
|
222 |
|
223 |
|
224 |
|
225 |
<p><br> |
226 |
<a name="cpus"></a> |
227 |
<h3>Which CPU types does GXemul emulate?</h3> |
228 |
|
229 |
<h4>MIPS:</h4> |
230 |
|
231 |
Emulation of R4000, which is a 64-bit CPU, was my initial goal. |
232 |
R2000/R3000-like CPUs (32-bit), R1x000, and generic MIPS32/MIPS64-style |
233 |
CPUs are also emulated, and are hopefully almost as stable as the R4000 |
234 |
emulation. |
235 |
|
236 |
<p> |
237 |
I have written an experimental dynamic binary translation subsystem. |
238 |
This gives higher total performance than interpreting one instruction at a |
239 |
time and executing it. (If you wish to enable bintrans, add <b>-b</b> to |
240 |
the command line, but keep in mind that it is still experimental.) |
241 |
|
242 |
|
243 |
<h4>URISC:</h4> |
244 |
|
245 |
I have implemented an <a href="http://en.wikipedia.org/wiki/URISC">URISC</a> |
246 |
emulation mode, just for fun. The only instruction available in an URISC |
247 |
machine is "reverse subtract and skip on borrow". (It is probably not |
248 |
worth trying to do bintrans with URISC, because any reasonable URISC |
249 |
program relies on self-modifying code, which is bad for bintrans |
250 |
performance.) |
251 |
|
252 |
|
253 |
<h4>POWER/PowerPC</h4> |
254 |
|
255 |
There is some code for 64-bit (and 32-bit) POWER/PowerPC emulation, enough |
256 |
to run "Hello World", but not enough to run complete operating systems. |
257 |
This mode isn't really working yet. |
258 |
|
259 |
|
260 |
<h4>Other CPU types:</h4> |
261 |
|
262 |
Some other CPU architectures (such as x86) can also be partially emulated. |
263 |
These are not enabled by default though, because of their unstable-ness. |
264 |
|
265 |
|
266 |
|
267 |
|
268 |
|
269 |
<p><br> |
270 |
<a name="accuracy"></a> |
271 |
<h3>Emulation accuracy:</h3> |
272 |
|
273 |
GXemul is an instruction-level emulator; things that would happen in |
274 |
several steps within a real CPU are not taken into account (eg. pipe-line |
275 |
stalls or out-of-order execution). Still, instruction-level accuracy seems |
276 |
to be enough to be able to run complete guest operating systems inside the |
277 |
emulator. |
278 |
|
279 |
<p> |
280 |
Caches are by default not emulated. In some cases, the existance of caches |
281 |
is "faked" to let operating systems think that they are there. (There is |
282 |
some old code for R2000/R3000 caches, but it has probably suffered from |
283 |
bitrot by now.) |
284 |
|
285 |
<p> |
286 |
The emulator is <i>not</i> timing-accurate. It can be run in a |
287 |
"deterministic" mode, <tt><b>-D</b></tt>. The meaning of deterministic is |
288 |
simply that running two emulations with the same settings will result in |
289 |
identical runs. Obviously, this requires that no user interaction is |
290 |
taking place, and that clock speeds are fixed with the <tt><b>-I</b></tt> |
291 |
option. (Deterministic in this case does <i>not</i> mean that the emulation |
292 |
will be identical to some actual real-world machine.) |
293 |
|
294 |
|
295 |
|
296 |
|
297 |
|
298 |
<p><br> |
299 |
<a name="emulmodes"></a> |
300 |
<h3>Which machines does GXemul emulate?</h3> |
301 |
|
302 |
A few different machine types are emulated. The following machine types |
303 |
are emulated well enough to run at least one "guest OS": |
304 |
|
305 |
<p> |
306 |
<ul> |
307 |
<li><b>DECstation 5000/200</b> ("3max") |
308 |
<br>Serial controller (including keyboard and mouse), ethernet, |
309 |
SCSI, and graphical framebuffers. |
310 |
<p> |
311 |
<li><b>Acer Pica-61</b> (an ARC machine) |
312 |
<br>Serial controller, "VGA" text console, and SCSI. |
313 |
<p> |
314 |
<li><b>NEC MobilePro 770, 780, 800, and 880</b> (HPCmips machines) |
315 |
<br>Framebuffer, keyboard, and a PCMCIA IDE controller. |
316 |
<p> |
317 |
<li><b>Cobalt</b> |
318 |
<br>Serial controller and PCI IDE. |
319 |
</ul> |
320 |
|
321 |
<p> |
322 |
There is code in GXemul for emulation of many other machine types; |
323 |
the degree to which these work range from "almost" being able to run |
324 |
a complete OS, to almost completely unsupported (perhaps just enough |
325 |
support to output a few boot messages via serial console). |
326 |
|
327 |
<p> |
328 |
In addition to emulating real machines, there is also a "test-machine". |
329 |
A test-machine consists of one or more CPUs and a few experimental |
330 |
devices such as: |
331 |
|
332 |
<p> |
333 |
<ul> |
334 |
<li>a console I/O device (putchar() and getchar()...) |
335 |
<li>an inter-processor communication device, for SMP experiments |
336 |
<li>a very simple linear framebuffer device (for graphics output) |
337 |
</ul> |
338 |
|
339 |
<p> |
340 |
This mode is useful if you wish to run experimental code, but do not |
341 |
wish to target any specific real-world machine type, for example for |
342 |
educational purposes. |
343 |
|
344 |
<p> |
345 |
You can read more about these experimental devices |
346 |
<a href="experiments.html#expdevices">here</a>. |
347 |
|
348 |
|
349 |
|
350 |
|
351 |
|
352 |
|
353 |
|
354 |
<p><br> |
355 |
<a name="guestos"></a> |
356 |
<h3>Which guest OSes are possible to run?</h3> |
357 |
|
358 |
This table lists the guest OSes that run well enough to be considered |
359 |
working in the emulator. They can boot from a harddisk image and be |
360 |
interacted with similar to a real machine. |
361 |
|
362 |
<p> |
363 |
<center><table border="0"> |
364 |
<tr> |
365 |
<td width="10"></td> |
366 |
<td align="center"><a href="20050317-example.png"><img src="20050317-example_small.png"></a></td> |
367 |
<td width="15"></td> |
368 |
<td><a href="http://www.netbsd.org/Ports/pmax/">NetBSD/pmax</a> |
369 |
<br>DECstation 5000/200</td> |
370 |
<td width="30"></td> |
371 |
<td align="center"><a href="20041024-netbsd-arc-installed.gif"><img src="20041024-netbsd-arc-installed_small.gif"></a></td> |
372 |
<td width="15"></td> |
373 |
<td><a href="http://www.netbsd.org/Ports/arc/">NetBSD/arc</a> |
374 |
<br>Acer Pica-61</td> |
375 |
|
376 |
</tr> |
377 |
|
378 |
<tr><td height="10"></td></tr> |
379 |
|
380 |
<tr> |
381 |
<td></td> |
382 |
<td align="center"><a href="openbsd-pmax-20040710.png"><img src="openbsd-pmax-20040710_small.png"></a></td> |
383 |
<td></td> |
384 |
<td><a href="http://www.openbsd.org/pmax.html">OpenBSD/pmax</a> |
385 |
<br>DECstation 5000/200</td> |
386 |
<td></td> |
387 |
<td align="center"><a href="20041024-openbsd-arc-installed.gif"><img src="20041024-openbsd-arc-installed_small.gif"></a></td> |
388 |
<td></td> |
389 |
<td><a href="http://www.openbsd.org/arc.html">OpenBSD/arc</a> |
390 |
<br>Acer Pica-61</td> |
391 |
</tr> |
392 |
|
393 |
<tr><td height="10"></td></tr> |
394 |
|
395 |
<tr> |
396 |
<td></td> |
397 |
<td align="center"><a href="ultrix4.5-20040706.png"><img src="ultrix4.5-20040706_small.gif"></a></td> |
398 |
<td></td> |
399 |
<td>Ultrix/RISC<br>DECstation 5000/200</td> |
400 |
<td></td> |
401 |
<td align="center"><a href="20041213-debian_4.png"><img src="20041213-debian_4_small.gif"></a></td> |
402 |
<td></td> |
403 |
<td><a href="http://www.debian.org/">Debian GNU/Linux</a> <super>*</super> |
404 |
<br>DECstation 5000/200</td> |
405 |
</tr> |
406 |
|
407 |
<tr><td height="10"></td></tr> |
408 |
|
409 |
<tr> |
410 |
<td></td> |
411 |
<td align="center"><a href="sprite-20040711.png"><img src="sprite-20040711_small.png"></a></td> |
412 |
<td></td> |
413 |
<td><a href="http://www.cs.berkeley.edu/projects/sprite/retrospective.html">Sprite</a> |
414 |
<br>DECstation 5000/200</td> |
415 |
<td></td> |
416 |
<td align="center"><a href="20041129-redhat_mips.png"><img src="20041129-redhat_mips_small.png"></a></td> |
417 |
<td></td> |
418 |
<td>Redhat Linux <super>*</super> |
419 |
<br>DECstation 5000/200</td> |
420 |
</tr> |
421 |
|
422 |
<tr><td height="10"></td></tr> |
423 |
|
424 |
<tr> |
425 |
<td></td> |
426 |
<td align="center"><a href="20050427-netbsd-hpcmips-2.png"><img src="20050427-netbsd-hpcmips-2_small.png"></a></td> |
427 |
<td></td> |
428 |
<td><a href="http://www.netbsd.org/Ports/hpcmips/">NetBSD/hpcmips</a> |
429 |
<br>NEC MobilePro 770, 780, 800, 880</td> |
430 |
<td></td> |
431 |
<td align="center"><a href="20050413-netbsd-cobalt.png"><img src="20050413-netbsd-cobalt_small.png"></a></td> |
432 |
<td></td> |
433 |
<td><a href="http://www.netbsd.org/Ports/cobalt/">NetBSD/cobalt</a> |
434 |
<br>Cobalt</td> |
435 |
</tr> |
436 |
|
437 |
</table></center> |
438 |
|
439 |
|
440 |
<p><br> |
441 |
|
442 |
<super>*</super> Although Linux runs under DECstation emulation, the |
443 |
default 2.4.27 kernel in Debian GNU/Linux does not support keyboards on |
444 |
the 5000/200 (the specific DECstation model being emulated), so when the |
445 |
login prompt is reached you cannot interact with the system. Kaj-Michael |
446 |
Lang has compiled and made available a newer kernel from the current |
447 |
mips-linux development tree. You can find it here: <a |
448 |
href="http://home.tal.org/~milang/o2/kernels/">http://home.tal.org/~milang/o2/kernels</a>/<a |
449 |
href="http://home.tal.org/~milang/o2/kernels/vmlinux-2.4.29-rc2-r3k-mipsel-decstation">vmlinux-2.4.29-rc2-r3k-mipsel-decstation</a> |
450 |
This newer kernel supports keyboard input, but it does not have Debian's |
451 |
ethernet patches, so you will not be able to use keyboard/framebuffer |
452 |
<i>and</i> networking at the same time. |
453 |
|
454 |
|
455 |
</body> |
456 |
</html> |