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<b>GXemul documentation:</b></font> |
<b>Gavare's eXperimental Emulator: </b></font> |
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<font color="#000000" size="6"><b>Introduction</b> |
<font color="#000000" size="6"><b>Introduction</b> |
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$Id: intro.html,v 1.46 2005/06/04 12:02:17 debug Exp $ |
$Id: intro.html,v 1.61 2005/08/16 05:15:24 debug Exp $ |
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Copyright (C) 2003-2005 Anders Gavare. All rights reserved. |
Copyright (C) 2003-2005 Anders Gavare. All rights reserved. |
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<li><a href="#cpus">Which CPU types does GXemul emulate?</a> |
<li><a href="#cpus">Which CPU types does GXemul emulate?</a> |
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<li><a href="#accuracy">Emulation accuracy</a> |
<li><a href="#accuracy">Emulation accuracy</a> |
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<li><a href="#emulmodes">Which machines does GXemul emulate?</a> |
<li><a href="#emulmodes">Which machines does GXemul emulate?</a> |
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<li><a href="#guestos">Which guest OSes are possible to run?</a> |
<li><a href="#guestos">Which guest OSes are possible to run in GXemul?</a> |
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<a name="overview"></a> |
<a name="overview"></a> |
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<h3>Overview:</h3> |
<h3>Overview:</h3> |
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GXemul is a machine emulator, which can be used to experiment with |
GXemul is an experimental instruction-level machine emulator. It can be |
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binary code for (among others) MIPS-based machines. Several emulation |
used to run binary code for MIPS-based machines, regardless of host |
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modes are available. For some emulation modes, processors and surrounding |
platform. Several emulation modes are available. For some modes, |
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hardware components are emulated well enough to let unmodified operating |
processors and surrounding hardware components are emulated well enough to |
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systems run as if they were running on a real machine. |
let unmodified operating systems run as if they were running on a real |
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machine. |
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<p>(Non-MIPS emulation modes are also under development, but so far none |
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of those modes has reached the completeness required to run unmodified |
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operating systems.) |
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<p> |
<p>Devices and CPUs are not simulated with 100% accuracy. They are only |
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Devices and CPUs are not simulated with 100% accuracy. They are only |
``faked'' well enough to make operating systems (e.g. NetBSD) run without |
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"faked" well enough to make operating systems (eg NetBSD) run without |
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complaining too much. Still, the emulator could be of interest for |
complaining too much. Still, the emulator could be of interest for |
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academic research and experiments, such as when learning how to write |
academic research and experiments, such as when learning how to write |
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operating system code. |
operating system code. |
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<p> |
<p>The emulator is written in C, does not depend on external libraries |
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The emulator is written in C, does not depend on external libraries (except |
(except X11, but that is optional), and should compile and run on most |
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X11, but that is optional), and should compile and run on most Unix-like |
Unix-like systems. If it doesn't, then that is a bug. |
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systems. If it doesn't, then that is a bug. |
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(You do not need any MIPS compiler toolchain to build or use GXemul. |
<p>The emulator contains code which tries to emulate the workings of CPUs |
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If you need to compile MIPS binaries from sources, then of course you need |
and surrounding hardware found in real machines, but it does not contain |
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such a toolchain, but that is completely separate from GXemul.) |
any ROM code. You will need some form of program (in binary form) to run |
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in the emulator. For many emulation modes, PROM calls are handled by the |
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<p> |
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The emulator contains code which tries to emulate the workings of CPUs and |
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surrounding hardware found in real machines, but it does not contain any |
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ROM code. You will need some form of program (in binary form) to run in |
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the emulator. For many emulation modes, PROM calls are handled by the |
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emulator itself, so you do not need to use any ROM image at all. |
emulator itself, so you do not need to use any ROM image at all. |
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<p> |
<p>You can use pre-compiled kernels (for example NetBSD kernels, or |
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You can use pre-compiled kernels (for example NetBSD kernels, or Linux), |
Linux), or other programs that are in binary format, and in some cases |
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or other programs that are in binary format, and in some cases even actual |
even actual ROM images. A couple of different file formats are supported |
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ROM images. A couple of different file formats are supported (ELF, a.out, |
(ELF, a.out, ECOFF, SREC, and raw binaries). |
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ECOFF, SREC, and raw binaries). |
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<p> |
<p>If you do not have a kernel as a separate file, but you have a bootable |
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If you do not have a kernel as a separate file, but you have a bootable |
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disk image, then it is sometimes possible to boot directly from that |
disk image, then it is sometimes possible to boot directly from that |
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image. (This works for example with DECstation emulation, or when booting |
image. (This works for example with DECstation emulation, or when booting |
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from ISO9660 CDROM images.) |
from ISO9660 CDROM images.) |
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<p><br> |
<p><br> |
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<a name="free"></a> |
<a name="free"></a> |
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<h3>Is GXemul Free software?</h3> |
<h3>Is GXemul Free software?</h3> |
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four freedoms associated with Free software, <a |
four freedoms associated with Free software, <a |
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href="http://www.gnu.org/philosophy/free-sw.html">http://www.gnu.org/philosophy/free-sw.html</a>.) |
href="http://www.gnu.org/philosophy/free-sw.html">http://www.gnu.org/philosophy/free-sw.html</a>.) |
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<p> |
<p>The code I have written is released under a 3-clause BSD-style license |
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The code I have written is released under a 3-clause BSD-style license |
(or "revised BSD-style" if one wants to use <a |
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(or "revised BSD-style" if one wants to use |
href="http://www.gnu.org/philosophy/bsd.html">GNU jargon</a>). Apart from |
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<a href="http://www.gnu.org/philosophy/bsd.html">GNU jargon</a>). |
the code I have written, some files are copied from other sources such as |
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Apart from the code I have written, some files are copied from other sources |
NetBSD, for example header files containing symbolic names of bitfields in |
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such as NetBSD, for example header files containing symbolic names of |
device registers. They are also covered by similar licenses, but with some |
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bitfields in device registers. They are also covered by similar licenses, |
additional clauses. The main point, however, is that the licenses require |
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but with some additional clauses. If you plan to redistribute GXemul |
that the original Copyright and license terms are included when you make a |
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(for example as a binary package), or reuse code from GXemul, |
copy or modification. |
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then you should check those files for their license terms. |
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<p>If you plan to redistribute GXemul <i>without</i> supplying the source |
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code, then you need to comply with each individual source file some other |
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way, for example by writing additional documentation containing copyright |
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notes. I have not done this, since I do not plan on making distributions |
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without source code. You need to check all individual files for details. |
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The "easiest way out" if you plan to redistribute code from GXemul is, of |
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course, to let it remain open source and simply supply the source code. |
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<p>(If a stable release of GXemul is packaged into binary form, and it is |
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obvious which version of GXemul was used to build the package, then it can |
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be argued that the source code is available, just not in that specific |
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package. Common sense should be used in this case, and not pedanticism.) |
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<p> |
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(The licenses usually require that the original Copyright and license |
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terms are included when you make a copy or modification. The "easiest way |
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out" if you plan to redistribute code from GXemul is to simply supply |
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the source code. You should however check individual files for details.) |
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$ <b>make</b> |
$ <b>make</b> |
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</pre> |
</pre> |
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<p> |
<p>This should work on most Unix-like systems. If it doesn't, then |
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This should work on most Unix-like systems. If it doesn't, then |
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mail me a bug report. |
mail me a bug report. |
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<p> |
<p>The emulator's performance is highly dependent on both runtime settings |
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(Note for Windows users: there is a possibility that some releases |
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and/or snapshots will also work with Cygwin, but I can't promise that.) |
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<p> |
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The emulator's performance is highly dependent on both runtime settings |
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and on compiler settings, so you might want to experiment with different |
and on compiler settings, so you might want to experiment with different |
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CC and CFLAGS environment variable values. For example, on a modern PC, |
CC and CFLAGS environment variable values. For example, on a modern PC, |
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you could try the following: |
you could try the following: |
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<p> |
<p><pre> |
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<pre> |
$ <b>CFLAGS="-mcpu=pentium4 -O3" ./configure</b> |
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$ <b>CFLAGS="-mcpu=pentium4 -O3" ./configure</b> |
$ <b>make</b> |
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$ <b>make</b> |
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</pre> |
</pre> |
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<p> |
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Run <b><tt>./configure --help</tt></b> to get a list of configure options. (The |
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possible options differ between different releases and snapshots.) |
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CPUs are also emulated, and are hopefully almost as stable as the R4000 |
CPUs are also emulated, and are hopefully almost as stable as the R4000 |
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emulation. |
emulation. |
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<p> |
<p>I have written an experimental dynamic binary translation subsystem. |
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I have written an experimental dynamic binary translation subsystem. |
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This gives higher total performance than interpreting one instruction at a |
This gives higher total performance than interpreting one instruction at a |
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time and executing it. (If you wish to enable bintrans, add <b>-b</b> to |
time and executing it. (If you wish to disable bintrans, add <b>-B</b> to |
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the command line, but keep in mind that it is still experimental.) |
the command line.) |
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<h4>URISC:</h4> |
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I have implemented an <a href="http://en.wikipedia.org/wiki/URISC">URISC</a> |
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emulation mode, just for fun. The only instruction available in an URISC |
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machine is "reverse subtract and skip on borrow". (It is probably not |
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worth trying to do bintrans with URISC, because any reasonable URISC |
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program relies on self-modifying code, which is bad for bintrans |
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performance.) |
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<h4>POWER/PowerPC</h4> |
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There is some code for 64-bit (and 32-bit) POWER/PowerPC emulation, enough |
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to run "Hello World", but not enough to run complete operating systems. |
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This mode isn't really working yet. |
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<h4>Other CPU types:</h4> |
<h4>Other CPU types:</h4> |
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Some other CPU architectures (such as x86) can also be partially emulated. |
Some other CPU architectures can also be partially emulated. These are not |
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These are not enabled by default though, because of their unstable-ness. |
working well enough yet to run guest operating systems. |
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to be enough to be able to run complete guest operating systems inside the |
to be enough to be able to run complete guest operating systems inside the |
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emulator. |
emulator. |
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<p> |
<p>Caches are by default not emulated. In some cases, the existance of |
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Caches are by default not emulated. In some cases, the existance of caches |
caches is "faked" to let operating systems think that they are there. |
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is "faked" to let operating systems think that they are there. (There is |
(There is some old code for R2000/R3000 caches, but it has probably |
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some old code for R2000/R3000 caches, but it has probably suffered from |
suffered from bitrot by now.) |
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bitrot by now.) |
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<p>The emulator is <i>not</i> timing-accurate. It can be run in a |
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<p> |
"deterministic" mode, <tt><b>-D</b></tt>. The meaning of deterministic is |
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The emulator is <i>not</i> timing-accurate. It can be run in a |
simply that running two emulations with the same settings will result in |
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"deterministic" mode, <tt><b>-D</b></tt>. The meaning of deterministic is |
identical runs. Obviously, this requires that no user interaction is |
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simply that running two emulations with the same settings will result in |
taking place, and that clock speeds are fixed with the <tt><b>-I</b></tt> |
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identical runs. Obviously, this requires that no user interaction is |
option. (Deterministic in this case does <i>not</i> mean that the |
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taking place, and that clock speeds are fixed with the <tt><b>-I</b></tt> |
emulation will be identical to some actual real-world machine.) |
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option. (Deterministic in this case does <i>not</i> mean that the emulation |
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will be identical to some actual real-world machine.) |
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<p> |
<p> |
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<li><b>Cobalt</b> |
<li><b>Cobalt</b> |
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<br>Serial controller and PCI IDE. |
<br>Serial controller and PCI IDE. |
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<p> |
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<li><b>Malta (evbmips)</b> |
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<br>Serial controller and PCI IDE. |
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<p> |
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<li><b>SGI O2 ("IP32")</b> |
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<br>Serial controller and ethernet. <small>(Enough for |
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root-on-nfs, but not for disk boot.)</small> |
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</ul> |
</ul> |
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<p> |
<p>There is code in GXemul for emulation of many other machine types; the |
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There is code in GXemul for emulation of many other machine types; |
degree to which these work range from almost being able to run a complete |
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the degree to which these work range from "almost" being able to run |
OS, to almost completely unsupported (perhaps just enough support to |
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a complete OS, to almost completely unsupported (perhaps just enough |
output a few boot messages via serial console). |
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support to output a few boot messages via serial console). |
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<p>In addition to emulating real machines, there is also a "test-machine". |
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<p> |
A test-machine consists of one or more CPUs and a few experimental devices |
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In addition to emulating real machines, there is also a "test-machine". |
such as: |
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A test-machine consists of one or more CPUs and a few experimental |
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devices such as: |
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<p> |
<p> |
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<ul> |
<ul> |
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<li>a console I/O device (putchar() and getchar()...) |
<li>a console I/O device (putchar() and getchar()...) |
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<li>an inter-processor communication device, for SMP experiments |
<li>an inter-processor communication device, for SMP experiments |
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<li>a very simple linear framebuffer device (for graphics output) |
<li>a very simple linear framebuffer device (for graphics output) |
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<li>a simple SCSI disk controller |
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<li>a simple ethernet controller |
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</ul> |
</ul> |
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<p> |
<p>This mode is useful if you wish to run experimental code, but do not |
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This mode is useful if you wish to run experimental code, but do not |
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wish to target any specific real-world machine type, for example for |
wish to target any specific real-world machine type, for example for |
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educational purposes. |
educational purposes. |
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<p> |
<p>You can read more about these experimental devices <a |
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You can read more about these experimental devices |
href="experiments.html#expdevices">here</a>. |
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<a href="experiments.html#expdevices">here</a>. |
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<p><br> |
<p><br> |
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<a name="guestos"></a> |
<a name="guestos"></a> |
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<h3>Which guest OSes are possible to run?</h3> |
<h3>Which guest OSes are possible to run in GXemul?</h3> |
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This table lists the guest OSes that run well enough to be considered |
This table lists the guest OSes that run well enough to be considered |
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working in the emulator. They can boot from a harddisk image and be |
working in the emulator. They can boot from a harddisk image and be |
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<br>Cobalt</td> |
<br>Cobalt</td> |
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</tr> |
</tr> |
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<tr><td height="10"></td></tr> |
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<tr> |
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<td></td> |
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<td align="center"><a href="20050626-netbsd-sgimips-netboot.png"><img src="20050626-netbsd-sgimips-netboot_small.png"></a></td> |
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<td></td> |
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<td><a href="http://www.netbsd.org/Ports/sgimips/">NetBSD/sgimips</a> |
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<br>SGI O2 ("IP32")</td> |
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<td></td> |
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<td align="center"><a href="20050622-netbsd-evbmips-malta.png"><img src="20050622-netbsd-evbmips-malta_small.png"></a></td> |
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<td></td> |
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<td><a href="http://www.netbsd.org/Ports/evbmips/">NetBSD/evbmips</a> |
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<br>5Kc (and 4Kc) Malta<br>evaluation boards</td> |
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<td></td> |
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</tr> |
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</table></center> |
</table></center> |
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