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<head><title>GXemul documentation: Introduction</title> |
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<b>GXemul documentation: Introduction</b></font></td></tr> |
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$Id: intro.html,v 1.30 2005/04/07 15:43:15 debug Exp $ |
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Copyright (C) 2003-2005 Anders Gavare. All rights reserved. |
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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: |
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1. Redistributions of source code must retain the above copyright |
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notice, this list of conditions and the following disclaimer. |
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3. The name of the author may not be used to endorse or promote products |
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<a href="./">Back to the index</a> |
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<p><br> |
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<h2>Introduction</h2> |
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<p> |
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<ul> |
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<li><a href="#overview">Overview</a> |
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<li><a href="#free">Is GXemul free software?</a> |
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<li><a href="#build">How to compile/build the emulator</a> |
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<li><a href="#cpus">Which CPU types does GXemul emulate?</a> |
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<li><a href="#accuracy">Emulation accuracy</a> |
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<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> |
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</ul> |
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<p><br> |
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<a name="overview"></a> |
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<h3>Overview:</h3> |
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GXemul is a machine emulator, which can be used to experiment with |
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binary code for (among others) MIPS-based machines. Several emulation |
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modes are available. For some emulation modes, processors and surrounding |
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hardware components are emulated well enough to let unmodified operating |
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systems run as if they were running on a real machine. |
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<p> |
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It is important to keep in mind that devices and CPUs are not really |
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emulated correctly, they are only "faked" well enough to make eg. NetBSD |
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run. Still, the emulator could be of interest for academic research and |
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experiments, such as when learning how to write an OS for a real machine, |
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or profiling SMP, memory, or system call usage. |
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<p> |
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The emulator is written in C, does not depend on external libraries (except |
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X11, but that is optional), and should compile and run on most Unix-like |
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systems. If it doesn't, then that is a bug. |
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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. |
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<p> |
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You can use pre-compiled kernels (for example NetBSD kernels, or Linux), |
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or other programs that are in binary format, and in some cases even actual |
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ROM images. A couple of different file formats are supported (ELF, a.out, |
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ECOFF, SREC, raw binaries). |
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<p> |
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(You do not need any MIPS compiler toolchain to build or use GXemul. |
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If you need to compile MIPS binaries from sources, then of course you need |
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such a toolchain, but that is completely separate from GXemul. There |
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is a <a href="technical.html#regtest">regression testing</a> framework, |
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which requires that a GNU CC for mips64-unknown-elf or similar is available. |
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For simply building and using the emulator, it is not required.) |
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<p><br> |
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<a name="free"></a> |
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<h3>Is GXemul free software?</h3> |
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Yes. I have released GXemul under a free license. |
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(For a definitions of the four freedoms associated with free software, |
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please read <a href="http://www.gnu.org/philosophy/free-sw.html"> |
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http://www.gnu.org/philosophy/free-sw.html</a>.) |
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<p> |
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The code I have written is released under a 3-clause BSD-style license |
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(or "revised BSD-style" if one wants to use |
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<a href="http://www.gnu.org/philosophy/bsd.html">GNU jargon</a>.) |
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Apart from the code I have written, some files are copied from other sources |
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such as NetBSD, for example header files containing symbolic names of |
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bitfields in device registers. They are also covered by similar licenses, |
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but with some additional clauses. If you plan to redistribute GXemul |
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(for example as a binary package), or reuse code from GXemul, |
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then you should check those files for their license terms. |
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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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<p><br> |
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<a name="build"></a> |
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<h3>How to compile/build the emulator:</h3> |
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Uncompress the .tar.gz distribution file, and run |
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<pre> |
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$ <b>./configure</b> |
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$ <b>make</b> |
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</pre> |
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<p> |
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This should work on most Unix-like systems. If it doesn't, then please |
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mail me a bug report. |
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<p> |
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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 |
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CC and CFLAGS environment variable values. For example, on a modern PC, |
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you could try the following: |
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<p> |
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<pre> |
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$ <b>CFLAGS="-mcpu=pentium4 -O3" ./configure</b> |
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$ <b>make</b> |
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</pre> |
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<p> |
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Run <b>./configure --help</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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<p> |
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Once you have built GXemul, running it should be rather straight-forward. |
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To exit the emulator, type CTRL-C to enter the |
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single-step debugger, and then type <b>quit</b>. By typing CTRL-B instead, |
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a CTRL-C is sent to the emulated program. |
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<p><br> |
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<a name="cpus"></a> |
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<h3>Which CPU types does GXemul emulate?</h3> |
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<h4>MIPS:</h4> |
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Emulation of R4000, which is a 64-bit CPU, was my initial goal. Right |
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now, R2000/R3000-like CPUs are also emulated (32-bit), and emulation of |
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R1x000 (at least the parts that are similar to R4000) is beginning to work |
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as expected. Code targeted for MIPS32 and MIPS64 also often work. |
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<p> |
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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 |
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time and executing it. (If you wish to enable bintrans, add <b>-b</b> to |
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the command line, but keep in mind that it is still experimental.) |
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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>Other CPU types:</h4> |
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There is some code for 64-bit (and 32-bit) POWER/PowerPC emulation too, |
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but it only works for "Hello World" and similarly trivial programs. (There |
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are some other CPU modes too, but they are working even less.) |
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<p><br> |
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<a name="accuracy"></a> |
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<h3>Emulation accuracy:</h3> |
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GXemul is an instruction-level simulator; things that would happen in |
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several steps within a real CPU are not taken into account (eg. pipe-line |
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stages or out-of-order execution). Still, instruction-level accuracy seems |
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to be enough to be able to run complete guest operating systems inside the |
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emulator. |
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<p><br> |
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<a name="emulmodes"></a> |
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<h3>Which machines does GXemul emulate?</h3> |
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|
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A few different machine types are emulated. The machine types that are |
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emulated best at the moment are: |
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<p> |
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<ul> |
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<li><b>DECstation 5000/200</b> ("pmax") |
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<br>(Serial controller (including keyboard and mouse), ethernet, |
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SCSI, and graphical framebuffers.) |
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<p> |
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<li><b>Acer Pica-61</b> (an ARC machine) |
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<br>(Serial controller, "VGA" text console, and SCSI.) |
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<p> |
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<li><b>NEC MobilePro 770, 780, 800, and 880</b> (HPCmips machines) |
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<br>(Framebuffer, keyboard, and a PCMCIA IDE controller.) |
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</ul> |
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<p> |
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There is code in GXemul for emulation of many other machine types; |
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the degree to which these work range from "almost" being able to run |
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a complete OS, to almost completely unsupported (perhaps just enough |
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support to output a few boot messages via serial console). |
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|
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<p> |
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In addition to specific machine types, a "test-machine" can be emulated. |
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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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|
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<p> |
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<ul> |
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<li>a console I/O device (putchar() and getchar()...) |
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<li>an inter-processor communication device, for SMP experiments |
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<li>a very simple linear framebuffer device (for graphics output) |
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</ul> |
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<p> |
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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 |
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educational purposes. |
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<p> |
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You can read more about these experimental devices |
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<a href="experiments.html#expdevices">here</a>. |
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<p><br> |
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<a name="guestos"></a> |
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<h3>Which guest OSes are possible to run?</h3> |
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|
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This table sums up 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 |
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interacted with similar to a real machine: |
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<p><br> |
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<center> |
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<table border="0"> |
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<tr><td> |
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<table border="0"> |
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<tr><td align="center"> |
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<table border="0"> |
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<tr> |
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<td valign="top"><b><u>Guest OS:</u></b></td> |
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<td width="15"> </td> |
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<td valign="top"><b><u>Emulation mode:</u></b></td> |
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<td width="35"> </td> |
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<td valign="top"><b><u>Guest OS:</u></b></td> |
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<td width="15"> </td> |
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<td valign="top"><b><u>Emulation mode:</u></b></td> |
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</tr> |
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|
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<tr> |
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<td height="1"></td> |
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</tr> |
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|
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<tr> |
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<td valign="top"><a href="http://www.netbsd.org/Ports/pmax/">NetBSD/pmax</a></td> |
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<td></td> |
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<td valign="top">DECstation</td> |
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<td></td> |
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<td valign="top"><a href="http://www.netbsd.org/Ports/arc/">NetBSD/arc</a></td> |
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<td></td> |
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<td valign="top">ARC (Acer Pica)</td> |
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</tr> |
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<tr> |
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<td valign="top"><a href="http://www.openbsd.org/pmax.html">OpenBSD/pmax</a></td> |
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<td></td> |
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<td valign="top">DECstation</td> |
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<td></td> |
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<td valign="top"><a href="http://www.openbsd.org/arc.html">OpenBSD/arc</a></td> |
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<td></td> |
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<td valign="top">ARC (Acer Pica)</td> |
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</tr> |
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|
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<tr> |
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<td valign="top">Ultrix/RISC</td> |
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<td></td> |
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<td valign="top">DECstation</td> |
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<td></td> |
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<td valign="top"><a href="http://www.cs.berkeley.edu/projects/sprite/retrospective.html">Sprite</a></td> |
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<td></td> |
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<td valign="top">DECstation</td> |
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</tr> |
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<tr> |
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<td valign="top">Redhat Linux<super>*</super></td> |
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<td></td> |
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<td valign="top">DECstation</td> |
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<td></td> |
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<td valign="top"><a href="http://www.debian.org/">Debian GNU/Linux</a><super>*</super></td> |
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<td></td> |
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<td valign="top">DECstation</td> |
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</tr> |
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|
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<tr> |
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<td valign="top"><a href="http://www.netbsd.org/Ports/hpcmips/">NetBSD/hpcmips</a></td> |
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<td></td> |
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<td valign="top">NEC MobilePro</td> |
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</tr> |
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</table> |
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</td></tr> |
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|
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<tr><td height="15"> </td></tr> |
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|
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<tr><td> |
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<center> |
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<table border="0"> |
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<tr> |
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<td width=160 align=center><a href="netbsd-pmax-20040630.png"><img src="netbsd-pmax-20040630_small.png"></a></td> |
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<td width=160 align=center><a href="openbsd-pmax-20040710.png"><img src="openbsd-pmax-20040710_small.png"></a></td> |
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<td width=160 align=center><a href="ultrix4.5-20040706.png"><img src="ultrix4.5-20040706_small.gif"></a></td> |
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</tr> |
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<tr> |
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<td align=center>NetBSD/pmax 1.6.2</td> |
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<td align=center>OpenBSD/pmax 2.8</td> |
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<td align=center>Ultrix 4.5</td> |
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</tr> |
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<tr> |
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<td height=10> </td> |
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</tr> |
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<tr> |
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<td width=160 align=center><a href="20041024-netbsd-arc-installed.gif"><img src="20041024-netbsd-arc-installed_small.gif"></a></td> |
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<td width=160 align=center><a href="20041024-openbsd-arc-installed.gif"><img src="20041024-openbsd-arc-installed_small.gif"></a></td> |
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<td width=160 align=center><a href="sprite-20040711.png"><img src="sprite-20040711_small.png"></a></td> |
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</tr> |
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<tr> |
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<td align=center>NetBSD/arc 1.6.2</td> |
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<td align=center>OpenBSD/arc 2.3</td> |
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<td align=center>Sprite</td> |
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</tr> |
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<tr> |
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<td height=10> </td> |
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</tr> |
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<tr> |
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<td width=160 align=center><a href="20041129-redhat_mips.png"><img src="20041129-redhat_mips_small.png"></a></td> |
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<td width=160 align=center><a href="20041213-debian_4.png"><img src="20041213-debian_4_small.gif"></a></td> |
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<td width=160 align=center><a href="20050331-netbsd-hpcmips.png"><img src="20050331-netbsd-hpcmips_small.png"></a></td> |
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</tr> |
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<tr> |
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<td align=center>Redhat Linux<super>*</super></td> |
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<td align=center>Debian GNU/Linux<super>*</super></td> |
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<td align=center>NetBSD/hpcmips</td> |
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</tr> |
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</table> |
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</center> |
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</td></tr> |
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</table> |
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</td></tr> |
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</table> |
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</center> |
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<p><br> |
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|
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(<super>*</super> Although Linux runs under DECstation emulation, the |
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default kernel in Debian GNU/Linux does not support keyboards on the 5000/200 |
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(the specific DECstation model being emulated), so when the login prompt |
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is reached you cannot interact with the system. |
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Kaj-Michael Lang has compiled and made available a newer kernel from the |
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current mips-linux development tree. You can find it here: |
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<a href="http://home.tal.org/~milang/o2/kernels/">http://home.tal.org/~milang/o2/kernels</a>/<a 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> |
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This newer kernel supports keyboard input, but it does not have Debian's |
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ethernet patches, so you will not be able to use keyboard/framebuffer |
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<i>and</i> networking at the same time.) |
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<p> |
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It is non-trivial to get a specific operating system or OS kernel to |
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run in the emulator, so don't expect the list above to grow too quickly. |
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<p> |
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There is no guarantee that anything specific will run in the emulator, but |
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NetBSD is a good starting point for someone who wants to experiment. |
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</p> |
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</body> |
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