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<html><head><title>Gavare's eXperimental Emulator: Experimenting with GXemul</title> |
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<td align="left" valign=center bgcolor="#d0efff"><font color="#6060e0" size="6"> |
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<b>Gavare's eXperimental Emulator:</b></font><br> |
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<font color="#000000" size="6"><b>Experimenting with GXemul</b> |
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</font></td></tr></table></td></tr></table><p> |
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<!-- |
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$Id: experiments.html,v 1.105 2006/12/30 13:30:50 debug Exp $ |
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Copyright (C) 2003-2007 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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2. Redistributions in binary form must reproduce the above copyright |
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notice, this list of conditions and the following disclaimer in the |
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3. The name of the author may not be used to endorse or promote products |
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derived from this software without specific prior written permission. |
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THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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--> |
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<a href="./">Back to the index</a> |
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|
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<p><br> |
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<h2>Experimenting with GXemul</h2> |
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|
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<p> |
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<ul> |
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<li><a href="#hello">Hello world</a> |
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<li><a href="#expdevices">Experimental devices</a> |
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</ul> |
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|
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<p><br> |
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<a name="hello"></a> |
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<h3>Hello world:</h3> |
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|
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You might want to use the emulator to develop programs on your own, |
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not just run precompiled kernels such as NetBSD. To get started, I recommend |
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that you do two things: |
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|
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<p> |
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<ul> |
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<li>Build and install a cross-compiler for your chosen target. |
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GCC is usually a good compiler choice, because it is portable |
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and in wide-spread use. (Other compilers should work too.) |
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|
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<p> |
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<li>Compile the Hello World demo program for your chosen target, and run |
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it in the emulator. |
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</ul> |
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|
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<p>The Hello World demo program is included in the GXemul source |
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code distribution, in the <a href="../demos/hello/"><tt>demos/hello/</tt></a> |
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subdirectory. The README files in the demo directories have several |
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examples of how the demo programs can be built. |
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|
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<p>Hopefully this is enough to get you inspired. :-) |
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<p><br> |
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<a name="expdevices"></a> |
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<h3>Experimental devices:</h3> |
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|
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The emulator has several modes where it doesn't emulate any real machine. |
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It can either run in "bare" mode, where no devices are included by default |
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(just the CPU), or in a "test" mode where some simple devices are |
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emulated. |
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<p>The test machines (<tt>testmips</tt>, <tt>testppc</tt>, etc) have the |
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following experimental devices: |
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|
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<p> |
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<center><table border="0" width="80%"> |
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|
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<tr> |
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<td align="left" valign="top" width="200"> |
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<a name="expdevices_cons"><b><tt>cons</tt>:</b></a> |
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<p>A simple console device, for writing |
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characters to the controlling terminal |
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and receiving keypresses. |
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<p>Source code: <font color="#0000f0"><tt>src/devices/dev_cons.c</tt></font> |
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<p>Include file: <font color="#0000f0"><tt>dev_cons.h</tt></font> |
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<br>Default physical address:  <font color="#0000f0">0x10000000</font> |
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</td> |
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<td align="left" valign="top" width="25"> </td> |
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<td align="left" valign="top"> |
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<table border="0"> |
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<tr> |
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<td align="left" valign="top"><i><u>Offset:</u></i> </td> |
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<td align="left" valign="top"><i><u>Effect:</u></i></td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x00</tt></td> |
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<td align="left" valign="top"> |
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Read: <b><tt>getchar()</tt></b> (non-blocking; returns |
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<tt>0</tt> if no char was available)<br> |
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Write: <b><tt>putchar(ch)</tt></b></td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x10</tt></td> |
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<td align="left" valign="top">Read or write: <b><tt>halt()</tt></b><br> |
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(Useful for exiting the emulator.)</td> |
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</tr> |
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</table> |
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</td> |
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</tr> |
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|
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<tr height="15"> |
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<td height="15"> </td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"> |
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<a name="expdevices_mp"><b><tt>mp</tt>:</b></a> |
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<p>This device controls the behaviour of CPUs in an emulated |
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multi-processor system. |
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<p>Source code: <font color="#0000f0"><tt>src/devices/dev_mp.c</tt></font> |
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<p>Include file: <font color="#0000f0"><tt>dev_mp.h</tt></font> |
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<br>Default physical address:  <font color="#0000f0">0x11000000</font> |
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</td> |
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<td></td> |
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<td align="left" valign="top"> |
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<table border="0"> |
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<tr> |
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<td align="left" valign="top"><i><u>Offset:</u></i> </td> |
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<td align="left" valign="top"><i><u>Effect:</u></i></td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0000</tt></td> |
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<td align="left" valign="top">Read: <b><tt>whoami()</tt></b>. |
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Returns the id of the CPU doing the read.</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0010</tt></td> |
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<td align="left" valign="top">Read: <b><tt>ncpus()</tt></b>. |
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Returns the number of CPUs in the system.</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0020</tt></td> |
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<td align="left" valign="top">Write: <b><tt>startupcpu(i)</tt></b>. |
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Starts CPU i. It begins execution at the address |
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set by a write to startupaddr (see below).</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0030</tt></td> |
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<td align="left" valign="top">Write: <b><tt>startupaddr(addr)</tt></b>. |
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Sets the starting address for CPUs.</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0040</tt></td> |
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<td align="left" valign="top">Write: <b><tt>pause_addr(addr)</tt></b>. |
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Sets the pause address. (NOTE: This is not |
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used anymore.)</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0050</tt></td> |
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<td align="left" valign="top">Write: <b><tt>pause_cpu(i)</tt></b>. |
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Pauses all CPUs <i>except</i> CPU i.</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0060</tt></td> |
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<td align="left" valign="top">Write: <b><tt>unpause_cpu(i)</tt></b>. |
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Unpauses CPU i.</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0070</tt></td> |
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<td align="left" valign="top">Write: <b><tt>startupstack(addr)</tt></b>. |
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Sets the startup stack address. (CPUs started with |
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startupcpu() above will have their stack pointer |
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set to this value.)</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0080</tt></td> |
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<td align="left" valign="top">Read: <b><tt>hardware_random()</tt></b>. |
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This produces a "random" number.</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0090</tt></td> |
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<td align="left" valign="top">Read: <b><tt>memory()</tt></b>. |
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Returns the number of bytes of RAM in the system.</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x00a0</tt></td> |
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<td align="left" valign="top">Write: <b><tt>ipi_one((nr << 16) + cpuid)</tt></b>. |
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Sends IPI <tt>nr</tt> to a specific CPU.</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x00b0</tt></td> |
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<td align="left" valign="top">Write: <b><tt>ipi_many((nr << 16) + cpuid)</tt></b>. |
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Sends IPI <tt>nr</tt> to all CPUs <i>except</i> |
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the specified one.</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x00c0</tt></td> |
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<td align="left" valign="top">Read: <b><tt>ipi_read()</tt></b>. |
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Returns the next pending IPI. 0 is returned if there is no |
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pending IPI (so 0 shouldn't be used for valid IPIs). |
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Hardware int 6 is deasserted when the IPI queue is empty. |
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<br>Write: <b><tt>ipi_flush()</tt></b>. |
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Clears the IPI queue, discarding any pending IPIs.</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x00d0</tt></td> |
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<td align="left" valign="top">Read: <b><tt>ncycles()</tt></b>. |
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Returns approximately the number of cycles executed. |
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Note: this value is not updated for every instruction, |
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so it cannot be used for small measurements.</td> |
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</tr> |
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</table> |
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</td> |
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</tr> |
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|
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<tr height="15"> |
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<td height="15"> </td> |
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</tr> |
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|
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<tr> |
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<td align="left" valign="top"> |
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<a name="expdevices_fb"><b><tt>fb</tt>:</b></a> |
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<p>A simple linear framebuffer, for graphics output. |
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640 x 480 pixels, 3 bytes per pixel (red, green, blue, 8 bits each). |
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<p>Source code: <font color="#0000f0"><tt>src/devices/dev_fb.c</tt></font> |
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<p>Include file: <font color="#0000f0"><tt>dev_fb.h</tt></font> |
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<br>Default physical address:  <font color="#0000f0">0x12000000</font> |
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</td> |
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<td></td> |
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<td align="left" valign="top"> |
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<table border="0"> |
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<tr> |
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<td align="left" valign="top"><i><u>Offset:</u></i> </td> |
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<td align="left" valign="top"><i><u>Effect:</u></i></td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x00000-</tt><br><tt>0xe0fff</tt></td> |
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<td align="left" valign="top">Read: read pixel values. |
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<br>Write: write pixel values.</td> |
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</tr> |
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</table> |
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</td> |
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</tr> |
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|
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<tr height="15"> |
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<td height="15"> </td> |
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</tr> |
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|
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<tr> |
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<td align="left" valign="top"> |
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<a name="expdevices_disk"><b><tt>disk</tt>:</b></a> |
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<p>Disk controller, which can read from and write |
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to emulated IDE disks. It does not use interrupts; read and |
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write operations finish instantaneously. |
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<p>Source code: <font color="#0000f0"><tt>src/devices/dev_disk.c</tt></font> |
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<p>Include file: <font color="#0000f0"><tt>dev_disk.h</tt></font> |
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<br>Default physical address:  <font color="#0000f0">0x13000000</font> |
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</td> |
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<td></td> |
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<td align="left" valign="top"> |
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<table border="0"> |
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<tr> |
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<td align="left" valign="top"><i><u>Offset:</u></i> </td> |
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<td align="left" valign="top"><i><u>Effect:</u></i></td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0000</tt></td> |
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<td align="left" valign="top">Write: Set the offset (in bytes) from the beginning |
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of the disk image. This offset will be used for the next read/write operation.</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0010</tt></td> |
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<td align="left" valign="top">Write: Select the IDE ID to be used in the next |
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read/write operation.</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0020</tt></td> |
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<td align="left" valign="top">Write: Start a read or write operation. |
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(Writing <tt>0</tt> means a Read operation, a <tt>1</tt> means a |
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Write operation.)</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0030</tt></td> |
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<td align="left" valign="top">Read: Get status of the last operation. |
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(Status 0 means failure, non-zero means success.)</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x4000-</tt><br><tt>0x41ff</tt> </td> |
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<td align="left" valign="top">Read/Write: 512 bytes data buffer.</td> |
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</tr> |
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</table> |
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</td> |
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</tr> |
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|
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<tr height="15"> |
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<td height="15"> </td> |
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</tr> |
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|
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<tr> |
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<td align="left" valign="top"> |
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<a name="expdevices_ether"><b><tt>ether</tt>:</b></a> |
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<p>A simple ethernet controller, enough to send |
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and receive packets on a simulated network. |
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<p>Source code: <font color="#0000f0"><tt>src/devices/dev_ether.c</tt></font> |
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<p>Include file: <font color="#0000f0"><tt>dev_ether.h</tt></font> |
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<br>Default physical address:  <font color="#0000f0">0x14000000</font> |
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</td> |
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<td></td> |
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<td align="left" valign="top"> |
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<table border="0"> |
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<tr> |
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<td align="left" valign="top"><i><u>Offset:</u></i> </td> |
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<td align="left" valign="top"><i><u>Effect:</u></i></td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0000-</tt><br><tt>0x3fff</tt></td> |
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<td align="left" valign="top">Read/write buffer for the packet to be sent/received.</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x4000</tt></td> |
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<td align="left" valign="top">Read: status word, one or more of these: |
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<br><tt>0x01</tt> = something was received (because of |
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the last command) |
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<br><tt>0x02</tt> = more packets are available |
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<br><i>NOTE:</i> Whenever the status word is non-zero, |
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an interrupt is asserted. Reading the status word |
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clears it, and deasserts the interrupt.</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x4010</tt></td> |
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<td align="left" valign="top">Read: get the Length of the received packet |
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<br>Write: set the Length of the next packet to transmit</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x4020</tt></td> |
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<td align="left" valign="top">Write: command: |
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<br><tt>0x00:</tt> receive a packet |
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<br><tt>0x01:</tt> send a packet</td> |
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</tr> |
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</table> |
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</td> |
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</tr> |
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|
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<tr height="15"> |
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<td height="15"> </td> |
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</tr> |
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|
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<tr> |
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<td align="left" valign="top"> |
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<a name="expdevices_rtc"><b><tt>rtc</tt>:</b></a> |
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<p>A Real-Time Clock, used to retrieve the current time |
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and to cause periodic interrupts. |
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<p>Source code: <font color="#0000f0"><tt>src/devices/dev_rtc.c</tt></font> |
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<p>Include file: <font color="#0000f0"><tt>dev_rtc.h</tt></font> |
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<br>Default physical address:  <font color="#0000f0">0x15000000</font> |
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</td> |
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<td></td> |
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<td align="left" valign="top"> |
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<table border="0"> |
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<tr> |
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<td align="left" valign="top"><i><u>Offset:</u></i> </td> |
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<td align="left" valign="top"><i><u>Effect:</u></i></td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0000</tt></td> |
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<td align="left" valign="top">Read or Write: Trigger a clock update (a gettimeofday() on the host).</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0010</tt></td> |
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<td align="left" valign="top">Read: Seconds since 1st January 1970</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0020</tt></td> |
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<td align="left" valign="top">Read: Microseconds</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0100</tt></td> |
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<td align="left" valign="top">Read: Get the current |
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timer interrupt frequency.<br>Write: Set the timer |
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interrupt frequency. (Writing 0 disables the timer.)</td> |
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</tr> |
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<tr> |
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<td align="left" valign="top"><tt>0x0110</tt></td> |
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<td align="left" valign="top">Read or Write: Acknowledge |
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one timer interrupt. (Note that if multiple interrupts |
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are pending, only one is acknowledged.)</td> |
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</tr> |
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</table> |
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</td> |
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</tr> |
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|
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</table></center> |
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|
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<p> |
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While these devices may resemble real-world hardware, they are |
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intentionally made simpler to use. (An exception is the framebuffer; |
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some machines actually have simple linear framebuffers like this.) |
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|
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<p>If the physical address is <tt>0x10000000</tt>, then for MIPS that |
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means that it can be accessed at virtual address |
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<tt>0xffffffffb0000000</tt>. (Actually it can be accessed at |
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<tt>0xffffffff90000000</tt> too, but devices should usually be accessed in |
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a non-cached manner.) |
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|
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<p>When using the Alpha, ARM, or PPC test machines, the addresses are |
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<tt>0x10000000</tt>, <tt>0x11000000</tt> etc., so no need to add any |
| 433 |
virtual displacement. |
| 434 |
|
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<p>The <tt>mp</tt>, <tt>disk</tt>, and <tt>ether</tt> devices are agnostic |
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when it comes to word-length. For example, when reading offset |
| 437 |
<tt>0x0000</tt> of the <tt>mp</tt> device, you may use any kind of read |
| 438 |
(an 8-bit read will work just as well as a 64-bit read, although the value |
| 439 |
will be truncated to 8 bits in the first case). You can <i>not</i>, |
| 440 |
however, read one byte from <tt>0x0000</tt> and one from <tt>0x0001</tt>, |
| 441 |
and combine the result. The read from <tt>0x0001</tt> will be invalid. |
| 442 |
|
| 443 |
<p>The <tt>cons</tt> device should be accessed using 8-bit reads |
| 444 |
and writes. Doing a getchar() (ie reading from offset <tt>0x00</tt>) |
| 445 |
returns <tt>0</tt> if no character was available. Whenever a character is |
| 446 |
available, the <tt>cons</tt> device' interrupt is asserted. When there are |
| 447 |
no more available characters, the interrupt is deasserted. (Remember that |
| 448 |
the interrupt has to be unmasked to be able to actually cause an |
| 449 |
interrupt.) |
| 450 |
|
| 451 |
<p>IPIs (inter-processor interrupts) are controlled by the <tt>mp</tt> |
| 452 |
device. Whenever an IPI is "sent" from a source to one or more target |
| 453 |
CPUs, the interrupt is asserted on the target CPUs, and the IPI number is |
| 454 |
added last in the IPI queue for each of the target CPUs. It is then up to |
| 455 |
those CPUs to individually read from offset <tt>0x00c0</tt>, to figure out |
| 456 |
what kind of IPI it was. |
| 457 |
|
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|
| 459 |
|
| 460 |
<p>Interrupt mappings are as follows: |
| 461 |
|
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<p><center> |
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<table border="1"> |
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<tr><td align="center"> |
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<b><tt>testmips</tt></b> |
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</td></tr> |
| 467 |
<tr><td> |
| 468 |
<table border="0"> |
| 469 |
<tr><td align="center">IRQ:</td><td> </td> |
| 470 |
<td>Used for:</td></tr> |
| 471 |
<tr><td align="center">7</td><td></td> |
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<td>MIPS count/compare interrupt</td></tr> |
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<tr><td align="center">6</td><td></td> |
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<td><tt>mp</tt> (inter-processor interrupts)</td></tr> |
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<tr><td align="center">4</td><td></td> |
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<td><tt>rtc</tt></td></tr> |
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<tr><td align="center">3</td><td></td> |
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<td><tt>ether</tt></td></tr> |
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<tr><td align="center">2</td><td></td> |
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<td><tt>cons</tt></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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|
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<p>Other machines: TODO |
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|
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|
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<p><br> |
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|
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|
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|
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</p> |
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|
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</body> |
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</html> |
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