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-
-The guest OS running inside the emulator uses a private IPv4 address, such -as 10.0.0.1, and the emulator acts as a NAT-like gateway/firewall at IPv4 -address 10.0.0.254. To the outside world it will seem like it is the host's -OS that connects to other machines on the internet, not the guest OS. -
-NOTE: This is still experimental! -As of 2004-07-21, ARP + ICMP + UDP + TCP are emulated well enough to let -NetBSD and OpenBSD install via ftp, and use the network for many normal -activities, but not everything works yet. - - - -
-However, if you think that you can port an operating system -to, say, the Silicon Graphics machine mode of GXemul and hope that your -operating system will run on a real SGI machine, then you will most -likely fail. GXemul simply does not emulate things well enough for that to work. -Another example would be specific CPU details; if your code depends on, -say, R10000 specifics, chances are that GXemul will not be sufficient. +
Important things to keep in mind: -
-In many cases, hardware devices in GXemul are only implemented well -enough to fool eg. NetBSD that they are working correctly, while in -fact they don't work very much at all. Please keep this in mind, if you plan -to use GXemul when porting your code to MIPS. +
+
+
+ If you are developing a driver for a device which is emulated by + GXemul, and your driver does not seem to be working, then the + probability of a bug in GXemul's implementation of the device is + very much higher than that of a bug in your driver. +
+ The device implementations in GXemul are based on the assumption + that the emulated OS is already developed and bug-free. They are + not primarily intended to be used for development of new device + driver code in operating systems, so if you do that, then be + prepared for bugs and inconsitencies. +
+
+
The bottom line is that GXemul can be useful as yet another way to test +your code during development, but it should not be fully relied on. @@ -120,22 +130,22 @@
-
-Here are some examples. If you want to run a NetBSD/pmax kernel on an -emulated DECstation machine, you would use a command line such as this: +Here are some examples. If you want to run a NetBSD/pmax +kernel on an emulated DECstation +machine, you would use a command line such as this:
- $ gxemul -E dec -e 3max -b -d pmax_diskimage.fs netbsd-pmax-INSTALL + $ gxemul -e 3max -d pmax_diskimage.fs netbsd-pmax-INSTALL-
-NOTE: For some emulation modes, such as the DECstation mode, you do -not have to specify the name of the kernel, if the disk image is -bootable! -
-It is possible to have more than one disk. For each -d argument, a disk + +
NOTE: For some emulation modes, such as the DECstation mode, you do +not actually have to specify the name of the kernel, if the disk +image is bootable! + +
It is possible to have more than one disk. For each -d argument, a disk image is added; the first will be SCSI target 0, the second will be target 1, and so on, unless you specify explicitly which ID number the devices should have.
- $ gxemul -E dec -e 3max -b -d disk0.raw -d disk1.raw -d 5:disk2.raw netbsd-pmax-INSTALL + $ gxemul -e 3max -d disk0.raw -d disk1.raw -d 5:disk2.raw netbsd-pmax-INSTALLNote: In the example above, disk2.raw will get scsi id 5. -
-If a filename has a 'c' prefix, or ends with ".iso", then it is assumed to be + +
If a filename has a 'c' prefix, or ends with ".iso", then it is assumed to be a CDROM device (this can be overridden with a 'd' prefix, to force a read/write disk). For example, the following command would start the emulator with two CDROM images, and one harddisk image:
- $ gxemul -E dec -e 3max -b -d image.iso -d disk0.img -d c:second_cdrom.img netbsd-pmax-INSTALL + $ gxemul -e 3max -d image.iso -d disk0.img -d c:second_cdrom.img netbsd-pmax-INSTALLUsually, the device with the lowest id becomes the boot device. To override this, add a 'b' prefix to one of the devices:
- $ gxemul -E dec -e 3max -b -d rootdisk.img -d bc:install-cd.iso name_of_kernel + $ gxemul -e 3max -d rootdisk.img -d bc:install-cd.iso name_of_kernelIf you have a physical CD-ROM drive on the host machine, say /dev/cd0c, you can use it as a CD-ROM directly accessible from within the emulator:
- $ gxemul -E dec -e 3max -b -d rootdisk.img -d bc:/dev/cd0c name_of_kernel + $ gxemul -e 3max -d rootdisk.img -d bc:/dev/cd0c name_of_kernelIt is probably possible to use harddisks as well this way, but I would not recommend it. -
+ + + + + + +
+Note: Tape support is most likely very buggy, +because it has not been tested much, and has probably also suffered +from bit-rot by now. + + + + + + +
+
+ gxemul -XEcats -d nbsd_cats.img netbsd.aout-GENERIC.gz + ++
+ touch overlay.img overlay.img.map + gxemul -XEcats -d 0:nbsd_cats.img -d V0:overlay.img netbsd.aout-GENERIC.gz + ++
+ rm -f overlay.img overlay.img.map + touch overlay.img overlay.img.map + ++ and then simply start the emulator again, with the newly created + overlay image. +
It is also possible to add multiple overlays. In that case, writes +always go the the last added overlay. + +
GXemul uses Unix' way of supporting files with "holes", +so even if ls -l overlay.img says that the overlay is several +gigabytes large, du overlay.img should reveal that only the +blocks that have actually been written to have been stored in the +overlay, e.g.:
+ $ ls -l + .. + -rw-r--r-- 1 debug wheel 3072319488 Mar 24 11:59 nbsd_cats.img + -rw-r--r-- 1 debug wheel 2465354 Mar 24 11:44 netbsd.aout-GENERIC.gz + -rw-r--r-- 1 debug wheel 2930841600 Mar 24 14:02 overlay.img + -rw-r--r-- 1 debug wheel 715538 Mar 24 14:02 overlay.img.map + $ du overlay.img + 864 overlay.img + ++ +
The .map file is simply a raw bitmap telling which blocks of the +overlay file that are in use. + + + + + +
There is another way of transfering files which works for any kind of +emulated machine which supports disks (either SCSI or IDE). Any file can +be supplied as a disk image. For example, consider the following:
+ $ gxemul -XEcats -d nbsd_cats.img -d archive.tar.gz netbsd-GENERIC ++This will start NetBSD/cats with nbsd_cats.img as IDE master on +controller 0 (wd0), and archive.tar.gz as IDE slave on controller +0 (wd1). From inside NetBSD, it is now possible to extract the files using +the following command:
+ (inside emulated NetBSD/cats) + # tar zxvf /dev/wd1c ++Don't worry if NetBSD complains about lack of disklabel; it doesn't +matter. On some machines, NetBSD uses wd1d instead of +wd1c for the entire disk. +There is also a minor problem: reading the end of the disk image. If you +experience problems untaring archives like this, then pad out the archive +first with some zeroes. + +
Transfering files out from the emulated operating system to the +host can be done the same way. First, prepare an empty archive file:
+ $ dd if=/dev/zero of=newarchive.tar bs=1024 count=1 seek=10000 +This example created a 10 MB empty file. Then, start the emulator +like this:
+ $ gxemul -XEcats -d nbsd_cats.img -d archive.tar netbsd-GENERIC ++and transfer files by creating an archive directly onto the disk image:
+ (inside emulated NetBSD/cats) + # tar cvf /dev/wd1c filenames ++where filenames are the files or directories to transfer. + + +
There is some skeleton code for running userland programs as well. This +will not emulate any particular machine, but instead try to translate +syscalls from e.g. NetBSD/pmax into the host's OS' syscalls. Right now, +this is just a proof-of-concept, to show that it could work; there's lots +of work left to do to make it actually run useful programs.
@@ -321,6 +456,7 @@ tab.csbnet.se +
-The easiest way is to hook up a serial console. The terminal must be + +
The easiest way is to hook up a serial console. The terminal must be able to capture output to a file. -
-These are approximately the commands that I used: + +
These are approximately the commands that I used:
>>cnfg Show machine configuration
@@ -389,29 +528,30 @@
>>e -x 0xbfc00000:0xbfffffff Dump the PROM data
--Remember that DECstations are little endian, so if the dump data + +
Remember that DECstations are little endian, so if the dump data looks like this:
bfc00000: 0x0bf0007e
then the bytes in memory are actually 0x7e, 0x00, 0xf0, and 0x0b.
--At 9600 bps, about 10KB can be dumped per minute, so it takes a while. + +
At 9600 bps, about 10KB can be dumped per minute, so it takes a while. Once enough of the PROM has been dumped, you can press CTRL-C to break out. Then, restore the more environment variable:
>>setenv more 24
--Now, convert the data you just saved (little-endian words -> bytes), + +
Now, convert the data you just saved (little-endian words -> bytes), and store in a file. Let's call this file DECstation5000_125_promdump.bin.
$ decprom_dump_txt_to_bin DECstation5000_125_promdump.txt DECstation5000_125_promdump.bin
+
This binary image can now be used in the emulator:
- $ gxemul -E dec -e 3min -Q -M128 -q 0xbfc00000:DECstation5000_125_promdump.bin + $ gxemul -e 3min -Q -M128 -q 0xbfc00000:DECstation5000_125_promdump.bin KN02-BA V5.7e ?TFL: 3/scc/access (1:Ln1 reg-12: actual=0x00 xpctd=0x01) [KN02-BA] @@ -452,39 +592,74 @@ osconsole=3 >>-(Note: at the moment, this doesn't work. I must have broken something when -fixing something else, but this is what it looked like at the time.) -
-During bootup, the PROM complains a lot about hardware failures. + +
(Note: at the moment, this doesn't work. +I must have broken something when fixing something else, but this +is what it looked like at the time.) + +
During bootup, the PROM complains a lot about hardware failures. That's because the emulator doesn't emulate the hardware well enough yet. -
-The command line options used are: -E dec for DECstation, -e 3min for -"model 3" (5000/1xx), -Q to supress the emulator's own PROM -call emulation, -M128 for 128MB RAM (because GXemul doesn't correctly + +
The command line options used are: -e 3min for +"DECstation 3min" (5000/1xx), -Q to supress the emulator's own PROM +call emulation, -M128 for 128MB RAM (because GXemul doesn't correctly emulate memory detection well enough for the PROM to accept, so it will -always believe there is 128MB ram anyway), and -q to supress debug messages. -The 0xbfc00000 in front of the filename tells GXemul that it is a raw +always believe there is 128MB ram anyway), and -q to supress debug messages. +The 0xbfc00000 in front of the filename tells GXemul that it is a raw binary file which should be loaded at a specific virtual address.
-
-For the O2, a suitable command to dump the prom memory range is +machines as well. I have also tried this on an SGI IP32 ("O2"), in addition +to the DECstation. + +
For the O2, a suitable command to dump the prom memory range is
>> dump -b 0xBFC00000:0xBFC80000Make sure you capture all the output (via serial console) into a file, -and then run experiments/sgiprom_to_bin on the captured file. -
-(2005-01-16: The emulator doesn't really emulate the IP32 well enough to -actually run the PROM image without using special hacks, but it might do -so some time in the future.) +and then run experiments/sgiprom_to_bin on the captured file. +
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The photo on the left is from the real machine. The other two are +screenshots of the PROM running experimentally in GXemul, using -Y2 +framebuffer scaledown. + +
Normally during bootup, the IP32 PROM does a Power-On test which makes +sure that the caches and other things are working properly. GXemul doesn't +emulate all those things well enough for the tests to pass. The +experimental screenshots above were taken with cache detection skipped +manually. + +
+In other words: don't expect this to work out-of-the-box with GXemul right +now. It might work once I've added correct cache emulation. + +
The command line used to start the emulator, once correct cache +emulation has been implemented, would be something like gxemul -XQeo2 +0xbfc00000:prom.bin. + +
The same caution applies when dealing with SGI PROMs as with +DECstation PROMs: GXemul doesn't really emulate the hardware, it only +"fakes" devices well enough to fool some things, primarily NetBSD, that +it is emulating a real machine. ROM code is usually a lot more +picky about the details. + +
The graphics used in the O2 is (as far as I know) undocumented. Combining +some traces of info from how Linux/O2 draws to the screen with some +reverse-engineering of my own, I've implemented enough of the controller to +let the PROM draw rectangles and bitmaps, but not much more. The SCSI +controller is not implemented yet either.