b8e4cd2bb3
It boots FreeBSD from a running MS-DOS system. It's compiled using some MS-DOS tools, but there is a binary hidden in the uuencoded file. (Go ahead, flame me if you can come up with a solution for the problem. Just saying "this is bad" doesn't count!) Rod, you were right: one would have to deal with weird interfaces to the memory managers, and it seems that Christian found them all, and made them work. Thanks Christian! Reviewed by: phk Submitted by: DI. Christian Gusenbauer <cg@fimp01.fim.uni-linz.ac.at> Christians README: ------------------ Hi Everybody! This is version 1.5 of "fbsdboot", a program that allows you to boot a kernel from a MS-DOS partition or a FreeBSD partition. This program runs using DOS. It works with various memory managers (like EMM386, 386MAX) under certain circumstances. First, a FreeBSD kernel is always loaded to memory starting at 0x100000. To assure that loading the kernel *does not* overwrite memory used by memory managers, high memory for the kernel is allocated and after loading the kernel it's moved to 0x100000. Second, there are many ways to switch to protected mode which is necessary to start the kernel. Each BIOS gives you the possibility to use INT15H (AH=89H) to do that. But some memory-managers like 386max does not allow you to use this method. An other way to do the switch is to use DPMI services, but they do not guarantee, that the protected mode application is executed with privilege level 0. Therefore this method is *not* used. VCPI services offer another way to switch to protected mode, and VCPI servers are built into "emm386.exe", "386max" and "qemm". That's why, this method is implemented in fbsdboot.exe. Fbsdboot.exe tries to switch to protected mode using VCPI services. If they're not available INT15H is used to do the switch. If that fails, it's not possible for this version of fbsdboot.exe to boot a kernel :-(. You can get commandline options of fbsdboot if you start it with "-?" as option! I don't know, if fbsdboot works with QEMM, as I don't have the possibility to test it. Enjoy and have fun! Christian. cg@fimp01.fim.uni-linz.ac.at PS: Many thanks to Bruce Evans for his assistance!
42 lines
1.6 KiB
Plaintext
42 lines
1.6 KiB
Plaintext
Hi Everybody!
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This is version 1.5 of "fbsdboot", a program that allows you to boot a kernel
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from a MS-DOS partition or a FreeBSD partition. This program runs using DOS.
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It works with various memory managers (like EMM386, 386MAX) under certain
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circumstances.
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First, a FreeBSD kernel is always loaded to memory starting at 0x100000. To
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assure that loading the kernel *does not* overwrite memory used by memory
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managers, high memory for the kernel is allocated and after loading the kernel
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it's moved to 0x100000.
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Second, there are many ways to switch to protected mode which is necessary to
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start the kernel. Each BIOS gives you the possibility to use INT15H (AH=89H)
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to do that. But some memory-managers like 386max does not allow you to use
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this method.
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An other way to do the switch is to use DPMI services, but they do not
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guarantee, that the protected mode application is executed with privilege
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level 0. Therefore this method is *not* used.
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VCPI services offer another way to switch to protected mode, and VCPI servers
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are built into "emm386.exe", "386max" and "qemm". That's why, this method is
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implemented in fbsdboot.exe.
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Fbsdboot.exe tries to switch to protected mode using VCPI services. If they're
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not available INT15H is used to do the switch. If that fails, it's not possible
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for this version of fbsdboot.exe to boot a kernel :-(.
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You can get commandline options of fbsdboot if you start it with "-?" as option!
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I don't know, if fbsdboot works with QEMM, as I don't have the possibility to
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test it.
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Enjoy and have fun!
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Christian.
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cg@fimp01.fim.uni-linz.ac.at
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PS: Many thanks to Bruce Evans for his assistance!
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