42 lines
1.6 KiB
Plaintext
42 lines
1.6 KiB
Plaintext
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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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