jhb at FreeBSD.org
Tue May 31 13:56:52 PDT 2005
On Tuesday 31 May 2005 11:06 am, Michael Reifenberger wrote:
> On Tue, 31 May 2005, David O'Brien wrote:
> > Ha!! We can only have 1 sector worth of code in boot0. At this point we
> > only have a few bytes of free code space. No where near enough to do the
> > long mode switch.
> Sorry. I didnt meant boot0 but btx. I do know that boot0 is too small.
> But btx is already switching to protected mode so it should be possible
> to switch to 64bit mode too.
Note that the loader uses the BIOS (via virtual 8086 mode) to do all the disk
I/O, etc. Since long mode doesn't support vm86 mode, you'd end up with a
loader that couldn't do any I/O to load the kernel, etc. unless you started
including device drivers for all the different storage and networking
hardware, etc. A 64-bit loader really isn't feasible unless your 64-bit
machine includes firmware that you can use from 64-bit mode like EFI on ia64
or OFW on sparc. You probably want to stick with a 32-bit loader on amd64
John Baldwin <jhb at FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve" = http://www.FreeBSD.org
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