Date: Wed, 17 Jun 2009 20:09:12 +0800 From: Adrian Chadd <adrian@freebsd.org> To: rick-freebsd2008@kiwi-computer.com Cc: freebsd-hackers@freebsd.org Subject: Re: Loader reading FAT Message-ID: <d763ac660906170509rb2ed252i7bec83decb971e69@mail.gmail.com> In-Reply-To: <20090616172306.GA91395@keira.kiwi-computer.com> References: <200906162350.40221.doconnor@gsoft.com.au> <20090616172306.GA91395@keira.kiwi-computer.com>
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2009/6/17 Rick C. Petty <rick-freebsd2008@kiwi-computer.com>: > I read somewhere that there isn't enough space in the boot2 loader to put > such logic. =A0You're only guaranteed 15 512-byte sectors or 7680 bytes, = if > you use any UFS partition. =A0It's pretty tight; I think you will find it > difficult to insert another file system in there, especially one as > complicated as msdos. =A0libstand is 223 KB, so it's not as trivial as yo= u > think. > > Theoretically it would be possible: for example, if you're willing to set > aside a separate partition you would have as much room as you want. =A0Or= if > you put it at the front of a UFS partition, you have just under 256 KB of > room since our UFS code will search for the superblock at a byte offset o= f > 262144, but there aren't any knobs to newfs so you'd have to hack it > together. =A0Take a look at /usr/src/sys/boot/i386/boot2/ for starters. This is why I pointed out the NetBSD DOS bootloader stuff. In effect, you could "just" boot a FreeBSD install by teaching the NetBSD bootloader and loader(8) enough about each other to initialise loader; loader then has much more memory to play with understanding multiple filesystems and slicing/labelling methods. Boot0, boot1, boot2 wouldn't even be involved. Adrian
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