On Fri, Mar 21, 2008 at 12:26 AM, Pavel Roskin <[EMAIL PROTECTED]> wrote: > On Thu, 2008-03-20 at 20:28 +0800, Bean wrote: > > > I think using a separate sector to store the information is not very > > practical. First of all, we need to modify all of the file system > > modules to support this new feature, which require non trivial work > > and testing. > > I'm afraid you misunderstood something. Are you talking about the > bootloader or about the utility for creating the sector? The bootloader > should write only by the block number. No filesystem code is involved. > > The utility only needs to know which filesystems are safe to write to. > It should also know the sector number, but I think LILO can do it > somehow without any filesystem support. Even GRUB should be able to do > it if it doesn't embed the core image. The worst case scenario is that > we add some tracing code to our filesystem implementation (userspace > only), which would record the last sector accessed for reading. This > way we'll know the location of the file by reading from it. > > > > Besides, some file system doesn't have space for extra > > sector, for example, fat12/fat16. It would be annoying if this > > function can't be used on such fs. > > What extra space are you talking about? I actually think FAT is one of > the easiest filesystems to support because it has no checksums, no > compression, no tail packing and no sparse files. A 512-byte long file > would always occupy exactly one sector.
I'm sorry, i do misunderstand your point. i thought you mean saving the information in some reserved sector of file system. > > > > Perhaps we can just embed the information in core.img itself. We use > > blocklist to find out the disk location and write to it. As core.img > > is normally too big to fit within a filesystem cluster, we don't have > > to worry about inline data. Also, we can read from the sector and > > verify its content first, so that we won't overwrite other area even > > if blocklist give incorrect result. > > I don't see much difference between using core.img and a separate file, > except that using a separate file gives more flexibility. > > By the way, you are inconsistent here. If writing a separate file > requires changes to all filesystems, how come writing to core.img > doesn't require it? > > The only difference in my proposal is to have the blocklist (consisting > of one sector) in the writable file itself, not in the bootloader. > Yes, using core.img and a separate file is not that different. but if we use normal file, we must create a large enough one. -- Bean _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org http://lists.gnu.org/mailman/listinfo/grub-devel
