Hi,
I'm trying to figure out generally how GRUB works. I'm interested in getting into some kernel hacking (gnumach/hurd), rather than GRUB hacking, but am trying to get a feel for what happens before the kernel gets to execute. Your doc at http://www.gnu.org/manual/grub-0.90/html_mono/grub.html, together with the partition documentation at http://www.win.tue.nl/~aeb/partitions/partition_tables.html have given me a pretty good idea, but I would appreciate it if you could spare some time to answer the following questions. If you like, I could type up the answers & submit a patch to the grub.html doc (or the base document if this is generated from something else)... Alternatively, if there is more documentation on GRUB somewhere, please point me at it! 1. where does the stage1.5 get written to on a hard-drive? (*) if using FFS or ReiserFS, and there is sufficient space in the "boot area" reserved by these filesystems, is that space used? Is it the first choice location? (*) does GRUB check the partition table to look for "gaps" between partitions, and assume that they are available for use? If so, what kinds of gaps qualify (eg would space after the last partition be used?) [a note in the existing doc implies that the first partition *often* starts at (cyl=0,head=1,sector=0) rather than immediately after the MBR (cyl=0,head=0,sector=1), but not always] (*) if there aren't any gaps between partitions, then what does grub do? does it resize partitions? does it print an error message & give up? does it write the stage1.5 into the filesystem containing the boot partition? 2. What are the implications of "defrag"-type operations on a filesystem containing a stage2 (or a stage1.5 if these do get stored within filesystems)? Considering the stage1 or stage1.5 has a "block-list" pointing to it, I presume this is unhealthy... 3. Is there a copy of the "multiboot standard" document anywhere? 4. Where does GRUB get its file-system implementations from? Are they taken from linux/hurd/bsd, or rewrites? If taken from a kernel release, do they need to be modified to run in the GRUB environment (eg if grub doesn't have paging enabled)? Related issue: will GRUB support booting to ext3/jfs/jffs/etc partitions? 5. When invoking the kernel's entrypoint, is the CPU in 16-bit or 32-bit mode? 6. What exactly is the entry point to the GNUMACH kernel from grub? Yes, I know this isn't exactly a GRUB question, but it is related to Q6 above. Symbol boot_entry[i386/i386at/boothdr.S] looks a very likely candidate, provided that the transition to 32-bit mode has already happened. However, there is this critical variable "phys_mem_va" that appears to be initialised in only one place: function i16_init(void) in i16_init.c. I can't see how this 16-bit code could have been called, because the multiboot header defined in boothdr.S appears to tell grub that the entry point is boot_entry. But that phys_mem_va variable is pretty important! Can anyone help me out on this? Thanks in advance, Simon _______________________________________________ Bug-grub mailing list [EMAIL PROTECTED] http://mail.gnu.org/mailman/listinfo/bug-grub
