Bit a bit, progress continues: I have some crappy UI semi-ready, to improve on later, and I'm now battling with the INT13h handler to perform the actual mapping - had to rescue the big old "Architecture Programmer's Manual" in order to do PIC code without the amd64 rip-relative addressing. However, I haven't yet found a way to install some kind of "hook" so that it will be called when the boot command is issued, preferable just before calling grub_X_real_boot. However, I didn't go to great lengths to find it... Anyone here willing to enlighten me or should I find my own way through the darkness (again ¬¬)? I'd like to change/add the smallest amount of code possible, but for the sake of modularity I prefer a pre-boot hook system rather than a one-time solution.
Habbit 2008/5/30 Pavel Roskin <[EMAIL PROTECTED]>: > Quoting Javier Martín <[EMAIL PROTECTED]>: > >> Then "drivemap" it is. I've already been delving into the depths of The >> Source, though I'd have preferred it to be commented a bit more >> exhaustively. Some times it's difficult to guess which methods to call, >> and it took me a bit to realize that I had to check with the disk >> "device" to see if it was a BIOS drive. Seems I had the wrong conception >> of what the disk "device" should be. > > I suggest a simple approach starting from what can be done. There will be a > small resident piece of code installed to intercept interrupt 0x13 and > replace the driver number according to the map. We should keep that code > simple. > > The resident code should go through the list of the mapped drives, and if > there is an entry in the table, replace the drive number. That's two bytes > for an entry. > > I think the user interface should operate directly on that unidirectional > map rather that with some complex swap rules that are translated to the map. > Sure, it won't be nice if some device is seen as two devices, especially if > the OS uses BIOS. But GRUB cannot prevent all stupid actions by users. > >> By the way, floppies are usually also "BIOS drives". Should the command >> filter them out as sources for mapping? I think so, because OS loaders >> usually have different code for reading floppies and HDs. Concretely, >> floppy code usually makes some assumptions about drive geometry, uses >> only old CHS-like interfaces, and some things more I cannot remember >> now... it's been long since I wrote anything distantly similar to a >> bootloader. > > We may still want to map a hard drive as a floppy. I can imagine that some > floppy readers may be seen as hard drives by the BIOS. > > I think it's not the most important thing at the moment. If there is a > substantial risk of data corruption due to floppy-to-hdd remapping or > duplicate drives, we can introduce extra safety checks. > > -- > Regards, > Pavel Roskin > > > _______________________________________________ > Grub-devel mailing list > Grub-devel@gnu.org > http://lists.gnu.org/mailman/listinfo/grub-devel >
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