On Mon, 2013-08-05 at 23:55 +0200, Laszlo Ersek wrote: > On 08/05/13 23:41, Borislav Petkov wrote: > > On Mon, Aug 05, 2013 at 02:37:08PM -0700, H. Peter Anvin wrote: > >> All of this would be a non-problem if there weren't buggy > >> implementations which can't run *without* SetVirtualAddressMap(). > > > > Oh, you mean, if we were to call the runtime services through their > > physical addresses? > > I heard that there was a (U)EFI firmware implementation that didn't even > implement SetVirtualAddressMap(). It was okay because the main OS for > that platform didn't want to call it, it thunked to physical mode for > each runtime service call. > > (This is not hearsay; I'm omitting the specifics because I'm not sure if > I'm allowed to give any. I've heard about this stuff from a direct > colleague who used to work on these systems.) That's actually the way all non-x86 unix systems operate. If you look in the firmware mechanisms for almost every non-x86 system in the Linux kernel architecture directories they do this if they have to access firmware from Linux (we do it a lot on parisc to get the IODC to give us the device inventory for instance). I strongly suspect the origin of this weirdness is that once upon a time windows didn't run with a separated address space and so needed a way of accessing firmware in the same address space, hence the pointer relocation trick, but even windows hasn't needed this for a while. James -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
