On 11/29/17 09:48, Borislav Petkov wrote: > On Wed, Nov 29, 2017 at 08:08:31PM +0300, Kirill A. Shutemov wrote: >> We're really early in the boot -- startup_64 in decompression code -- and >> I don't know a way print a message there. Is there a way? >> >> no_longmode handled by just hanging the machine. Is it enough for no_la57 >> case too? > > Patch pls. > I don't think there is any way to get a message out here. It's too late to use the firmware, and too early to use anything native. no_longmode in startup_64 is an oxymoron -- it simply can't happen, although of course we can enter at the 32-bit entry point with that problem. We can hang the machine, or we can triple-fault it in the hope of triggering a reset, and that way if the bootloader has been configured with a backup kernel there is a hope of recovery. Triple-faulting is trivial: push $0 push $0 lidt (%rsp) /* %esp for 32-bit mode */ ud2 /* WTF? */ 1: hlt jmp 1b This will either hang the machine or reboot it, depending on if the reboot-on-triple-fault logic in the chipset actually works. -hpa -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
