Linus Torvalds <torva...@linux-foundation.org> writes: > On Tue, Sep 29, 2015 at 1:35 PM, Andy Lutomirski <l...@amacapital.net> wrote: >> >> Does anyone know what happens if you stick a non-accessed segment in >> the GDT, map the GDT RO, and access it? > > You should get a #PF, as you guess, but go ahead and test it if you > want to make sure.
I tested this by accident once when workinng on what has become known as coreboot. Early in boot with your GDT in a EEPROM switching from real mode to 32bit protected mode causes a write and locks up the machine when the hardware declines the write to the GDT to set the accessed bit. As I recall the write kept being retried and retried and retried... Setting the access bit in the GDT cleared up the problem and I did not look back. Way up in 64bit mode something might be different, but I don't know why cpu designeres would waste the silicon. Eric -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
