Messages in this thread | | | Date | Sat, 28 Mar 1998 15:06:54 +0100 (CET) | From | Marek Habersack <> | Subject | Re: GGI Project Unhappy On Linux |
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On Sat, 28 Mar 1998, Matthew Kirkwood wrote:
> > > A process running at ring 0 can still disable interrupts, DMA into > > > kernel memory, etc... > > > > But the Xserver isn't running in the kernel mode. > > I may have missed something, but the difference between iopl 3 and "kernel > mode" is...? Hmm... It's enormous. The ring-0 code can do anything to your machine including memory management, LDT/GDT/IDT management, virtual memory management - everything your CPU and your hardware is capable of. The IOPL 3 merely (yeah...) allows the application to output to any of the ports of your hardware. That can crash the system, but usually the application are not allowed to access ALL ports - the IOPL at the end of the TSS is used to enable/disable access to the hardware ports. So the graphics application is allowed to trash only the video card registers - that can only hurt your display (unless your video card is buggy and freezes the bus ;-))
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