> The bigger problems are that X11 is subject to being killed with sig 9
> (which with a horrible kernel hack can be blocked for iopl3 processes)
Is that so horrible? If X is going to bang hardware like kernel code,
it may as well act like kernel code.
> The related problems are SAK - which is defined to kill all processes
> on that VT and out of resource kills from the kernel (oom()). SAK is
> not that big a deal - a setuid "sak signal" ioctl akin to the way you
> take over console switching covers it.
Yes, as long as X won't let a user remap SAK.
> I'd agree however - you don't need to put all mode switching code in
> kernel if you allow iopl3 proceses to lock out sig 9 and you provide
> a sak hook. Oom should be solvable its just harder
Oom is easy: mlockall()
If X is going to play with hardware, then mlockall() is simply the
correct solution. X already disables interrupts sometimes. X can use
DMA too then, though a system call to get physical addresses would help.
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