Messages in this thread | | | Date | Sat, 18 Jul 1998 00:59:03 +0200 (MET DST) | From | MOLNAR Ingo <> | Subject | Re: I/O permissions for V86 tasks (Enhanced V86 Mode)? |
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On Fri, 17 Jul 1998, Kendall Bennett wrote:
> Now this means that the kernel *could* be modified such that the I/O > bitmap is not allocated at all by default for a task, and the > allocation of the I/O bitmap is staved off until a task calls the > ioperm() system call. [...]
the problem is that the ->iomap pointer within the TSS is only 16 bits :( This means we'd have to allocate the bitmap within 64k of the address of the (already allocated) task structure. It's highly unlikely that this can be done cleanly :( Maybe we could 'relocate' the task, but this is way too much work and complexity, as all possible data structures that somehow might reference this task have to be fixed up.
a better solution is to add a new CLONE_ flag, which says that the new task should have an 8k IO bitmap. (this is quite easy, we just have to allocate 4 pages when creating the new task, instead of the current 2)
there is a cleanliness issue here though, this really does not belong to CLONE_ flags, but i have no better idea how to tell the kernel that we need an 8k bitmap for that given task ...
-- mingo
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