Chagas, Jason writes:
> That's right, 'pgd' is a pointer to the translation table (TB) and 'address'
> contains the virtual address being mapped. Shifting the virtual address
> [right] by 18 (the most significant 11 bits - 31-20) yield the address of
> first-level descriptor in the translation table with the first two least
> significant bits (1-0) set to zero. Oddly enough, the function below is
> shifts by 20. I just wondering if anyone could explain it to me...
It is correct. sizeof(mm->pgd) = 4, so adding an integer to the pointer
actually does the equivalent of (int)(mm->pgd) + 4*(integer), which will
give you your 18 ( (a >> 20) * 4 == (a >> 18) with bottom two bits cleared)
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