cpu_get_pgd()

There's a call to cpu_get_pgd() from do_translation_fault() that reads the TTBR to reach the pgd pointer.

Why not use pgd_offset(current->mm, addr)?

Thanks,

Bahadir

Because current->mm might not refer to the page table which is currently being used by the hardware. Think about this sequence:

task = current
schedule()
next = some_other_task
switch_mm(next)
IRQ occurs, handler is in a module which is unmapped in next's mm but exists in task's mm
prefetch fault occurs

Now at this point, if we look at current->mm, we find that the entry exists. If we used this, and just returned, we'd repeat the prefetch fault, and make no progress.

So we have to read the page tables which the hardware is currently using to ensure that we update the right set of page tables.