Hi Ed, > For example, if the kernel tries to write through an invalid pointer, > you get something predictable like an oops. That's because the MMU > catches the invalid address, even though the CPU is in superuser mode. > Then do_page_fault runs and handles the kernel bug. So the kernel uses paging too? What is the reason/benefit for doing so? Is it so the kernel doesn't have to turn paging off and on when going back and forth between kernel and user mode? > I don't think you can do this: > > *(__pa(p)) = 100; > > ... because (in lowmem x86), that __pa macro is going to subtract > 0xc0000000 from the (virtual) address, meaning that it's now a > userland address! But the addresses from pgd_offset and pmd_offset don't call __va() before returning the value, so that means what they return is a physical address, right? > It's not magic. The translations for addresses greater than > 0xC0000000 are in the TLB and the page tables just like the others. Where is this set up? Is it in head.S? Thanks, Kirk -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
