On Wed, May 25, 2016 at 09:29:27AM -0400, Dave Anderson wrote: > > > ----- Original Message ----- > > On Tue, May 24, 2016 at 09:35:54AM -0400, Dave Anderson wrote: > > > > > > > > > ----- Original Message ----- > > > > > > > > > > > > Now that PHYS_OFFSET is defined as "memstart_addr", we can get the > > > > > > value > > > > > > if we can access this symbol (on a live system). > > > > > > > > > > When PHYS_OFFSET/memstart_addr is bumped up from the actual base of > > > > > physical > > > > > memory, is the physical memory below it no longer used/accessible? > > > > > > > > Yes, it is! That is what Ard has managed to do in his series of > > > > KASLR-related patches. > > > > > > How is it accessed via a kernel virtual address? Or is only accessible > > > when > > > mapped into a vmalloc() or user-space address? > > > > Through a linear(unity) mapping above PAGE_OFFSET. > > I'm still confused... > > Does PAGE_OFFSET+0 still refer to PHYS_OFFSET?
No, it doesn't if CONFIG_RANDOMIZE_RAM. See a kernel boot message about "Virtual kernel memory layout" That is why PHYS_OFFSET can now be negative. Thanks, Tahahiro AKASHI > I'm trying to wrap my head around > how __virt_to_phys() would work for the memory below the bumped-up > PHYS_OFFSET. > > Dave > > > > > -- > Crash-utility mailing list > Crash-utility@redhat.com > https://www.redhat.com/mailman/listinfo/crash-utility -- Thanks, -Takahiro AKASHI -- Crash-utility mailing list Crash-utility@redhat.com https://www.redhat.com/mailman/listinfo/crash-utility
