From: Michal Suchánek > Sent: 09 May 2019 14:38 ... > > The problem is the combination of some new code called via printk(), > > check_pointer() which calls probe_kernel_read(). That then calls > > allow_user_access() (PPC_KUAP) and that uses mmu_has_feature() too early > > (before we've patched features). > > There is early_mmu_has_feature for this case. mmu_has_feature does not > work before patching so parts of kernel that can run before patching > must use the early_ variant which actually runs code reading the > feature bitmap to determine the answer. Does the early_ variant get patched so the it is reasonably efficient after the 'patching' is done? Or should there be a third version which gets patched across? David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
