On Sat, Aug 06, 2016 at 09:15:30AM -0400, Brian Gerst wrote: > On Sat, Aug 6, 2016 at 1:25 AM, Borislav Petkov <b...@alien8.de> wrote: > > On Fri, Aug 05, 2016 at 11:01:57AM -0500, Josh Poimboeuf wrote: > >> The 8 should be changed to SIZEOF_PTREGS in a later patch > >> ("x86/asm/head: standardize the end of the stack for idle tasks"). > > > > But SIZEOF_PTREGS is 21*8. I don't understand. > > This patch is only for the boot cpu's idle thread. All other kernel > threads, including idle threads for the secondary cpus, already have > the pt_regs area reserved.
Ah, you're right, it does only affect the boot CPU's idle thread. (To be clear, I think you're talking about patch 41/44, and not the temporary stack for the verify_cpu() call which I referred to above.) > My best guess for the current 8 byte > padding is to make sure thread_info is calculated properly (by masking > off the low bits from RSP). > > Also, this fix should be applied to 32-bit, but make sure to account > for TOP_OF_KERNEL_STACK_PADDING. Ok. -- Josh