On Wed, Nov 1, 2017 at 3:23 AM, Borislav Petkov <[email protected]> wrote: > On Thu, Oct 26, 2017 at 01:26:49AM -0700, Andy Lutomirski wrote: >> On x86_64, we can easily calculate sp0 when needed instead of >> storing it in thread_struct. >> >> On x86_32, a similar cleanup would be possible, but it would require >> cleaning up the vm86 code first, and that can wait for a later >> cleanup series. >> >> Signed-off-by: Andy Lutomirski <[email protected]> > > ... > >> @@ -816,23 +825,6 @@ static inline void spin_lock_prefetch(const void *x) >> .addr_limit = KERNEL_DS, \ >> } >> >> -/* >> - * TOP_OF_KERNEL_STACK_PADDING reserves 8 bytes on top of the ring0 stack. >> - * This is necessary to guarantee that the entire "struct pt_regs" >> - * is accessible even if the CPU haven't stored the SS/ESP registers >> - * on the stack (interrupt gate does not save these registers >> - * when switching to the same priv ring). >> - * Therefore beware: accessing the ss/esp fields of the >> - * "struct pt_regs" is possible, but they may contain the >> - * completely wrong values. >> - */ > > Why are we removing the explaination of TOP_OF_KERNEL_STACK_PADDING? Is > that going to change later?
There's another nearly identical explanatory comment, so it seemed redundant.
