On Feb 27, 2015 8:13 AM, "Denys Vlasenko" <[email protected]> wrote: > > On 02/27/2015 01:07 AM, Andy Lutomirski wrote: > > This will make modifying the semantics of kernel_stack easier. > > > > Cc: Konrad Rzeszutek Wilk <[email protected]> > > Cc: Boris Ostrovsky <[email protected]> > > Cc: Rusty Russell <[email protected]> > > Signed-off-by: Andy Lutomirski <[email protected]> > > --- > > arch/x86/include/asm/thread_info.h | 3 +-- > > arch/x86/kernel/traps.c | 2 +- > > 2 files changed, 2 insertions(+), 3 deletions(-) > > > > diff --git a/arch/x86/include/asm/thread_info.h > > b/arch/x86/include/asm/thread_info.h > > index e82e95abc92b..92549053d86d 100644 > > --- a/arch/x86/include/asm/thread_info.h > > +++ b/arch/x86/include/asm/thread_info.h > > @@ -163,8 +163,7 @@ DECLARE_PER_CPU(unsigned long, kernel_stack); > > static inline struct thread_info *current_thread_info(void) > > { > > struct thread_info *ti; > > - ti = (void *)(this_cpu_read_stable(kernel_stack) + > > - KERNEL_STACK_OFFSET - THREAD_SIZE); > > + ti = (void *)(this_cpu_sp0() - THREAD_SIZE); > > return ti; > > } > > > > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > > index c74f2f5652da..d287ea779728 100644 > > --- a/arch/x86/kernel/traps.c > > +++ b/arch/x86/kernel/traps.c > > @@ -174,7 +174,7 @@ void ist_begin_non_atomic(struct pt_regs *regs) > > * will catch asm bugs and any attempt to use ist_preempt_enable > > * from double_fault. > > */ > > - BUG_ON(((current_stack_pointer() ^ this_cpu_read_stable(kernel_stack)) > > + BUG_ON(((current_stack_pointer() ^ (this_cpu_sp0() - 1)) > > & ~(THREAD_SIZE - 1)) != 0); > > While we are at it, I propose a more readable version of this check: > > BUG_ON(this_cpu_sp0() - current_stack_pointer() >= THREAD_SIZE); > > Yes, I am aware that it is not equivalent to the existing condition > - it uses the fact that this_cpu_sp0(), previous check > wasn't making that assumption. But that assumption is true, > so shouldn't be a problem.
You're missing an absolute value in here, though. This isn't a check for overflow; it's a check that we aren't on an IST or other per cpu stack. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
