On Thu, Sep 17, 2015 at 11:33:44AM +0100, James Morse wrote:
> Hi Will,
>
> On 16/09/15 12:25, Will Deacon wrote:
> > On Sun, Sep 13, 2015 at 03:42:17PM +0100, Jungseok Lee wrote:
> >> diff --git a/arch/arm64/include/asm/thread_info.h
> >> b/arch/arm64/include/asm/thread_info.h
> >> index dcd06d1..44839c0 100644
> >> --- a/arch/arm64/include/asm/thread_info.h
> >> +++ b/arch/arm64/include/asm/thread_info.h
> >> @@ -73,8 +73,11 @@ static inline struct thread_info
> >> *current_thread_info(void) __attribute_const__;
> >>
> >> static inline struct thread_info *current_thread_info(void)
> >> {
> >> - return (struct thread_info *)
> >> - (current_stack_pointer & ~(THREAD_SIZE - 1));
> >> + unsigned long sp_el0;
> >> +
> >> + asm volatile("mrs %0, sp_el0" : "=r" (sp_el0));
> >> +
> >> + return (struct thread_info *)(sp_el0 & ~(THREAD_SIZE - 1));
> >
> > This looks like it will generate worse code than our current implementation,
> > thanks to the asm volatile. Maybe just add something like a global
> > current_stack_pointer_el0?
>
> Like current_stack_pointer does?:
> > register unsigned long current_stack_pointer_el0 asm ("sp_el0");
>
> Unfortunately the compiler won't accept this, as it doesn't like the
> register name, it also won't accept instructions in this asm string.
But once we do SPSel = 0, can we not just use the SP register here?
(I haven't read the rest of the patch yet)
--
Catalin
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