On 02/27/2015 01:07 AM, Andy Lutomirski wrote:
> This will make modifying the semantics of kernel_stack easier.
>
> Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
> Cc: Boris Ostrovsky <boris.ostrov...@oracle.com>
> Cc: Rusty Russell <ru...@rustcorp.com.au>
> Signed-off-by: Andy Lutomirski <l...@amacapital.net>
> ---
> 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.
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