x86/asm/entry: Switch all C consumers of kernel_stack to this_cpu_sp0()

This will make modifying the semantics of kernel_stack easier.

The change to ist_begin_non_atomic() is necessary because sp0 no
longer points to the same THREAD_SIZE-aligned region as RSP;
it's one byte too high for that.  At Denys' suggestion, rather
than offsetting it, just check explicitly that we're in the
correct range ending at sp0.  This has the added benefit that we
no longer assume that the thread stack is aligned to
THREAD_SIZE.

Suggested-by: Denys Vlasenko <dvlasenk@redhat.com>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/ef8254ad414cbb8034c9a56396eeb24f5dd5b0de.1425611534.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 1d4e4f279a3281e094684ad29bd4b544d37af6ab..a2fa1899494eb2b3e0cc62554843aa43b4b44c8d 100644 (file)
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -159,8 +159,7 @@ 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 9965bd1916db95407e7687d6c6cb5ed38e4fffa1..fa290586ed3721fa526eeee22903ff30994622e2 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -174,8 +174,8 @@ 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))
-               & ~(THREAD_SIZE - 1)) != 0);
+       BUG_ON((unsigned long)(this_cpu_sp0() - current_stack_pointer()) >=
+              THREAD_SIZE);
 
        preempt_count_sub(HARDIRQ_OFFSET);
 }