x86/traps: Use a new on_thread_stack() helper to clean up an assertion

commit 3383642c2f9d4f5b4fa37436db4a109a1a10018c upstream.

Let's keep the stack-related logic together rather than open-coding
a comparison in an assertion in the traps code.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/856b15bee1f55017b8f79d3758b0d51c48a08cf8.1509609304.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 5c090050f75cd01bc7ef2573e8965c54e91b6c41..2db7cf720b04b2d067df4f3138f2914de0e5cc0f 100644 (file)
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -542,6 +542,12 @@ static inline unsigned long current_top_of_stack(void)
 #endif
 }
 
+static inline bool on_thread_stack(void)
+{
+       return (unsigned long)(current_top_of_stack() -
+                              current_stack_pointer) < THREAD_SIZE;
+}
+
 #ifdef CONFIG_PARAVIRT
 #include <asm/paravirt.h>
 #else

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 5a6b8f809792bfb1de41063ad3247d53b2f54537..d366adfc61dabe19e7d82cc522fe2835502e4ee1 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -141,8 +141,7 @@ 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((unsigned long)(current_top_of_stack() -
-                              current_stack_pointer) >= THREAD_SIZE);
+       BUG_ON(!on_thread_stack());
 
        preempt_enable_no_resched();
 }