x86/fpu: Move math_state_restore() to fpu/core.c

It's another piece of FPU internals that is better off close to
the other FPU internals.

Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/fpu/core.c

@@ -227,6 +227,48 @@ static int fpu__unlazy_stopped(struct task_struct *child)
 	return 0;
 }
 
+/*
+ * 'math_state_restore()' saves the current math information in the
+ * old math state array, and gets the new ones from the current task
+ *
+ * Careful.. There are problems with IBM-designed IRQ13 behaviour.
+ * Don't touch unless you *really* know how it works.
+ *
+ * Must be called with kernel preemption disabled (eg with local
+ * local interrupts as in the case of do_device_not_available).
+ */
+void math_state_restore(void)
+{
+	struct task_struct *tsk = current;
+
+	if (!tsk_used_math(tsk)) {
+		local_irq_enable();
+		/*
+		 * does a slab alloc which can sleep
+		 */
+		if (fpstate_alloc_init(tsk)) {
+			/*
+			 * ran out of memory!
+			 */
+			do_group_exit(SIGKILL);
+			return;
+		}
+		local_irq_disable();
+	}
+
+	/* Avoid __kernel_fpu_begin() right after __thread_fpu_begin() */
+	kernel_fpu_disable();
+	__thread_fpu_begin(tsk);
+	if (unlikely(restore_fpu_checking(tsk))) {
+		fpu_reset_state(tsk);
+		force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
+	} else {
+		tsk->thread.fpu.counter++;
+	}
+	kernel_fpu_enable();
+}
+EXPORT_SYMBOL_GPL(math_state_restore);
+
 void fpu__flush_thread(struct task_struct *tsk)
 {
 	if (!use_eager_fpu()) {

arch/x86/kernel/traps.c

@@ -826,48 +826,6 @@ asmlinkage __visible void __attribute__((weak)) smp_threshold_interrupt(void)
 {
 }
 
-/*
- * 'math_state_restore()' saves the current math information in the
- * old math state array, and gets the new ones from the current task
- *
- * Careful.. There are problems with IBM-designed IRQ13 behaviour.
- * Don't touch unless you *really* know how it works.
- *
- * Must be called with kernel preemption disabled (eg with local
- * local interrupts as in the case of do_device_not_available).
- */
-void math_state_restore(void)
-{
-	struct task_struct *tsk = current;
-
-	if (!tsk_used_math(tsk)) {
-		local_irq_enable();
-		/*
-		 * does a slab alloc which can sleep
-		 */
-		if (fpstate_alloc_init(tsk)) {
-			/*
-			 * ran out of memory!
-			 */
-			do_group_exit(SIGKILL);
-			return;
-		}
-		local_irq_disable();
-	}
-
-	/* Avoid __kernel_fpu_begin() right after __thread_fpu_begin() */
-	kernel_fpu_disable();
-	__thread_fpu_begin(tsk);
-	if (unlikely(restore_fpu_checking(tsk))) {
-		fpu_reset_state(tsk);
-		force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
-	} else {
-		tsk->thread.fpu.counter++;
-	}
-	kernel_fpu_enable();
-}
-EXPORT_SYMBOL_GPL(math_state_restore);
-
 dotraplinkage void
 do_device_not_available(struct pt_regs *regs, long error_code)
 {