x86_32: introduce restore_fpu_checking()

Impact: cleanup, prepare FPU code unificaton

Like on x86_64, return an error from restore_fpu and kill the task
if it fails.

Also rename restore_fpu to restore_fpu_checking which allows ifdefs
to be removed in math_state_restore().

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
LKML-Reference: <1239190320-23952-1-git-send-email-jirislaby@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/include/asm/i387.h

@@ -185,12 +185,10 @@ static inline void tolerant_fwait(void)
 	asm volatile("fnclex ; fwait");
 }
 
-static inline void restore_fpu(struct task_struct *tsk)
+static inline int restore_fpu_checking(struct task_struct *tsk)
 {
-	if (task_thread_info(tsk)->status & TS_XSAVE) {
-		xrstor_checking(&tsk->thread.xstate->xsave);
-		return;
-	}
+	if (task_thread_info(tsk)->status & TS_XSAVE)
+		return xrstor_checking(&tsk->thread.xstate->xsave);
 	/*
 	 * The "nop" is needed to make the instructions the same
 	 * length.
@@ -200,6 +198,7 @@ static inline void restore_fpu(struct task_struct *tsk)
 		"fxrstor %1",
 		X86_FEATURE_FXSR,
 		"m" (tsk->thread.xstate->fxsave));
+	return 0;
 }
 
 /* We need a safe address that is cheap to find and that is already

arch/x86/kernel/traps.c

@@ -839,9 +839,6 @@ asmlinkage void math_state_restore(void)
 	}
 
 	clts();				/* Allow maths ops (or we recurse) */
-#ifdef CONFIG_X86_32
-	restore_fpu(tsk);
-#else
 	/*
 	 * Paranoid restore. send a SIGSEGV if we fail to restore the state.
 	 */
@@ -850,7 +847,7 @@ asmlinkage void math_state_restore(void)
 		force_sig(SIGSEGV, tsk);
 		return;
 	}
-#endif
+
 	thread->status |= TS_USEDFPU;	/* So we fnsave on switch_to() */
 	tsk->fpu_counter++;
 }