powerpc: Introduce function emulate_math()

There are two invocations of do_mathemu() in traps.c. And the codes
in these two places are almost the same. Introduce a locale function
to eliminate the duplication. With this change we can also make sure
that in program_check_exception() the PPC_WARN_EMULATED is invoked for
the correctly emulated math instructions.
Signed-off-by: Kevin Hao <haokexin@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/traps.c

@@ -1055,11 +1055,41 @@ int is_valid_bugaddr(unsigned long addr)
 	return is_kernel_addr(addr);
 }
 
+#ifdef CONFIG_MATH_EMULATION
+static int emulate_math(struct pt_regs *regs)
+{
+	int ret;
+	extern int do_mathemu(struct pt_regs *regs);
+
+	ret = do_mathemu(regs);
+	if (ret >= 0)
+		PPC_WARN_EMULATED(math, regs);
+
+	switch (ret) {
+	case 0:
+		emulate_single_step(regs);
+		return 0;
+	case 1: {
+			int code = 0;
+			code = __parse_fpscr(current->thread.fpscr.val);
+			_exception(SIGFPE, regs, code, regs->nip);
+			return 0;
+		}
+	case -EFAULT:
+		_exception(SIGSEGV, regs, SEGV_MAPERR, regs->nip);
+		return 0;
+	}
+
+	return -1;
+}
+#else
+static inline int emulate_math(struct pt_regs *regs) { return -1; }
+#endif
+
 void __kprobes program_check_exception(struct pt_regs *regs)
 {
 	enum ctx_state prev_state = exception_enter();
 	unsigned int reason = get_reason(regs);
-	extern int do_mathemu(struct pt_regs *regs);
 
 	/* We can now get here via a FP Unavailable exception if the core
 	 * has no FPU, in that case the reason flags will be 0 */
@@ -1125,7 +1155,6 @@ void __kprobes program_check_exception(struct pt_regs *regs)
 	if (!arch_irq_disabled_regs(regs))
 		local_irq_enable();
 
-#ifdef CONFIG_MATH_EMULATION
 	/* (reason & REASON_ILLEGAL) would be the obvious thing here,
 	 * but there seems to be a hardware bug on the 405GP (RevD)
 	 * that means ESR is sometimes set incorrectly - either to
@@ -1134,22 +1163,8 @@ void __kprobes program_check_exception(struct pt_regs *regs)
 	 * instruction or only on FP instructions, whether there is a
 	 * pattern to occurrences etc. -dgibson 31/Mar/2003
 	 */
-	switch (do_mathemu(regs)) {
-	case 0:
-		emulate_single_step(regs);
-		goto bail;
-	case 1: {
-			int code = 0;
-			code = __parse_fpscr(current->thread.fpscr.val);
-			_exception(SIGFPE, regs, code, regs->nip);
-			goto bail;
-		}
-	case -EFAULT:
-		_exception(SIGSEGV, regs, SEGV_MAPERR, regs->nip);
+	if (!emulate_math(regs))
 		goto bail;
-	}
-	/* fall through on any other errors */
-#endif /* CONFIG_MATH_EMULATION */
 
 	/* Try to emulate it if we should. */
 	if (reason & (REASON_ILLEGAL | REASON_PRIVILEGED)) {
@@ -1428,11 +1443,6 @@ void performance_monitor_exception(struct pt_regs *regs)
 #ifdef CONFIG_8xx
 void SoftwareEmulation(struct pt_regs *regs)
 {
-	extern int do_mathemu(struct pt_regs *);
-#if defined(CONFIG_MATH_EMULATION)
-	int errcode;
-#endif
-
 	CHECK_FULL_REGS(regs);
 
 	if (!user_mode(regs)) {
@@ -1440,31 +1450,10 @@ void SoftwareEmulation(struct pt_regs *regs)
 		die("Kernel Mode Software FPU Emulation", regs, SIGFPE);
 	}
 
-#ifdef CONFIG_MATH_EMULATION
-	errcode = do_mathemu(regs);
-	if (errcode >= 0)
-		PPC_WARN_EMULATED(math, regs);
-
-	switch (errcode) {
-	case 0:
-		emulate_single_step(regs);
-		return;
-	case 1: {
-			int code = 0;
-			code = __parse_fpscr(current->thread.fpscr.val);
-			_exception(SIGFPE, regs, code, regs->nip);
-			return;
-		}
-	case -EFAULT:
-		_exception(SIGSEGV, regs, SEGV_MAPERR, regs->nip);
+	if (!emulate_math(regs))
 		return;
-	default:
-		_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
-		return;
-	}
-#else
+
 	_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
-#endif
 }
 #endif /* CONFIG_8xx */