microblaze: Simplify syscall rutine

Syscall can be called only from userspace that's why
we don't need to check which space kernel come from.

Kernel syscall calling is not check and shouldn't come
throught this part of code.
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/kernel/entry.S

@@ -318,42 +318,23 @@
  * are masked. This is nice, means we don't have to CLI before state save
  */
 C_ENTRY(_user_exception):
-	swi	r1, r0, TOPHYS(PER_CPU(ENTRY_SP)) /* save stack */
 	addi	r14, r14, 4	/* return address is 4 byte after call */
+	swi	r1, r0, TOPHYS(PER_CPU(ENTRY_SP)) /* save stack */
 
-	mfs	r1, rmsr
-	nop
-	andi	r1, r1, MSR_UMS
-	bnei	r1, 1f
-
-/* Kernel-mode state save - kernel execve */
-	lwi	r1, r0, TOPHYS(PER_CPU(ENTRY_SP)); /* Reload kernel stack-ptr*/
-	tophys(r1,r1);
-
-	addik	r1, r1, -STATE_SAVE_SIZE; /* Make room on the stack. */
-	SAVE_REGS
-
-	swi	r1, r1, PTO + PT_MODE; /* pt_regs -> kernel mode */
-	brid	2f;
-	nop;				/* Fill delay slot */
-
-/* User-mode state save.  */
-1:
 	lwi	r1, r0, TOPHYS(PER_CPU(CURRENT_SAVE)); /* get saved current */
 	tophys(r1,r1);
 	lwi	r1, r1, TS_THREAD_INFO;	/* get stack from task_struct */
-/* calculate kernel stack pointer from task struct 8k */
-	addik	r1, r1, THREAD_SIZE;
-	tophys(r1,r1);
-
-	addik	r1, r1, -STATE_SAVE_SIZE; /* Make room on the stack.  */
+	/* MS these three instructions can be added to one */
+	/* addik	r1, r1, THREAD_SIZE; */
+	/* tophys(r1,r1); */
+	/* addik	r1, r1, -STATE_SAVE_SIZE; */
+	addik r1, r1, THREAD_SIZE + CONFIG_KERNEL_BASE_ADDR - CONFIG_KERNEL_START - STATE_SAVE_SIZE;
 	SAVE_REGS
 
-	swi	r0, r1, PTO + PT_MODE;			/* Was in user-mode. */
 	lwi	r11, r0, TOPHYS(PER_CPU(ENTRY_SP));
 	swi	r11, r1, PTO+PT_R1;		/* Store user SP.  */
 	clear_ums;
-2:	lwi	CURRENT_TASK, r0, TOPHYS(PER_CPU(CURRENT_SAVE));
+	lwi	CURRENT_TASK, r0, TOPHYS(PER_CPU(CURRENT_SAVE));
 	/* Save away the syscall number.  */
 	swi	r12, r1, PTO+PT_R0;
 	tovirt(r1,r1)
@@ -423,9 +404,6 @@ C_ENTRY(ret_from_trap):
 	swi	r3, r1, PTO + PT_R3
 	swi	r4, r1, PTO + PT_R4
 
-	lwi	r11, r1, PTO + PT_MODE;
-/* See if returning to kernel mode, if so, skip resched &c.  */
-	bnei	r11, 2f;
 	/* We're returning to user mode, so check for various conditions that
 	 * trigger rescheduling. */
 	/* FIXME: Restructure all these flag checks. */
@@ -468,16 +446,6 @@ C_ENTRY(ret_from_trap):
 	RESTORE_REGS;
 	addik	r1, r1, STATE_SAVE_SIZE		/* Clean up stack space.  */
 	lwi	r1, r1, PT_R1 - PT_SIZE;/* Restore user stack pointer. */
-	bri	6f;
-
-/* Return to kernel state.  */
-2:	set_bip;			/*  Ints masked for state restore */
-	VM_OFF;
-	tophys(r1,r1);
-	RESTORE_REGS;
-	addik	r1, r1, STATE_SAVE_SIZE		/* Clean up stack space.  */
-	tovirt(r1,r1);
-6:
 TRAP_return:		/* Make global symbol for debugging */
 	rtbd	r14, 0;	/* Instructions to return from an IRQ */
 	nop;