microblaze: switch to generic kernel_thread()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/microblaze/Kconfig

@@ -26,6 +26,7 @@ config MICROBLAZE
 	select GENERIC_ATOMIC64
 	select GENERIC_CLOCKEVENTS
 	select MODULES_USE_ELF_RELA
+	select GENERIC_KERNEL_THREAD
 
 config SWAP
 	def_bool n

arch/microblaze/include/asm/processor.h

@@ -31,6 +31,7 @@ extern const struct seq_operations cpuinfo_op;
 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long usp);
 
 extern void ret_from_fork(void);
+extern void ret_from_kernel_thread(void);
 
 # endif /* __ASSEMBLY__ */
 
@@ -78,11 +79,6 @@ extern unsigned long thread_saved_pc(struct task_struct *t);
 
 extern unsigned long get_wchan(struct task_struct *p);
 
-/*
- * create a kernel thread without removing it from tasklists
- */
-extern int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
-
 # define KSTK_EIP(tsk)	(0)
 # define KSTK_ESP(tsk)	(0)
 
@@ -131,8 +127,6 @@ extern inline void release_thread(struct task_struct *dead_task)
 {
 }
 
-extern int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
-
 /* Free current thread data structures etc.  */
 static inline void exit_thread(void)
 {

arch/microblaze/kernel/entry-nommu.S

@@ -474,6 +474,14 @@ ENTRY(ret_from_fork)
 	brid	ret_to_user
 	nop
 
+ENTRY(ret_from_kernel_thread)
+	brlid	r15, schedule_tail
+	addk	r5, r0, r3
+	brald	r15, r20
+	addk	r5, r0, r19
+	brid	sys_exit	/* won't be returning... */
+	addk	r5, r0, r0
+
 work_pending:
 	enable_irq
 

arch/microblaze/kernel/entry.S

@@ -484,6 +484,15 @@ C_ENTRY(ret_from_fork):
 	brid	ret_from_trap;	/* Do normal trap return */
 	add	r3, r0, r0;	/* Child's fork call should return 0. */
 
+C_ENTRY(ret_from_kernel_thread):
+	bralid	r15, schedule_tail; /* ...which is schedule_tail's arg */
+	add	r5, r3, r0;	/* switch_thread returns the prev task */
+				/* ( in the delay slot ) */
+	brald	r15, r20	/* fn was left in r20 */
+	addk	r5, r0, r19	/* ... and argument - in r19 */
+	brid	sys_exit	/* won't be returning... */
+	addk	r5, r0, r0
+
 C_ENTRY(sys_vfork):
 	brid	microblaze_vfork	/* Do real work (tail-call) */
 	addik	r5, r1, 0

arch/microblaze/kernel/process.c

@@ -119,46 +119,38 @@ void flush_thread(void)
 }
 
 int copy_thread(unsigned long clone_flags, unsigned long usp,
-		unsigned long unused,
+		unsigned long arg,
 		struct task_struct *p, struct pt_regs *regs)
 {
 	struct pt_regs *childregs = task_pt_regs(p);
 	struct thread_info *ti = task_thread_info(p);
 
+	if (unlikely(p->flags & PF_KTHREAD)) {
+		/* if we're creating a new kernel thread then just zeroing all
+		 * the registers. That's OK for a brand new thread.*/
+		memset(childregs, 0, sizeof(struct pt_regs));
+		memset(&ti->cpu_context, 0, sizeof(struct cpu_context));
+		ti->cpu_context.r1  = (unsigned long)childregs;
+		ti->cpu_context.r20 = (unsigned long)usp; /* fn */
+		ti->cpu_context.r19 = (unsigned long)arg;
+		childregs->pt_mode = 1;
+		local_save_flags(childregs->msr);
+#ifdef CONFIG_MMU
+		ti->cpu_context.msr = childregs->msr & ~MSR_IE;
+#endif
+		ti->cpu_context.r15 = (unsigned long)ret_from_kernel_thread - 8;
+		return 0;
+	}
 	*childregs = *regs;
-	if (user_mode(regs))
-		childregs->r1 = usp;
-	else
-		childregs->r1 = ((unsigned long) ti) + THREAD_SIZE;
+	childregs->r1 = usp;
 
-#ifndef CONFIG_MMU
 	memset(&ti->cpu_context, 0, sizeof(struct cpu_context));
 	ti->cpu_context.r1 = (unsigned long)childregs;
+#ifndef CONFIG_MMU
 	ti->cpu_context.msr = (unsigned long)childregs->msr;
 #else
+	childregs->msr |= MSR_UMS;
 
-	/* if creating a kernel thread then update the current reg (we don't
-	 * want to use the parent's value when restoring by POP_STATE) */
-	if (kernel_mode(regs))
-		/* save new current on stack to use POP_STATE */
-		childregs->CURRENT_TASK = (unsigned long)p;
-	/* if returning to user then use the parent's value of this register */
-
-	/* if we're creating a new kernel thread then just zeroing all
-	 * the registers. That's OK for a brand new thread.*/
-	/* Pls. note that some of them will be restored in POP_STATE */
-	if (kernel_mode(regs))
-		memset(&ti->cpu_context, 0, sizeof(struct cpu_context));
-	/* if this thread is created for fork/vfork/clone, then we want to
-	 * restore all the parent's context */
-	/* in addition to the registers which will be restored by POP_STATE */
-	else {
-		ti->cpu_context = *(struct cpu_context *)regs;
-		childregs->msr |= MSR_UMS;
-	}
-
-	/* FIXME STATE_SAVE_PT_OFFSET; */
-	ti->cpu_context.r1  = (unsigned long)childregs;
 	/* we should consider the fact that childregs is a copy of the parent
 	 * regs which were saved immediately after entering the kernel state
 	 * before enabling VM. This MSR will be restored in switch_to and
@@ -209,29 +201,6 @@ unsigned long thread_saved_pc(struct task_struct *tsk)
 }
 #endif
 
-static void kernel_thread_helper(int (*fn)(void *), void *arg)
-{
-	fn(arg);
-	do_exit(-1);
-}
-
-int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
-{
-	struct pt_regs regs;
-
-	memset(&regs, 0, sizeof(regs));
-	/* store them in non-volatile registers */
-	regs.r5 = (unsigned long)fn;
-	regs.r6 = (unsigned long)arg;
-	local_save_flags(regs.msr);
-	regs.pc = (unsigned long)kernel_thread_helper;
-	regs.pt_mode = 1;
-
-	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0,
-			&regs, 0, NULL, NULL);
-}
-EXPORT_SYMBOL_GPL(kernel_thread);
-
 unsigned long get_wchan(struct task_struct *p)
 {
 /* TBD (used by procfs) */