mn10300: split ret_from_fork, simplify kernel_thread()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

5 files changed, 27 insertions, 71 deletions

diff --git a/arch/mn10300/kernel/Makefile b/arch/mn10300/kernel/Makefile
index d06749173d6..142c1290668 100644
--- a/arch/mn10300/kernel/Makefile
+++ b/arch/mn10300/kernel/Makefile
@@ -7,7 +7,7 @@ fpu-obj-y := fpu-nofpu.o fpu-nofpu-low.o
 fpu-obj-$(CONFIG_FPU) := fpu.o fpu-low.o
 
 obj-y   := process.o signal.o entry.o traps.o irq.o \
-           ptrace.o setup.o time.o sys_mn10300.o io.o kthread.o \
+           ptrace.o setup.o time.o sys_mn10300.o io.o \
            switch_to.o mn10300_ksyms.o kernel_execve.o $(fpu-obj-y) \
            csrc-mn10300.o cevt-mn10300.o
 
diff --git a/arch/mn10300/kernel/entry.S b/arch/mn10300/kernel/entry.S
index 8e11f9f4899..000f144230a 100644
--- a/arch/mn10300/kernel/entry.S
+++ b/arch/mn10300/kernel/entry.S
@@ -55,6 +55,13 @@ ENTRY(ret_from_fork)
         mov     d0,(REG_D0,fp)
         jmp     syscall_exit
 
+ENTRY(ret_from_kernel_thread)
+        call    schedule_tail[],0
+        mov     (REG_D0,fp),d0
+        mov     (REG_A0,fp),a0
+        calls   (a0)
+        jmp     sys_exit
+
 ###############################################################################
 #
 # system call handler
diff --git a/arch/mn10300/kernel/internal.h b/arch/mn10300/kernel/internal.h
index 2df440105a8..561785581f6 100644
--- a/arch/mn10300/kernel/internal.h
+++ b/arch/mn10300/kernel/internal.h
@@ -15,14 +15,10 @@ struct clocksource;
 struct clock_event_device;
 
 /*
- * kthread.S
- */
-extern int kernel_thread_helper(int);
-
-/*
  * entry.S
  */
 extern void ret_from_fork(struct task_struct *) __attribute__((noreturn));
+extern void ret_from_kernel_thread(struct task_struct *) __attribute__((noreturn));
 
 /*
  * smp-low.S
diff --git a/arch/mn10300/kernel/kthread.S b/arch/mn10300/kernel/kthread.S
deleted file mode 100644
index b5ae467ac5e..00000000000
--- a/arch/mn10300/kernel/kthread.S
+++ /dev/null
@@ -1,31 +0,0 @@
-/* MN10300 Kernel thread trampoline function
- *
- * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
- * Written by Mark Salter (msalter@redhat.com)
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public Licence
- * as published by the Free Software Foundation; either version
- * 2 of the Licence, or (at your option) any later version.
- */
-        .text
-
-###############################################################################
-#
-# kernel_thread_helper - trampoline for kernel_thread()
-#
-# On entry:
-#   A2 = address of function to call
-#   D2 = function argument
-#
-###############################################################################
-        .globl  kernel_thread_helper
-        .type   kernel_thread_helper,@function
-kernel_thread_helper:
-        mov     do_exit,d1
-        mov     d1,(sp)
-        mov     d1,mdr
-        mov     d2,d0
-        jmp     (a2)
-
-        .size   kernel_thread_helper,.-kernel_thread_helper
diff --git a/arch/mn10300/kernel/process.c b/arch/mn10300/kernel/process.c
index 7dab0cd3646..be87fbee4da 100644
--- a/arch/mn10300/kernel/process.c
+++ b/arch/mn10300/kernel/process.c
@@ -166,13 +166,11 @@ void show_regs(struct pt_regs *regs)
  */
 int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 {
-        struct pt_regs regs;
+        struct pt_regs regs = {
+                .a0 = (unsigned long) fn;
+                .d0 = (unsigned long) arg;
+        };
 
-        memset(&regs, 0, sizeof(regs));
-
-        regs.a2 = (unsigned long) fn;
-        regs.d2 = (unsigned long) arg;
-        regs.pc = (unsigned long) kernel_thread_helper;
         local_save_flags(regs.epsw);
         regs.epsw |= EPSW_IE | EPSW_IM_7;
 
@@ -180,7 +178,6 @@ int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
         return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0,
                        NULL, NULL);
 }
-EXPORT_SYMBOL(kernel_thread);
 
 /*
  * free current thread data structures etc..
@@ -227,49 +224,36 @@ int copy_thread(unsigned long clone_flags,
                 struct task_struct *p, struct pt_regs *kregs)
 {
         struct thread_info *ti = task_thread_info(p);
-        struct pt_regs *c_uregs, *c_kregs, *uregs;
+        struct pt_regs *c_regs;
         unsigned long c_ksp;
 
-        uregs = current->thread.uregs;
-
         c_ksp = (unsigned long) task_stack_page(p) + THREAD_SIZE;
 
         /* allocate the userspace exception frame and set it up */
         c_ksp -= sizeof(struct pt_regs);
-        c_uregs = (struct pt_regs *) c_ksp;
+        c_regs = (struct pt_regs *) c_ksp;
 
-        p->thread.uregs = c_uregs;
-        *c_uregs = *uregs;
-        c_uregs->sp = c_usp;
-        c_uregs->epsw &= ~EPSW_FE; /* my FPU */
+        p->thread.uregs = c_regs;
+        *c_regs = *kregs;
+        c_regs->sp = c_usp;
+        c_regs->epsw &= ~EPSW_FE; /* my FPU */
 
         c_ksp -= 12; /* allocate function call ABI slack */
 
         /* the new TLS pointer is passed in as arg #5 to sys_clone() */
         if (clone_flags & CLONE_SETTLS)
-                c_uregs->e2 = current_frame()->d3;
-
-        /* set up the return kernel frame if called from kernel_thread() */
-        c_kregs = c_uregs;
-        if (kregs != uregs) {
-                c_ksp -= sizeof(struct pt_regs);
-                c_kregs = (struct pt_regs *) c_ksp;
-                *c_kregs = *kregs;
-                c_kregs->sp = c_usp;
-                c_kregs->next = c_uregs;
-#ifdef CONFIG_MN10300_CURRENT_IN_E2
-                c_kregs->e2 = (unsigned long) p; /* current */
-#endif
+                c_regs->e2 = current_frame()->d3;
 
-                c_ksp -= 12; /* allocate function call ABI slack */
-        }
+        if (unlikely(!user_mode(kregs)))
+                p->thread.pc    = (unsigned long) ret_from_kernel_thread;
+        else
+                p->thread.pc    = (unsigned long) ret_from_fork;
 
         /* set up things up so the scheduler can start the new task */
-        ti->frame       = c_kregs;
-        p->thread.a3    = (unsigned long) c_kregs;
+        ti->frame       = c_regs;
+        p->thread.a3    = (unsigned long) c_regs;
         p->thread.sp    = c_ksp;
-        p->thread.pc    = (unsigned long) ret_from_fork;
-        p->thread.wchan = (unsigned long) ret_from_fork;
+        p->thread.wchan = p->thread.pc;
         p->thread.usp   = c_usp;
 
         return 0;