m68k: split ret_from_fork(), simplify kernel_thread()

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

4 files changed, 36 insertions, 62 deletions

diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index b22df9410dce..ccda007ba40f 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -13,6 +13,7 @@ config M68K
         select FPU if MMU
         select ARCH_WANT_IPC_PARSE_VERSION
         select ARCH_USES_GETTIMEOFFSET if MMU && !COLDFIRE
+        select GENERIC_KERNEL_THREAD
 
 config RWSEM_GENERIC_SPINLOCK
         bool
diff --git a/arch/m68k/include/asm/processor.h b/arch/m68k/include/asm/processor.h
index 9b4c82c1ef47..ae700f49e51d 100644
--- a/arch/m68k/include/asm/processor.h
+++ b/arch/m68k/include/asm/processor.h
@@ -154,8 +154,6 @@ static 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..
  */
diff --git a/arch/m68k/kernel/entry.S b/arch/m68k/kernel/entry.S
index 165ee9f9d5c9..8a01f580a024 100644
--- a/arch/m68k/kernel/entry.S
+++ b/arch/m68k/kernel/entry.S
@@ -111,6 +111,17 @@ ENTRY(ret_from_fork)
         addql   #4,%sp
         jra     ret_from_exception
 
+ENTRY(ret_from_kernel_thread)
+        | a3 contains the kernel thread payload, d7 - its argument
+        movel   %d1,%sp@-
+        jsr     schedule_tail
+        GET_CURRENT(%d0)
+        movel   %d7,(%sp)
+        jsr     %a3@
+        addql   #4,%sp
+        movel   %d0,(%sp)
+        jra     sys_exit
+
 #if defined(CONFIG_COLDFIRE) || !defined(CONFIG_MMU)
 
 #ifdef TRAP_DBG_INTERRUPT
diff --git a/arch/m68k/kernel/process.c b/arch/m68k/kernel/process.c
index c488e3cfab53..b3d4760c9750 100644
--- a/arch/m68k/kernel/process.c
+++ b/arch/m68k/kernel/process.c
@@ -34,6 +34,7 @@
 
 
 asmlinkage void ret_from_fork(void);
+asmlinkage void ret_from_kernel_thread(void);
 
 
 /*
@@ -120,51 +121,6 @@ void show_regs(struct pt_regs * regs)
                 printk("USP: %08lx\n", rdusp());
 }
 
-/*
- * Create a kernel thread
- */
-int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
-{
-        int pid;
-        mm_segment_t fs;
-
-        fs = get_fs();
-        set_fs (KERNEL_DS);
-
-        {
-        register long retval __asm__ ("d0");
-        register long clone_arg __asm__ ("d1") = flags | CLONE_VM | CLONE_UNTRACED;
-
-        retval = __NR_clone;
-        __asm__ __volatile__
-          ("clrl %%d2\n\t"
-           "trap #0\n\t"                /* Linux/m68k system call */
-           "tstl %0\n\t"                /* child or parent */
-           "jne 1f\n\t"                 /* parent - jump */
-#ifdef CONFIG_MMU
-           "lea %%sp@(%c7),%6\n\t"      /* reload current */
-           "movel %6@,%6\n\t"
-#endif
-           "movel %3,%%sp@-\n\t"        /* push argument */
-           "jsr %4@\n\t"                /* call fn */
-           "movel %0,%%d1\n\t"          /* pass exit value */
-           "movel %2,%%d0\n\t"          /* exit */
-           "trap #0\n"
-           "1:"
-           : "+d" (retval)
-           : "i" (__NR_clone), "i" (__NR_exit),
-             "r" (arg), "a" (fn), "d" (clone_arg), "r" (current),
-             "i" (-THREAD_SIZE)
-           : "d2");
-
-        pid = retval;
-        }
-
-        set_fs (fs);
-        return pid;
-}
-EXPORT_SYMBOL(kernel_thread);
-
 void flush_thread(void)
 {
         current->thread.fs = __USER_DS;
@@ -216,30 +172,18 @@ asmlinkage int m68k_clone(struct pt_regs *regs)
 }
 
 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;
-        struct switch_stack * childstack, *stack;
-        unsigned long *retp;
+        struct switch_stack *childstack;
 
         childregs = (struct pt_regs *) (task_stack_page(p) + THREAD_SIZE) - 1;
-
-        *childregs = *regs;
-        childregs->d0 = 0;
-
-        retp = ((unsigned long *) regs);
-        stack = ((struct switch_stack *) retp) - 1;
-
         childstack = ((struct switch_stack *) childregs) - 1;
-        *childstack = *stack;
-        childstack->retpc = (unsigned long)ret_from_fork;
 
         p->thread.usp = usp;
         p->thread.ksp = (unsigned long)childstack;
-
-        if (clone_flags & CLONE_SETTLS)
-                task_thread_info(p)->tp_value = regs->d5;
+        p->thread.esp0 = (unsigned long)childregs;
 
         /*
          * Must save the current SFC/DFC value, NOT the value when
@@ -247,6 +191,26 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
          */
         p->thread.fs = get_fs().seg;
 
+        if (unlikely(!regs)) {
+                /* kernel thread */
+                memset(childstack, 0,
+                        sizeof(struct switch_stack) + sizeof(struct pt_regs));
+                childregs->sr = PS_S;
+                childstack->a3 = usp; /* function */
+                childstack->d7 = arg;
+                childstack->retpc = (unsigned long)ret_from_kernel_thread;
+                p->thread.usp = 0;
+                return 0;
+        }
+        *childregs = *regs;
+        childregs->d0 = 0;
+
+        *childstack = ((struct switch_stack *) regs)[-1];
+        childstack->retpc = (unsigned long)ret_from_fork;
+
+        if (clone_flags & CLONE_SETTLS)
+                task_thread_info(p)->tp_value = regs->d5;
+
 #ifdef CONFIG_FPU
         if (!FPU_IS_EMU) {
                 /* Copy the current fpu state */