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>

5 files changed, 39 insertions, 58 deletions

diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
index 4cba7439f9de..3b8df669eecd 100644
--- a/arch/microblaze/Kconfig
+++ b/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
diff --git a/arch/microblaze/include/asm/processor.h b/arch/microblaze/include/asm/processor.h
index af2bb9652392..0759153e8117 100644
--- a/arch/microblaze/include/asm/processor.h
+++ b/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)
 {
diff --git a/arch/microblaze/kernel/entry-nommu.S b/arch/microblaze/kernel/entry-nommu.S
index 75c3ea1f48a1..c47e92cd7e78 100644
--- a/arch/microblaze/kernel/entry-nommu.S
+++ b/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
 
diff --git a/arch/microblaze/kernel/entry.S b/arch/microblaze/kernel/entry.S
index 1cf702ab7463..be76d1338be0 100644
--- a/arch/microblaze/kernel/entry.S
+++ b/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
diff --git a/arch/microblaze/kernel/process.c b/arch/microblaze/kernel/process.c
index 1944e00f07e1..cbf8bb92f159 100644
--- a/arch/microblaze/kernel/process.c
+++ b/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) */