parisc: switch to generic kernel_thread()

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

arch/parisc/Kconfig

@@ -22,6 +22,7 @@ config PARISC
 	select GENERIC_STRNCPY_FROM_USER
 	select HAVE_MOD_ARCH_SPECIFIC
 	select MODULES_USE_ELF_RELA
+	select GENERIC_KERNEL_THREAD
 
 	help
 	  The PA-RISC microprocessor is designed by Hewlett-Packard and used

arch/parisc/kernel/entry.S

@@ -707,60 +707,10 @@ ENTRY(end_fault_vector)
 	.import		handle_interruption,code
 	.import		do_cpu_irq_mask,code
 
-	/*
-	 * r26 = function to be called
-	 * r25 = argument to pass in
-	 * r24 = flags for do_fork()
-	 *
-	 * Kernel threads don't ever return, so they don't need
-	 * a true register context. We just save away the arguments
-	 * for copy_thread/ret_ to properly set up the child.
-	 */
-
-#define CLONE_VM 0x100	/* Must agree with <linux/sched.h> */
-#define CLONE_UNTRACED 0x00800000
-
-	.import do_fork
-ENTRY(__kernel_thread)
-	STREG	%r2, -RP_OFFSET(%r30)
-
-	copy	%r30, %r1
-	ldo	PT_SZ_ALGN(%r30),%r30
-#ifdef CONFIG_64BIT
-	/* Yo, function pointers in wide mode are little structs... -PB */
-	ldd	24(%r26), %r2
-	STREG	%r2, PT_GR27(%r1)	/* Store childs %dp */
-	ldd	16(%r26), %r26
-
-	STREG	%r22, PT_GR22(%r1)	/* save r22 (arg5) */
-	copy	%r0, %r22		/* user_tid */
-#endif
-	STREG	%r26, PT_GR26(%r1)  /* Store function & argument for child */
-	STREG	%r25, PT_GR25(%r1)
-	ldil	L%CLONE_UNTRACED, %r26
-	ldo	CLONE_VM(%r26), %r26   /* Force CLONE_VM since only init_mm */
-	or	%r26, %r24, %r26      /* will have kernel mappings.	 */
-	ldi	1, %r25			/* stack_start, signals kernel thread */
-	stw	%r0, -52(%r30)	     	/* user_tid */
-#ifdef CONFIG_64BIT
-	ldo	-16(%r30),%r29		/* Reference param save area */
-#endif
-	BL	do_fork, %r2
-	copy	%r1, %r24		/* pt_regs */
-
-	/* Parent Returns here */
-
-	LDREG	-PT_SZ_ALGN-RP_OFFSET(%r30), %r2
-	ldo	-PT_SZ_ALGN(%r30), %r30
-	bv	%r0(%r2)
-	nop
-ENDPROC(__kernel_thread)
-
 	/*
 	 * Child Returns here
 	 *
-	 * copy_thread moved args from temp save area set up above
-	 * into task save area.
+	 * copy_thread moved args into task save area.
 	 */
 
 ENTRY(ret_from_kernel_thread)
@@ -773,7 +723,6 @@ ENTRY(ret_from_kernel_thread)
 	LDREG	TASK_PT_GR25(%r1), %r26
 #ifdef CONFIG_64BIT
 	LDREG	TASK_PT_GR27(%r1), %r27
-	LDREG	TASK_PT_GR22(%r1), %r22
 #endif
 	LDREG	TASK_PT_GR26(%r1), %r1
 	ble	0(%sr7, %r1)

arch/parisc/kernel/process.c

@@ -164,23 +164,6 @@ void machine_power_off(void)
 void (*pm_power_off)(void) = machine_power_off;
 EXPORT_SYMBOL(pm_power_off);
 
-/*
- * Create a kernel thread
- */
-
-extern pid_t __kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
-pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
-{
-
-	/*
-	 * FIXME: Once we are sure we don't need any debug here,
-	 *	  kernel_thread can become a #define.
-	 */
-
-	return __kernel_thread(fn, arg, flags);
-}
-EXPORT_SYMBOL(kernel_thread);
-
 /*
  * Free current thread data structures etc..
  */
@@ -256,8 +239,8 @@ sys_vfork(struct pt_regs *regs)
 
 int
 copy_thread(unsigned long clone_flags, unsigned long usp,
-	    unsigned long unused,	/* in ia64 this is "user_stack_size" */
-	    struct task_struct * p, struct pt_regs * pregs)
+	    unsigned long arg,
+	    struct task_struct *p, struct pt_regs *pregs)
 {
 	struct pt_regs * cregs = &(p->thread.regs);
 	void *stack = task_stack_page(p);
@@ -271,21 +254,8 @@ copy_thread(unsigned long clone_flags, unsigned long usp,
 	extern void * const hpux_child_return;
 #endif
 
-	*cregs = *pregs;
-
-	/* Set the return value for the child.  Note that this is not
-           actually restored by the syscall exit path, but we put it
-           here for consistency in case of signals. */
-	cregs->gr[28] = 0; /* child */
-
-	/*
-	 * We need to differentiate between a user fork and a
-	 * kernel fork. We can't use user_mode, because the
-	 * the syscall path doesn't save iaoq. Right now
-	 * We rely on the fact that kernel_thread passes
-	 * in zero for usp.
-	 */
-	if (usp == 1) {
+	if (unlikely((p->flags & PF_KTHREAD) && usp != 0)) {
+		memset(cregs, 0, sizeof(struct pt_regs));
 		/* kernel thread */
 		cregs->ksp = (unsigned long)stack + THREAD_SZ_ALGN;
 		/* Must exit via ret_from_kernel_thread in order
@@ -297,10 +267,12 @@ copy_thread(unsigned long clone_flags, unsigned long usp,
 		 * ret_from_kernel_thread.
 		 */
 #ifdef CONFIG_64BIT
-		cregs->gr[27] = pregs->gr[27];
+		cregs->gr[27] = ((unsigned long *)usp)[3];
+		cregs->gr[26] = ((unsigned long *)usp)[2];
+#else
+		cregs->gr[26] = usp;
 #endif
-		cregs->gr[26] = pregs->gr[26];
-		cregs->gr[25] = pregs->gr[25];
+		cregs->gr[25] = arg;
 	} else {
 		/* user thread */
 		/*
@@ -308,6 +280,13 @@ copy_thread(unsigned long clone_flags, unsigned long usp,
 		 * for setting gr[21].
 		 */
 
+		*cregs = *pregs;
+
+		/* Set the return value for the child.  Note that this is not
+		   actually restored by the syscall exit path, but we put it
+		   here for consistency in case of signals. */
+		cregs->gr[28] = 0; /* child */
+
 		/* Use same stack depth as parent */
 		cregs->ksp = (unsigned long)stack
 			+ (pregs->gr[21] & (THREAD_SIZE - 1));