arch/s390/kernel/process.c - LeafOS-Devices/android_kernel_samsung_gta4xl - Gitiles

 /*
  *  arch/s390/kernel/process.c
  *
  *  S390 version
  *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
  *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
  *               Hartmut Penner (hp@de.ibm.com),
  *               Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com),
  *
  *  Derived from "arch/i386/kernel/process.c"
  *    Copyright (C) 1995, Linus Torvalds
  */

 /*
  * This file handles the architecture-dependent parts of process handling..
  */

 #include <linux/compiler.h>
 #include <linux/cpu.h>
 #include <linux/errno.h>
 #include <linux/sched.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/fs.h>
 #include <linux/smp.h>
 #include <linux/stddef.h>
 #include <linux/unistd.h>
 #include <linux/ptrace.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/user.h>
 #include <linux/a.out.h>
 #include <linux/interrupt.h>
 #include <linux/delay.h>
 #include <linux/reboot.h>
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/notifier.h>
 #include <linux/utsname.h>
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
 #include <asm/system.h>
 #include <asm/io.h>
 #include <asm/processor.h>
 #include <asm/irq.h>
 #include <asm/timer.h>
 #include <asm/cpu.h>

 asmlinkage void ret_from_fork(void) asm ("ret_from_fork");

 /*
  * Return saved PC of a blocked thread. used in kernel/sched.
  * resume in entry.S does not create a new stack frame, it
  * just stores the registers %r6-%r15 to the frame given by
  * schedule. We want to return the address of the caller of
  * schedule, so we have to walk the backchain one time to
  * find the frame schedule() store its return address.
  */
 unsigned long thread_saved_pc(struct task_struct *tsk)
 {
 	struct stack_frame *sf, *low, *high;

 	if (!tsk || !task_stack_page(tsk))
 		return 0;
 	low = task_stack_page(tsk);
 	high = (struct stack_frame *) task_pt_regs(tsk);
 	sf = (struct stack_frame *) (tsk->thread.ksp & PSW_ADDR_INSN);
 	if (sf <= low || sf > high)
 		return 0;
 	sf = (struct stack_frame *) (sf->back_chain & PSW_ADDR_INSN);
 	if (sf <= low || sf > high)
 		return 0;
 	return sf->gprs[8];
 }

 /*
  * Need to know about CPUs going idle?
  */
 static ATOMIC_NOTIFIER_HEAD(idle_chain);

 int register_idle_notifier(struct notifier_block *nb)
 {
 	return atomic_notifier_chain_register(&idle_chain, nb);
 }
 EXPORT_SYMBOL(register_idle_notifier);

 int unregister_idle_notifier(struct notifier_block *nb)
 {
 	return atomic_notifier_chain_unregister(&idle_chain, nb);
 }
 EXPORT_SYMBOL(unregister_idle_notifier);

 void do_monitor_call(struct pt_regs *regs, long interruption_code)
 {
 #ifdef CONFIG_SMP
 	struct s390_idle_data *idle;

 	idle = &__get_cpu_var(s390_idle);
 	spin_lock(&idle->lock);
 	idle->idle_time += get_clock() - idle->idle_enter;
 	idle->in_idle = 0;
 	spin_unlock(&idle->lock);
 #endif
 	/* disable monitor call class 0 */
 	__ctl_clear_bit(8, 15);

 	atomic_notifier_call_chain(&idle_chain, S390_CPU_NOT_IDLE,
 				   (void *)(long) smp_processor_id());
 }

 extern void s390_handle_mcck(void);
 /*
  * The idle loop on a S390...
  */
 static void default_idle(void)
 {
 	int cpu, rc;
 #ifdef CONFIG_SMP
 	struct s390_idle_data *idle;
 #endif

 	/* CPU is going idle. */
 	cpu = smp_processor_id();

 	local_irq_disable();
 	if (need_resched()) {
 		local_irq_enable();
 		return;
 	}

 	rc = atomic_notifier_call_chain(&idle_chain,
 					S390_CPU_IDLE, (void *)(long) cpu);
 	if (rc != NOTIFY_OK && rc != NOTIFY_DONE)
 		BUG();
 	if (rc != NOTIFY_OK) {
 		local_irq_enable();
 		return;
 	}

 	/* enable monitor call class 0 */
 	__ctl_set_bit(8, 15);

 #ifdef CONFIG_HOTPLUG_CPU
 	if (cpu_is_offline(cpu)) {
 		preempt_enable_no_resched();
 		cpu_die();
 	}
 #endif

 	local_mcck_disable();
 	if (test_thread_flag(TIF_MCCK_PENDING)) {
 		local_mcck_enable();
 		local_irq_enable();
 		s390_handle_mcck();
 		return;
 	}
 #ifdef CONFIG_SMP
 	idle = &__get_cpu_var(s390_idle);
 	spin_lock(&idle->lock);
 	idle->idle_count++;
 	idle->in_idle = 1;
 	idle->idle_enter = get_clock();
 	spin_unlock(&idle->lock);
 #endif
 	trace_hardirqs_on();
 	/* Wait for external, I/O or machine check interrupt. */
 	__load_psw_mask(psw_kernel_bits | PSW_MASK_WAIT |
 			PSW_MASK_IO | PSW_MASK_EXT);
 }

 void cpu_idle(void)
 {
 	for (;;) {
 		while (!need_resched())
 			default_idle();

 		preempt_enable_no_resched();
 		schedule();
 		preempt_disable();
 	}
 }

 void show_regs(struct pt_regs *regs)
 {
 	print_modules();
 	printk("CPU: %d %s %s %.*s\n",
 	       task_thread_info(current)->cpu, print_tainted(),
 	       init_utsname()->release,
 	       (int)strcspn(init_utsname()->version, " "),
 	       init_utsname()->version);
 	printk("Process %s (pid: %d, task: %p, ksp: %p)\n",
 	       current->comm, current->pid, current,
 	       (void *) current->thread.ksp);
 	show_registers(regs);
 	/* Show stack backtrace if pt_regs is from kernel mode */
 	if (!(regs->psw.mask & PSW_MASK_PSTATE))
 		show_trace(NULL, (unsigned long *) regs->gprs[15]);
 }

 extern void kernel_thread_starter(void);

 asm(
 	".align 4\n"
 	"kernel_thread_starter:\n"
 	"    la    2,0(10)\n"
 	"    basr  14,9\n"
 	"    la    2,0\n"
 	"    br    11\n");

 int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
 {
 	struct pt_regs regs;

 	memset(&regs, 0, sizeof(regs));
 	regs.psw.mask = psw_kernel_bits | PSW_MASK_IO | PSW_MASK_EXT;
 	regs.psw.addr = (unsigned long) kernel_thread_starter | PSW_ADDR_AMODE;
 	regs.gprs[9] = (unsigned long) fn;
 	regs.gprs[10] = (unsigned long) arg;
 	regs.gprs[11] = (unsigned long) do_exit;
 	regs.orig_gpr2 = -1;

 	/* Ok, create the new process.. */
 	return do_fork(flags | CLONE_VM | CLONE_UNTRACED,
 		       0, &regs, 0, NULL, NULL);
 }

 /*
  * Free current thread data structures etc..
  */
 void exit_thread(void)
 {
 }

 void flush_thread(void)
 {
 	clear_used_math();
 	clear_tsk_thread_flag(current, TIF_USEDFPU);
 }

 void release_thread(struct task_struct *dead_task)
 {
 }

 int copy_thread(int nr, unsigned long clone_flags, unsigned long new_stackp,
 	unsigned long unused,
         struct task_struct * p, struct pt_regs * regs)
 {
         struct fake_frame
           {
 	    struct stack_frame sf;
             struct pt_regs childregs;
           } *frame;

         frame = container_of(task_pt_regs(p), struct fake_frame, childregs);
         p->thread.ksp = (unsigned long) frame;
 	/* Store access registers to kernel stack of new process. */
         frame->childregs = *regs;
 	frame->childregs.gprs[2] = 0;	/* child returns 0 on fork. */
         frame->childregs.gprs[15] = new_stackp;
         frame->sf.back_chain = 0;

         /* new return point is ret_from_fork */
         frame->sf.gprs[8] = (unsigned long) ret_from_fork;

         /* fake return stack for resume(), don't go back to schedule */
         frame->sf.gprs[9] = (unsigned long) frame;

 	/* Save access registers to new thread structure. */
 	save_access_regs(&p->thread.acrs[0]);

 #ifndef CONFIG_64BIT
         /*
 	 * save fprs to current->thread.fp_regs to merge them with
 	 * the emulated registers and then copy the result to the child.
 	 */
 	save_fp_regs(&current->thread.fp_regs);
 	memcpy(&p->thread.fp_regs, &current->thread.fp_regs,
 	       sizeof(s390_fp_regs));
 	/* Set a new TLS ?  */
 	if (clone_flags & CLONE_SETTLS)
 		p->thread.acrs[0] = regs->gprs[6];
 #else /* CONFIG_64BIT */
 	/* Save the fpu registers to new thread structure. */
 	save_fp_regs(&p->thread.fp_regs);
 	/* Set a new TLS ?  */
 	if (clone_flags & CLONE_SETTLS) {
 		if (test_thread_flag(TIF_31BIT)) {
 			p->thread.acrs[0] = (unsigned int) regs->gprs[6];
 		} else {
 			p->thread.acrs[0] = (unsigned int)(regs->gprs[6] >> 32);
 			p->thread.acrs[1] = (unsigned int) regs->gprs[6];
 		}
 	}
 #endif /* CONFIG_64BIT */
 	/* start new process with ar4 pointing to the correct address space */
 	p->thread.mm_segment = get_fs();
         /* Don't copy debug registers */
         memset(&p->thread.per_info,0,sizeof(p->thread.per_info));

         return 0;
 }

 asmlinkage long sys_fork(void)
 {
 	struct pt_regs *regs = task_pt_regs(current);
 	return do_fork(SIGCHLD, regs->gprs[15], regs, 0, NULL, NULL);
 }

 asmlinkage long sys_clone(void)
 {
 	struct pt_regs *regs = task_pt_regs(current);
 	unsigned long clone_flags;
 	unsigned long newsp;
 	int __user *parent_tidptr, *child_tidptr;

 	clone_flags = regs->gprs[3];
 	newsp = regs->orig_gpr2;
 	parent_tidptr = (int __user *) regs->gprs[4];
 	child_tidptr = (int __user *) regs->gprs[5];
 	if (!newsp)
 		newsp = regs->gprs[15];
 	return do_fork(clone_flags, newsp, regs, 0,
 		       parent_tidptr, child_tidptr);
 }

 /*
  * This is trivial, and on the face of it looks like it
  * could equally well be done in user mode.
  *
  * Not so, for quite unobvious reasons - register pressure.
  * In user mode vfork() cannot have a stack frame, and if
  * done by calling the "clone()" system call directly, you
  * do not have enough call-clobbered registers to hold all
  * the information you need.
  */
 asmlinkage long sys_vfork(void)
 {
 	struct pt_regs *regs = task_pt_regs(current);
 	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD,
 		       regs->gprs[15], regs, 0, NULL, NULL);
 }

 asmlinkage void execve_tail(void)
 {
 	task_lock(current);
 	current->ptrace &= ~PT_DTRACE;
 	task_unlock(current);
 	current->thread.fp_regs.fpc = 0;
 	if (MACHINE_HAS_IEEE)
 		asm volatile("sfpc %0,%0" : : "d" (0));
 }

 /*
  * sys_execve() executes a new program.
  */
 asmlinkage long sys_execve(void)
 {
 	struct pt_regs *regs = task_pt_regs(current);
 	char *filename;
 	unsigned long result;
 	int rc;

 	filename = getname((char __user *) regs->orig_gpr2);
 	if (IS_ERR(filename)) {
 		result = PTR_ERR(filename);
 		goto out;
 	}
 	rc = do_execve(filename, (char __user * __user *) regs->gprs[3],
 		       (char __user * __user *) regs->gprs[4], regs);
 	if (rc) {
 		result = rc;
 		goto out_putname;
 	}
 	execve_tail();
 	result = regs->gprs[2];
 out_putname:
 	putname(filename);
 out:
 	return result;
 }

 /*
  * fill in the FPU structure for a core dump.
  */
 int dump_fpu (struct pt_regs * regs, s390_fp_regs *fpregs)
 {
 #ifndef CONFIG_64BIT
         /*
 	 * save fprs to current->thread.fp_regs to merge them with
 	 * the emulated registers and then copy the result to the dump.
 	 */
 	save_fp_regs(&current->thread.fp_regs);
 	memcpy(fpregs, &current->thread.fp_regs, sizeof(s390_fp_regs));
 #else /* CONFIG_64BIT */
 	save_fp_regs(fpregs);
 #endif /* CONFIG_64BIT */
 	return 1;
 }

 unsigned long get_wchan(struct task_struct *p)
 {
 	struct stack_frame *sf, *low, *high;
 	unsigned long return_address;
 	int count;

 	if (!p || p == current || p->state == TASK_RUNNING || !task_stack_page(p))
 		return 0;
 	low = task_stack_page(p);
 	high = (struct stack_frame *) task_pt_regs(p);
 	sf = (struct stack_frame *) (p->thread.ksp & PSW_ADDR_INSN);
 	if (sf <= low || sf > high)
 		return 0;
 	for (count = 0; count < 16; count++) {
 		sf = (struct stack_frame *) (sf->back_chain & PSW_ADDR_INSN);
 		if (sf <= low || sf > high)
 			return 0;
 		return_address = sf->gprs[8] & PSW_ADDR_INSN;
 		if (!in_sched_functions(return_address))
 			return return_address;
 	}
 	return 0;
 }
	/*
	* arch/s390/kernel/process.c
	*
	* S390 version
	* Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
	* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
	* Hartmut Penner (hp@de.ibm.com),
	* Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com),
	*
	* Derived from "arch/i386/kernel/process.c"
	* Copyright (C) 1995, Linus Torvalds
	*/

	/*
	* This file handles the architecture-dependent parts of process handling..
	*/

	#include <linux/compiler.h>
	#include <linux/cpu.h>
	#include <linux/errno.h>
	#include <linux/sched.h>
	#include <linux/kernel.h>
	#include <linux/mm.h>
	#include <linux/fs.h>
	#include <linux/smp.h>
	#include <linux/stddef.h>
	#include <linux/unistd.h>
	#include <linux/ptrace.h>
	#include <linux/slab.h>
	#include <linux/vmalloc.h>
	#include <linux/user.h>
	#include <linux/a.out.h>
	#include <linux/interrupt.h>
	#include <linux/delay.h>
	#include <linux/reboot.h>
	#include <linux/init.h>
	#include <linux/module.h>
	#include <linux/notifier.h>
	#include <linux/utsname.h>
	#include <asm/uaccess.h>
	#include <asm/pgtable.h>
	#include <asm/system.h>
	#include <asm/io.h>
	#include <asm/processor.h>
	#include <asm/irq.h>
	#include <asm/timer.h>
	#include <asm/cpu.h>

	asmlinkage void ret_from_fork(void) asm ("ret_from_fork");

	/*
	* Return saved PC of a blocked thread. used in kernel/sched.
	* resume in entry.S does not create a new stack frame, it
	* just stores the registers %r6-%r15 to the frame given by
	* schedule. We want to return the address of the caller of
	* schedule, so we have to walk the backchain one time to
	* find the frame schedule() store its return address.
	*/
	unsigned long thread_saved_pc(struct task_struct *tsk)
	{
	struct stack_frame sf, low, *high;

	if (!tsk \|\| !task_stack_page(tsk))
	return 0;
	low = task_stack_page(tsk);
	high = (struct stack_frame *) task_pt_regs(tsk);
	sf = (struct stack_frame *) (tsk->thread.ksp & PSW_ADDR_INSN);
	if (sf <= low \|\| sf > high)
	return 0;
	sf = (struct stack_frame *) (sf->back_chain & PSW_ADDR_INSN);
	if (sf <= low \|\| sf > high)
	return 0;
	return sf->gprs[8];
	}

	/*
	* Need to know about CPUs going idle?
	*/
	static ATOMIC_NOTIFIER_HEAD(idle_chain);

	int register_idle_notifier(struct notifier_block *nb)
	{
	return atomic_notifier_chain_register(&idle_chain, nb);
	}
	EXPORT_SYMBOL(register_idle_notifier);

	int unregister_idle_notifier(struct notifier_block *nb)
	{
	return atomic_notifier_chain_unregister(&idle_chain, nb);
	}
	EXPORT_SYMBOL(unregister_idle_notifier);

	void do_monitor_call(struct pt_regs *regs, long interruption_code)
	{
	#ifdef CONFIG_SMP
	struct s390_idle_data *idle;

	idle = &__get_cpu_var(s390_idle);
	spin_lock(&idle->lock);
	idle->idle_time += get_clock() - idle->idle_enter;
	idle->in_idle = 0;
	spin_unlock(&idle->lock);
	#endif
	/* disable monitor call class 0 */
	__ctl_clear_bit(8, 15);

	atomic_notifier_call_chain(&idle_chain, S390_CPU_NOT_IDLE,
	(void *)(long) smp_processor_id());
	}

	extern void s390_handle_mcck(void);
	/*
	* The idle loop on a S390...
	*/
	static void default_idle(void)
	{
	int cpu, rc;
	#ifdef CONFIG_SMP
	struct s390_idle_data *idle;
	#endif

	/* CPU is going idle. */
	cpu = smp_processor_id();

	local_irq_disable();
	if (need_resched()) {
	local_irq_enable();
	return;
	}

	rc = atomic_notifier_call_chain(&idle_chain,
	S390_CPU_IDLE, (void *)(long) cpu);
	if (rc != NOTIFY_OK && rc != NOTIFY_DONE)
	BUG();
	if (rc != NOTIFY_OK) {
	local_irq_enable();
	return;
	}

	/* enable monitor call class 0 */
	__ctl_set_bit(8, 15);

	#ifdef CONFIG_HOTPLUG_CPU
	if (cpu_is_offline(cpu)) {
	preempt_enable_no_resched();
	cpu_die();
	}
	#endif

	local_mcck_disable();
	if (test_thread_flag(TIF_MCCK_PENDING)) {
	local_mcck_enable();
	local_irq_enable();
	s390_handle_mcck();
	return;
	}
	#ifdef CONFIG_SMP
	idle = &__get_cpu_var(s390_idle);
	spin_lock(&idle->lock);
	idle->idle_count++;
	idle->in_idle = 1;
	idle->idle_enter = get_clock();
	spin_unlock(&idle->lock);
	#endif
	trace_hardirqs_on();
	/* Wait for external, I/O or machine check interrupt. */
	__load_psw_mask(psw_kernel_bits \| PSW_MASK_WAIT \|
	PSW_MASK_IO \| PSW_MASK_EXT);
	}

	void cpu_idle(void)
	{
	for (;;) {
	while (!need_resched())
	default_idle();

	preempt_enable_no_resched();
	schedule();
	preempt_disable();
	}
	}

	void show_regs(struct pt_regs *regs)
	{
	print_modules();
	printk("CPU: %d %s %s %.*s\n",
	task_thread_info(current)->cpu, print_tainted(),
	init_utsname()->release,
	(int)strcspn(init_utsname()->version, " "),
	init_utsname()->version);
	printk("Process %s (pid: %d, task: %p, ksp: %p)\n",
	current->comm, current->pid, current,
	(void *) current->thread.ksp);
	show_registers(regs);
	/* Show stack backtrace if pt_regs is from kernel mode */
	if (!(regs->psw.mask & PSW_MASK_PSTATE))
	show_trace(NULL, (unsigned long *) regs->gprs[15]);
	}

	extern void kernel_thread_starter(void);

	asm(
	".align 4\n"
	"kernel_thread_starter:\n"
	" la 2,0(10)\n"
	" basr 14,9\n"
	" la 2,0\n"
	" br 11\n");

	int kernel_thread(int (fn)(void ), void * arg, unsigned long flags)
	{
	struct pt_regs regs;

	memset(&regs, 0, sizeof(regs));
	regs.psw.mask = psw_kernel_bits \| PSW_MASK_IO \| PSW_MASK_EXT;
	regs.psw.addr = (unsigned long) kernel_thread_starter \| PSW_ADDR_AMODE;
	regs.gprs[9] = (unsigned long) fn;
	regs.gprs[10] = (unsigned long) arg;
	regs.gprs[11] = (unsigned long) do_exit;
	regs.orig_gpr2 = -1;

	/* Ok, create the new process.. */
	return do_fork(flags \| CLONE_VM \| CLONE_UNTRACED,
	0, &regs, 0, NULL, NULL);
	}

	/*
	* Free current thread data structures etc..
	*/
	void exit_thread(void)
	{
	}

	void flush_thread(void)
	{
	clear_used_math();
	clear_tsk_thread_flag(current, TIF_USEDFPU);
	}

	void release_thread(struct task_struct *dead_task)
	{
	}

	int copy_thread(int nr, unsigned long clone_flags, unsigned long new_stackp,
	unsigned long unused,
	struct task_struct * p, struct pt_regs * regs)
	{
	struct fake_frame
	{
	struct stack_frame sf;
	struct pt_regs childregs;
	} *frame;

	frame = container_of(task_pt_regs(p), struct fake_frame, childregs);
	p->thread.ksp = (unsigned long) frame;
	/* Store access registers to kernel stack of new process. */
	frame->childregs = *regs;
	frame->childregs.gprs[2] = 0; /* child returns 0 on fork. */
	frame->childregs.gprs[15] = new_stackp;
	frame->sf.back_chain = 0;

	/* new return point is ret_from_fork */
	frame->sf.gprs[8] = (unsigned long) ret_from_fork;

	/* fake return stack for resume(), don't go back to schedule */
	frame->sf.gprs[9] = (unsigned long) frame;

	/* Save access registers to new thread structure. */
	save_access_regs(&p->thread.acrs[0]);

	#ifndef CONFIG_64BIT
	/*
	* save fprs to current->thread.fp_regs to merge them with
	* the emulated registers and then copy the result to the child.
	*/
	save_fp_regs(&current->thread.fp_regs);
	memcpy(&p->thread.fp_regs, &current->thread.fp_regs,
	sizeof(s390_fp_regs));
	/* Set a new TLS ? */
	if (clone_flags & CLONE_SETTLS)
	p->thread.acrs[0] = regs->gprs[6];
	#else /* CONFIG_64BIT */
	/* Save the fpu registers to new thread structure. */
	save_fp_regs(&p->thread.fp_regs);
	/* Set a new TLS ? */
	if (clone_flags & CLONE_SETTLS) {
	if (test_thread_flag(TIF_31BIT)) {
	p->thread.acrs[0] = (unsigned int) regs->gprs[6];
	} else {
	p->thread.acrs[0] = (unsigned int)(regs->gprs[6] >> 32);
	p->thread.acrs[1] = (unsigned int) regs->gprs[6];
	}
	}
	#endif /* CONFIG_64BIT */
	/* start new process with ar4 pointing to the correct address space */
	p->thread.mm_segment = get_fs();
	/* Don't copy debug registers */
	memset(&p->thread.per_info,0,sizeof(p->thread.per_info));

	return 0;
	}

	asmlinkage long sys_fork(void)
	{
	struct pt_regs *regs = task_pt_regs(current);
	return do_fork(SIGCHLD, regs->gprs[15], regs, 0, NULL, NULL);
	}

	asmlinkage long sys_clone(void)
	{
	struct pt_regs *regs = task_pt_regs(current);
	unsigned long clone_flags;
	unsigned long newsp;
	int __user parent_tidptr, child_tidptr;

	clone_flags = regs->gprs[3];
	newsp = regs->orig_gpr2;
	parent_tidptr = (int __user *) regs->gprs[4];
	child_tidptr = (int __user *) regs->gprs[5];
	if (!newsp)
	newsp = regs->gprs[15];
	return do_fork(clone_flags, newsp, regs, 0,
	parent_tidptr, child_tidptr);
	}

	/*
	* This is trivial, and on the face of it looks like it
	* could equally well be done in user mode.
	*
	* Not so, for quite unobvious reasons - register pressure.
	* In user mode vfork() cannot have a stack frame, and if
	* done by calling the "clone()" system call directly, you
	* do not have enough call-clobbered registers to hold all
	* the information you need.
	*/
	asmlinkage long sys_vfork(void)
	{
	struct pt_regs *regs = task_pt_regs(current);
	return do_fork(CLONE_VFORK \| CLONE_VM \| SIGCHLD,
	regs->gprs[15], regs, 0, NULL, NULL);
	}

	asmlinkage void execve_tail(void)
	{
	task_lock(current);
	current->ptrace &= ~PT_DTRACE;
	task_unlock(current);
	current->thread.fp_regs.fpc = 0;
	if (MACHINE_HAS_IEEE)
	asm volatile("sfpc %0,%0" : : "d" (0));
	}

	/*
	* sys_execve() executes a new program.
	*/
	asmlinkage long sys_execve(void)
	{
	struct pt_regs *regs = task_pt_regs(current);
	char *filename;
	unsigned long result;
	int rc;

	filename = getname((char __user *) regs->orig_gpr2);
	if (IS_ERR(filename)) {
	result = PTR_ERR(filename);
	goto out;
	}
	rc = do_execve(filename, (char __user * __user *) regs->gprs[3],
	(char __user * __user *) regs->gprs[4], regs);
	if (rc) {
	result = rc;
	goto out_putname;
	}
	execve_tail();
	result = regs->gprs[2];
	out_putname:
	putname(filename);
	out:
	return result;
	}

	/*
	* fill in the FPU structure for a core dump.
	*/
	int dump_fpu (struct pt_regs * regs, s390_fp_regs *fpregs)
	{
	#ifndef CONFIG_64BIT
	/*
	* save fprs to current->thread.fp_regs to merge them with
	* the emulated registers and then copy the result to the dump.
	*/
	save_fp_regs(&current->thread.fp_regs);
	memcpy(fpregs, &current->thread.fp_regs, sizeof(s390_fp_regs));
	#else /* CONFIG_64BIT */
	save_fp_regs(fpregs);
	#endif /* CONFIG_64BIT */
	return 1;
	}

	unsigned long get_wchan(struct task_struct *p)
	{
	struct stack_frame sf, low, *high;
	unsigned long return_address;
	int count;

	if (!p \|\| p == current \|\| p->state == TASK_RUNNING \|\| !task_stack_page(p))
	return 0;
	low = task_stack_page(p);
	high = (struct stack_frame *) task_pt_regs(p);
	sf = (struct stack_frame *) (p->thread.ksp & PSW_ADDR_INSN);
	if (sf <= low \|\| sf > high)
	return 0;
	for (count = 0; count < 16; count++) {
	sf = (struct stack_frame *) (sf->back_chain & PSW_ADDR_INSN);
	if (sf <= low \|\| sf > high)
	return 0;
	return_address = sf->gprs[8] & PSW_ADDR_INSN;
	if (!in_sched_functions(return_address))
	return return_address;
	}
	return 0;
	}