/*
   *  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/smp.h>
  #include <linux/smp_lock.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 <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>

  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)
  {
  	/* disable monitor call class 0 */
  	__ctl_clear_bit(8, 15);

  	atomic_notifier_call_chain(&idle_chain, 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;

  	/* 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,
  			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;
  	}

  	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)
  {
  	struct task_struct *tsk = current;

          printk("CPU:    %d    %s
  ", task_thread_info(tsk)->cpu, print_tainted());

          printk("Process %s (pid: %d, task: %p, ksp: %p)
  ",
  	       current->comm, current->pid, (void *) tsk,
  	       (void *) tsk->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
  "

  	"kernel_thread_starter:
  "
  	"    la    2,0(10)
  "
  	"    basr  14,9
  "
  	"    la    2,0
  "
  	"    br    11
  ");
  
  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));
          p->thread.user_seg = __pa((unsigned long) p->mm->pgd) | _SEGMENT_TABLE;
  	/* 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);
          p->thread.user_seg = __pa((unsigned long) p->mm->pgd) | _REGION_TABLE;
  	/* 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(struct pt_regs regs)
  {
  	return do_fork(SIGCHLD, regs.gprs[15], &regs, 0, NULL, NULL);
  }
  
  asmlinkage long sys_clone(struct pt_regs regs)
  {
          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(struct pt_regs regs)
  {
  	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD,
  		       regs.gprs[15], &regs, 0, NULL, NULL);
  }
  
  /*
   * sys_execve() executes a new program.
   */
  asmlinkage long sys_execve(struct pt_regs regs)
  {
          int error;
          char * filename;
  
          filename = getname((char __user *) regs.orig_gpr2);
          error = PTR_ERR(filename);
          if (IS_ERR(filename))
                  goto out;
          error = do_execve(filename, (char __user * __user *) regs.gprs[3],
  			  (char __user * __user *) regs.gprs[4], &regs);
  	if (error == 0) {
  		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));
  	}
          putname(filename);
  out:
          return error;
  }
  
  
  /*
   * 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;
  }