/*
 *  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/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 <linux/tick.h>
#include <linux/elfcore.h>
#include <linux/kernel_stat.h>
#include <linux/syscalls.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 "entry.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];
}

extern void s390_handle_mcck(void);
/*
 * The idle loop on a S390...
 */
static void default_idle(void)
{
        /* CPU is going idle. */
        local_irq_disable();
        if (need_resched()) {
                local_irq_enable();
                return;
        }
#ifdef CONFIG_HOTPLUG_CPU
        if (cpu_is_offline(smp_processor_id())) {
                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();
        /* Don't trace preempt off for idle. */
        stop_critical_timings();
        /* Stop virtual timer and halt the cpu. */
        vtime_stop_cpu();
        /* Reenable preemption tracer. */
        start_critical_timings();
}

void cpu_idle(void)
{
        for (;;) {
                tick_nohz_stop_sched_tick(1);
                while (!need_resched())
                        default_idle();
                tick_nohz_restart_sched_tick();
                preempt_enable_no_resched();
                schedule();
                preempt_disable();
        }
}

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;
}

SYSCALL_DEFINE0(fork)
{
        struct pt_regs *regs = task_pt_regs(current);
        return do_fork(SIGCHLD, regs->gprs[15], regs, 0, NULL, NULL);
}

SYSCALL_DEFINE0(clone)
{
        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.
 */
SYSCALL_DEFINE0(vfork)
{
        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.
 */
SYSCALL_DEFINE0(execve)
{
        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;
}