/*
 *  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..
 */

#define __KERNEL_SYSCALLS__
#include <stdarg.h>

#include <linux/config.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 <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/irq.h>

asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");

/*
 * The idle loop on a S390...
 */

int cpu_idle(void *unused)
{
        psw_t wait_psw;
        unsigned long reg;

        /* endless idle loop with no priority at all */
        init_idle();
        current->nice = 20;
        current->counter = -100;
        while (1) {
                __cli();
                if (current->need_resched) {
                        __sti();
                        schedule();
                        check_pgt_cache();
                        continue;
                }

                /* 
                 * Wait for external, I/O or machine check interrupt and
                 * switch of machine check bit after the wait has ended.
                 */
                wait_psw.mask = _WAIT_PSW_MASK;
                asm volatile (
                        "    larl  %0,0f\n"
                        "    stg   %0,8(%1)\n"
                        "    lpswe 0(%1)\n"
                        "0:  larl  %0,1f\n"
                        "    stg   %0,8(%1)\n"
                        "    ni    1(%1),0xf9\n"
                        "    lpswe 0(%1)\n"
                        "1:"
                        : "=&a" (reg) : "a" (&wait_psw) : "memory", "cc" );
        }
}

extern void show_registers(struct pt_regs *regs);
extern void show_trace(unsigned long *sp);

void show_regs(struct pt_regs *regs)
{
        struct task_struct *tsk = current;

        printk("CPU:    %d    %s\n", tsk->processor, print_tainted());
        printk("Process %s (pid: %d, task: %016lx, ksp: %016lx)\n",
               current->comm, current->pid, (unsigned long) tsk,
               tsk->thread.ksp);

        show_registers(regs);
        /* Show stack backtrace if pt_regs is from kernel mode */
        if (!(regs->psw.mask & PSW_PROBLEM_STATE))
                show_trace((unsigned long *) regs->gprs[15]);
}

int arch_kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
{
        int clone_arg = flags | CLONE_VM;
        int retval;

        __asm__ __volatile__(
                "     slgr  2,2\n"
                "     lgr   3,%1\n"
                "     lg    4,%6\n"     /* load kernel stack ptr of parent */
                "     svc   %b2\n"                     /* Linux system call*/
                "     clg   4,%6\n"    /* compare ksp's: child or parent ? */
                "     je    0f\n"                          /* parent - jump*/
                "     lg    15,%6\n"            /* fix kernel stack pointer*/
                "     aghi  15,%7\n"
                "     xc    0(160,15),0(15)\n"          /* clear save area */
                "     lgr   2,%4\n"                        /* load argument*/
                "     basr  14,%5\n"                             /* call fn*/
                "     svc   %b3\n"                     /* Linux system call*/
                "0:   lgr   %0,2"
                : "=a" (retval)
                : "d" (clone_arg), "i" (__NR_clone), "i" (__NR_exit),
                  "d" (arg), "a" (fn), "i" (__LC_KERNEL_STACK) ,
                  "i" (-STACK_FRAME_OVERHEAD)
                : "2", "3", "4" );
        return retval;
}

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

void flush_thread(void)
{

        current->used_math = 0;
        current->flags &= ~PF_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 stack_frame
          {
            unsigned long back_chain;
            unsigned long eos;
            unsigned long glue1;
            unsigned long glue2;
            unsigned long scratch[2];
            unsigned long gprs[10];    /* gprs 6 -15                       */
            unsigned long fprs[2];     /* fpr 4 and 6                      */
            unsigned long empty[2];
            struct pt_regs childregs;
          } *frame;

        frame = (struct stack_frame *) (4*PAGE_SIZE + (unsigned long) p) -1;
        p->thread.ksp = (unsigned long) frame;
        frame->childregs = *regs;
        frame->childregs.gprs[15] = new_stackp;
        frame->back_chain = frame->eos = 0;

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

        /* fake return stack for resume(), don't go back to schedule */
        frame->gprs[9] = (unsigned long) frame;
        /* save fprs, if used in last task */
        save_fp_regs(&p->thread.fp_regs);
        p->thread.user_seg = __pa((unsigned long) p->mm->pgd) | _REGION_TABLE;
        /* start new process with ar4 pointing to the correct address space */
        p->thread.ar4 = get_fs().ar4;
        /* Don't copy debug registers */
        memset(&p->thread.per_info,0,sizeof(p->thread.per_info));
        return 0;
}

/* 
 * Allocation and freeing of basic task resources. 
 * The task struct and the stack go together.
 *
 * NOTE: An order-2 allocation can easily fail.  If this
 *       happens we fall back to using vmalloc ...
 */

struct task_struct *alloc_task_struct(void)
{
        struct task_struct *tsk = __get_free_pages(GFP_KERNEL, 2);
        if (!tsk)
                tsk = vmalloc(16384);
        if (!tsk)
                return NULL;

        atomic_set((atomic_t *)(tsk + 1), 1);
        return tsk;
}

void free_task_struct(struct task_struct *tsk)
{
        if (atomic_dec_and_test((atomic_t *)(tsk + 1)))
        {
                if ((unsigned long)tsk < VMALLOC_START)
                        free_pages((unsigned long)tsk, 2);
                else
                        vfree(tsk);
        }
}

void get_task_struct(struct task_struct *tsk)
{
        atomic_inc((atomic_t *)(tsk + 1));
}


asmlinkage int sys_fork(struct pt_regs regs)
{
        return do_fork(SIGCHLD, regs.gprs[15], &regs, 0);
}

asmlinkage int sys_clone(struct pt_regs regs)
{
        unsigned long clone_flags;
        unsigned long newsp;

        clone_flags = regs.gprs[3];
        newsp = regs.orig_gpr2;
        if (!newsp)
                newsp = regs.gprs[15];
        return do_fork(clone_flags, newsp, &regs, 0);
}

/*
 * 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 int sys_vfork(struct pt_regs regs)
{
        return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD,
                       regs.gprs[15], &regs, 0);
}

/*
 * sys_execve() executes a new program.
 */
asmlinkage int sys_execve(struct pt_regs regs)
{
        int error;
        char * filename;

        filename = getname((char *) regs.orig_gpr2);
        error = PTR_ERR(filename);
        if (IS_ERR(filename))
                goto out;
        error = do_execve(filename, (char **) regs.gprs[3], (char **) regs.gprs[4], &regs);
        if (error == 0)
        {
                current->ptrace &= ~PT_DTRACE;
                current->thread.fp_regs.fpc=0;
                __asm__ __volatile__
                        ("sr  0,0\n\t"
                         "sfpc 0,0\n\t"
                         : : :"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)
{
        save_fp_regs(fpregs);
        return 1;
}

/*
 * fill in the user structure for a core dump..
 */
void dump_thread(struct pt_regs * regs, struct user * dump)
{

/* changed the size calculations - should hopefully work better. lbt */
        dump->magic = CMAGIC;
        dump->start_code = 0;
        dump->start_stack = regs->gprs[15] & ~(PAGE_SIZE - 1);
        dump->u_tsize = ((unsigned long) current->mm->end_code) >> PAGE_SHIFT;
        dump->u_dsize = ((unsigned long) (current->mm->brk + (PAGE_SIZE-1))) >> PAGE_SHIFT;
        dump->u_dsize -= dump->u_tsize;
        dump->u_ssize = 0;
        if (dump->start_stack < TASK_SIZE)
                dump->u_ssize = ((unsigned long) (TASK_SIZE - dump->start_stack)) >> PAGE_SHIFT;
        memcpy(&dump->regs.gprs[0],regs,sizeof(s390_regs));
        dump_fpu (regs, &dump->regs.fp_regs);
        memcpy(&dump->regs.per_info,&current->thread.per_info,sizeof(per_struct));
}

/*
 * These bracket the sleeping functions..
 */
extern void scheduling_functions_start_here(void);
extern void scheduling_functions_end_here(void);
#define first_sched     ((unsigned long) scheduling_functions_start_here)
#define last_sched      ((unsigned long) scheduling_functions_end_here)

unsigned long get_wchan(struct task_struct *p)
{
        unsigned long r14, r15, bc;
        unsigned long stack_page;
        int count = 0;
        if (!p || p == current || p->state == TASK_RUNNING)
                return 0;
        stack_page = (unsigned long) p;
        r15 = p->thread.ksp;
        if (!stack_page || r15 < stack_page || r15 >= 16380+stack_page)
                return 0;
        bc = *(unsigned long *) r15;
        do {
                if (bc < stack_page || bc >= 16380+stack_page)
                        return 0;
                r14 = *(unsigned long *) (bc+112);
                if (r14 < first_sched || r14 >= last_sched)
                        return r14;
                bc = *(unsigned long *) bc;
        } while (count++ < 16);
        return 0;
}
#undef last_sched
#undef first_sched