/*
 * OpenRISC process.c
 *
 * Linux architectural port borrowing liberally from similar works of
 * others.  All original copyrights apply as per the original source
 * declaration.
 *
 * Modifications for the OpenRISC architecture:
 * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
 * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *
 * This file handles the architecture-dependent parts of process handling...
 */

#define __KERNEL_SYSCALLS__
#include <stdarg.h>

#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/elfcore.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/init_task.h>
#include <linux/mqueue.h>
#include <linux/fs.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/spr_defs.h>

#include <linux/smp.h>

/*
 * Pointer to Current thread info structure.
 *
 * Used at user space -> kernel transitions.
 */
struct thread_info *current_thread_info_set[NR_CPUS] = { &init_thread_info, };

void machine_restart(void)
{
        printk(KERN_INFO "*** MACHINE RESTART ***\n");
        __asm__("l.nop 1");
}

/*
 * Similar to machine_power_off, but don't shut off power.  Add code
 * here to freeze the system for e.g. post-mortem debug purpose when
 * possible.  This halt has nothing to do with the idle halt.
 */
void machine_halt(void)
{
        printk(KERN_INFO "*** MACHINE HALT ***\n");
        __asm__("l.nop 1");
}

/* If or when software power-off is implemented, add code here.  */
void machine_power_off(void)
{
        printk(KERN_INFO "*** MACHINE POWER OFF ***\n");
        __asm__("l.nop 1");
}

void (*pm_power_off) (void) = machine_power_off;

/*
 * When a process does an "exec", machine state like FPU and debug
 * registers need to be reset.  This is a hook function for that.
 * Currently we don't have any such state to reset, so this is empty.
 */
void flush_thread(void)
{
}

void show_regs(struct pt_regs *regs)
{
        extern void show_registers(struct pt_regs *regs);

        /* __PHX__ cleanup this mess */
        show_registers(regs);
}

unsigned long thread_saved_pc(struct task_struct *t)
{
        return (unsigned long)user_regs(t->stack)->pc;
}

void release_thread(struct task_struct *dead_task)
{
}

/*
 * Copy the thread-specific (arch specific) info from the current
 * process to the new one p
 */
extern asmlinkage void ret_from_fork(void);

int
copy_thread(unsigned long clone_flags, unsigned long usp,
            unsigned long unused, struct task_struct *p, struct pt_regs *regs)
{
        struct pt_regs *childregs;
        struct pt_regs *kregs;
        unsigned long sp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
        struct thread_info *ti;
        unsigned long top_of_kernel_stack;

        top_of_kernel_stack = sp;

        p->set_child_tid = p->clear_child_tid = NULL;

        /* Copy registers */
        /* redzone */
        sp -= STACK_FRAME_OVERHEAD;
        sp -= sizeof(struct pt_regs);
        childregs = (struct pt_regs *)sp;

        /* Copy parent registers */
        *childregs = *regs;

        if ((childregs->sr & SPR_SR_SM) == 1) {
                /* for kernel thread, set `current_thread_info'
                 * and stackptr in new task
                 */
                childregs->sp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
                childregs->gpr[10] = (unsigned long)task_thread_info(p);
        } else {
                childregs->sp = usp;
        }

        childregs->gpr[11] = 0; /* Result from fork() */

        /*
         * The way this works is that at some point in the future
         * some task will call _switch to switch to the new task.
         * That will pop off the stack frame created below and start
         * the new task running at ret_from_fork.  The new task will
         * do some house keeping and then return from the fork or clone
         * system call, using the stack frame created above.
         */
        /* redzone */
        sp -= STACK_FRAME_OVERHEAD;
        sp -= sizeof(struct pt_regs);
        kregs = (struct pt_regs *)sp;

        ti = task_thread_info(p);
        ti->ksp = sp;

        /* kregs->sp must store the location of the 'pre-switch' kernel stack
         * pointer... for a newly forked process, this is simply the top of
         * the kernel stack.
         */
        kregs->sp = top_of_kernel_stack;
        kregs->gpr[3] = (unsigned long)current; /* arg to schedule_tail */
        kregs->gpr[10] = (unsigned long)task_thread_info(p);
        kregs->gpr[9] = (unsigned long)ret_from_fork;

        return 0;
}

/*
 * Set up a thread for executing a new program
 */
void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
{
        unsigned long sr = regs->sr & ~SPR_SR_SM;

        set_fs(USER_DS);
        memset(regs->gpr, 0, sizeof(regs->gpr));

        regs->pc = pc;
        regs->sr = sr;
        regs->sp = sp;

/*      printk("start thread, ksp = %lx\n", current_thread_info()->ksp);*/
}

/* Fill in the fpu structure for a core dump.  */
int dump_fpu(struct pt_regs *regs, elf_fpregset_t * fpu)
{
        /* TODO */
        return 0;
}

extern struct thread_info *_switch(struct thread_info *old_ti,
                                   struct thread_info *new_ti);

struct task_struct *__switch_to(struct task_struct *old,
                                struct task_struct *new)
{
        struct task_struct *last;
        struct thread_info *new_ti, *old_ti;
        unsigned long flags;

        local_irq_save(flags);

        /* current_set is an array of saved current pointers
         * (one for each cpu). we need them at user->kernel transition,
         * while we save them at kernel->user transition
         */
        new_ti = new->stack;
        old_ti = old->stack;

        current_thread_info_set[smp_processor_id()] = new_ti;
        last = (_switch(old_ti, new_ti))->task;

        local_irq_restore(flags);

        return last;
}

/*
 * Write out registers in core dump format, as defined by the
 * struct user_regs_struct
 */
void dump_elf_thread(elf_greg_t *dest, struct pt_regs* regs)
{
        dest[0] = 0; /* r0 */
        memcpy(dest+1, regs->gpr+1, 31*sizeof(unsigned long));
        dest[32] = regs->pc;
        dest[33] = regs->sr;
        dest[34] = 0;
        dest[35] = 0;
}

extern void _kernel_thread_helper(void);

void __noreturn kernel_thread_helper(int (*fn) (void *), void *arg)
{
        do_exit(fn(arg));
}

/*
 * Create a kernel thread.
 */
int kernel_thread(int (*fn) (void *), void *arg, unsigned long flags)
{
        struct pt_regs regs;

        memset(&regs, 0, sizeof(regs));

        regs.gpr[20] = (unsigned long)fn;
        regs.gpr[22] = (unsigned long)arg;
        regs.sr = mfspr(SPR_SR);
        regs.pc = (unsigned long)_kernel_thread_helper;

        return do_fork(flags | CLONE_VM | CLONE_UNTRACED,
                       0, &regs, 0, NULL, NULL);
}

/*
 * sys_execve() executes a new program.
 */
asmlinkage long _sys_execve(const char __user *name,
                            const char __user * const __user *argv,
                            const char __user * const __user *envp,
                            struct pt_regs *regs)
{
        int error;
        char *filename;

        filename = getname(name);
        error = PTR_ERR(filename);

        if (IS_ERR(filename))
                goto out;

        error = do_execve(filename, argv, envp, regs);
        putname(filename);

out:
        return error;
}

unsigned long get_wchan(struct task_struct *p)
{
        /* TODO */

        return 0;
}

int kernel_execve(const char *filename, char *const argv[], char *const envp[])
{
        register long __res asm("r11") = __NR_execve;
        register long __a asm("r3") = (long)(filename);
        register long __b asm("r4") = (long)(argv);
        register long __c asm("r5") = (long)(envp);
        __asm__ volatile ("l.sys 1"
                          : "=r" (__res), "=r"(__a), "=r"(__b), "=r"(__c)
                          : "0"(__res), "1"(__a), "2"(__b), "3"(__c)
                          : "r6", "r7", "r8", "r12", "r13", "r15",
                            "r17", "r19", "r21", "r23", "r25", "r27",
                            "r29", "r31");
        __asm__ volatile ("l.nop");
        return __res;
}