// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * 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 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/sched/debug.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/kernel.h>
#include <linux/export.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 <linux/uaccess.h>
#include <asm/pgtable.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");
}

/*
 * Send the doze signal to the cpu if available.
 * Make sure, that all interrupts are enabled
 */
void arch_cpu_idle(void)
{
        local_irq_enable();
        if (mfspr(SPR_UPR) & SPR_UPR_PMP)
                mtspr(SPR_PMR, mfspr(SPR_PMR) | SPR_PMR_DME);
}

void (*pm_power_off) (void) = machine_power_off;
EXPORT_SYMBOL(pm_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);

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

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);

/*
 * copy_thread
 * @clone_flags: flags
 * @usp: user stack pointer or fn for kernel thread
 * @arg: arg to fn for kernel thread; always NULL for userspace thread
 * @p: the newly created task
 * @regs: CPU context to copy for userspace thread; always NULL for kthread
 *
 * At the top of a newly initialized kernel stack are two stacked pt_reg
 * structures.  The first (topmost) is the userspace context of the thread.
 * The second is the kernelspace context of the thread.
 *
 * A kernel thread will not be returning to userspace, so the topmost pt_regs
 * struct can be uninitialized; it _does_ need to exist, though, because
 * a kernel thread can become a userspace thread by doing a kernel_execve, in
 * which case the topmost context will be initialized and used for 'returning'
 * to userspace.
 *
 * The second pt_reg struct needs to be initialized to 'return' to
 * ret_from_fork.  A kernel thread will need to set r20 to the address of
 * a function to call into (with arg in r22); userspace threads need to set
 * r20 to NULL in which case ret_from_fork will just continue a return to
 * userspace.
 *
 * A kernel thread 'fn' may return; this is effectively what happens when
 * kernel_execve is called.  In that case, the userspace pt_regs must have
 * been initialized (which kernel_execve takes care of, see start_thread
 * below); ret_from_fork will then continue its execution causing the
 * 'kernel thread' to return to userspace as a userspace thread.
 */

int
copy_thread(unsigned long clone_flags, unsigned long usp,
            unsigned long arg, struct task_struct *p)
{
        struct pt_regs *userregs;
        struct pt_regs *kregs;
        unsigned long sp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
        unsigned long top_of_kernel_stack;

        top_of_kernel_stack = sp;

        /* Locate userspace context on stack... */
        sp -= STACK_FRAME_OVERHEAD;     /* redzone */
        sp -= sizeof(struct pt_regs);
        userregs = (struct pt_regs *) sp;

        /* ...and kernel context */
        sp -= STACK_FRAME_OVERHEAD;     /* redzone */
        sp -= sizeof(struct pt_regs);
        kregs = (struct pt_regs *)sp;

        if (unlikely(p->flags & PF_KTHREAD)) {
                memset(kregs, 0, sizeof(struct pt_regs));
                kregs->gpr[20] = usp; /* fn, kernel thread */
                kregs->gpr[22] = arg;
        } else {
                *userregs = *current_pt_regs();

                if (usp)
                        userregs->sp = usp;

                /*
                 * For CLONE_SETTLS set "tp" (r10) to the TLS pointer passed to sys_clone.
                 *
                 * The kernel entry is:
                 *      int clone (long flags, void *child_stack, int *parent_tid,
                 *              int *child_tid, struct void *tls)
                 *
                 * This makes the source r7 in the kernel registers.
                 */
                if (clone_flags & CLONE_SETTLS)
                        userregs->gpr[10] = userregs->gpr[7];

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

                kregs->gpr[20] = 0;     /* Userspace thread */
        }

        /*
         * _switch wants the kernel stack page in pt_regs->sp so that it
         * can restore it to thread_info->ksp... see _switch for details.
         */
        kregs->sp = top_of_kernel_stack;
        kregs->gpr[9] = (unsigned long)ret_from_fork;

        task_thread_info(p)->ksp = (unsigned long)kregs;

        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 = mfspr(SPR_SR) & ~SPR_SR_SM;

        memset(regs, 0, sizeof(struct pt_regs));

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

/* 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);
extern int lwa_flag;

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;

        lwa_flag = 0;

        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;
}

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

        return 0;
}