/*
 * Copyright (C) 2015 Anton Ivanov (aivanov@{brocade.com,kot-begemot.co.uk})
 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Copyright 2003 PathScale, Inc.
 * Licensed under the GPL
 */

#include <linux/stddef.h>
#include <linux/err.h>
#include <linux/hardirq.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/personality.h>
#include <linux/proc_fs.h>
#include <linux/ptrace.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/seq_file.h>
#include <linux/tick.h>
#include <linux/threads.h>
#include <linux/tracehook.h>
#include <asm/current.h>
#include <asm/pgtable.h>
#include <asm/mmu_context.h>
#include <linux/uaccess.h>
#include <as-layout.h>
#include <kern_util.h>
#include <os.h>
#include <skas.h>
#include <timer-internal.h>

/*
 * This is a per-cpu array.  A processor only modifies its entry and it only
 * cares about its entry, so it's OK if another processor is modifying its
 * entry.
 */
struct cpu_task cpu_tasks[NR_CPUS] = { [0 ... NR_CPUS - 1] = { -1, NULL } };

static inline int external_pid(void)
{
        /* FIXME: Need to look up userspace_pid by cpu */
        return userspace_pid[0];
}

int pid_to_processor_id(int pid)
{
        int i;

        for (i = 0; i < ncpus; i++) {
                if (cpu_tasks[i].pid == pid)
                        return i;
        }
        return -1;
}

void free_stack(unsigned long stack, int order)
{
        free_pages(stack, order);
}

unsigned long alloc_stack(int order, int atomic)
{
        unsigned long page;
        gfp_t flags = GFP_KERNEL;

        if (atomic)
                flags = GFP_ATOMIC;
        page = __get_free_pages(flags, order);

        return page;
}

static inline void set_current(struct task_struct *task)
{
        cpu_tasks[task_thread_info(task)->cpu] = ((struct cpu_task)
                { external_pid(), task });
}

extern void arch_switch_to(struct task_struct *to);

void *__switch_to(struct task_struct *from, struct task_struct *to)
{
        to->thread.prev_sched = from;
        set_current(to);

        switch_threads(&from->thread.switch_buf, &to->thread.switch_buf);
        arch_switch_to(current);

        return current->thread.prev_sched;
}

void interrupt_end(void)
{
        struct pt_regs *regs = &current->thread.regs;

        if (need_resched())
                schedule();
        if (test_thread_flag(TIF_SIGPENDING))
                do_signal(regs);
        if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
                tracehook_notify_resume(regs);
}

int get_current_pid(void)
{
        return task_pid_nr(current);
}

/*
 * This is called magically, by its address being stuffed in a jmp_buf
 * and being longjmp-d to.
 */
void new_thread_handler(void)
{
        int (*fn)(void *), n;
        void *arg;

        if (current->thread.prev_sched != NULL)
                schedule_tail(current->thread.prev_sched);
        current->thread.prev_sched = NULL;

        fn = current->thread.request.u.thread.proc;
        arg = current->thread.request.u.thread.arg;

        /*
         * callback returns only if the kernel thread execs a process
         */
        n = fn(arg);
        userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);
}

/* Called magically, see new_thread_handler above */
void fork_handler(void)
{
        force_flush_all();

        schedule_tail(current->thread.prev_sched);

        /*
         * XXX: if interrupt_end() calls schedule, this call to
         * arch_switch_to isn't needed. We could want to apply this to
         * improve performance. -bb
         */
        arch_switch_to(current);

        current->thread.prev_sched = NULL;

        userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);
}

int copy_thread(unsigned long clone_flags, unsigned long sp,
                unsigned long arg, struct task_struct * p)
{
        void (*handler)(void);
        int kthread = current->flags & PF_KTHREAD;
        int ret = 0;

        p->thread = (struct thread_struct) INIT_THREAD;

        if (!kthread) {
                memcpy(&p->thread.regs.regs, current_pt_regs(),
                       sizeof(p->thread.regs.regs));
                PT_REGS_SET_SYSCALL_RETURN(&p->thread.regs, 0);
                if (sp != 0)
                        REGS_SP(p->thread.regs.regs.gp) = sp;

                handler = fork_handler;

                arch_copy_thread(&current->thread.arch, &p->thread.arch);
        } else {
                get_safe_registers(p->thread.regs.regs.gp, p->thread.regs.regs.fp);
                p->thread.request.u.thread.proc = (int (*)(void *))sp;
                p->thread.request.u.thread.arg = (void *)arg;
                handler = new_thread_handler;
        }

        new_thread(task_stack_page(p), &p->thread.switch_buf, handler);

        if (!kthread) {
                clear_flushed_tls(p);

                /*
                 * Set a new TLS for the child thread?
                 */
                if (clone_flags & CLONE_SETTLS)
                        ret = arch_copy_tls(p);
        }

        return ret;
}

void initial_thread_cb(void (*proc)(void *), void *arg)
{
        int save_kmalloc_ok = kmalloc_ok;

        kmalloc_ok = 0;
        initial_thread_cb_skas(proc, arg);
        kmalloc_ok = save_kmalloc_ok;
}

void arch_cpu_idle(void)
{
        cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
        os_idle_sleep(UM_NSEC_PER_SEC);
        local_irq_enable();
}

int __cant_sleep(void) {
        return in_atomic() || irqs_disabled() || in_interrupt();
        /* Is in_interrupt() really needed? */
}

int user_context(unsigned long sp)
{
        unsigned long stack;

        stack = sp & (PAGE_MASK << CONFIG_KERNEL_STACK_ORDER);
        return stack != (unsigned long) current_thread_info();
}

extern exitcall_t __uml_exitcall_begin, __uml_exitcall_end;

void do_uml_exitcalls(void)
{
        exitcall_t *call;

        call = &__uml_exitcall_end;
        while (--call >= &__uml_exitcall_begin)
                (*call)();
}

char *uml_strdup(const char *string)
{
        return kstrdup(string, GFP_KERNEL);
}
EXPORT_SYMBOL(uml_strdup);

int copy_to_user_proc(void __user *to, void *from, int size)
{
        return copy_to_user(to, from, size);
}

int copy_from_user_proc(void *to, void __user *from, int size)
{
        return copy_from_user(to, from, size);
}

int clear_user_proc(void __user *buf, int size)
{
        return clear_user(buf, size);
}

int cpu(void)
{
        return current_thread_info()->cpu;
}

static atomic_t using_sysemu = ATOMIC_INIT(0);
int sysemu_supported;

void set_using_sysemu(int value)
{
        if (value > sysemu_supported)
                return;
        atomic_set(&using_sysemu, value);
}

int get_using_sysemu(void)
{
        return atomic_read(&using_sysemu);
}

static int sysemu_proc_show(struct seq_file *m, void *v)
{
        seq_printf(m, "%d\n", get_using_sysemu());
        return 0;
}

static int sysemu_proc_open(struct inode *inode, struct file *file)
{
        return single_open(file, sysemu_proc_show, NULL);
}

static ssize_t sysemu_proc_write(struct file *file, const char __user *buf,
                                 size_t count, loff_t *pos)
{
        char tmp[2];

        if (copy_from_user(tmp, buf, 1))
                return -EFAULT;

        if (tmp[0] >= '0' && tmp[0] <= '2')
                set_using_sysemu(tmp[0] - '0');
        /* We use the first char, but pretend to write everything */
        return count;
}

static const struct file_operations sysemu_proc_fops = {
        .owner          = THIS_MODULE,
        .open           = sysemu_proc_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = single_release,
        .write          = sysemu_proc_write,
};

int __init make_proc_sysemu(void)
{
        struct proc_dir_entry *ent;
        if (!sysemu_supported)
                return 0;

        ent = proc_create("sysemu", 0600, NULL, &sysemu_proc_fops);

        if (ent == NULL)
        {
                printk(KERN_WARNING "Failed to register /proc/sysemu\n");
                return 0;
        }

        return 0;
}

late_initcall(make_proc_sysemu);

int singlestepping(void * t)
{
        struct task_struct *task = t ? t : current;

        if (!(task->ptrace & PT_DTRACE))
                return 0;

        if (task->thread.singlestep_syscall)
                return 1;

        return 2;
}

/*
 * Only x86 and x86_64 have an arch_align_stack().
 * All other arches have "#define arch_align_stack(x) (x)"
 * in their asm/exec.h
 * As this is included in UML from asm-um/system-generic.h,
 * we can use it to behave as the subarch does.
 */
#ifndef arch_align_stack
unsigned long arch_align_stack(unsigned long sp)
{
        if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
                sp -= get_random_int() % 8192;
        return sp & ~0xf;
}
#endif

unsigned long get_wchan(struct task_struct *p)
{
        unsigned long stack_page, sp, ip;
        bool seen_sched = 0;

        if ((p == NULL) || (p == current) || (p->state == TASK_RUNNING))
                return 0;

        stack_page = (unsigned long) task_stack_page(p);
        /* Bail if the process has no kernel stack for some reason */
        if (stack_page == 0)
                return 0;

        sp = p->thread.switch_buf->JB_SP;
        /*
         * Bail if the stack pointer is below the bottom of the kernel
         * stack for some reason
         */
        if (sp < stack_page)
                return 0;

        while (sp < stack_page + THREAD_SIZE) {
                ip = *((unsigned long *) sp);
                if (in_sched_functions(ip))
                        /* Ignore everything until we're above the scheduler */
                        seen_sched = 1;
                else if (kernel_text_address(ip) && seen_sched)
                        return ip;

                sp += sizeof(unsigned long);
        }

        return 0;
}

int elf_core_copy_fpregs(struct task_struct *t, elf_fpregset_t *fpu)
{
        int cpu = current_thread_info()->cpu;

        return save_i387_registers(userspace_pid[cpu], (unsigned long *) fpu);
}