process.c

Go to the documentation of this file.

/*
 * 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/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 <asm/uaccess.h>
#include <as-layout.h>
#include <kern_util.h>
#include <os.h>
#include <skas.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);

    do {
        current->thread.saved_task = NULL;

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

        arch_switch_to(current);

        if (current->thread.saved_task)
            show_regs(&(current->thread.regs));
        to = current->thread.saved_task;
        from = current;
    } while (current->thread.saved_task);

    return current->thread.prev_sched;
}

void interrupt_end(void)
{
    if (need_resched())
        schedule();
    if (test_thread_flag(TIF_SIGPENDING))
        do_signal();
    if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
        tracehook_notify_resume(&current->thread.regs);
}

void exit_thread(void)
{
}

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);
}

/* 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);
}

int copy_thread(unsigned long clone_flags, unsigned long sp,
        unsigned long arg, struct task_struct * p,
        struct pt_regs *regs)
{
    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, &regs->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 default_idle(void)
{
    unsigned long long nsecs;

    while (1) {
        /* endless idle loop with no priority at all */

        /*
         * although we are an idle CPU, we do not want to
         * get into the scheduler unnecessarily.
         */
        if (need_resched())
            schedule();

        tick_nohz_idle_enter();
        rcu_idle_enter();
        nsecs = disable_timer();
        idle_sleep(nsecs);
        rcu_idle_exit();
        tick_nohz_idle_exit();
    }
}

void cpu_idle(void)
{
    cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
    default_idle();
}

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 strlen_user_proc(char __user *str)
{
    return strlen_user(str);
}

int smp_sigio_handler(void)
{
#ifdef CONFIG_SMP
    int cpu = current_thread_info()->cpu;
    IPI_handler(cpu);
    if (cpu != 0)
        return 1;
#endif
    return 0;
}

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/system.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_fp_registers(userspace_pid[cpu], (unsigned long *) fpu);
}