exitcode.c

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/*
 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include <linux/ctype.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/types.h>
#include <asm/uaccess.h>

/*
 * If read and write race, the read will still atomically read a valid
 * value.
 */
int uml_exitcode = 0;

static int exitcode_proc_show(struct seq_file *m, void *v)
{
    int val;

    /*
     * Save uml_exitcode in a local so that we don't need to guarantee
     * that sprintf accesses it atomically.
     */
    val = uml_exitcode;
    seq_printf(m, "%d\n", val);
    return 0;
}

static int exitcode_proc_open(struct inode *inode, struct file *file)
{
    return single_open(file, exitcode_proc_show, NULL);
}

static ssize_t exitcode_proc_write(struct file *file,
        const char __user *buffer, size_t count, loff_t *pos)
{
    char *end, buf[sizeof("nnnnn\0")];
    int tmp;

    if (copy_from_user(buf, buffer, count))
        return -EFAULT;

    tmp = simple_strtol(buf, &end, 0);
    if ((*end != '\0') && !isspace(*end))
        return -EINVAL;

    uml_exitcode = tmp;
    return count;
}

static const struct file_operations exitcode_proc_fops = {
    .owner      = THIS_MODULE,
    .open       = exitcode_proc_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = single_release,
    .write      = exitcode_proc_write,
};

static int make_proc_exitcode(void)
{
    struct proc_dir_entry *ent;

    ent = proc_create("exitcode", 0600, NULL, &exitcode_proc_fops);
    if (ent == NULL) {
        printk(KERN_WARNING "make_proc_exitcode : Failed to register "
               "/proc/exitcode\n");
        return 0;
    }
    return 0;
}

__initcall(make_proc_exitcode);