arch/um/drivers/mmapper_kern.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * arch/um/drivers/mmapper_kern.c
   4  *
   5  * BRIEF MODULE DESCRIPTION
   6  *
   7  * Copyright (C) 2000 RidgeRun, Inc.
   8  * Author: RidgeRun, Inc.
   9  *         Greg Lonnon glonnon@ridgerun.com or info@ridgerun.com
  10  *
  11  */
  12
  13 #include <linux/stddef.h>
  14 #include <linux/types.h>
  15 #include <linux/fs.h>
  16 #include <linux/init.h>
  17 #include <linux/miscdevice.h>
  18 #include <linux/module.h>
  19 #include <linux/mm.h>
  20
  21 #include <linux/uaccess.h>
  22 #include <mem_user.h>
  23
  24 /* These are set in mmapper_init, which is called at boot time */
  25 static unsigned long mmapper_size;
  26 static unsigned long p_buf;
  27 static char *v_buf;
  28
  29 static ssize_t mmapper_read(struct file *file, char __user *buf, size_t count,
  30                             loff_t *ppos)
  31 {
  32         return simple_read_from_buffer(buf, count, ppos, v_buf, mmapper_size);
  33 }
  34
  35 static ssize_t mmapper_write(struct file *file, const char __user *buf,
  36                              size_t count, loff_t *ppos)
  37 {
  38         if (*ppos > mmapper_size)
  39                 return -EINVAL;
  40
  41         return simple_write_to_buffer(v_buf, mmapper_size, ppos, buf, count);
  42 }
  43
  44 static long mmapper_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
  45 {
  46         return -ENOIOCTLCMD;
  47 }
  48
  49 static int mmapper_mmap(struct file *file, struct vm_area_struct *vma)
  50 {
  51         int ret = -EINVAL;
  52         int size;
  53
  54         if (vma->vm_pgoff != 0)
  55                 goto out;
  56
  57         size = vma->vm_end - vma->vm_start;
  58         if (size > mmapper_size)
  59                 return -EFAULT;
  60
  61         /*
  62          * XXX A comment above remap_pfn_range says it should only be
  63          * called when the mm semaphore is held
  64          */
  65         if (remap_pfn_range(vma, vma->vm_start, p_buf >> PAGE_SHIFT, size,
  66                             vma->vm_page_prot))
  67                 goto out;
  68         ret = 0;
  69 out:
  70         return ret;
  71 }
  72
  73 static int mmapper_open(struct inode *inode, struct file *file)
  74 {
  75         return 0;
  76 }
  77
  78 static int mmapper_release(struct inode *inode, struct file *file)
  79 {
  80         return 0;
  81 }
  82
  83 static const struct file_operations mmapper_fops = {
  84         .owner          = THIS_MODULE,
  85         .read           = mmapper_read,
  86         .write          = mmapper_write,
  87         .unlocked_ioctl = mmapper_ioctl,
  88         .mmap           = mmapper_mmap,
  89         .open           = mmapper_open,
  90         .release        = mmapper_release,
  91         .llseek         = default_llseek,
  92 };
  93
  94 /*
  95  * No locking needed - only used (and modified) by below initcall and exitcall.
  96  */
  97 static struct miscdevice mmapper_dev = {
  98         .minor          = MISC_DYNAMIC_MINOR,
  99         .name           = "mmapper",
 100         .fops           = &mmapper_fops
 101 };
 102
 103 static int __init mmapper_init(void)
 104 {
 105         int err;
 106
 107         printk(KERN_INFO "Mapper v0.1\n");
 108
 109         v_buf = (char *) find_iomem("mmapper", &mmapper_size);
 110         if (mmapper_size == 0) {
 111                 printk(KERN_ERR "mmapper_init - find_iomem failed\n");
 112                 return -ENODEV;
 113         }
 114         p_buf = __pa(v_buf);
 115
 116         err = misc_register(&mmapper_dev);
 117         if (err) {
 118                 printk(KERN_ERR "mmapper - misc_register failed, err = %d\n",
 119                        err);
 120                 return err;
 121         }
 122         return 0;
 123 }
 124
 125 static void mmapper_exit(void)
 126 {
 127         misc_deregister(&mmapper_dev);
 128 }
 129
 130 module_init(mmapper_init);
 131 module_exit(mmapper_exit);
 132
 133 MODULE_AUTHOR("Greg Lonnon <glonnon@ridgerun.com>");
 134 MODULE_DESCRIPTION("DSPLinux simulator mmapper driver");
 135 MODULE_LICENSE("GPL");