drivers/s390/char/vmcp.c

   1 /*
   2  * Copyright (C) 2004,2005 IBM Corporation
   3  * Interface implementation for communication with the z/VM control program
   4  * Author(s): Christian Borntraeger <cborntra@de.ibm.com>
   5  *
   6  *
   7  * z/VMs CP offers the possibility to issue commands via the diagnose code 8
   8  * this driver implements a character device that issues these commands and
   9  * returns the answer of CP.
  10
  11  * The idea of this driver is based on cpint from Neale Ferguson and #CP in CMS
  12  */
  13
  14 #include <linux/fs.h>
  15 #include <linux/init.h>
  16 #include <linux/kernel.h>
  17 #include <linux/miscdevice.h>
  18 #include <linux/module.h>
  19 #include <asm/cpcmd.h>
  20 #include <asm/debug.h>
  21 #include <asm/uaccess.h>
  22 #include "vmcp.h"
  23
  24 MODULE_LICENSE("GPL");
  25 MODULE_AUTHOR("Christian Borntraeger <cborntra@de.ibm.com>");
  26 MODULE_DESCRIPTION("z/VM CP interface");
  27
  28 static debug_info_t *vmcp_debug;
  29
  30 static int vmcp_open(struct inode *inode, struct file *file)
  31 {
  32         struct vmcp_session *session;
  33
  34         if (!capable(CAP_SYS_ADMIN))
  35                 return -EPERM;
  36
  37         session = kmalloc(sizeof(*session), GFP_KERNEL);
  38         if (!session)
  39                 return -ENOMEM;
  40         session->bufsize = PAGE_SIZE;
  41         session->response = NULL;
  42         session->resp_size = 0;
  43         init_MUTEX(&session->mutex);
  44         file->private_data = session;
  45         return nonseekable_open(inode, file);
  46 }
  47
  48 static int vmcp_release(struct inode *inode, struct file *file)
  49 {
  50         struct vmcp_session *session;
  51
  52         session = (struct vmcp_session *)file->private_data;
  53         file->private_data = NULL;
  54         free_pages((unsigned long)session->response, get_order(session->bufsize));
  55         kfree(session);
  56         return 0;
  57 }
  58
  59 static ssize_t
  60 vmcp_read(struct file *file, char __user * buff, size_t count, loff_t * ppos)
  61 {
  62         size_t tocopy;
  63         struct vmcp_session *session;
  64
  65         session = (struct vmcp_session *)file->private_data;
  66         if (down_interruptible(&session->mutex))
  67                 return -ERESTARTSYS;
  68         if (!session->response) {
  69                 up(&session->mutex);
  70                 return 0;
  71         }
  72         if (*ppos > session->resp_size) {
  73                 up(&session->mutex);
  74                 return 0;
  75         }
  76         tocopy = min(session->resp_size - (size_t) (*ppos), count);
  77         tocopy = min(tocopy,session->bufsize - (size_t) (*ppos));
  78
  79         if (copy_to_user(buff, session->response + (*ppos), tocopy)) {
  80                 up(&session->mutex);
  81                 return -EFAULT;
  82         }
  83         up(&session->mutex);
  84         *ppos += tocopy;
  85         return tocopy;
  86 }
  87
  88 static ssize_t
  89 vmcp_write(struct file *file, const char __user * buff, size_t count,
  90            loff_t * ppos)
  91 {
  92         char *cmd;
  93         struct vmcp_session *session;
  94
  95         if (count > 240)
  96                 return -EINVAL;
  97         cmd = kmalloc(count + 1, GFP_KERNEL);
  98         if (!cmd)
  99                 return -ENOMEM;
 100         if (copy_from_user(cmd, buff, count)) {
 101                 kfree(cmd);
 102                 return -EFAULT;
 103         }
 104         cmd[count] = '\0';
 105         session = (struct vmcp_session *)file->private_data;
 106         if (down_interruptible(&session->mutex)) {
 107                 kfree(cmd);
 108                 return -ERESTARTSYS;
 109         }
 110         if (!session->response)
 111                 session->response = (char *)__get_free_pages(GFP_KERNEL
 112                                                 | __GFP_REPEAT  | GFP_DMA,
 113                                                 get_order(session->bufsize));
 114         if (!session->response) {
 115                 up(&session->mutex);
 116                 kfree(cmd);
 117                 return -ENOMEM;
 118         }
 119         debug_text_event(vmcp_debug, 1, cmd);
 120         session->resp_size = cpcmd(cmd, session->response,
 121                                      session->bufsize,
 122                                      &session->resp_code);
 123         up(&session->mutex);
 124         kfree(cmd);
 125         *ppos = 0;              /* reset the file pointer after a command */
 126         return count;
 127 }
 128
 129
 130 /*
 131  * These ioctls are available, as the semantics of the diagnose 8 call
 132  * does not fit very well into a Linux call. Diagnose X'08' is described in
 133  * CP Programming Services SC24-6084-00
 134  *
 135  * VMCP_GETCODE: gives the CP return code back to user space
 136  * VMCP_SETBUF: sets the response buffer for the next write call. diagnose 8
 137  * expects adjacent pages in real storage and to make matters worse, we
 138  * dont know the size of the response. Therefore we default to PAGESIZE and
 139  * let userspace to change the response size, if userspace expects a bigger
 140  * response
 141  */
 142 static long vmcp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 143 {
 144         struct vmcp_session *session;
 145         int temp;
 146
 147         session = (struct vmcp_session *)file->private_data;
 148         if (down_interruptible(&session->mutex))
 149                 return -ERESTARTSYS;
 150         switch (cmd) {
 151         case VMCP_GETCODE:
 152                 temp = session->resp_code;
 153                 up(&session->mutex);
 154                 return put_user(temp, (int __user *)arg);
 155         case VMCP_SETBUF:
 156                 free_pages((unsigned long)session->response,
 157                                 get_order(session->bufsize));
 158                 session->response=NULL;
 159                 temp = get_user(session->bufsize, (int __user *)arg);
 160                 if (get_order(session->bufsize) > 8) {
 161                         session->bufsize = PAGE_SIZE;
 162                         temp = -EINVAL;
 163                 }
 164                 up(&session->mutex);
 165                 return temp;
 166         case VMCP_GETSIZE:
 167                 temp = session->resp_size;
 168                 up(&session->mutex);
 169                 return put_user(temp, (int __user *)arg);
 170         default:
 171                 up(&session->mutex);
 172                 return -ENOIOCTLCMD;
 173         }
 174 }
 175
 176 static const struct file_operations vmcp_fops = {
 177         .owner          = THIS_MODULE,
 178         .open           = &vmcp_open,
 179         .release        = &vmcp_release,
 180         .read           = &vmcp_read,
 181         .llseek         = &no_llseek,
 182         .write          = &vmcp_write,
 183         .unlocked_ioctl = &vmcp_ioctl,
 184         .compat_ioctl   = &vmcp_ioctl
 185 };
 186
 187 static struct miscdevice vmcp_dev = {
 188         .name   = "vmcp",
 189         .minor  = MISC_DYNAMIC_MINOR,
 190         .fops   = &vmcp_fops,
 191 };
 192
 193 static int __init vmcp_init(void)
 194 {
 195         int ret;
 196
 197         if (!MACHINE_IS_VM) {
 198                 printk(KERN_WARNING
 199                        "z/VM CP interface is only available under z/VM\n");
 200                 return -ENODEV;
 201         }
 202         ret = misc_register(&vmcp_dev);
 203         if (!ret)
 204                 printk(KERN_INFO "z/VM CP interface loaded\n");
 205         else
 206                 printk(KERN_WARNING
 207                        "z/VM CP interface not loaded. Could not register misc device.\n");
 208         vmcp_debug = debug_register("vmcp", 1, 1, 240);
 209         debug_register_view(vmcp_debug, &debug_hex_ascii_view);
 210         return ret;
 211 }
 212
 213 static void __exit vmcp_exit(void)
 214 {
 215         WARN_ON(misc_deregister(&vmcp_dev) != 0);
 216         debug_unregister(vmcp_debug);
 217         printk(KERN_INFO "z/VM CP interface unloaded.\n");
 218 }
 219
 220 module_init(vmcp_init);
 221 module_exit(vmcp_exit);