drivers/s390/char/vmcp.c

   1 /*
   2  * Copyright IBM Corp. 2004,2010
   3  * Interface implementation for communication with the z/VM control program
   4  *
   5  * Author(s): Christian Borntraeger <borntraeger@de.ibm.com>
   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/slab.h>
  19 #include <asm/compat.h>
  20 #include <asm/cpcmd.h>
  21 #include <asm/debug.h>
  22 #include <asm/uaccess.h>
  23 #include "vmcp.h"
  24
  25 static debug_info_t *vmcp_debug;
  26
  27 static int vmcp_open(struct inode *inode, struct file *file)
  28 {
  29         struct vmcp_session *session;
  30
  31         if (!capable(CAP_SYS_ADMIN))
  32                 return -EPERM;
  33
  34         session = kmalloc(sizeof(*session), GFP_KERNEL);
  35         if (!session)
  36                 return -ENOMEM;
  37
  38         session->bufsize = PAGE_SIZE;
  39         session->response = NULL;
  40         session->resp_size = 0;
  41         mutex_init(&session->mutex);
  42         file->private_data = session;
  43         return nonseekable_open(inode, file);
  44 }
  45
  46 static int vmcp_release(struct inode *inode, struct file *file)
  47 {
  48         struct vmcp_session *session;
  49
  50         session = (struct vmcp_session *)file->private_data;
  51         file->private_data = NULL;
  52         free_pages((unsigned long)session->response, get_order(session->bufsize));
  53         kfree(session);
  54         return 0;
  55 }
  56
  57 static ssize_t
  58 vmcp_read(struct file *file, char __user *buff, size_t count, loff_t *ppos)
  59 {
  60         ssize_t ret;
  61         size_t size;
  62         struct vmcp_session *session;
  63
  64         session = file->private_data;
  65         if (mutex_lock_interruptible(&session->mutex))
  66                 return -ERESTARTSYS;
  67         if (!session->response) {
  68                 mutex_unlock(&session->mutex);
  69                 return 0;
  70         }
  71         size = min_t(size_t, session->resp_size, session->bufsize);
  72         ret = simple_read_from_buffer(buff, count, ppos,
  73                                         session->response, size);
  74
  75         mutex_unlock(&session->mutex);
  76
  77         return ret;
  78 }
  79
  80 static ssize_t
  81 vmcp_write(struct file *file, const char __user *buff, size_t count,
  82            loff_t *ppos)
  83 {
  84         char *cmd;
  85         struct vmcp_session *session;
  86
  87         if (count > 240)
  88                 return -EINVAL;
  89         cmd = kmalloc(count + 1, GFP_KERNEL);
  90         if (!cmd)
  91                 return -ENOMEM;
  92         if (copy_from_user(cmd, buff, count)) {
  93                 kfree(cmd);
  94                 return -EFAULT;
  95         }
  96         cmd[count] = '\0';
  97         session = (struct vmcp_session *)file->private_data;
  98         if (mutex_lock_interruptible(&session->mutex)) {
  99                 kfree(cmd);
 100                 return -ERESTARTSYS;
 101         }
 102         if (!session->response)
 103                 session->response = (char *)__get_free_pages(GFP_KERNEL
 104                                                 | __GFP_REPEAT | GFP_DMA,
 105                                                 get_order(session->bufsize));
 106         if (!session->response) {
 107                 mutex_unlock(&session->mutex);
 108                 kfree(cmd);
 109                 return -ENOMEM;
 110         }
 111         debug_text_event(vmcp_debug, 1, cmd);
 112         session->resp_size = cpcmd(cmd, session->response, session->bufsize,
 113                                    &session->resp_code);
 114         mutex_unlock(&session->mutex);
 115         kfree(cmd);
 116         *ppos = 0;              /* reset the file pointer after a command */
 117         return count;
 118 }
 119
 120
 121 /*
 122  * These ioctls are available, as the semantics of the diagnose 8 call
 123  * does not fit very well into a Linux call. Diagnose X'08' is described in
 124  * CP Programming Services SC24-6084-00
 125  *
 126  * VMCP_GETCODE: gives the CP return code back to user space
 127  * VMCP_SETBUF: sets the response buffer for the next write call. diagnose 8
 128  * expects adjacent pages in real storage and to make matters worse, we
 129  * dont know the size of the response. Therefore we default to PAGESIZE and
 130  * let userspace to change the response size, if userspace expects a bigger
 131  * response
 132  */
 133 static long vmcp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 134 {
 135         struct vmcp_session *session;
 136         int __user *argp;
 137         int temp;
 138
 139         session = (struct vmcp_session *)file->private_data;
 140         if (is_compat_task())
 141                 argp = compat_ptr(arg);
 142         else
 143                 argp = (int __user *)arg;
 144         if (mutex_lock_interruptible(&session->mutex))
 145                 return -ERESTARTSYS;
 146         switch (cmd) {
 147         case VMCP_GETCODE:
 148                 temp = session->resp_code;
 149                 mutex_unlock(&session->mutex);
 150                 return put_user(temp, argp);
 151         case VMCP_SETBUF:
 152                 free_pages((unsigned long)session->response,
 153                                 get_order(session->bufsize));
 154                 session->response=NULL;
 155                 temp = get_user(session->bufsize, argp);
 156                 if (get_order(session->bufsize) > 8) {
 157                         session->bufsize = PAGE_SIZE;
 158                         temp = -EINVAL;
 159                 }
 160                 mutex_unlock(&session->mutex);
 161                 return temp;
 162         case VMCP_GETSIZE:
 163                 temp = session->resp_size;
 164                 mutex_unlock(&session->mutex);
 165                 return put_user(temp, argp);
 166         default:
 167                 mutex_unlock(&session->mutex);
 168                 return -ENOIOCTLCMD;
 169         }
 170 }
 171
 172 static const struct file_operations vmcp_fops = {
 173         .owner          = THIS_MODULE,
 174         .open           = vmcp_open,
 175         .release        = vmcp_release,
 176         .read           = vmcp_read,
 177         .write          = vmcp_write,
 178         .unlocked_ioctl = vmcp_ioctl,
 179         .compat_ioctl   = vmcp_ioctl,
 180 };
 181
 182 static struct miscdevice vmcp_dev = {
 183         .name   = "vmcp",
 184         .minor  = MISC_DYNAMIC_MINOR,
 185         .fops   = &vmcp_fops,
 186 };
 187
 188 static int __init vmcp_init(void)
 189 {
 190         int ret;
 191
 192         if (!MACHINE_IS_VM)
 193                 return 0;
 194
 195         vmcp_debug = debug_register("vmcp", 1, 1, 240);
 196         if (!vmcp_debug)
 197                 return -ENOMEM;
 198
 199         ret = debug_register_view(vmcp_debug, &debug_hex_ascii_view);
 200         if (ret) {
 201                 debug_unregister(vmcp_debug);
 202                 return ret;
 203         }
 204
 205         ret = misc_register(&vmcp_dev);
 206         if (ret)
 207                 debug_unregister(vmcp_debug);
 208         return ret;
 209 }
 210 device_initcall(vmcp_init);