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/compat.h>
  17 #include <linux/kernel.h>
  18 #include <linux/miscdevice.h>
  19 #include <linux/slab.h>
  20 #include <asm/compat.h>
  21 #include <asm/cpcmd.h>
  22 #include <asm/debug.h>
  23 #include <asm/uaccess.h>
  24 #include "vmcp.h"
  25
  26 static debug_info_t *vmcp_debug;
  27
  28 static int vmcp_open(struct inode *inode, struct file *file)
  29 {
  30         struct vmcp_session *session;
  31
  32         if (!capable(CAP_SYS_ADMIN))
  33                 return -EPERM;
  34
  35         session = kmalloc(sizeof(*session), GFP_KERNEL);
  36         if (!session)
  37                 return -ENOMEM;
  38
  39         session->bufsize = PAGE_SIZE;
  40         session->response = NULL;
  41         session->resp_size = 0;
  42         mutex_init(&session->mutex);
  43         file->private_data = session;
  44         return nonseekable_open(inode, file);
  45 }
  46
  47 static int vmcp_release(struct inode *inode, struct file *file)
  48 {
  49         struct vmcp_session *session;
  50
  51         session = file->private_data;
  52         file->private_data = NULL;
  53         free_pages((unsigned long)session->response, get_order(session->bufsize));
  54         kfree(session);
  55         return 0;
  56 }
  57
  58 static ssize_t
  59 vmcp_read(struct file *file, char __user *buff, size_t count, loff_t *ppos)
  60 {
  61         ssize_t ret;
  62         size_t size;
  63         struct vmcp_session *session;
  64
  65         session = file->private_data;
  66         if (mutex_lock_interruptible(&session->mutex))
  67                 return -ERESTARTSYS;
  68         if (!session->response) {
  69                 mutex_unlock(&session->mutex);
  70                 return 0;
  71         }
  72         size = min_t(size_t, session->resp_size, session->bufsize);
  73         ret = simple_read_from_buffer(buff, count, ppos,
  74                                         session->response, size);
  75
  76         mutex_unlock(&session->mutex);
  77
  78         return ret;
  79 }
  80
  81 static ssize_t
  82 vmcp_write(struct file *file, const char __user *buff, size_t count,
  83            loff_t *ppos)
  84 {
  85         char *cmd;
  86         struct vmcp_session *session;
  87
  88         if (count > 240)
  89                 return -EINVAL;
  90         cmd = kmalloc(count + 1, GFP_KERNEL);
  91         if (!cmd)
  92                 return -ENOMEM;
  93         if (copy_from_user(cmd, buff, count)) {
  94                 kfree(cmd);
  95                 return -EFAULT;
  96         }
  97         cmd[count] = '\0';
  98         session = file->private_data;
  99         if (mutex_lock_interruptible(&session->mutex)) {
 100                 kfree(cmd);
 101                 return -ERESTARTSYS;
 102         }
 103         if (!session->response)
 104                 session->response = (char *)__get_free_pages(GFP_KERNEL
 105                                                 | __GFP_REPEAT | GFP_DMA,
 106                                                 get_order(session->bufsize));
 107         if (!session->response) {
 108                 mutex_unlock(&session->mutex);
 109                 kfree(cmd);
 110                 return -ENOMEM;
 111         }
 112         debug_text_event(vmcp_debug, 1, cmd);
 113         session->resp_size = cpcmd(cmd, session->response, session->bufsize,
 114                                    &session->resp_code);
 115         mutex_unlock(&session->mutex);
 116         kfree(cmd);
 117         *ppos = 0;              /* reset the file pointer after a command */
 118         return count;
 119 }
 120
 121
 122 /*
 123  * These ioctls are available, as the semantics of the diagnose 8 call
 124  * does not fit very well into a Linux call. Diagnose X'08' is described in
 125  * CP Programming Services SC24-6084-00
 126  *
 127  * VMCP_GETCODE: gives the CP return code back to user space
 128  * VMCP_SETBUF: sets the response buffer for the next write call. diagnose 8
 129  * expects adjacent pages in real storage and to make matters worse, we
 130  * dont know the size of the response. Therefore we default to PAGESIZE and
 131  * let userspace to change the response size, if userspace expects a bigger
 132  * response
 133  */
 134 static long vmcp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 135 {
 136         struct vmcp_session *session;
 137         int __user *argp;
 138         int temp;
 139
 140         session = file->private_data;
 141         if (is_compat_task())
 142                 argp = compat_ptr(arg);
 143         else
 144                 argp = (int __user *)arg;
 145         if (mutex_lock_interruptible(&session->mutex))
 146                 return -ERESTARTSYS;
 147         switch (cmd) {
 148         case VMCP_GETCODE:
 149                 temp = session->resp_code;
 150                 mutex_unlock(&session->mutex);
 151                 return put_user(temp, argp);
 152         case VMCP_SETBUF:
 153                 free_pages((unsigned long)session->response,
 154                                 get_order(session->bufsize));
 155                 session->response=NULL;
 156                 temp = get_user(session->bufsize, argp);
 157                 if (get_order(session->bufsize) > 8) {
 158                         session->bufsize = PAGE_SIZE;
 159                         temp = -EINVAL;
 160                 }
 161                 mutex_unlock(&session->mutex);
 162                 return temp;
 163         case VMCP_GETSIZE:
 164                 temp = session->resp_size;
 165                 mutex_unlock(&session->mutex);
 166                 return put_user(temp, argp);
 167         default:
 168                 mutex_unlock(&session->mutex);
 169                 return -ENOIOCTLCMD;
 170         }
 171 }
 172
 173 static const struct file_operations vmcp_fops = {
 174         .owner          = THIS_MODULE,
 175         .open           = vmcp_open,
 176         .release        = vmcp_release,
 177         .read           = vmcp_read,
 178         .write          = vmcp_write,
 179         .unlocked_ioctl = vmcp_ioctl,
 180         .compat_ioctl   = vmcp_ioctl,
 181         .llseek         = no_llseek,
 182 };
 183
 184 static struct miscdevice vmcp_dev = {
 185         .name   = "vmcp",
 186         .minor  = MISC_DYNAMIC_MINOR,
 187         .fops   = &vmcp_fops,
 188 };
 189
 190 static int __init vmcp_init(void)
 191 {
 192         int ret;
 193
 194         if (!MACHINE_IS_VM)
 195                 return 0;
 196
 197         vmcp_debug = debug_register("vmcp", 1, 1, 240);
 198         if (!vmcp_debug)
 199                 return -ENOMEM;
 200
 201         ret = debug_register_view(vmcp_debug, &debug_hex_ascii_view);
 202         if (ret) {
 203                 debug_unregister(vmcp_debug);
 204                 return ret;
 205         }
 206
 207         ret = misc_register(&vmcp_dev);
 208         if (ret)
 209                 debug_unregister(vmcp_debug);
 210         return ret;
 211 }
 212 device_initcall(vmcp_init);