drivers/s390/char/vmcp.c

   1 /*
   2  * Copyright IBM Corp. 2004,2007
   3  * Interface implementation for communication with the z/VM control program
   4  * Author(s): Christian Borntraeger <borntraeger@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 #define KMSG_COMPONENT "vmcp"
  15 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  16
  17 #include <linux/fs.h>
  18 #include <linux/init.h>
  19 #include <linux/kernel.h>
  20 #include <linux/miscdevice.h>
  21 #include <linux/module.h>
  22 #include <linux/slab.h>
  23 #include <asm/compat.h>
  24 #include <asm/cpcmd.h>
  25 #include <asm/debug.h>
  26 #include <asm/uaccess.h>
  27 #include "vmcp.h"
  28
  29 MODULE_LICENSE("GPL");
  30 MODULE_AUTHOR("Christian Borntraeger <borntraeger@de.ibm.com>");
  31 MODULE_DESCRIPTION("z/VM CP interface");
  32
  33 static debug_info_t *vmcp_debug;
  34
  35 static int vmcp_open(struct inode *inode, struct file *file)
  36 {
  37         struct vmcp_session *session;
  38
  39         if (!capable(CAP_SYS_ADMIN))
  40                 return -EPERM;
  41
  42         session = kmalloc(sizeof(*session), GFP_KERNEL);
  43         if (!session)
  44                 return -ENOMEM;
  45
  46         session->bufsize = PAGE_SIZE;
  47         session->response = NULL;
  48         session->resp_size = 0;
  49         mutex_init(&session->mutex);
  50         file->private_data = session;
  51         return nonseekable_open(inode, file);
  52 }
  53
  54 static int vmcp_release(struct inode *inode, struct file *file)
  55 {
  56         struct vmcp_session *session;
  57
  58         session = (struct vmcp_session *)file->private_data;
  59         file->private_data = NULL;
  60         free_pages((unsigned long)session->response, get_order(session->bufsize));
  61         kfree(session);
  62         return 0;
  63 }
  64
  65 static ssize_t
  66 vmcp_read(struct file *file, char __user *buff, size_t count, loff_t *ppos)
  67 {
  68         ssize_t ret;
  69         size_t size;
  70         struct vmcp_session *session;
  71
  72         session = file->private_data;
  73         if (mutex_lock_interruptible(&session->mutex))
  74                 return -ERESTARTSYS;
  75         if (!session->response) {
  76                 mutex_unlock(&session->mutex);
  77                 return 0;
  78         }
  79         size = min_t(size_t, session->resp_size, session->bufsize);
  80         ret = simple_read_from_buffer(buff, count, ppos,
  81                                         session->response, size);
  82
  83         mutex_unlock(&session->mutex);
  84
  85         return ret;
  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 (mutex_lock_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                 mutex_unlock(&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, session->bufsize,
 121                                    &session->resp_code);
 122         mutex_unlock(&session->mutex);
 123         kfree(cmd);
 124         *ppos = 0;              /* reset the file pointer after a command */
 125         return count;
 126 }
 127
 128
 129 /*
 130  * These ioctls are available, as the semantics of the diagnose 8 call
 131  * does not fit very well into a Linux call. Diagnose X'08' is described in
 132  * CP Programming Services SC24-6084-00
 133  *
 134  * VMCP_GETCODE: gives the CP return code back to user space
 135  * VMCP_SETBUF: sets the response buffer for the next write call. diagnose 8
 136  * expects adjacent pages in real storage and to make matters worse, we
 137  * dont know the size of the response. Therefore we default to PAGESIZE and
 138  * let userspace to change the response size, if userspace expects a bigger
 139  * response
 140  */
 141 static long vmcp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 142 {
 143         struct vmcp_session *session;
 144         int __user *argp;
 145         int temp;
 146
 147         session = (struct vmcp_session *)file->private_data;
 148         if (is_compat_task())
 149                 argp = compat_ptr(arg);
 150         else
 151                 argp = (int __user *)arg;
 152         if (mutex_lock_interruptible(&session->mutex))
 153                 return -ERESTARTSYS;
 154         switch (cmd) {
 155         case VMCP_GETCODE:
 156                 temp = session->resp_code;
 157                 mutex_unlock(&session->mutex);
 158                 return put_user(temp, argp);
 159         case VMCP_SETBUF:
 160                 free_pages((unsigned long)session->response,
 161                                 get_order(session->bufsize));
 162                 session->response=NULL;
 163                 temp = get_user(session->bufsize, argp);
 164                 if (get_order(session->bufsize) > 8) {
 165                         session->bufsize = PAGE_SIZE;
 166                         temp = -EINVAL;
 167                 }
 168                 mutex_unlock(&session->mutex);
 169                 return temp;
 170         case VMCP_GETSIZE:
 171                 temp = session->resp_size;
 172                 mutex_unlock(&session->mutex);
 173                 return put_user(temp, argp);
 174         default:
 175                 mutex_unlock(&session->mutex);
 176                 return -ENOIOCTLCMD;
 177         }
 178 }
 179
 180 static const struct file_operations vmcp_fops = {
 181         .owner          = THIS_MODULE,
 182         .open           = vmcp_open,
 183         .release        = vmcp_release,
 184         .read           = vmcp_read,
 185         .write          = vmcp_write,
 186         .unlocked_ioctl = vmcp_ioctl,
 187         .compat_ioctl   = vmcp_ioctl,
 188 };
 189
 190 static struct miscdevice vmcp_dev = {
 191         .name   = "vmcp",
 192         .minor  = MISC_DYNAMIC_MINOR,
 193         .fops   = &vmcp_fops,
 194 };
 195
 196 static int __init vmcp_init(void)
 197 {
 198         int ret;
 199
 200         if (!MACHINE_IS_VM) {
 201                 pr_warning("The z/VM CP interface device driver cannot be "
 202                            "loaded without z/VM\n");
 203                 return -ENODEV;
 204         }
 205
 206         vmcp_debug = debug_register("vmcp", 1, 1, 240);
 207         if (!vmcp_debug)
 208                 return -ENOMEM;
 209
 210         ret = debug_register_view(vmcp_debug, &debug_hex_ascii_view);
 211         if (ret) {
 212                 debug_unregister(vmcp_debug);
 213                 return ret;
 214         }
 215
 216         ret = misc_register(&vmcp_dev);
 217         if (ret) {
 218                 debug_unregister(vmcp_debug);
 219                 return ret;
 220         }
 221
 222         return 0;
 223 }
 224
 225 static void __exit vmcp_exit(void)
 226 {
 227         misc_deregister(&vmcp_dev);
 228         debug_unregister(vmcp_debug);
 229 }
 230
 231 module_init(vmcp_init);
 232 module_exit(vmcp_exit);