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 #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 <borntraeger@de.ibm.com>");
  26 MODULE_DESCRIPTION("z/VM CP interface");
  27
  28 #define PRINTK_HEADER "vmcp: "
  29
  30 static debug_info_t *vmcp_debug;
  31
  32 static int vmcp_open(struct inode *inode, struct file *file)
  33 {
  34         struct vmcp_session *session;
  35
  36         if (!capable(CAP_SYS_ADMIN))
  37                 return -EPERM;
  38
  39         session = kmalloc(sizeof(*session), GFP_KERNEL);
  40         if (!session)
  41                 return -ENOMEM;
  42         session->bufsize = PAGE_SIZE;
  43         session->response = NULL;
  44         session->resp_size = 0;
  45         mutex_init(&session->mutex);
  46         file->private_data = session;
  47         return nonseekable_open(inode, file);
  48 }
  49
  50 static int vmcp_release(struct inode *inode, struct file *file)
  51 {
  52         struct vmcp_session *session;
  53
  54         session = (struct vmcp_session *)file->private_data;
  55         file->private_data = NULL;
  56         free_pages((unsigned long)session->response, get_order(session->bufsize));
  57         kfree(session);
  58         return 0;
  59 }
  60
  61 static ssize_t
  62 vmcp_read(struct file *file, char __user *buff, size_t count, loff_t *ppos)
  63 {
  64         size_t tocopy;
  65         struct vmcp_session *session;
  66
  67         session = (struct vmcp_session *)file->private_data;
  68         if (mutex_lock_interruptible(&session->mutex))
  69                 return -ERESTARTSYS;
  70         if (!session->response) {
  71                 mutex_unlock(&session->mutex);
  72                 return 0;
  73         }
  74         if (*ppos > session->resp_size) {
  75                 mutex_unlock(&session->mutex);
  76                 return 0;
  77         }
  78         tocopy = min(session->resp_size - (size_t) (*ppos), count);
  79         tocopy = min(tocopy, session->bufsize - (size_t) (*ppos));
  80
  81         if (copy_to_user(buff, session->response + (*ppos), tocopy)) {
  82                 mutex_unlock(&session->mutex);
  83                 return -EFAULT;
  84         }
  85         mutex_unlock(&session->mutex);
  86         *ppos += tocopy;
  87         return tocopy;
  88 }
  89
  90 static ssize_t
  91 vmcp_write(struct file *file, const char __user *buff, size_t count,
  92            loff_t *ppos)
  93 {
  94         char *cmd;
  95         struct vmcp_session *session;
  96
  97         if (count > 240)
  98                 return -EINVAL;
  99         cmd = kmalloc(count + 1, GFP_KERNEL);
 100         if (!cmd)
 101                 return -ENOMEM;
 102         if (copy_from_user(cmd, buff, count)) {
 103                 kfree(cmd);
 104                 return -EFAULT;
 105         }
 106         cmd[count] = '\0';
 107         session = (struct vmcp_session *)file->private_data;
 108         if (mutex_lock_interruptible(&session->mutex)) {
 109                 kfree(cmd);
 110                 return -ERESTARTSYS;
 111         }
 112         if (!session->response)
 113                 session->response = (char *)__get_free_pages(GFP_KERNEL
 114                                                 | __GFP_REPEAT | GFP_DMA,
 115                                                 get_order(session->bufsize));
 116         if (!session->response) {
 117                 mutex_unlock(&session->mutex);
 118                 kfree(cmd);
 119                 return -ENOMEM;
 120         }
 121         debug_text_event(vmcp_debug, 1, cmd);
 122         session->resp_size = cpcmd(cmd, session->response, session->bufsize,
 123                                    &session->resp_code);
 124         mutex_unlock(&session->mutex);
 125         kfree(cmd);
 126         *ppos = 0;              /* reset the file pointer after a command */
 127         return count;
 128 }
 129
 130
 131 /*
 132  * These ioctls are available, as the semantics of the diagnose 8 call
 133  * does not fit very well into a Linux call. Diagnose X'08' is described in
 134  * CP Programming Services SC24-6084-00
 135  *
 136  * VMCP_GETCODE: gives the CP return code back to user space
 137  * VMCP_SETBUF: sets the response buffer for the next write call. diagnose 8
 138  * expects adjacent pages in real storage and to make matters worse, we
 139  * dont know the size of the response. Therefore we default to PAGESIZE and
 140  * let userspace to change the response size, if userspace expects a bigger
 141  * response
 142  */
 143 static long vmcp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 144 {
 145         struct vmcp_session *session;
 146         int temp;
 147
 148         session = (struct vmcp_session *)file->private_data;
 149         if (mutex_lock_interruptible(&session->mutex))
 150                 return -ERESTARTSYS;
 151         switch (cmd) {
 152         case VMCP_GETCODE:
 153                 temp = session->resp_code;
 154                 mutex_unlock(&session->mutex);
 155                 return put_user(temp, (int __user *)arg);
 156         case VMCP_SETBUF:
 157                 free_pages((unsigned long)session->response,
 158                                 get_order(session->bufsize));
 159                 session->response=NULL;
 160                 temp = get_user(session->bufsize, (int __user *)arg);
 161                 if (get_order(session->bufsize) > 8) {
 162                         session->bufsize = PAGE_SIZE;
 163                         temp = -EINVAL;
 164                 }
 165                 mutex_unlock(&session->mutex);
 166                 return temp;
 167         case VMCP_GETSIZE:
 168                 temp = session->resp_size;
 169                 mutex_unlock(&session->mutex);
 170                 return put_user(temp, (int __user *)arg);
 171         default:
 172                 mutex_unlock(&session->mutex);
 173                 return -ENOIOCTLCMD;
 174         }
 175 }
 176
 177 static const struct file_operations vmcp_fops = {
 178         .owner          = THIS_MODULE,
 179         .open           = vmcp_open,
 180         .release        = vmcp_release,
 181         .read           = vmcp_read,
 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                 PRINT_WARN("z/VM CP interface is only available under z/VM\n");
 199                 return -ENODEV;
 200         }
 201         vmcp_debug = debug_register("vmcp", 1, 1, 240);
 202         if (!vmcp_debug) {
 203                 PRINT_ERR("z/VM CP interface not loaded. Could not register "
 204                            "debug feature\n");
 205                 return -ENOMEM;
 206         }
 207         ret = debug_register_view(vmcp_debug, &debug_hex_ascii_view);
 208         if (ret) {
 209                 PRINT_ERR("z/VM CP interface not loaded. Could not register "
 210                           "debug feature view. Error code: %d\n", ret);
 211                 debug_unregister(vmcp_debug);
 212                 return ret;
 213         }
 214         ret = misc_register(&vmcp_dev);
 215         if (ret) {
 216                 PRINT_ERR("z/VM CP interface not loaded. Could not register "
 217                            "misc device. Error code: %d\n", ret);
 218                 debug_unregister(vmcp_debug);
 219                 return ret;
 220         }
 221         PRINT_INFO("z/VM CP interface loaded\n");
 222         return 0;
 223 }
 224
 225 static void __exit vmcp_exit(void)
 226 {
 227         misc_deregister(&vmcp_dev);
 228         debug_unregister(vmcp_debug);
 229         PRINT_INFO("z/VM CP interface unloaded.\n");
 230 }
 231
 232 module_init(vmcp_init);
 233 module_exit(vmcp_exit);