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         ssize_t ret;
  65         size_t size;
  66         struct vmcp_session *session;
  67
  68         session = file->private_data;
  69         if (mutex_lock_interruptible(&session->mutex))
  70                 return -ERESTARTSYS;
  71         if (!session->response) {
  72                 mutex_unlock(&session->mutex);
  73                 return 0;
  74         }
  75         size = min_t(size_t, session->resp_size, session->bufsize);
  76         ret = simple_read_from_buffer(buff, count, ppos,
  77                                         session->response, size);
  78
  79         mutex_unlock(&session->mutex);
  80
  81         return ret;
  82 }
  83
  84 static ssize_t
  85 vmcp_write(struct file *file, const char __user *buff, size_t count,
  86            loff_t *ppos)
  87 {
  88         char *cmd;
  89         struct vmcp_session *session;
  90
  91         if (count > 240)
  92                 return -EINVAL;
  93         cmd = kmalloc(count + 1, GFP_KERNEL);
  94         if (!cmd)
  95                 return -ENOMEM;
  96         if (copy_from_user(cmd, buff, count)) {
  97                 kfree(cmd);
  98                 return -EFAULT;
  99         }
 100         cmd[count] = '\0';
 101         session = (struct vmcp_session *)file->private_data;
 102         if (mutex_lock_interruptible(&session->mutex)) {
 103                 kfree(cmd);
 104                 return -ERESTARTSYS;
 105         }
 106         if (!session->response)
 107                 session->response = (char *)__get_free_pages(GFP_KERNEL
 108                                                 | __GFP_REPEAT | GFP_DMA,
 109                                                 get_order(session->bufsize));
 110         if (!session->response) {
 111                 mutex_unlock(&session->mutex);
 112                 kfree(cmd);
 113                 return -ENOMEM;
 114         }
 115         debug_text_event(vmcp_debug, 1, cmd);
 116         session->resp_size = cpcmd(cmd, session->response, session->bufsize,
 117                                    &session->resp_code);
 118         mutex_unlock(&session->mutex);
 119         kfree(cmd);
 120         *ppos = 0;              /* reset the file pointer after a command */
 121         return count;
 122 }
 123
 124
 125 /*
 126  * These ioctls are available, as the semantics of the diagnose 8 call
 127  * does not fit very well into a Linux call. Diagnose X'08' is described in
 128  * CP Programming Services SC24-6084-00
 129  *
 130  * VMCP_GETCODE: gives the CP return code back to user space
 131  * VMCP_SETBUF: sets the response buffer for the next write call. diagnose 8
 132  * expects adjacent pages in real storage and to make matters worse, we
 133  * dont know the size of the response. Therefore we default to PAGESIZE and
 134  * let userspace to change the response size, if userspace expects a bigger
 135  * response
 136  */
 137 static long vmcp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 138 {
 139         struct vmcp_session *session;
 140         int temp;
 141
 142         session = (struct vmcp_session *)file->private_data;
 143         if (mutex_lock_interruptible(&session->mutex))
 144                 return -ERESTARTSYS;
 145         switch (cmd) {
 146         case VMCP_GETCODE:
 147                 temp = session->resp_code;
 148                 mutex_unlock(&session->mutex);
 149                 return put_user(temp, (int __user *)arg);
 150         case VMCP_SETBUF:
 151                 free_pages((unsigned long)session->response,
 152                                 get_order(session->bufsize));
 153                 session->response=NULL;
 154                 temp = get_user(session->bufsize, (int __user *)arg);
 155                 if (get_order(session->bufsize) > 8) {
 156                         session->bufsize = PAGE_SIZE;
 157                         temp = -EINVAL;
 158                 }
 159                 mutex_unlock(&session->mutex);
 160                 return temp;
 161         case VMCP_GETSIZE:
 162                 temp = session->resp_size;
 163                 mutex_unlock(&session->mutex);
 164                 return put_user(temp, (int __user *)arg);
 165         default:
 166                 mutex_unlock(&session->mutex);
 167                 return -ENOIOCTLCMD;
 168         }
 169 }
 170
 171 static const struct file_operations vmcp_fops = {
 172         .owner          = THIS_MODULE,
 173         .open           = vmcp_open,
 174         .release        = vmcp_release,
 175         .read           = vmcp_read,
 176         .write          = vmcp_write,
 177         .unlocked_ioctl = vmcp_ioctl,
 178         .compat_ioctl   = vmcp_ioctl,
 179 };
 180
 181 static struct miscdevice vmcp_dev = {
 182         .name   = "vmcp",
 183         .minor  = MISC_DYNAMIC_MINOR,
 184         .fops   = &vmcp_fops,
 185 };
 186
 187 static int __init vmcp_init(void)
 188 {
 189         int ret;
 190
 191         if (!MACHINE_IS_VM) {
 192                 PRINT_WARN("z/VM CP interface is only available under z/VM\n");
 193                 return -ENODEV;
 194         }
 195
 196         vmcp_debug = debug_register("vmcp", 1, 1, 240);
 197         if (!vmcp_debug)
 198                 return -ENOMEM;
 199
 200         ret = debug_register_view(vmcp_debug, &debug_hex_ascii_view);
 201         if (ret) {
 202                 debug_unregister(vmcp_debug);
 203                 return ret;
 204         }
 205
 206         ret = misc_register(&vmcp_dev);
 207         if (ret) {
 208                 debug_unregister(vmcp_debug);
 209                 return ret;
 210         }
 211
 212         return 0;
 213 }
 214
 215 static void __exit vmcp_exit(void)
 216 {
 217         misc_deregister(&vmcp_dev);
 218         debug_unregister(vmcp_debug);
 219 }
 220
 221 module_init(vmcp_init);
 222 module_exit(vmcp_exit);