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 <asm/compat.h>
  23 #include <asm/cpcmd.h>
  24 #include <asm/debug.h>
  25 #include <asm/uaccess.h>
  26 #include "vmcp.h"
  27
  28 MODULE_LICENSE("GPL");
  29 MODULE_AUTHOR("Christian Borntraeger <borntraeger@de.ibm.com>");
  30 MODULE_DESCRIPTION("z/VM CP interface");
  31
  32 static debug_info_t *vmcp_debug;
  33
  34 static int vmcp_open(struct inode *inode, struct file *file)
  35 {
  36         struct vmcp_session *session;
  37
  38         if (!capable(CAP_SYS_ADMIN))
  39                 return -EPERM;
  40
  41         session = kmalloc(sizeof(*session), GFP_KERNEL);
  42         if (!session)
  43                 return -ENOMEM;
  44
  45         session->bufsize = PAGE_SIZE;
  46         session->response = NULL;
  47         session->resp_size = 0;
  48         mutex_init(&session->mutex);
  49         file->private_data = session;
  50         return nonseekable_open(inode, file);
  51 }
  52
  53 static int vmcp_release(struct inode *inode, struct file *file)
  54 {
  55         struct vmcp_session *session;
  56
  57         session = (struct vmcp_session *)file->private_data;
  58         file->private_data = NULL;
  59         free_pages((unsigned long)session->response, get_order(session->bufsize));
  60         kfree(session);
  61         return 0;
  62 }
  63
  64 static ssize_t
  65 vmcp_read(struct file *file, char __user *buff, size_t count, loff_t *ppos)
  66 {
  67         ssize_t ret;
  68         size_t size;
  69         struct vmcp_session *session;
  70
  71         session = file->private_data;
  72         if (mutex_lock_interruptible(&session->mutex))
  73                 return -ERESTARTSYS;
  74         if (!session->response) {
  75                 mutex_unlock(&session->mutex);
  76                 return 0;
  77         }
  78         size = min_t(size_t, session->resp_size, session->bufsize);
  79         ret = simple_read_from_buffer(buff, count, ppos,
  80                                         session->response, size);
  81
  82         mutex_unlock(&session->mutex);
  83
  84         return ret;
  85 }
  86
  87 static ssize_t
  88 vmcp_write(struct file *file, const char __user *buff, size_t count,
  89            loff_t *ppos)
  90 {
  91         char *cmd;
  92         struct vmcp_session *session;
  93
  94         if (count > 240)
  95                 return -EINVAL;
  96         cmd = kmalloc(count + 1, GFP_KERNEL);
  97         if (!cmd)
  98                 return -ENOMEM;
  99         if (copy_from_user(cmd, buff, count)) {
 100                 kfree(cmd);
 101                 return -EFAULT;
 102         }
 103         cmd[count] = '\0';
 104         session = (struct vmcp_session *)file->private_data;
 105         if (mutex_lock_interruptible(&session->mutex)) {
 106                 kfree(cmd);
 107                 return -ERESTARTSYS;
 108         }
 109         if (!session->response)
 110                 session->response = (char *)__get_free_pages(GFP_KERNEL
 111                                                 | __GFP_REPEAT | GFP_DMA,
 112                                                 get_order(session->bufsize));
 113         if (!session->response) {
 114                 mutex_unlock(&session->mutex);
 115                 kfree(cmd);
 116                 return -ENOMEM;
 117         }
 118         debug_text_event(vmcp_debug, 1, cmd);
 119         session->resp_size = cpcmd(cmd, session->response, session->bufsize,
 120                                    &session->resp_code);
 121         mutex_unlock(&session->mutex);
 122         kfree(cmd);
 123         *ppos = 0;              /* reset the file pointer after a command */
 124         return count;
 125 }
 126
 127
 128 /*
 129  * These ioctls are available, as the semantics of the diagnose 8 call
 130  * does not fit very well into a Linux call. Diagnose X'08' is described in
 131  * CP Programming Services SC24-6084-00
 132  *
 133  * VMCP_GETCODE: gives the CP return code back to user space
 134  * VMCP_SETBUF: sets the response buffer for the next write call. diagnose 8
 135  * expects adjacent pages in real storage and to make matters worse, we
 136  * dont know the size of the response. Therefore we default to PAGESIZE and
 137  * let userspace to change the response size, if userspace expects a bigger
 138  * response
 139  */
 140 static long vmcp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 141 {
 142         struct vmcp_session *session;
 143         int __user *argp;
 144         int temp;
 145
 146         session = (struct vmcp_session *)file->private_data;
 147         if (is_compat_task())
 148                 argp = compat_ptr(arg);
 149         else
 150                 argp = (int __user *)arg;
 151         if (mutex_lock_interruptible(&session->mutex))
 152                 return -ERESTARTSYS;
 153         switch (cmd) {
 154         case VMCP_GETCODE:
 155                 temp = session->resp_code;
 156                 mutex_unlock(&session->mutex);
 157                 return put_user(temp, argp);
 158         case VMCP_SETBUF:
 159                 free_pages((unsigned long)session->response,
 160                                 get_order(session->bufsize));
 161                 session->response=NULL;
 162                 temp = get_user(session->bufsize, argp);
 163                 if (get_order(session->bufsize) > 8) {
 164                         session->bufsize = PAGE_SIZE;
 165                         temp = -EINVAL;
 166                 }
 167                 mutex_unlock(&session->mutex);
 168                 return temp;
 169         case VMCP_GETSIZE:
 170                 temp = session->resp_size;
 171                 mutex_unlock(&session->mutex);
 172                 return put_user(temp, argp);
 173         default:
 174                 mutex_unlock(&session->mutex);
 175                 return -ENOIOCTLCMD;
 176         }
 177 }
 178
 179 static const struct file_operations vmcp_fops = {
 180         .owner          = THIS_MODULE,
 181         .open           = vmcp_open,
 182         .release        = vmcp_release,
 183         .read           = vmcp_read,
 184         .write          = vmcp_write,
 185         .unlocked_ioctl = vmcp_ioctl,
 186         .compat_ioctl   = vmcp_ioctl,
 187 };
 188
 189 static struct miscdevice vmcp_dev = {
 190         .name   = "vmcp",
 191         .minor  = MISC_DYNAMIC_MINOR,
 192         .fops   = &vmcp_fops,
 193 };
 194
 195 static int __init vmcp_init(void)
 196 {
 197         int ret;
 198
 199         if (!MACHINE_IS_VM) {
 200                 pr_warning("The z/VM CP interface device driver cannot be "
 201                            "loaded without z/VM\n");
 202                 return -ENODEV;
 203         }
 204
 205         vmcp_debug = debug_register("vmcp", 1, 1, 240);
 206         if (!vmcp_debug)
 207                 return -ENOMEM;
 208
 209         ret = debug_register_view(vmcp_debug, &debug_hex_ascii_view);
 210         if (ret) {
 211                 debug_unregister(vmcp_debug);
 212                 return ret;
 213         }
 214
 215         ret = misc_register(&vmcp_dev);
 216         if (ret) {
 217                 debug_unregister(vmcp_debug);
 218                 return ret;
 219         }
 220
 221         return 0;
 222 }
 223
 224 static void __exit vmcp_exit(void)
 225 {
 226         misc_deregister(&vmcp_dev);
 227         debug_unregister(vmcp_debug);
 228 }
 229
 230 module_init(vmcp_init);
 231 module_exit(vmcp_exit);