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