drivers/s390/char/vmcp.c

   1 /*
   2  * Copyright IBM Corp. 2004, 2010
   3  * Interface implementation for communication with the z/VM control program
   4  *
   5  * Author(s): Christian Borntraeger <borntraeger@de.ibm.com>
   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/compat.h>
  17 #include <linux/kernel.h>
  18 #include <linux/miscdevice.h>
  19 #include <linux/slab.h>
  20 #include <linux/export.h>
  21 #include <asm/compat.h>
  22 #include <asm/cpcmd.h>
  23 #include <asm/debug.h>
  24 #include <asm/uaccess.h>
  25 #include "vmcp.h"
  26
  27 static debug_info_t *vmcp_debug;
  28
  29 static int vmcp_open(struct inode *inode, struct file *file)
  30 {
  31         struct vmcp_session *session;
  32
  33         if (!capable(CAP_SYS_ADMIN))
  34                 return -EPERM;
  35
  36         session = kmalloc(sizeof(*session), GFP_KERNEL);
  37         if (!session)
  38                 return -ENOMEM;
  39
  40         session->bufsize = PAGE_SIZE;
  41         session->response = NULL;
  42         session->resp_size = 0;
  43         mutex_init(&session->mutex);
  44         file->private_data = session;
  45         return nonseekable_open(inode, file);
  46 }
  47
  48 static int vmcp_release(struct inode *inode, struct file *file)
  49 {
  50         struct vmcp_session *session;
  51
  52         session = file->private_data;
  53         file->private_data = NULL;
  54         free_pages((unsigned long)session->response, get_order(session->bufsize));
  55         kfree(session);
  56         return 0;
  57 }
  58
  59 static ssize_t
  60 vmcp_read(struct file *file, char __user *buff, size_t count, loff_t *ppos)
  61 {
  62         ssize_t ret;
  63         size_t size;
  64         struct vmcp_session *session;
  65
  66         session = file->private_data;
  67         if (mutex_lock_interruptible(&session->mutex))
  68                 return -ERESTARTSYS;
  69         if (!session->response) {
  70                 mutex_unlock(&session->mutex);
  71                 return 0;
  72         }
  73         size = min_t(size_t, session->resp_size, session->bufsize);
  74         ret = simple_read_from_buffer(buff, count, ppos,
  75                                         session->response, size);
  76
  77         mutex_unlock(&session->mutex);
  78
  79         return ret;
  80 }
  81
  82 static ssize_t
  83 vmcp_write(struct file *file, const char __user *buff, size_t count,
  84            loff_t *ppos)
  85 {
  86         char *cmd;
  87         struct vmcp_session *session;
  88
  89         if (count > 240)
  90                 return -EINVAL;
  91         cmd = memdup_user_nul(buff, count);
  92         if (IS_ERR(cmd))
  93                 return PTR_ERR(cmd);
  94         session = file->private_data;
  95         if (mutex_lock_interruptible(&session->mutex)) {
  96                 kfree(cmd);
  97                 return -ERESTARTSYS;
  98         }
  99         if (!session->response)
 100                 session->response = (char *)__get_free_pages(GFP_KERNEL
 101                                                 | __GFP_REPEAT | GFP_DMA,
 102                                                 get_order(session->bufsize));
 103         if (!session->response) {
 104                 mutex_unlock(&session->mutex);
 105                 kfree(cmd);
 106                 return -ENOMEM;
 107         }
 108         debug_text_event(vmcp_debug, 1, cmd);
 109         session->resp_size = cpcmd(cmd, session->response, session->bufsize,
 110                                    &session->resp_code);
 111         mutex_unlock(&session->mutex);
 112         kfree(cmd);
 113         *ppos = 0;              /* reset the file pointer after a command */
 114         return count;
 115 }
 116
 117
 118 /*
 119  * These ioctls are available, as the semantics of the diagnose 8 call
 120  * does not fit very well into a Linux call. Diagnose X'08' is described in
 121  * CP Programming Services SC24-6084-00
 122  *
 123  * VMCP_GETCODE: gives the CP return code back to user space
 124  * VMCP_SETBUF: sets the response buffer for the next write call. diagnose 8
 125  * expects adjacent pages in real storage and to make matters worse, we
 126  * dont know the size of the response. Therefore we default to PAGESIZE and
 127  * let userspace to change the response size, if userspace expects a bigger
 128  * response
 129  */
 130 static long vmcp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 131 {
 132         struct vmcp_session *session;
 133         int __user *argp;
 134         int temp;
 135
 136         session = file->private_data;
 137         if (is_compat_task())
 138                 argp = compat_ptr(arg);
 139         else
 140                 argp = (int __user *)arg;
 141         if (mutex_lock_interruptible(&session->mutex))
 142                 return -ERESTARTSYS;
 143         switch (cmd) {
 144         case VMCP_GETCODE:
 145                 temp = session->resp_code;
 146                 mutex_unlock(&session->mutex);
 147                 return put_user(temp, argp);
 148         case VMCP_SETBUF:
 149                 free_pages((unsigned long)session->response,
 150                                 get_order(session->bufsize));
 151                 session->response=NULL;
 152                 temp = get_user(session->bufsize, argp);
 153                 if (get_order(session->bufsize) > 8) {
 154                         session->bufsize = PAGE_SIZE;
 155                         temp = -EINVAL;
 156                 }
 157                 mutex_unlock(&session->mutex);
 158                 return temp;
 159         case VMCP_GETSIZE:
 160                 temp = session->resp_size;
 161                 mutex_unlock(&session->mutex);
 162                 return put_user(temp, argp);
 163         default:
 164                 mutex_unlock(&session->mutex);
 165                 return -ENOIOCTLCMD;
 166         }
 167 }
 168
 169 static const struct file_operations vmcp_fops = {
 170         .owner          = THIS_MODULE,
 171         .open           = vmcp_open,
 172         .release        = vmcp_release,
 173         .read           = vmcp_read,
 174         .write          = vmcp_write,
 175         .unlocked_ioctl = vmcp_ioctl,
 176         .compat_ioctl   = vmcp_ioctl,
 177         .llseek         = no_llseek,
 178 };
 179
 180 static struct miscdevice vmcp_dev = {
 181         .name   = "vmcp",
 182         .minor  = MISC_DYNAMIC_MINOR,
 183         .fops   = &vmcp_fops,
 184 };
 185
 186 static int __init vmcp_init(void)
 187 {
 188         int ret;
 189
 190         if (!MACHINE_IS_VM)
 191                 return 0;
 192
 193         vmcp_debug = debug_register("vmcp", 1, 1, 240);
 194         if (!vmcp_debug)
 195                 return -ENOMEM;
 196
 197         ret = debug_register_view(vmcp_debug, &debug_hex_ascii_view);
 198         if (ret) {
 199                 debug_unregister(vmcp_debug);
 200                 return ret;
 201         }
 202
 203         ret = misc_register(&vmcp_dev);
 204         if (ret)
 205                 debug_unregister(vmcp_debug);
 206         return ret;
 207 }
 208 device_initcall(vmcp_init);