drivers/s390/char/vmcp.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright IBM Corp. 2004, 2010
   4  * Interface implementation for communication with the z/VM control program
   5  *
   6  * Author(s): Christian Borntraeger <borntraeger@de.ibm.com>
   7  *
   8  * z/VMs CP offers the possibility to issue commands via the diagnose code 8
   9  * this driver implements a character device that issues these commands and
  10  * returns the answer of CP.
  11  *
  12  * The idea of this driver is based on cpint from Neale Ferguson and #CP in CMS
  13  */
  14
  15 #include <linux/fs.h>
  16 #include <linux/init.h>
  17 #include <linux/compat.h>
  18 #include <linux/kernel.h>
  19 #include <linux/miscdevice.h>
  20 #include <linux/slab.h>
  21 #include <linux/uaccess.h>
  22 #include <linux/export.h>
  23 #include <linux/mutex.h>
  24 #include <linux/cma.h>
  25 #include <linux/mm.h>
  26 #include <asm/cpcmd.h>
  27 #include <asm/debug.h>
  28 #include <asm/vmcp.h>
  29
  30 struct vmcp_session {
  31         char *response;
  32         unsigned int bufsize;
  33         unsigned int cma_alloc : 1;
  34         int resp_size;
  35         int resp_code;
  36         struct mutex mutex;
  37 };
  38
  39 static debug_info_t *vmcp_debug;
  40
  41 static unsigned long vmcp_cma_size __initdata = CONFIG_VMCP_CMA_SIZE * 1024 * 1024;
  42 static struct cma *vmcp_cma;
  43
  44 static int __init early_parse_vmcp_cma(char *p)
  45 {
  46         vmcp_cma_size = ALIGN(memparse(p, NULL), PAGE_SIZE);
  47         return 0;
  48 }
  49 early_param("vmcp_cma", early_parse_vmcp_cma);
  50
  51 void __init vmcp_cma_reserve(void)
  52 {
  53         if (!MACHINE_IS_VM)
  54                 return;
  55         cma_declare_contiguous(0, vmcp_cma_size, 0, 0, 0, false, "vmcp", &vmcp_cma);
  56 }
  57
  58 static void vmcp_response_alloc(struct vmcp_session *session)
  59 {
  60         struct page *page = NULL;
  61         int nr_pages, order;
  62
  63         order = get_order(session->bufsize);
  64         nr_pages = ALIGN(session->bufsize, PAGE_SIZE) >> PAGE_SHIFT;
  65         /*
  66          * For anything below order 3 allocations rely on the buddy
  67          * allocator. If such low-order allocations can't be handled
  68          * anymore the system won't work anyway.
  69          */
  70         if (order > 2)
  71                 page = cma_alloc(vmcp_cma, nr_pages, 0, false);
  72         if (page) {
  73                 session->response = (char *)page_to_phys(page);
  74                 session->cma_alloc = 1;
  75                 return;
  76         }
  77         session->response = (char *)__get_free_pages(GFP_KERNEL | __GFP_RETRY_MAYFAIL, order);
  78 }
  79
  80 static void vmcp_response_free(struct vmcp_session *session)
  81 {
  82         int nr_pages, order;
  83         struct page *page;
  84
  85         if (!session->response)
  86                 return;
  87         order = get_order(session->bufsize);
  88         nr_pages = ALIGN(session->bufsize, PAGE_SIZE) >> PAGE_SHIFT;
  89         if (session->cma_alloc) {
  90                 page = phys_to_page((unsigned long)session->response);
  91                 cma_release(vmcp_cma, page, nr_pages);
  92                 session->cma_alloc = 0;
  93         } else {
  94                 free_pages((unsigned long)session->response, order);
  95         }
  96         session->response = NULL;
  97 }
  98
  99 static int vmcp_open(struct inode *inode, struct file *file)
 100 {
 101         struct vmcp_session *session;
 102
 103         if (!capable(CAP_SYS_ADMIN))
 104                 return -EPERM;
 105
 106         session = kmalloc(sizeof(*session), GFP_KERNEL);
 107         if (!session)
 108                 return -ENOMEM;
 109
 110         session->bufsize = PAGE_SIZE;
 111         session->response = NULL;
 112         session->resp_size = 0;
 113         mutex_init(&session->mutex);
 114         file->private_data = session;
 115         return nonseekable_open(inode, file);
 116 }
 117
 118 static int vmcp_release(struct inode *inode, struct file *file)
 119 {
 120         struct vmcp_session *session;
 121
 122         session = file->private_data;
 123         file->private_data = NULL;
 124         vmcp_response_free(session);
 125         kfree(session);
 126         return 0;
 127 }
 128
 129 static ssize_t
 130 vmcp_read(struct file *file, char __user *buff, size_t count, loff_t *ppos)
 131 {
 132         ssize_t ret;
 133         size_t size;
 134         struct vmcp_session *session;
 135
 136         session = file->private_data;
 137         if (mutex_lock_interruptible(&session->mutex))
 138                 return -ERESTARTSYS;
 139         if (!session->response) {
 140                 mutex_unlock(&session->mutex);
 141                 return 0;
 142         }
 143         size = min_t(size_t, session->resp_size, session->bufsize);
 144         ret = simple_read_from_buffer(buff, count, ppos,
 145                                         session->response, size);
 146
 147         mutex_unlock(&session->mutex);
 148
 149         return ret;
 150 }
 151
 152 static ssize_t
 153 vmcp_write(struct file *file, const char __user *buff, size_t count,
 154            loff_t *ppos)
 155 {
 156         char *cmd;
 157         struct vmcp_session *session;
 158
 159         if (count > 240)
 160                 return -EINVAL;
 161         cmd = memdup_user_nul(buff, count);
 162         if (IS_ERR(cmd))
 163                 return PTR_ERR(cmd);
 164         session = file->private_data;
 165         if (mutex_lock_interruptible(&session->mutex)) {
 166                 kfree(cmd);
 167                 return -ERESTARTSYS;
 168         }
 169         if (!session->response)
 170                 vmcp_response_alloc(session);
 171         if (!session->response) {
 172                 mutex_unlock(&session->mutex);
 173                 kfree(cmd);
 174                 return -ENOMEM;
 175         }
 176         debug_text_event(vmcp_debug, 1, cmd);
 177         session->resp_size = cpcmd(cmd, session->response, session->bufsize,
 178                                    &session->resp_code);
 179         mutex_unlock(&session->mutex);
 180         kfree(cmd);
 181         *ppos = 0;              /* reset the file pointer after a command */
 182         return count;
 183 }
 184
 185
 186 /*
 187  * These ioctls are available, as the semantics of the diagnose 8 call
 188  * does not fit very well into a Linux call. Diagnose X'08' is described in
 189  * CP Programming Services SC24-6084-00
 190  *
 191  * VMCP_GETCODE: gives the CP return code back to user space
 192  * VMCP_SETBUF: sets the response buffer for the next write call. diagnose 8
 193  * expects adjacent pages in real storage and to make matters worse, we
 194  * dont know the size of the response. Therefore we default to PAGESIZE and
 195  * let userspace to change the response size, if userspace expects a bigger
 196  * response
 197  */
 198 static long vmcp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 199 {
 200         struct vmcp_session *session;
 201         int ret = -ENOTTY;
 202         int __user *argp;
 203
 204         session = file->private_data;
 205         if (is_compat_task())
 206                 argp = compat_ptr(arg);
 207         else
 208                 argp = (int __user *)arg;
 209         if (mutex_lock_interruptible(&session->mutex))
 210                 return -ERESTARTSYS;
 211         switch (cmd) {
 212         case VMCP_GETCODE:
 213                 ret = put_user(session->resp_code, argp);
 214                 break;
 215         case VMCP_SETBUF:
 216                 vmcp_response_free(session);
 217                 ret = get_user(session->bufsize, argp);
 218                 if (ret)
 219                         session->bufsize = PAGE_SIZE;
 220                 if (!session->bufsize || get_order(session->bufsize) > 8) {
 221                         session->bufsize = PAGE_SIZE;
 222                         ret = -EINVAL;
 223                 }
 224                 break;
 225         case VMCP_GETSIZE:
 226                 ret = put_user(session->resp_size, argp);
 227                 break;
 228         default:
 229                 break;
 230         }
 231         mutex_unlock(&session->mutex);
 232         return ret;
 233 }
 234
 235 static const struct file_operations vmcp_fops = {
 236         .owner          = THIS_MODULE,
 237         .open           = vmcp_open,
 238         .release        = vmcp_release,
 239         .read           = vmcp_read,
 240         .write          = vmcp_write,
 241         .unlocked_ioctl = vmcp_ioctl,
 242         .compat_ioctl   = vmcp_ioctl,
 243         .llseek         = no_llseek,
 244 };
 245
 246 static struct miscdevice vmcp_dev = {
 247         .name   = "vmcp",
 248         .minor  = MISC_DYNAMIC_MINOR,
 249         .fops   = &vmcp_fops,
 250 };
 251
 252 static int __init vmcp_init(void)
 253 {
 254         int ret;
 255
 256         if (!MACHINE_IS_VM)
 257                 return 0;
 258
 259         vmcp_debug = debug_register("vmcp", 1, 1, 240);
 260         if (!vmcp_debug)
 261                 return -ENOMEM;
 262
 263         ret = debug_register_view(vmcp_debug, &debug_hex_ascii_view);
 264         if (ret) {
 265                 debug_unregister(vmcp_debug);
 266                 return ret;
 267         }
 268
 269         ret = misc_register(&vmcp_dev);
 270         if (ret)
 271                 debug_unregister(vmcp_debug);
 272         return ret;
 273 }
 274 device_initcall(vmcp_init);