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 if (!p) 47 return 1; 48 vmcp_cma_size = ALIGN(memparse(p, NULL), PAGE_SIZE); 49 return 0; 50 } 51 early_param("vmcp_cma", early_parse_vmcp_cma); 52 53 void __init vmcp_cma_reserve(void) 54 { 55 if (!MACHINE_IS_VM) 56 return; 57 cma_declare_contiguous(0, vmcp_cma_size, 0, 0, 0, false, "vmcp", &vmcp_cma); 58 } 59 60 static void vmcp_response_alloc(struct vmcp_session *session) 61 { 62 struct page *page = NULL; 63 int nr_pages, order; 64 65 order = get_order(session->bufsize); 66 nr_pages = ALIGN(session->bufsize, PAGE_SIZE) >> PAGE_SHIFT; 67 /* 68 * For anything below order 3 allocations rely on the buddy 69 * allocator. If such low-order allocations can't be handled 70 * anymore the system won't work anyway. 71 */ 72 if (order > 2) 73 page = cma_alloc(vmcp_cma, nr_pages, 0, false); 74 if (page) { 75 session->response = (char *)page_to_virt(page); 76 session->cma_alloc = 1; 77 return; 78 } 79 session->response = (char *)__get_free_pages(GFP_KERNEL | __GFP_RETRY_MAYFAIL, order); 80 } 81 82 static void vmcp_response_free(struct vmcp_session *session) 83 { 84 int nr_pages, order; 85 struct page *page; 86 87 if (!session->response) 88 return; 89 order = get_order(session->bufsize); 90 nr_pages = ALIGN(session->bufsize, PAGE_SIZE) >> PAGE_SHIFT; 91 if (session->cma_alloc) { 92 page = virt_to_page((unsigned long)session->response); 93 cma_release(vmcp_cma, page, nr_pages); 94 session->cma_alloc = 0; 95 } else { 96 free_pages((unsigned long)session->response, order); 97 } 98 session->response = NULL; 99 } 100 101 static int vmcp_open(struct inode *inode, struct file *file) 102 { 103 struct vmcp_session *session; 104 105 if (!capable(CAP_SYS_ADMIN)) 106 return -EPERM; 107 108 session = kmalloc(sizeof(*session), GFP_KERNEL); 109 if (!session) 110 return -ENOMEM; 111 112 session->bufsize = PAGE_SIZE; 113 session->response = NULL; 114 session->resp_size = 0; 115 mutex_init(&session->mutex); 116 file->private_data = session; 117 return nonseekable_open(inode, file); 118 } 119 120 static int vmcp_release(struct inode *inode, struct file *file) 121 { 122 struct vmcp_session *session; 123 124 session = file->private_data; 125 file->private_data = NULL; 126 vmcp_response_free(session); 127 kfree(session); 128 return 0; 129 } 130 131 static ssize_t 132 vmcp_read(struct file *file, char __user *buff, size_t count, loff_t *ppos) 133 { 134 ssize_t ret; 135 size_t size; 136 struct vmcp_session *session; 137 138 session = file->private_data; 139 if (mutex_lock_interruptible(&session->mutex)) 140 return -ERESTARTSYS; 141 if (!session->response) { 142 mutex_unlock(&session->mutex); 143 return 0; 144 } 145 size = min_t(size_t, session->resp_size, session->bufsize); 146 ret = simple_read_from_buffer(buff, count, ppos, 147 session->response, size); 148 149 mutex_unlock(&session->mutex); 150 151 return ret; 152 } 153 154 static ssize_t 155 vmcp_write(struct file *file, const char __user *buff, size_t count, 156 loff_t *ppos) 157 { 158 char *cmd; 159 struct vmcp_session *session; 160 161 if (count > 240) 162 return -EINVAL; 163 cmd = memdup_user_nul(buff, count); 164 if (IS_ERR(cmd)) 165 return PTR_ERR(cmd); 166 session = file->private_data; 167 if (mutex_lock_interruptible(&session->mutex)) { 168 kfree(cmd); 169 return -ERESTARTSYS; 170 } 171 if (!session->response) 172 vmcp_response_alloc(session); 173 if (!session->response) { 174 mutex_unlock(&session->mutex); 175 kfree(cmd); 176 return -ENOMEM; 177 } 178 debug_text_event(vmcp_debug, 1, cmd); 179 session->resp_size = cpcmd(cmd, session->response, session->bufsize, 180 &session->resp_code); 181 mutex_unlock(&session->mutex); 182 kfree(cmd); 183 *ppos = 0; /* reset the file pointer after a command */ 184 return count; 185 } 186 187 188 /* 189 * These ioctls are available, as the semantics of the diagnose 8 call 190 * does not fit very well into a Linux call. Diagnose X'08' is described in 191 * CP Programming Services SC24-6084-00 192 * 193 * VMCP_GETCODE: gives the CP return code back to user space 194 * VMCP_SETBUF: sets the response buffer for the next write call. diagnose 8 195 * expects adjacent pages in real storage and to make matters worse, we 196 * dont know the size of the response. Therefore we default to PAGESIZE and 197 * let userspace to change the response size, if userspace expects a bigger 198 * response 199 */ 200 static long vmcp_ioctl(struct file *file, unsigned int cmd, unsigned long arg) 201 { 202 struct vmcp_session *session; 203 int ret = -ENOTTY; 204 int __user *argp; 205 206 session = file->private_data; 207 if (is_compat_task()) 208 argp = compat_ptr(arg); 209 else 210 argp = (int __user *)arg; 211 if (mutex_lock_interruptible(&session->mutex)) 212 return -ERESTARTSYS; 213 switch (cmd) { 214 case VMCP_GETCODE: 215 ret = put_user(session->resp_code, argp); 216 break; 217 case VMCP_SETBUF: 218 vmcp_response_free(session); 219 ret = get_user(session->bufsize, argp); 220 if (ret) 221 session->bufsize = PAGE_SIZE; 222 if (!session->bufsize || get_order(session->bufsize) > 8) { 223 session->bufsize = PAGE_SIZE; 224 ret = -EINVAL; 225 } 226 break; 227 case VMCP_GETSIZE: 228 ret = put_user(session->resp_size, argp); 229 break; 230 default: 231 break; 232 } 233 mutex_unlock(&session->mutex); 234 return ret; 235 } 236 237 static const struct file_operations vmcp_fops = { 238 .owner = THIS_MODULE, 239 .open = vmcp_open, 240 .release = vmcp_release, 241 .read = vmcp_read, 242 .write = vmcp_write, 243 .unlocked_ioctl = vmcp_ioctl, 244 .compat_ioctl = vmcp_ioctl, 245 .llseek = no_llseek, 246 }; 247 248 static struct miscdevice vmcp_dev = { 249 .name = "vmcp", 250 .minor = MISC_DYNAMIC_MINOR, 251 .fops = &vmcp_fops, 252 }; 253 254 static int __init vmcp_init(void) 255 { 256 int ret; 257 258 if (!MACHINE_IS_VM) 259 return 0; 260 261 vmcp_debug = debug_register("vmcp", 1, 1, 240); 262 if (!vmcp_debug) 263 return -ENOMEM; 264 265 ret = debug_register_view(vmcp_debug, &debug_hex_ascii_view); 266 if (ret) { 267 debug_unregister(vmcp_debug); 268 return ret; 269 } 270 271 ret = misc_register(&vmcp_dev); 272 if (ret) 273 debug_unregister(vmcp_debug); 274 return ret; 275 } 276 device_initcall(vmcp_init); 277