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); 275