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
early_parse_vmcp_cma(char * p)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
vmcp_cma_reserve(void)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
vmcp_response_alloc(struct vmcp_session * session)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
vmcp_response_free(struct vmcp_session * session)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(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
vmcp_open(struct inode * inode,struct file * file)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
vmcp_release(struct inode * inode,struct file * file)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
vmcp_read(struct file * file,char __user * buff,size_t count,loff_t * ppos)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
vmcp_write(struct file * file,const char __user * buff,size_t count,loff_t * ppos)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 */
vmcp_ioctl(struct file * file,unsigned int cmd,unsigned long arg)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
vmcp_init(void)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