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/machine.h>
27 #include <asm/cpcmd.h>
28 #include <asm/debug.h>
29 #include <asm/vmcp.h>
30
31 struct vmcp_session {
32 char *response;
33 unsigned int bufsize;
34 unsigned int cma_alloc : 1;
35 int resp_size;
36 int resp_code;
37 struct mutex mutex;
38 };
39
40 static debug_info_t *vmcp_debug;
41
42 static unsigned long vmcp_cma_size __initdata = CONFIG_VMCP_CMA_SIZE * 1024 * 1024;
43 static struct cma *vmcp_cma;
44
early_parse_vmcp_cma(char * p)45 static int __init early_parse_vmcp_cma(char *p)
46 {
47 if (!p)
48 return 1;
49 vmcp_cma_size = ALIGN(memparse(p, NULL), PAGE_SIZE);
50 return 0;
51 }
52 early_param("vmcp_cma", early_parse_vmcp_cma);
53
vmcp_cma_reserve(void)54 void __init vmcp_cma_reserve(void)
55 {
56 if (!machine_is_vm())
57 return;
58 cma_declare_contiguous(0, vmcp_cma_size, 0, 0, 0, false, "vmcp", &vmcp_cma);
59 }
60
vmcp_response_alloc(struct vmcp_session * session)61 static void vmcp_response_alloc(struct vmcp_session *session)
62 {
63 struct page *page = NULL;
64 int nr_pages, order;
65
66 order = get_order(session->bufsize);
67 nr_pages = ALIGN(session->bufsize, PAGE_SIZE) >> PAGE_SHIFT;
68 /*
69 * For anything below order 3 allocations rely on the buddy
70 * allocator. If such low-order allocations can't be handled
71 * anymore the system won't work anyway.
72 */
73 if (order > 2)
74 page = cma_alloc(vmcp_cma, nr_pages, 0, false);
75 if (page) {
76 session->response = (char *)page_to_virt(page);
77 session->cma_alloc = 1;
78 return;
79 }
80 session->response = (char *)__get_free_pages(GFP_KERNEL | __GFP_RETRY_MAYFAIL, order);
81 }
82
vmcp_response_free(struct vmcp_session * session)83 static void vmcp_response_free(struct vmcp_session *session)
84 {
85 int nr_pages, order;
86 struct page *page;
87
88 if (!session->response)
89 return;
90 order = get_order(session->bufsize);
91 nr_pages = ALIGN(session->bufsize, PAGE_SIZE) >> PAGE_SHIFT;
92 if (session->cma_alloc) {
93 page = virt_to_page(session->response);
94 cma_release(vmcp_cma, page, nr_pages);
95 session->cma_alloc = 0;
96 } else {
97 free_pages((unsigned long)session->response, order);
98 }
99 session->response = NULL;
100 }
101
vmcp_open(struct inode * inode,struct file * file)102 static int vmcp_open(struct inode *inode, struct file *file)
103 {
104 struct vmcp_session *session;
105
106 if (!capable(CAP_SYS_ADMIN))
107 return -EPERM;
108
109 session = kmalloc(sizeof(*session), GFP_KERNEL);
110 if (!session)
111 return -ENOMEM;
112
113 session->bufsize = PAGE_SIZE;
114 session->response = NULL;
115 session->resp_size = 0;
116 mutex_init(&session->mutex);
117 file->private_data = session;
118 return nonseekable_open(inode, file);
119 }
120
vmcp_release(struct inode * inode,struct file * file)121 static int vmcp_release(struct inode *inode, struct file *file)
122 {
123 struct vmcp_session *session;
124
125 session = file->private_data;
126 file->private_data = NULL;
127 vmcp_response_free(session);
128 kfree(session);
129 return 0;
130 }
131
132 static ssize_t
vmcp_read(struct file * file,char __user * buff,size_t count,loff_t * ppos)133 vmcp_read(struct file *file, char __user *buff, size_t count, loff_t *ppos)
134 {
135 ssize_t ret;
136 size_t size;
137 struct vmcp_session *session;
138
139 session = file->private_data;
140 if (mutex_lock_interruptible(&session->mutex))
141 return -ERESTARTSYS;
142 if (!session->response) {
143 mutex_unlock(&session->mutex);
144 return 0;
145 }
146 size = min_t(size_t, session->resp_size, session->bufsize);
147 ret = simple_read_from_buffer(buff, count, ppos,
148 session->response, size);
149
150 mutex_unlock(&session->mutex);
151
152 return ret;
153 }
154
155 static ssize_t
vmcp_write(struct file * file,const char __user * buff,size_t count,loff_t * ppos)156 vmcp_write(struct file *file, const char __user *buff, size_t count,
157 loff_t *ppos)
158 {
159 char *cmd;
160 struct vmcp_session *session;
161
162 if (count > 240)
163 return -EINVAL;
164 cmd = memdup_user_nul(buff, count);
165 if (IS_ERR(cmd))
166 return PTR_ERR(cmd);
167 session = file->private_data;
168 if (mutex_lock_interruptible(&session->mutex)) {
169 kfree(cmd);
170 return -ERESTARTSYS;
171 }
172 if (!session->response)
173 vmcp_response_alloc(session);
174 if (!session->response) {
175 mutex_unlock(&session->mutex);
176 kfree(cmd);
177 return -ENOMEM;
178 }
179 debug_text_event(vmcp_debug, 1, cmd);
180 session->resp_size = cpcmd(cmd, session->response, session->bufsize,
181 &session->resp_code);
182 mutex_unlock(&session->mutex);
183 kfree(cmd);
184 *ppos = 0; /* reset the file pointer after a command */
185 return count;
186 }
187
188
189 /*
190 * These ioctls are available, as the semantics of the diagnose 8 call
191 * does not fit very well into a Linux call. Diagnose X'08' is described in
192 * CP Programming Services SC24-6084-00
193 *
194 * VMCP_GETCODE: gives the CP return code back to user space
195 * VMCP_SETBUF: sets the response buffer for the next write call. diagnose 8
196 * expects adjacent pages in real storage and to make matters worse, we
197 * dont know the size of the response. Therefore we default to PAGESIZE and
198 * let userspace to change the response size, if userspace expects a bigger
199 * response
200 */
vmcp_ioctl(struct file * file,unsigned int cmd,unsigned long arg)201 static long vmcp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
202 {
203 struct vmcp_session *session;
204 int ret = -ENOTTY;
205 int __user *argp;
206
207 session = file->private_data;
208 if (is_compat_task())
209 argp = compat_ptr(arg);
210 else
211 argp = (int __user *)arg;
212 if (mutex_lock_interruptible(&session->mutex))
213 return -ERESTARTSYS;
214 switch (cmd) {
215 case VMCP_GETCODE:
216 ret = put_user(session->resp_code, argp);
217 break;
218 case VMCP_SETBUF:
219 vmcp_response_free(session);
220 ret = get_user(session->bufsize, argp);
221 if (ret)
222 session->bufsize = PAGE_SIZE;
223 if (!session->bufsize || get_order(session->bufsize) > 8) {
224 session->bufsize = PAGE_SIZE;
225 ret = -EINVAL;
226 }
227 break;
228 case VMCP_GETSIZE:
229 ret = put_user(session->resp_size, argp);
230 break;
231 default:
232 break;
233 }
234 mutex_unlock(&session->mutex);
235 return ret;
236 }
237
238 static const struct file_operations vmcp_fops = {
239 .owner = THIS_MODULE,
240 .open = vmcp_open,
241 .release = vmcp_release,
242 .read = vmcp_read,
243 .write = vmcp_write,
244 .unlocked_ioctl = vmcp_ioctl,
245 .compat_ioctl = vmcp_ioctl,
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