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