xref: /openbmc/linux/drivers/s390/char/vmcp.c (revision 2d1494fb)
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