xref: /linux/drivers/s390/char/vmcp.c (revision f24e9f586b377749dff37554696cf3a105540c94)
1 /*
2  * Copyright (C) 2004,2005 IBM Corporation
3  * Interface implementation for communication with the z/VM control program
4  * Author(s): Christian Borntraeger <cborntra@de.ibm.com>
5  *
6  *
7  * z/VMs CP offers the possibility to issue commands via the diagnose code 8
8  * this driver implements a character device that issues these commands and
9  * returns the answer of CP.
10 
11  * The idea of this driver is based on cpint from Neale Ferguson and #CP in CMS
12  */
13 
14 #include <linux/fs.h>
15 #include <linux/init.h>
16 #include <linux/kernel.h>
17 #include <linux/miscdevice.h>
18 #include <linux/module.h>
19 #include <asm/cpcmd.h>
20 #include <asm/debug.h>
21 #include <asm/uaccess.h>
22 #include "vmcp.h"
23 
24 MODULE_LICENSE("GPL");
25 MODULE_AUTHOR("Christian Borntraeger <cborntra@de.ibm.com>");
26 MODULE_DESCRIPTION("z/VM CP interface");
27 
28 static debug_info_t *vmcp_debug;
29 
30 static int vmcp_open(struct inode *inode, struct file *file)
31 {
32 	struct vmcp_session *session;
33 
34 	if (!capable(CAP_SYS_ADMIN))
35 		return -EPERM;
36 
37 	session = kmalloc(sizeof(*session), GFP_KERNEL);
38 	if (!session)
39 		return -ENOMEM;
40 	session->bufsize = PAGE_SIZE;
41 	session->response = NULL;
42 	session->resp_size = 0;
43 	init_MUTEX(&session->mutex);
44 	file->private_data = session;
45 	return nonseekable_open(inode, file);
46 }
47 
48 static int vmcp_release(struct inode *inode, struct file *file)
49 {
50 	struct vmcp_session *session;
51 
52 	session = (struct vmcp_session *)file->private_data;
53 	file->private_data = NULL;
54 	free_pages((unsigned long)session->response, get_order(session->bufsize));
55 	kfree(session);
56 	return 0;
57 }
58 
59 static ssize_t
60 vmcp_read(struct file *file, char __user * buff, size_t count, loff_t * ppos)
61 {
62 	size_t tocopy;
63 	struct vmcp_session *session;
64 
65 	session = (struct vmcp_session *)file->private_data;
66 	if (down_interruptible(&session->mutex))
67 		return -ERESTARTSYS;
68 	if (!session->response) {
69 		up(&session->mutex);
70 		return 0;
71 	}
72 	if (*ppos > session->resp_size) {
73 		up(&session->mutex);
74 		return 0;
75 	}
76 	tocopy = min(session->resp_size - (size_t) (*ppos), count);
77 	tocopy = min(tocopy,session->bufsize - (size_t) (*ppos));
78 
79 	if (copy_to_user(buff, session->response + (*ppos), tocopy)) {
80 		up(&session->mutex);
81 		return -EFAULT;
82 	}
83 	up(&session->mutex);
84 	*ppos += tocopy;
85 	return tocopy;
86 }
87 
88 static ssize_t
89 vmcp_write(struct file *file, const char __user * buff, size_t count,
90 	   loff_t * ppos)
91 {
92 	char *cmd;
93 	struct vmcp_session *session;
94 
95 	if (count > 240)
96 		return -EINVAL;
97 	cmd = kmalloc(count + 1, GFP_KERNEL);
98 	if (!cmd)
99 		return -ENOMEM;
100 	if (copy_from_user(cmd, buff, count)) {
101 		kfree(cmd);
102 		return -EFAULT;
103 	}
104 	cmd[count] = '\0';
105 	session = (struct vmcp_session *)file->private_data;
106 	if (down_interruptible(&session->mutex)) {
107 		kfree(cmd);
108 		return -ERESTARTSYS;
109 	}
110 	if (!session->response)
111 		session->response = (char *)__get_free_pages(GFP_KERNEL
112 						| __GFP_REPEAT 	| GFP_DMA,
113 						get_order(session->bufsize));
114 	if (!session->response) {
115 		up(&session->mutex);
116 		kfree(cmd);
117 		return -ENOMEM;
118 	}
119 	debug_text_event(vmcp_debug, 1, cmd);
120 	session->resp_size = __cpcmd(cmd, session->response,
121 				     session->bufsize,
122 				     &session->resp_code);
123 	up(&session->mutex);
124 	kfree(cmd);
125 	*ppos = 0;		/* reset the file pointer after a command */
126 	return count;
127 }
128 
129 
130 /*
131  * These ioctls are available, as the semantics of the diagnose 8 call
132  * does not fit very well into a Linux call. Diagnose X'08' is described in
133  * CP Programming Services SC24-6084-00
134  *
135  * VMCP_GETCODE: gives the CP return code back to user space
136  * VMCP_SETBUF: sets the response buffer for the next write call. diagnose 8
137  * expects adjacent pages in real storage and to make matters worse, we
138  * dont know the size of the response. Therefore we default to PAGESIZE and
139  * let userspace to change the response size, if userspace expects a bigger
140  * response
141  */
142 static long vmcp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
143 {
144 	struct vmcp_session *session;
145 	int temp;
146 
147 	session = (struct vmcp_session *)file->private_data;
148 	if (down_interruptible(&session->mutex))
149 		return -ERESTARTSYS;
150 	switch (cmd) {
151 	case VMCP_GETCODE:
152 		temp = session->resp_code;
153 		up(&session->mutex);
154 		return put_user(temp, (int __user *)arg);
155 	case VMCP_SETBUF:
156 		free_pages((unsigned long)session->response,
157 				get_order(session->bufsize));
158 		session->response=NULL;
159 		temp = get_user(session->bufsize, (int __user *)arg);
160 		if (get_order(session->bufsize) > 8) {
161 			session->bufsize = PAGE_SIZE;
162 			temp = -EINVAL;
163 		}
164 		up(&session->mutex);
165 		return temp;
166 	case VMCP_GETSIZE:
167 		temp = session->resp_size;
168 		up(&session->mutex);
169 		return put_user(temp, (int __user *)arg);
170 	default:
171 		up(&session->mutex);
172 		return -ENOIOCTLCMD;
173 	}
174 }
175 
176 static struct file_operations vmcp_fops = {
177 	.owner		= THIS_MODULE,
178 	.open		= &vmcp_open,
179 	.release	= &vmcp_release,
180 	.read		= &vmcp_read,
181 	.llseek		= &no_llseek,
182 	.write		= &vmcp_write,
183 	.unlocked_ioctl	= &vmcp_ioctl,
184 	.compat_ioctl	= &vmcp_ioctl
185 };
186 
187 static struct miscdevice vmcp_dev = {
188 	.name	= "vmcp",
189 	.minor	= MISC_DYNAMIC_MINOR,
190 	.fops	= &vmcp_fops,
191 };
192 
193 static int __init vmcp_init(void)
194 {
195 	int ret;
196 
197 	if (!MACHINE_IS_VM) {
198 		printk(KERN_WARNING
199 		       "z/VM CP interface is only available under z/VM\n");
200 		return -ENODEV;
201 	}
202 	ret = misc_register(&vmcp_dev);
203 	if (!ret)
204 		printk(KERN_INFO "z/VM CP interface loaded\n");
205 	else
206 		printk(KERN_WARNING
207 		       "z/VM CP interface not loaded. Could not register misc device.\n");
208 	vmcp_debug = debug_register("vmcp", 1, 1, 240);
209 	debug_register_view(vmcp_debug, &debug_hex_ascii_view);
210 	return ret;
211 }
212 
213 static void __exit vmcp_exit(void)
214 {
215 	WARN_ON(misc_deregister(&vmcp_dev) != 0);
216 	debug_unregister(vmcp_debug);
217 	printk(KERN_INFO "z/VM CP interface unloaded.\n");
218 }
219 
220 module_init(vmcp_init);
221 module_exit(vmcp_exit);
222