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
30struct 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
39static debug_info_t *vmcp_debug;
40
41static unsigned long vmcp_cma_size __initdata = CONFIG_VMCP_CMA_SIZE * 1024 * 1024;
42static struct cma *vmcp_cma;
43
44static 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}
51early_param("vmcp_cma", early_parse_vmcp_cma);
52
53void __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
60static 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
82static 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
101static 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
120static 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
131static ssize_t
132vmcp_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
154static ssize_t
155vmcp_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 */
200static 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
237static 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
248static struct miscdevice vmcp_dev = {
249	.name	= "vmcp",
250	.minor	= MISC_DYNAMIC_MINOR,
251	.fops	= &vmcp_fops,
252};
253
254static 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}
276device_initcall(vmcp_init);
277