1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright IBM Corp. 2004, 2010
4 * Interface implementation for communication with the z/VM control program
6 * Author(s): Christian Borntraeger <borntraeger@de.ibm.com>
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.
12 * The idea of this driver is based on cpint from Neale Ferguson and #CP in CMS
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>
26 #include <asm/compat.h>
27 #include <asm/cpcmd.h>
28 #include <asm/debug.h>
34 unsigned int cma_alloc : 1;
40 static debug_info_t *vmcp_debug;
42 static unsigned long vmcp_cma_size __initdata = CONFIG_VMCP_CMA_SIZE * 1024 * 1024;
43 static struct cma *vmcp_cma;
45 static int __init early_parse_vmcp_cma(char *p)
47 vmcp_cma_size = ALIGN(memparse(p, NULL), PAGE_SIZE);
50 early_param("vmcp_cma", early_parse_vmcp_cma);
52 void __init vmcp_cma_reserve(void)
56 cma_declare_contiguous(0, vmcp_cma_size, 0, 0, 0, false, "vmcp", &vmcp_cma);
59 static void vmcp_response_alloc(struct vmcp_session *session)
61 struct page *page = NULL;
64 order = get_order(session->bufsize);
65 nr_pages = ALIGN(session->bufsize, PAGE_SIZE) >> PAGE_SHIFT;
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.
72 page = cma_alloc(vmcp_cma, nr_pages, 0, GFP_KERNEL);
74 session->response = (char *)page_to_phys(page);
75 session->cma_alloc = 1;
78 session->response = (char *)__get_free_pages(GFP_KERNEL | __GFP_RETRY_MAYFAIL, order);
81 static void vmcp_response_free(struct vmcp_session *session)
86 if (!session->response)
88 order = get_order(session->bufsize);
89 nr_pages = ALIGN(session->bufsize, PAGE_SIZE) >> PAGE_SHIFT;
90 if (session->cma_alloc) {
91 page = phys_to_page((unsigned long)session->response);
92 cma_release(vmcp_cma, page, nr_pages);
93 session->cma_alloc = 0;
95 free_pages((unsigned long)session->response, order);
97 session->response = NULL;
100 static int vmcp_open(struct inode *inode, struct file *file)
102 struct vmcp_session *session;
104 if (!capable(CAP_SYS_ADMIN))
107 session = kmalloc(sizeof(*session), GFP_KERNEL);
111 session->bufsize = PAGE_SIZE;
112 session->response = NULL;
113 session->resp_size = 0;
114 mutex_init(&session->mutex);
115 file->private_data = session;
116 return nonseekable_open(inode, file);
119 static int vmcp_release(struct inode *inode, struct file *file)
121 struct vmcp_session *session;
123 session = file->private_data;
124 file->private_data = NULL;
125 vmcp_response_free(session);
131 vmcp_read(struct file *file, char __user *buff, size_t count, loff_t *ppos)
135 struct vmcp_session *session;
137 session = file->private_data;
138 if (mutex_lock_interruptible(&session->mutex))
140 if (!session->response) {
141 mutex_unlock(&session->mutex);
144 size = min_t(size_t, session->resp_size, session->bufsize);
145 ret = simple_read_from_buffer(buff, count, ppos,
146 session->response, size);
148 mutex_unlock(&session->mutex);
154 vmcp_write(struct file *file, const char __user *buff, size_t count,
158 struct vmcp_session *session;
162 cmd = memdup_user_nul(buff, count);
165 session = file->private_data;
166 if (mutex_lock_interruptible(&session->mutex)) {
170 if (!session->response)
171 vmcp_response_alloc(session);
172 if (!session->response) {
173 mutex_unlock(&session->mutex);
177 debug_text_event(vmcp_debug, 1, cmd);
178 session->resp_size = cpcmd(cmd, session->response, session->bufsize,
179 &session->resp_code);
180 mutex_unlock(&session->mutex);
182 *ppos = 0; /* reset the file pointer after a command */
188 * These ioctls are available, as the semantics of the diagnose 8 call
189 * does not fit very well into a Linux call. Diagnose X'08' is described in
190 * CP Programming Services SC24-6084-00
192 * VMCP_GETCODE: gives the CP return code back to user space
193 * VMCP_SETBUF: sets the response buffer for the next write call. diagnose 8
194 * expects adjacent pages in real storage and to make matters worse, we
195 * dont know the size of the response. Therefore we default to PAGESIZE and
196 * let userspace to change the response size, if userspace expects a bigger
199 static long vmcp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
201 struct vmcp_session *session;
205 session = file->private_data;
206 if (is_compat_task())
207 argp = compat_ptr(arg);
209 argp = (int __user *)arg;
210 if (mutex_lock_interruptible(&session->mutex))
214 ret = put_user(session->resp_code, argp);
217 vmcp_response_free(session);
218 ret = get_user(session->bufsize, argp);
220 session->bufsize = PAGE_SIZE;
221 if (!session->bufsize || get_order(session->bufsize) > 8) {
222 session->bufsize = PAGE_SIZE;
227 ret = put_user(session->resp_size, argp);
232 mutex_unlock(&session->mutex);
236 static const struct file_operations vmcp_fops = {
237 .owner = THIS_MODULE,
239 .release = vmcp_release,
242 .unlocked_ioctl = vmcp_ioctl,
243 .compat_ioctl = vmcp_ioctl,
247 static struct miscdevice vmcp_dev = {
249 .minor = MISC_DYNAMIC_MINOR,
253 static int __init vmcp_init(void)
260 vmcp_debug = debug_register("vmcp", 1, 1, 240);
264 ret = debug_register_view(vmcp_debug, &debug_hex_ascii_view);
266 debug_unregister(vmcp_debug);
270 ret = misc_register(&vmcp_dev);
272 debug_unregister(vmcp_debug);
275 device_initcall(vmcp_init);