xref: /linux/drivers/char/adi.c (revision f4db95b68ae68ebaf91d35cc0487ac1cbd04261e)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Privileged ADI driver for sparc64
4  *
5  * Author: Tom Hromatka <tom.hromatka@oracle.com>
6  */
7 #include <linux/kernel.h>
8 #include <linux/miscdevice.h>
9 #include <linux/module.h>
10 #include <linux/proc_fs.h>
11 #include <linux/slab.h>
12 #include <linux/uaccess.h>
13 #include <asm/asi.h>
14 
15 #define MAX_BUF_SZ	PAGE_SIZE
16 
17 static int read_mcd_tag(unsigned long addr)
18 {
19 	long err;
20 	int ver;
21 
22 	__asm__ __volatile__(
23 		"1:	ldxa [%[addr]] %[asi], %[ver]\n"
24 		"	mov 0, %[err]\n"
25 		"2:\n"
26 		"	.section .fixup,#alloc,#execinstr\n"
27 		"	.align 4\n"
28 		"3:	sethi %%hi(2b), %%g1\n"
29 		"	jmpl  %%g1 + %%lo(2b), %%g0\n"
30 		"	mov %[invalid], %[err]\n"
31 		"	.previous\n"
32 		"	.section __ex_table, \"a\"\n"
33 		"	.align 4\n"
34 		"	.word  1b, 3b\n"
35 		"	.previous\n"
36 		: [ver] "=r" (ver), [err] "=r" (err)
37 		: [addr] "r"  (addr), [invalid] "i" (EFAULT),
38 		  [asi] "i" (ASI_MCD_REAL)
39 		: "memory", "g1"
40 		);
41 
42 	if (err)
43 		return -EFAULT;
44 	else
45 		return ver;
46 }
47 
48 static ssize_t adi_read(struct file *file, char __user *buf,
49 			size_t count, loff_t *offp)
50 {
51 	size_t ver_buf_sz, bytes_read = 0;
52 	int ver_buf_idx = 0;
53 	loff_t offset;
54 	u8 *ver_buf;
55 	ssize_t ret;
56 
57 	ver_buf_sz = min_t(size_t, count, MAX_BUF_SZ);
58 	ver_buf = kmalloc(ver_buf_sz, GFP_KERNEL);
59 	if (!ver_buf)
60 		return -ENOMEM;
61 
62 	offset = (*offp) * adi_blksize();
63 
64 	while (bytes_read < count) {
65 		ret = read_mcd_tag(offset);
66 		if (ret < 0)
67 			goto out;
68 
69 		ver_buf[ver_buf_idx] = (u8)ret;
70 		ver_buf_idx++;
71 		offset += adi_blksize();
72 
73 		if (ver_buf_idx >= ver_buf_sz) {
74 			if (copy_to_user(buf + bytes_read, ver_buf,
75 					 ver_buf_sz)) {
76 				ret = -EFAULT;
77 				goto out;
78 			}
79 
80 			bytes_read += ver_buf_sz;
81 			ver_buf_idx = 0;
82 
83 			ver_buf_sz = min(count - bytes_read,
84 					 (size_t)MAX_BUF_SZ);
85 		}
86 	}
87 
88 	(*offp) += bytes_read;
89 	ret = bytes_read;
90 out:
91 	kfree(ver_buf);
92 	return ret;
93 }
94 
95 static int set_mcd_tag(unsigned long addr, u8 ver)
96 {
97 	long err;
98 
99 	__asm__ __volatile__(
100 		"1:	stxa %[ver], [%[addr]] %[asi]\n"
101 		"	mov 0, %[err]\n"
102 		"2:\n"
103 		"	.section .fixup,#alloc,#execinstr\n"
104 		"	.align 4\n"
105 		"3:	sethi %%hi(2b), %%g1\n"
106 		"	jmpl %%g1 + %%lo(2b), %%g0\n"
107 		"	mov %[invalid], %[err]\n"
108 		"	.previous\n"
109 		"	.section __ex_table, \"a\"\n"
110 		"	.align 4\n"
111 		"	.word 1b, 3b\n"
112 		"	.previous\n"
113 		: [err] "=r" (err)
114 		: [ver] "r" (ver), [addr] "r"  (addr),
115 		  [invalid] "i" (EFAULT), [asi] "i" (ASI_MCD_REAL)
116 		: "memory", "g1"
117 		);
118 
119 	if (err)
120 		return -EFAULT;
121 	else
122 		return ver;
123 }
124 
125 static ssize_t adi_write(struct file *file, const char __user *buf,
126 			 size_t count, loff_t *offp)
127 {
128 	size_t ver_buf_sz, bytes_written = 0;
129 	loff_t offset;
130 	u8 *ver_buf;
131 	ssize_t ret;
132 	int i;
133 
134 	if (count <= 0)
135 		return -EINVAL;
136 
137 	ver_buf_sz = min_t(size_t, count, MAX_BUF_SZ);
138 	ver_buf = kmalloc(ver_buf_sz, GFP_KERNEL);
139 	if (!ver_buf)
140 		return -ENOMEM;
141 
142 	offset = (*offp) * adi_blksize();
143 
144 	do {
145 		if (copy_from_user(ver_buf, &buf[bytes_written],
146 				   ver_buf_sz)) {
147 			ret = -EFAULT;
148 			goto out;
149 		}
150 
151 		for (i = 0; i < ver_buf_sz; i++) {
152 			ret = set_mcd_tag(offset, ver_buf[i]);
153 			if (ret < 0)
154 				goto out;
155 
156 			offset += adi_blksize();
157 		}
158 
159 		bytes_written += ver_buf_sz;
160 		ver_buf_sz = min(count - bytes_written, (size_t)MAX_BUF_SZ);
161 	} while (bytes_written < count);
162 
163 	(*offp) += bytes_written;
164 	ret = bytes_written;
165 out:
166 	__asm__ __volatile__("membar #Sync");
167 	kfree(ver_buf);
168 	return ret;
169 }
170 
171 static loff_t adi_llseek(struct file *file, loff_t offset, int whence)
172 {
173 	loff_t ret = -EINVAL;
174 
175 	switch (whence) {
176 	case SEEK_END:
177 	case SEEK_DATA:
178 	case SEEK_HOLE:
179 		/* unsupported */
180 		return -EINVAL;
181 	case SEEK_CUR:
182 		if (offset == 0)
183 			return file->f_pos;
184 
185 		offset += file->f_pos;
186 		break;
187 	case SEEK_SET:
188 		break;
189 	}
190 
191 	if (offset != file->f_pos) {
192 		file->f_pos = offset;
193 		ret = offset;
194 	}
195 
196 	return ret;
197 }
198 
199 static const struct file_operations adi_fops = {
200 	.owner		= THIS_MODULE,
201 	.llseek		= adi_llseek,
202 	.read		= adi_read,
203 	.write		= adi_write,
204 	.fop_flags	= FOP_UNSIGNED_OFFSET,
205 };
206 
207 static struct miscdevice adi_miscdev = {
208 	.minor = MISC_DYNAMIC_MINOR,
209 	.name = KBUILD_MODNAME,
210 	.fops = &adi_fops,
211 };
212 
213 static int __init adi_init(void)
214 {
215 	if (!adi_capable())
216 		return -EPERM;
217 
218 	return misc_register(&adi_miscdev);
219 }
220 
221 static void __exit adi_exit(void)
222 {
223 	misc_deregister(&adi_miscdev);
224 }
225 
226 module_init(adi_init);
227 module_exit(adi_exit);
228 
229 MODULE_AUTHOR("Tom Hromatka <tom.hromatka@oracle.com>");
230 MODULE_DESCRIPTION("Privileged interface to ADI");
231 MODULE_VERSION("1.0");
232 MODULE_LICENSE("GPL v2");
233