aboutsummaryrefslogtreecommitdiff
path: root/arch/s390/mm/maccess.c
blob: 795a0a9bb2eba72875aa3a300f98929daa1c6c12 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
/*
 * Access kernel memory without faulting -- s390 specific implementation.
 *
 * Copyright IBM Corp. 2009
 *
 *   Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
 *
 */

#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/gfp.h>
#include <linux/cpu.h>
#include <asm/ctl_reg.h>

/*
 * This function writes to kernel memory bypassing DAT and possible
 * write protection. It copies one to four bytes from src to dst
 * using the stura instruction.
 * Returns the number of bytes copied or -EFAULT.
 */
static long probe_kernel_write_odd(void *dst, const void *src, size_t size)
{
	unsigned long count, aligned;
	int offset, mask;
	int rc = -EFAULT;

	aligned = (unsigned long) dst & ~3UL;
	offset = (unsigned long) dst & 3;
	count = min_t(unsigned long, 4 - offset, size);
	mask = (0xf << (4 - count)) & 0xf;
	mask >>= offset;
	asm volatile(
		"	bras	1,0f\n"
		"	icm	0,0,0(%3)\n"
		"0:	l	0,0(%1)\n"
		"	lra	%1,0(%1)\n"
		"1:	ex	%2,0(1)\n"
		"2:	stura	0,%1\n"
		"	la	%0,0\n"
		"3:\n"
		EX_TABLE(0b,3b) EX_TABLE(1b,3b) EX_TABLE(2b,3b)
		: "+d" (rc), "+a" (aligned)
		: "a" (mask), "a" (src) : "cc", "memory", "0", "1");
	return rc ? rc : count;
}

long probe_kernel_write(void *dst, const void *src, size_t size)
{
	long copied = 0;

	while (size) {
		copied = probe_kernel_write_odd(dst, src, size);
		if (copied < 0)
			break;
		dst += copied;
		src += copied;
		size -= copied;
	}
	return copied < 0 ? -EFAULT : 0;
}

static int __memcpy_real(void *dest, void *src, size_t count)
{
	register unsigned long _dest asm("2") = (unsigned long) dest;
	register unsigned long _len1 asm("3") = (unsigned long) count;
	register unsigned long _src  asm("4") = (unsigned long) src;
	register unsigned long _len2 asm("5") = (unsigned long) count;
	int rc = -EFAULT;

	asm volatile (
		"0:	mvcle	%1,%2,0x0\n"
		"1:	jo	0b\n"
		"	lhi	%0,0x0\n"
		"2:\n"
		EX_TABLE(1b,2b)
		: "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
		  "+d" (_len2), "=m" (*((long *) dest))
		: "m" (*((long *) src))
		: "cc", "memory");
	return rc;
}

/*
 * Copy memory in real mode (kernel to kernel)
 */
int memcpy_real(void *dest, void *src, size_t count)
{
	unsigned long flags;
	int rc;

	if (!count)
		return 0;
	local_irq_save(flags);
	__arch_local_irq_stnsm(0xfbUL);
	rc = __memcpy_real(dest, src, count);
	local_irq_restore(flags);
	return rc;
}

/*
 * Copy memory to absolute zero
 */
void copy_to_absolute_zero(void *dest, void *src, size_t count)
{
	unsigned long cr0;

	BUG_ON((unsigned long) dest + count >= sizeof(struct _lowcore));
	preempt_disable();
	__ctl_store(cr0, 0, 0);
	__ctl_clear_bit(0, 28); /* disable lowcore protection */
	memcpy_real(dest + store_prefix(), src, count);
	__ctl_load(cr0, 0, 0);
	preempt_enable();
}

/*
 * Copy memory from kernel (real) to user (virtual)
 */
int copy_to_user_real(void __user *dest, void *src, size_t count)
{
	int offs = 0, size, rc;
	char *buf;

	buf = (char *) __get_free_page(GFP_KERNEL);
	if (!buf)
		return -ENOMEM;
	rc = -EFAULT;
	while (offs < count) {
		size = min(PAGE_SIZE, count - offs);
		if (memcpy_real(buf, src + offs, size))
			goto out;
		if (copy_to_user(dest + offs, buf, size))
			goto out;
		offs += size;
	}
	rc = 0;
out:
	free_page((unsigned long) buf);
	return rc;
}

/*
 * Copy memory from user (virtual) to kernel (real)
 */
int copy_from_user_real(void *dest, void __user *src, size_t count)
{
	int offs = 0, size, rc;
	char *buf;

	buf = (char *) __get_free_page(GFP_KERNEL);
	if (!buf)
		return -ENOMEM;
	rc = -EFAULT;
	while (offs < count) {
		size = min(PAGE_SIZE, count - offs);
		if (copy_from_user(buf, src + offs, size))
			goto out;
		if (memcpy_real(dest + offs, buf, size))
			goto out;
		offs += size;
	}
	rc = 0;
out:
	free_page((unsigned long) buf);
	return rc;
}

/*
 * Check if physical address is within prefix or zero page
 */
static int is_swapped(unsigned long addr)
{
	unsigned long lc;
	int cpu;

	if (addr < sizeof(struct _lowcore))
		return 1;
	for_each_online_cpu(cpu) {
		lc = (unsigned long) lowcore_ptr[cpu];
		if (addr > lc + sizeof(struct _lowcore) - 1 || addr < lc)
			continue;
		return 1;
	}
	return 0;
}

/*
 * Return swapped prefix or zero page address
 */
static unsigned long get_swapped(unsigned long addr)
{
	unsigned long prefix = store_prefix();

	if (addr < sizeof(struct _lowcore))
		return addr + prefix;
	if (addr >= prefix && addr < prefix + sizeof(struct _lowcore))
		return addr - prefix;
	return addr;
}

/*
 * Convert a physical pointer for /dev/mem access
 *
 * For swapped prefix pages a new buffer is returned that contains a copy of
 * the absolute memory. The buffer size is maximum one page large.
 */
void *xlate_dev_mem_ptr(unsigned long addr)
{
	void *bounce = (void *) addr;
	unsigned long size;

	get_online_cpus();
	preempt_disable();
	if (is_swapped(addr)) {
		size = PAGE_SIZE - (addr & ~PAGE_MASK);
		bounce = (void *) __get_free_page(GFP_ATOMIC);
		if (bounce)
			memcpy_real(bounce, (void *) get_swapped(addr), size);
	}
	preempt_enable();
	put_online_cpus();
	return bounce;
}

/*
 * Free converted buffer for /dev/mem access (if necessary)
 */
void unxlate_dev_mem_ptr(unsigned long addr, void *buf)
{
	if ((void *) addr != buf)
		free_page((unsigned long) buf);
}