1/*
2 * Access kernel memory without faulting -- s390 specific implementation.
3 *
4 * Copyright IBM Corp. 2009, 2015
5 *
6 *   Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
7 *
8 */
9
10#include <linux/uaccess.h>
11#include <linux/kernel.h>
12#include <linux/types.h>
13#include <linux/errno.h>
14#include <linux/gfp.h>
15#include <linux/cpu.h>
16#include <asm/ctl_reg.h>
17#include <asm/io.h>
18
19static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
20{
21	unsigned long aligned, offset, count;
22	char tmp[8];
23
24	aligned = (unsigned long) dst & ~7UL;
25	offset = (unsigned long) dst & 7UL;
26	size = min(8UL - offset, size);
27	count = size - 1;
28	asm volatile(
29		"	bras	1,0f\n"
30		"	mvc	0(1,%4),0(%5)\n"
31		"0:	mvc	0(8,%3),0(%0)\n"
32		"	ex	%1,0(1)\n"
33		"	lg	%1,0(%3)\n"
34		"	lra	%0,0(%0)\n"
35		"	sturg	%1,%0\n"
36		: "+&a" (aligned), "+&a" (count), "=m" (tmp)
37		: "a" (&tmp), "a" (&tmp[offset]), "a" (src)
38		: "cc", "memory", "1");
39	return size;
40}
41
42/*
43 * s390_kernel_write - write to kernel memory bypassing DAT
44 * @dst: destination address
45 * @src: source address
46 * @size: number of bytes to copy
47 *
48 * This function writes to kernel memory bypassing DAT and possible page table
49 * write protection. It writes to the destination using the sturg instruction.
50 * Therefore we have a read-modify-write sequence: the function reads eight
51 * bytes from destination at an eight byte boundary, modifies the bytes
52 * requested and writes the result back in a loop.
53 *
54 * Note: this means that this function may not be called concurrently on
55 *	 several cpus with overlapping words, since this may potentially
56 *	 cause data corruption.
57 */
58void notrace s390_kernel_write(void *dst, const void *src, size_t size)
59{
60	long copied;
61
62	while (size) {
63		copied = s390_kernel_write_odd(dst, src, size);
64		dst += copied;
65		src += copied;
66		size -= copied;
67	}
68}
69
70static int __memcpy_real(void *dest, void *src, size_t count)
71{
72	register unsigned long _dest asm("2") = (unsigned long) dest;
73	register unsigned long _len1 asm("3") = (unsigned long) count;
74	register unsigned long _src  asm("4") = (unsigned long) src;
75	register unsigned long _len2 asm("5") = (unsigned long) count;
76	int rc = -EFAULT;
77
78	asm volatile (
79		"0:	mvcle	%1,%2,0x0\n"
80		"1:	jo	0b\n"
81		"	lhi	%0,0x0\n"
82		"2:\n"
83		EX_TABLE(1b,2b)
84		: "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
85		  "+d" (_len2), "=m" (*((long *) dest))
86		: "m" (*((long *) src))
87		: "cc", "memory");
88	return rc;
89}
90
91/*
92 * Copy memory in real mode (kernel to kernel)
93 */
94int memcpy_real(void *dest, void *src, size_t count)
95{
96	unsigned long flags;
97	int rc;
98
99	if (!count)
100		return 0;
101	local_irq_save(flags);
102	__arch_local_irq_stnsm(0xfbUL);
103	rc = __memcpy_real(dest, src, count);
104	local_irq_restore(flags);
105	return rc;
106}
107
108/*
109 * Copy memory in absolute mode (kernel to kernel)
110 */
111void memcpy_absolute(void *dest, void *src, size_t count)
112{
113	unsigned long cr0, flags, prefix;
114
115	flags = arch_local_irq_save();
116	__ctl_store(cr0, 0, 0);
117	__ctl_clear_bit(0, 28); /* disable lowcore protection */
118	prefix = store_prefix();
119	if (prefix) {
120		local_mcck_disable();
121		set_prefix(0);
122		memcpy(dest, src, count);
123		set_prefix(prefix);
124		local_mcck_enable();
125	} else {
126		memcpy(dest, src, count);
127	}
128	__ctl_load(cr0, 0, 0);
129	arch_local_irq_restore(flags);
130}
131
132/*
133 * Copy memory from kernel (real) to user (virtual)
134 */
135int copy_to_user_real(void __user *dest, void *src, unsigned long count)
136{
137	int offs = 0, size, rc;
138	char *buf;
139
140	buf = (char *) __get_free_page(GFP_KERNEL);
141	if (!buf)
142		return -ENOMEM;
143	rc = -EFAULT;
144	while (offs < count) {
145		size = min(PAGE_SIZE, count - offs);
146		if (memcpy_real(buf, src + offs, size))
147			goto out;
148		if (copy_to_user(dest + offs, buf, size))
149			goto out;
150		offs += size;
151	}
152	rc = 0;
153out:
154	free_page((unsigned long) buf);
155	return rc;
156}
157
158/*
159 * Check if physical address is within prefix or zero page
160 */
161static int is_swapped(unsigned long addr)
162{
163	unsigned long lc;
164	int cpu;
165
166	if (addr < sizeof(struct _lowcore))
167		return 1;
168	for_each_online_cpu(cpu) {
169		lc = (unsigned long) lowcore_ptr[cpu];
170		if (addr > lc + sizeof(struct _lowcore) - 1 || addr < lc)
171			continue;
172		return 1;
173	}
174	return 0;
175}
176
177/*
178 * Convert a physical pointer for /dev/mem access
179 *
180 * For swapped prefix pages a new buffer is returned that contains a copy of
181 * the absolute memory. The buffer size is maximum one page large.
182 */
183void *xlate_dev_mem_ptr(phys_addr_t addr)
184{
185	void *bounce = (void *) addr;
186	unsigned long size;
187
188	get_online_cpus();
189	preempt_disable();
190	if (is_swapped(addr)) {
191		size = PAGE_SIZE - (addr & ~PAGE_MASK);
192		bounce = (void *) __get_free_page(GFP_ATOMIC);
193		if (bounce)
194			memcpy_absolute(bounce, (void *) addr, size);
195	}
196	preempt_enable();
197	put_online_cpus();
198	return bounce;
199}
200
201/*
202 * Free converted buffer for /dev/mem access (if necessary)
203 */
204void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf)
205{
206	if ((void *) addr != buf)
207		free_page((unsigned long) buf);
208}
209