xref: /openbmc/linux/arch/s390/mm/maccess.c (revision 4800cd83)
1 /*
2  * Access kernel memory without faulting -- s390 specific implementation.
3  *
4  * Copyright IBM Corp. 2009
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 <asm/system.h>
15 
16 /*
17  * This function writes to kernel memory bypassing DAT and possible
18  * write protection. It copies one to four bytes from src to dst
19  * using the stura instruction.
20  * Returns the number of bytes copied or -EFAULT.
21  */
22 static long probe_kernel_write_odd(void *dst, void *src, size_t size)
23 {
24 	unsigned long count, aligned;
25 	int offset, mask;
26 	int rc = -EFAULT;
27 
28 	aligned = (unsigned long) dst & ~3UL;
29 	offset = (unsigned long) dst & 3;
30 	count = min_t(unsigned long, 4 - offset, size);
31 	mask = (0xf << (4 - count)) & 0xf;
32 	mask >>= offset;
33 	asm volatile(
34 		"	bras	1,0f\n"
35 		"	icm	0,0,0(%3)\n"
36 		"0:	l	0,0(%1)\n"
37 		"	lra	%1,0(%1)\n"
38 		"1:	ex	%2,0(1)\n"
39 		"2:	stura	0,%1\n"
40 		"	la	%0,0\n"
41 		"3:\n"
42 		EX_TABLE(0b,3b) EX_TABLE(1b,3b) EX_TABLE(2b,3b)
43 		: "+d" (rc), "+a" (aligned)
44 		: "a" (mask), "a" (src) : "cc", "memory", "0", "1");
45 	return rc ? rc : count;
46 }
47 
48 long probe_kernel_write(void *dst, void *src, size_t size)
49 {
50 	long copied = 0;
51 
52 	while (size) {
53 		copied = probe_kernel_write_odd(dst, src, size);
54 		if (copied < 0)
55 			break;
56 		dst += copied;
57 		src += copied;
58 		size -= copied;
59 	}
60 	return copied < 0 ? -EFAULT : 0;
61 }
62 
63 int memcpy_real(void *dest, void *src, size_t count)
64 {
65 	register unsigned long _dest asm("2") = (unsigned long) dest;
66 	register unsigned long _len1 asm("3") = (unsigned long) count;
67 	register unsigned long _src  asm("4") = (unsigned long) src;
68 	register unsigned long _len2 asm("5") = (unsigned long) count;
69 	unsigned long flags;
70 	int rc = -EFAULT;
71 
72 	if (!count)
73 		return 0;
74 	flags = __arch_local_irq_stnsm(0xf8UL);
75 	asm volatile (
76 		"0:	mvcle	%1,%2,0x0\n"
77 		"1:	jo	0b\n"
78 		"	lhi	%0,0x0\n"
79 		"2:\n"
80 		EX_TABLE(1b,2b)
81 		: "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
82 		  "+d" (_len2), "=m" (*((long *) dest))
83 		: "m" (*((long *) src))
84 		: "cc", "memory");
85 	arch_local_irq_restore(flags);
86 	return rc;
87 }
88