Commit | Line | Data |
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88df125f HC |
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 | } |