Heiko Carstens | 88df125 | 2009-06-12 10:26:42 +0200 | [diff] [blame] | 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 | } |