1 /* 2 * User address space access functions. 3 * 4 * For licencing details see kernel-base/COPYING 5 */ 6 7 #include <linux/highmem.h> 8 #include <linux/module.h> 9 10 #include <asm/word-at-a-time.h> 11 12 /* 13 * best effort, GUP based copy_from_user() that is NMI-safe 14 */ 15 unsigned long 16 copy_from_user_nmi(void *to, const void __user *from, unsigned long n) 17 { 18 unsigned long offset, addr = (unsigned long)from; 19 unsigned long size, len = 0; 20 struct page *page; 21 void *map; 22 int ret; 23 24 do { 25 ret = __get_user_pages_fast(addr, 1, 0, &page); 26 if (!ret) 27 break; 28 29 offset = addr & (PAGE_SIZE - 1); 30 size = min(PAGE_SIZE - offset, n - len); 31 32 map = kmap_atomic(page); 33 memcpy(to, map+offset, size); 34 kunmap_atomic(map); 35 put_page(page); 36 37 len += size; 38 to += size; 39 addr += size; 40 41 } while (len < n); 42 43 return len; 44 } 45 EXPORT_SYMBOL_GPL(copy_from_user_nmi); 46 47 /* 48 * Do a strncpy, return length of string without final '\0'. 49 * 'count' is the user-supplied count (return 'count' if we 50 * hit it), 'max' is the address space maximum (and we return 51 * -EFAULT if we hit it). 52 */ 53 static inline long do_strncpy_from_user(char *dst, const char __user *src, long count, unsigned long max) 54 { 55 long res = 0; 56 57 /* 58 * Truncate 'max' to the user-specified limit, so that 59 * we only have one limit we need to check in the loop 60 */ 61 if (max > count) 62 max = count; 63 64 while (max >= sizeof(unsigned long)) { 65 unsigned long c, mask; 66 67 /* Fall back to byte-at-a-time if we get a page fault */ 68 if (unlikely(__get_user(c,(unsigned long __user *)(src+res)))) 69 break; 70 mask = has_zero(c); 71 if (mask) { 72 mask = (mask - 1) & ~mask; 73 mask >>= 7; 74 *(unsigned long *)(dst+res) = c & mask; 75 return res + count_masked_bytes(mask); 76 } 77 *(unsigned long *)(dst+res) = c; 78 res += sizeof(unsigned long); 79 max -= sizeof(unsigned long); 80 } 81 82 while (max) { 83 char c; 84 85 if (unlikely(__get_user(c,src+res))) 86 return -EFAULT; 87 dst[res] = c; 88 if (!c) 89 return res; 90 res++; 91 max--; 92 } 93 94 /* 95 * Uhhuh. We hit 'max'. But was that the user-specified maximum 96 * too? If so, that's ok - we got as much as the user asked for. 97 */ 98 if (res >= count) 99 return res; 100 101 /* 102 * Nope: we hit the address space limit, and we still had more 103 * characters the caller would have wanted. That's an EFAULT. 104 */ 105 return -EFAULT; 106 } 107 108 /** 109 * strncpy_from_user: - Copy a NUL terminated string from userspace. 110 * @dst: Destination address, in kernel space. This buffer must be at 111 * least @count bytes long. 112 * @src: Source address, in user space. 113 * @count: Maximum number of bytes to copy, including the trailing NUL. 114 * 115 * Copies a NUL-terminated string from userspace to kernel space. 116 * 117 * On success, returns the length of the string (not including the trailing 118 * NUL). 119 * 120 * If access to userspace fails, returns -EFAULT (some data may have been 121 * copied). 122 * 123 * If @count is smaller than the length of the string, copies @count bytes 124 * and returns @count. 125 */ 126 long 127 strncpy_from_user(char *dst, const char __user *src, long count) 128 { 129 unsigned long max_addr, src_addr; 130 131 if (unlikely(count <= 0)) 132 return 0; 133 134 max_addr = current_thread_info()->addr_limit.seg; 135 src_addr = (unsigned long)src; 136 if (likely(src_addr < max_addr)) { 137 unsigned long max = max_addr - src_addr; 138 return do_strncpy_from_user(dst, src, count, max); 139 } 140 return -EFAULT; 141 } 142 EXPORT_SYMBOL(strncpy_from_user); 143