diff options
Diffstat (limited to 'arch/sparc/lib/usercopy.c')
| -rw-r--r-- | arch/sparc/lib/usercopy.c | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/arch/sparc/lib/usercopy.c b/arch/sparc/lib/usercopy.c index 14b363fec8a2..851cb75ce189 100644 --- a/arch/sparc/lib/usercopy.c +++ b/arch/sparc/lib/usercopy.c @@ -1,4 +1,6 @@ #include <linux/module.h> +#include <linux/uaccess.h> +#include <linux/errno.h> #include <linux/bug.h> void copy_from_user_overflow(void) @@ -6,3 +8,133 @@ void copy_from_user_overflow(void) WARN(1, "Buffer overflow detected!\n"); } EXPORT_SYMBOL(copy_from_user_overflow); + +#define REPEAT_BYTE(x) ((~0ul / 0xff) * (x)) + +/* Return the high bit set in the first byte that is a zero */ +static inline unsigned long has_zero(unsigned long a) +{ + return ((a - REPEAT_BYTE(0x01)) & ~a) & REPEAT_BYTE(0x80); +} + +static inline long find_zero(unsigned long c) +{ +#ifdef CONFIG_64BIT + if (!(c & 0xff00000000000000UL)) + return 0; + if (!(c & 0x00ff000000000000UL)) + return 1; + if (!(c & 0x0000ff0000000000UL)) + return 2; + if (!(c & 0x000000ff00000000UL)) + return 3; +#define __OFF 4 +#else +#define __OFF 0 +#endif + if (!(c & 0xff000000)) + return __OFF + 0; + if (!(c & 0x00ff0000)) + return __OFF + 1; + if (!(c & 0x0000ff00)) + return __OFF + 2; + return __OFF + 3; +#undef __OFF +} + +/* + * Do a strncpy, return length of string without final '\0'. + * 'count' is the user-supplied count (return 'count' if we + * hit it), 'max' is the address space maximum (and we return + * -EFAULT if we hit it). + */ +static inline long do_strncpy_from_user(char *dst, const char __user *src, long count, unsigned long max) +{ + long res = 0; + + /* + * Truncate 'max' to the user-specified limit, so that + * we only have one limit we need to check in the loop + */ + if (max > count) + max = count; + + if (((long) dst | (long) src) & (sizeof(long) - 1)) + goto byte_at_a_time; + + while (max >= sizeof(unsigned long)) { + unsigned long c; + + /* Fall back to byte-at-a-time if we get a page fault */ + if (unlikely(__get_user(c,(unsigned long __user *)(src+res)))) + break; + *(unsigned long *)(dst+res) = c; + if (has_zero(c)) + return res + find_zero(c); + res += sizeof(unsigned long); + max -= sizeof(unsigned long); + } + +byte_at_a_time: + while (max) { + char c; + + if (unlikely(__get_user(c,src+res))) + return -EFAULT; + dst[res] = c; + if (!c) + return res; + res++; + max--; + } + + /* + * Uhhuh. We hit 'max'. But was that the user-specified maximum + * too? If so, that's ok - we got as much as the user asked for. + */ + if (res >= count) + return res; + + /* + * Nope: we hit the address space limit, and we still had more + * characters the caller would have wanted. That's an EFAULT. + */ + return -EFAULT; +} + +/** + * strncpy_from_user: - Copy a NUL terminated string from userspace. + * @dst: Destination address, in kernel space. This buffer must be at + * least @count bytes long. + * @src: Source address, in user space. + * @count: Maximum number of bytes to copy, including the trailing NUL. + * + * Copies a NUL-terminated string from userspace to kernel space. + * + * On success, returns the length of the string (not including the trailing + * NUL). + * + * If access to userspace fails, returns -EFAULT (some data may have been + * copied). + * + * If @count is smaller than the length of the string, copies @count bytes + * and returns @count. + */ +long strncpy_from_user(char *dst, const char __user *src, long count) +{ + unsigned long max_addr, src_addr; + + if (unlikely(count <= 0)) + return 0; + + max_addr = ~0UL; + if (likely(segment_eq(get_fs(), USER_DS))) + max_addr = STACK_TOP; + src_addr = (unsigned long)src; + if (likely(src_addr < max_addr)) { + unsigned long max = max_addr - src_addr; + return do_strncpy_from_user(dst, src, count, max); + } + return -EFAULT; +} +EXPORT_SYMBOL(strncpy_from_user); |