diff options
Diffstat (limited to 'arch/x86/include/asm/word-at-a-time.h')
| -rw-r--r-- | arch/x86/include/asm/word-at-a-time.h | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/arch/x86/include/asm/word-at-a-time.h b/arch/x86/include/asm/word-at-a-time.h index 6fe6767b7124..e58f03b206c3 100644 --- a/arch/x86/include/asm/word-at-a-time.h +++ b/arch/x86/include/asm/word-at-a-time.h @@ -43,4 +43,37 @@ static inline unsigned long has_zero(unsigned long a) return ((a - REPEAT_BYTE(0x01)) & ~a) & REPEAT_BYTE(0x80); } +/* + * Load an unaligned word from kernel space. + * + * In the (very unlikely) case of the word being a page-crosser + * and the next page not being mapped, take the exception and + * return zeroes in the non-existing part. + */ +static inline unsigned long load_unaligned_zeropad(const void *addr) +{ + unsigned long ret, dummy; + + asm( + "1:\tmov %2,%0\n" + "2:\n" + ".section .fixup,\"ax\"\n" + "3:\t" + "lea %2,%1\n\t" + "and %3,%1\n\t" + "mov (%1),%0\n\t" + "leal %2,%%ecx\n\t" + "andl %4,%%ecx\n\t" + "shll $3,%%ecx\n\t" + "shr %%cl,%0\n\t" + "jmp 2b\n" + ".previous\n" + _ASM_EXTABLE(1b, 3b) + :"=&r" (ret),"=&c" (dummy) + :"m" (*(unsigned long *)addr), + "i" (-sizeof(unsigned long)), + "i" (sizeof(unsigned long)-1)); + return ret; +} + #endif /* _ASM_WORD_AT_A_TIME_H */ |