diff options
| -rw-r--r-- | drivers/char/random.c | 33 | ||||
| -rw-r--r-- | include/linux/random.h | 1 |
2 files changed, 34 insertions, 0 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 3efb3bf0ab83..40eb07e79b02 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -2119,6 +2119,39 @@ randomize_range(unsigned long start, unsigned long end, unsigned long len) return PAGE_ALIGN(get_random_int() % range + start); } +/** + * randomize_page - Generate a random, page aligned address + * @start: The smallest acceptable address the caller will take. + * @range: The size of the area, starting at @start, within which the + * random address must fall. + * + * If @start + @range would overflow, @range is capped. + * + * NOTE: Historical use of randomize_range, which this replaces, presumed that + * @start was already page aligned. We now align it regardless. + * + * Return: A page aligned address within [start, start + range). On error, + * @start is returned. + */ +unsigned long +randomize_page(unsigned long start, unsigned long range) +{ + if (!PAGE_ALIGNED(start)) { + range -= PAGE_ALIGN(start) - start; + start = PAGE_ALIGN(start); + } + + if (start > ULONG_MAX - range) + range = ULONG_MAX - start; + + range >>= PAGE_SHIFT; + + if (range == 0) + return start; + + return start + (get_random_long() % range << PAGE_SHIFT); +} + /* Interface for in-kernel drivers of true hardware RNGs. * Those devices may produce endless random bits and will be throttled * when our pool is full. diff --git a/include/linux/random.h b/include/linux/random.h index 3d6e9815cd85..26741892828a 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -35,6 +35,7 @@ extern const struct file_operations random_fops, urandom_fops; unsigned int get_random_int(void); unsigned long get_random_long(void); unsigned long randomize_range(unsigned long start, unsigned long end, unsigned long len); +unsigned long randomize_page(unsigned long start, unsigned long range); u32 prandom_u32(void); void prandom_bytes(void *buf, size_t nbytes); |