Messages in this thread Patch in this message | | | From | Jason Cooper <> | Subject | [RFC patch 1/6] random: Simplify API for random address requests | Date | Tue, 26 Jul 2016 03:01:55 +0000 |
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To date, all callers of randomize_range() have set the length to 0, and check for a zero return value. For the current callers, the only way to get zero returned is if end <= start. Since they are all adding a constant to the start address, this is unnecessary.
We can remove a bunch of needless checks by simplifying the API to do just what everyone wants, return an address between [start, start + range].
While we're here, s/get_random_int/get_random_long/. No current call site is adversely affected by get_random_int(), since all current range requests are < MAX_UINT. However, we should match caller expectations to avoid coming up short (ha!) in the future.
Signed-off-by: Jason Cooper <jason@lakedaemon.net> --- drivers/char/random.c | 17 ++++------------- include/linux/random.h | 2 +- 2 files changed, 5 insertions(+), 14 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c index 0158d3bff7e5..1251cb2cbab2 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1822,22 +1822,13 @@ unsigned long get_random_long(void) EXPORT_SYMBOL(get_random_long); /* - * randomize_range() returns a start address such that - * - * [...... <range> .....] - * start end - * - * a <range> with size "len" starting at the return value is inside in the - * area defined by [start, end], but is otherwise randomized. + * randomize_addr() returns a page aligned address within [start, start + + * range] */ unsigned long -randomize_range(unsigned long start, unsigned long end, unsigned long len) +randomize_addr(unsigned long start, unsigned long range) { - unsigned long range = end - len - start; - - if (end <= start + len) - return 0; - return PAGE_ALIGN(get_random_int() % range + start); + return PAGE_ALIGN(get_random_long() % range + start); } /* Interface for in-kernel drivers of true hardware RNGs. diff --git a/include/linux/random.h b/include/linux/random.h index e47e533742b5..1ad877a98186 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -34,7 +34,7 @@ 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_addr(unsigned long start, unsigned long range); u32 prandom_u32(void); void prandom_bytes(void *buf, size_t nbytes); -- 2.9.2
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