random: simplify API for random address requests

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 < UINT_MAX.  However, we should match caller expectations to
avoid coming up short (ha!) in the future.

All current callers to randomize_range() chose to use the start address if
randomize_range() failed.  Therefore, we simplify things by just returning
the start address on error.

randomize_range() will be removed once all callers have been converted
over to randomize_addr().

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Jason Cooper <[email protected]>
Acked-by: Kees Cook <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: "Roberts, William C" <[email protected]>
Cc: Yann Droneaud <[email protected]>
Cc: Russell King <[email protected]>
Cc: "Theodore Ts'o" <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H . Peter Anvin" <[email protected]>
Cc: Nick Kralevich <[email protected]>
Cc: Jeffrey Vander Stoep <[email protected]>
Cc: Daniel Cashman <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Guan Xuetao <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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