arm: mm: support ARCH_MMAP_RND_BITS

arm: arch_mmap_rnd() uses a hard-code value of 8 to generate the random
offset for the mmap base address.  This value represents a compromise
between increased ASLR effectiveness and avoiding address-space
fragmentation.  Replace it with a Kconfig option, which is sensibly
bounded, so that platform developers may choose where to place this
compromise.  Keep 8 as the minimum acceptable value.

[[email protected]: ARM: avoid ARCH_MMAP_RND_BITS for NOMMU]
Signed-off-by: Daniel Cashman <[email protected]>
Cc: Russell King <[email protected]>
Acked-by: Kees Cook <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Don Zickus <[email protected]>
Cc: Eric W. Biederman <[email protected]>
Cc: Heinrich Schuchardt <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Mark Salyzyn <[email protected]>
Cc: Jeff Vander Stoep <[email protected]>
Cc: Nick Kralevich <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Hector Marco-Gisbert <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions