arm: use generic mmap top-down layout and brk randomization

arm uses a top-down mmap layout by default that exactly fits the generic
functions, so get rid of arch specific code and use the generic version by
selecting ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT.

As ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT selects ARCH_HAS_ELF_RANDOMIZE,
use the generic version of arch_randomize_brk since it also fits.  Note
that this commit also removes the possibility for arm to have elf
randomization and no MMU: without MMU, the security added by randomization
is worth nothing.

Note that it is safe to remove STACK_RND_MASK since it matches the default
value.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Alexandre Ghiti <[email protected]>
Acked-by: Kees Cook <[email protected]>
Reviewed-by: Luis Chamberlain <[email protected]>
Cc: Albert Ou <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: James Hogan <[email protected]>
Cc: Palmer Dabbelt <[email protected]>
Cc: Paul Burton <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: Russell King <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 0 insertions, 5 deletions

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index f934a6739fc0..9485acc520a4 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -319,11 +319,6 @@ unsigned long get_wchan(struct task_struct *p)
 	return 0;
 }
 
-unsigned long arch_randomize_brk(struct mm_struct *mm)
-{
-	return randomize_page(mm->brk, 0x02000000);
-}
-
 #ifdef CONFIG_MMU
 #ifdef CONFIG_KUSER_HELPERS
 /*