mmap: arch_get_unmapped_area(): use proper mmap base for bottom up direction

This is more or less the generic variant of commit 41aacc1eea64 ("x86
get_unmapped_area: Access mmap_legacy_base through mm_struct member").

So effectively architectures which use an own arch_pick_mmap_layout()
implementation but call the generic arch_get_unmapped_area() now can
also randomize their mmap_base.

All architectures which have an own arch_pick_mmap_layout() and call the
generic arch_get_unmapped_area() (arm64, s390, tile) currently set
mmap_base to TASK_UNMAPPED_BASE.  This is also true for the generic
arch_pick_mmap_layout() function.  So this change is a no-op currently.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Radu Caragea <sinaelgl@gmail.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index 9d548512ff8a30498ce07f2e536f765e8bd54cca..fa206abb5c9de3614090732c9576303ea343facf 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1872,7 +1872,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
 
        info.flags = 0;
        info.length = len;
-       info.low_limit = TASK_UNMAPPED_BASE;
+       info.low_limit = mm->mmap_base;
        info.high_limit = TASK_SIZE;
        info.align_mask = 0;
        return vm_unmapped_area(&info);