x86/mm: Implement ASLR for hugetlb mappings

Matthew noticed that hugetlb mappings don't participate in ASLR on x86-64:

  %  for i in `seq 3`; do
  > tools/testing/selftests/vm/map_hugetlb | grep address
  > done
  Returned address is 0x2aaaaac00000
  Returned address is 0x2aaaaac00000
  Returned address is 0x2aaaaac00000

/proc/PID/maps entries for the mapping are always the same
(except inode number):

  2aaaaac00000-2aaabac00000 rw-p 00000000 00:0c 8200              /anon_hugepage (deleted)
  2aaaaac00000-2aaabac00000 rw-p 00000000 00:0c 256               /anon_hugepage (deleted)
  2aaaaac00000-2aaabac00000 rw-p 00000000 00:0c 7180              /anon_hugepage (deleted)

The reason is the generic hugetlb_get_unmapped_area() function
which is used on x86-64.  It doesn't support randomization and
use bottom-up unmapped area lookup, instead of usual top-down
on x86-64.

x86 has arch-specific hugetlb_get_unmapped_area(), but it's used
only on x86-32.

Let's use arch-specific hugetlb_get_unmapped_area() on x86-64
too. That adds ASLR and switches hugetlb mappings to use top-down
unmapped area lookup:

  %  for i in `seq 3`; do
  > tools/testing/selftests/vm/map_hugetlb | grep address
  > done
  Returned address is 0x7f4f08a00000
  Returned address is 0x7fdda4200000
  Returned address is 0x7febe0000000

/proc/PID/maps entries:

  7f4f08a00000-7f4f18a00000 rw-p 00000000 00:0c 1168              /anon_hugepage (deleted)
  7fdda4200000-7fddb4200000 rw-p 00000000 00:0c 7092              /anon_hugepage (deleted)
  7febe0000000-7febf0000000 rw-p 00000000 00:0c 7183              /anon_hugepage (deleted)

Unmapped area lookup policy for hugetlb mappings is consistent
with normal mappings now -- the only difference is alignment
requirements for huge pages.

libhugetlbfs test-suite didn't detect any regressions with the
patch applied (although it shows few failures on my machine
regardless the patch).

Signed-off-by: Kirill A. Shutemov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Mel Gorman <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions