mm: fix cache coloring on x86_64 architecture

Fix the x86-64 cache alignment code to take pgoff into account.  Use the
x86 and MIPS cache alignment code as the basis for a generic cache
alignment function.

The old x86 code will always align the mmap to aliasing boundaries,
even if the program mmaps the file with a non-zero pgoff.

If program A mmaps the file with pgoff 0, and program B mmaps the file
with pgoff 1.  The old code would align the mmaps, resulting in misaligned
pages:

  A:  0123
  B:  123

After this patch, they are aligned so the pages line up:

  A: 0123
  B:  123

Proposed by Rik van Riel.

Signed-off-by: Michel Lespinasse <walken@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
index f00d006d60fd..97ef74b88e0f 100644
--- a/arch/x86/kernel/sys_x86_64.c
+++ b/arch/x86/kernel/sys_x86_64.c
@@ -136,7 +136,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
         info.low_limit = begin;
         info.high_limit = end;
         info.align_mask = filp ? get_align_mask() : 0;
-        info.align_offset = 0;
+        info.align_offset = pgoff << PAGE_SHIFT;
         return vm_unmapped_area(&info);
 }
 
@@ -175,7 +175,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
         info.low_limit = PAGE_SIZE;
         info.high_limit = mm->mmap_base;
         info.align_mask = filp ? get_align_mask() : 0;
-        info.align_offset = 0;
+        info.align_offset = pgoff << PAGE_SHIFT;
         addr = vm_unmapped_area(&info);
         if (!(addr & ~PAGE_MASK))
                 return addr;