x86: Fix improper large page preservation

This patch fixes a bug in try_preserve_large_page() which may
result in improper large page preservation and improper
application of page attributes to the memory area outside of the
original change request.

More specifically, the problem manifests itself when set_memory_*()
is called for several pages at the beginning of the large page and
try_preserve_large_page() erroneously concludes that the change can
be applied to whole large page.

The fix consists of 3 parts:

  1. Addition of "required" protection attributes in
     static_protections(), so .data and .bss can be guaranteed to
     stay "RW"

  2. static_protections() is now called for every small
     page within large page to determine compatibility of new
     protection attributes (instead of just small pages within the
     requested range).

  3. Large page can be preserved only if attribute change is
     large-page-aligned and covers whole large page.

 -v1: Try_preserve_large_page() patch for Linux 2.6.34-rc2
 -v2: Replaced pfn check with address check for kernel rw-data

Signed-off-by: Siarhei Liakh <[email protected]>
Signed-off-by: Xuxian Jiang <[email protected]>
Reviewed-by: Suresh Siddha <[email protected]>
Cc: Arjan van de Ven <[email protected]>
Cc: James Morris <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Rusty Russell <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Cc: Dave Jones <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Linus Torvalds <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions