releases/4.6.5/arm64-mm-remove-page_mapping-check-in-__sync_icache_dcache.patch

   1 From 20c27a4270c775d7ed661491af8ac03264d60fc6 Mon Sep 17 00:00:00 2001
   2 From: Shaokun Zhang <zhangshaokun@hisilicon.com>
   3 Date: Tue, 21 Jun 2016 15:32:57 +0800
   4 Subject: arm64: mm: remove page_mapping check in __sync_icache_dcache
   5
   6 From: Shaokun Zhang <zhangshaokun@hisilicon.com>
   7
   8 commit 20c27a4270c775d7ed661491af8ac03264d60fc6 upstream.
   9
  10 __sync_icache_dcache unconditionally skips the cache maintenance for
  11 anonymous pages, under the assumption that flushing is only required in
  12 the presence of D-side aliases [see 7249b79f6b4cc ("arm64: Do not flush
  13 the D-cache for anonymous pages")].
  14
  15 Unfortunately, this breaks migration of anonymous pages holding
  16 self-modifying code, where userspace cannot be reasonably expected to
  17 reissue maintenance instructions in response to a migration.
  18
  19 This patch fixes the problem by removing the broken page_mapping(page)
  20 check from the cache syncing code, otherwise we may end up fetching and
  21 executing stale instructions from the PoU.
  22
  23 Cc: Catalin Marinas <catalin.marinas@arm.com>
  24 Cc: Will Deacon <will.deacon@arm.com>
  25 Cc: Mark Rutland <mark.rutland@arm.com>
  26 Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
  27 Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
  28 Signed-off-by: Will Deacon <will.deacon@arm.com>
  29 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  30
  31 ---
  32  arch/arm64/mm/flush.c |    4 ----
  33  1 file changed, 4 deletions(-)
  34
  35 --- a/arch/arm64/mm/flush.c
  36 +++ b/arch/arm64/mm/flush.c
  37 @@ -71,10 +71,6 @@ void __sync_icache_dcache(pte_t pte, uns
  38  {
  39         struct page *page = pte_page(pte);
  40
  41 -       /* no flushing needed for anonymous pages */
  42 -       if (!page_mapping(page))
  43 -               return;
  44 -
  45         if (!test_and_set_bit(PG_dcache_clean, &page->flags))
  46                 sync_icache_aliases(page_address(page),
  47                                     PAGE_SIZE << compound_order(page));