sh: Handle fixmap TLB eviction more coherently.

There was a race in the kmap_coherent() implementation. While we
guarded against preemption, there was nothing preventing eviction of
the pre-faulted fixmap entry from the UTLB. Under certain workloads
this would result in the fixmap entries used for cache colouring being
evicted from the UTLB in the midst of a copy_page().

In addition to pre-faulting, we also make sure to preserve the PTEs
in the kernel page table and introduce a cached PTE for kmap_coherent()
usage. This follows a similar change on MIPS ("[MIPS] Fix aliasing bug
in copy_to_user_page / copy_from_user_page").

Reported-by: Hideo Saito <saito@densan.co.jp>
Reported-by: CHIKAMA Masaki <masaki.chikama@gmail.com>
Tested-by: Yoshihiro Shimoda <shimoda.yoshihiro@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 9 insertions, 3 deletions

diff --git a/arch/sh/mm/init.c b/arch/sh/mm/init.c
index 4abf000..6cbef8c 100644
--- a/arch/sh/mm/init.c
+++ b/arch/sh/mm/init.c
@@ -137,6 +137,7 @@ void __init page_table_range_init(unsigned long start, unsigned long end,
 void __init paging_init(void)
 {
 	unsigned long max_zone_pfns[MAX_NR_ZONES];
+	unsigned long vaddr;
 	int nid;
 
 	/* We don't need to map the kernel through the TLB, as
@@ -148,10 +149,15 @@ void __init paging_init(void)
 	 * check for a null value. */
 	set_TTB(swapper_pg_dir);
 
-	/* Populate the relevant portions of swapper_pg_dir so that
+	/*
+	 * Populate the relevant portions of swapper_pg_dir so that
 	 * we can use the fixmap entries without calling kmalloc.
-	 * pte's will be filled in by __set_fixmap(). */
-	page_table_range_init(FIXADDR_START, FIXADDR_TOP, swapper_pg_dir);
+	 * pte's will be filled in by __set_fixmap().
+	 */
+	vaddr = __fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK;
+	page_table_range_init(vaddr, 0, swapper_pg_dir);
+
+	kmap_coherent_init();
 
 	memset(max_zone_pfns, 0, sizeof(max_zone_pfns));