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, 6 insertions, 0 deletions

diff --git a/arch/sh/include/asm/pgtable.h b/arch/sh/include/asm/pgtable.h
index 52220d70a096..b517ae08b9c0 100644
--- a/arch/sh/include/asm/pgtable.h
+++ b/arch/sh/include/asm/pgtable.h
@@ -148,6 +148,12 @@ extern void paging_init(void);
 extern void page_table_range_init(unsigned long start, unsigned long end,
                                   pgd_t *pgd);
 
+#if !defined(CONFIG_CACHE_OFF) && defined(CONFIG_CPU_SH4) && defined(CONFIG_MMU)
+extern void kmap_coherent_init(void);
+#else
+#define kmap_coherent_init()    do { } while (0)
+#endif
+
 #include <asm-generic/pgtable.h>
 
 #endif /* __ASM_SH_PGTABLE_H */