[ARM] Fix virtual to physical translation macro corner cases

The current use of these macros works well when the conversion is
entirely linear.  In this case, we can be assured that the following
holds true:

	__va(p + s) - s = __va(p)

However, this is not always the case, especially when there is a
non-linear conversion (eg, when there is a 3.5GB hole in memory.)
In this case, if 's' is the size of the region (eg, PAGE_SIZE) and
'p' is the final page, the above is most definitely not true.

So, we must ensure that __va() and __pa() are only used with valid
kernel direct mapped RAM addresses.  This patch tweaks the code
to achieve this.

Tested-by: Charles Moschel <fred99@carolina.rr.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 12 insertions, 8 deletions

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 310e479309ef..f1ef5613ccd4 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -490,26 +490,30 @@ core_initcall(consistent_init);
  */
 void dma_cache_maint(const void *start, size_t size, int direction)
 {
-        const void *end = start + size;
+        void (*inner_op)(const void *, const void *);
+        void (*outer_op)(unsigned long, unsigned long);
 
-        BUG_ON(!virt_addr_valid(start) || !virt_addr_valid(end - 1));
+        BUG_ON(!virt_addr_valid(start) || !virt_addr_valid(start + size - 1));
 
         switch (direction) {
         case DMA_FROM_DEVICE:           /* invalidate only */
-                dmac_inv_range(start, end);
-                outer_inv_range(__pa(start), __pa(end));
+                inner_op = dmac_inv_range;
+                outer_op = outer_inv_range;
                 break;
         case DMA_TO_DEVICE:             /* writeback only */
-                dmac_clean_range(start, end);
-                outer_clean_range(__pa(start), __pa(end));
+                inner_op = dmac_clean_range;
+                outer_op = outer_clean_range;
                 break;
         case DMA_BIDIRECTIONAL:         /* writeback and invalidate */
-                dmac_flush_range(start, end);
-                outer_flush_range(__pa(start), __pa(end));
+                inner_op = dmac_flush_range;
+                outer_op = outer_flush_range;
                 break;
         default:
                 BUG();
         }
+
+        inner_op(start, start + size);
+        outer_op(__pa(start), __pa(start) + size);
 }
 EXPORT_SYMBOL(dma_cache_maint);