[PATCH] powerpc: fix for hugepage areas straddling 4GB boundary

Commit 7d24f0b fixed bugs in the ppc64 SLB
miss handler with respect to hugepage handling, and in the process tweaked
the semantics of the hugepage address masks in mm_context_t.

Unfortunately, it left out a couple of necessary changes to go with that
change.  First, the in_hugepage_area() macro was not updated to match,
second prepare_hugepage_range() was not updated to correctly handle
hugepages regions which straddled the 4GB point.

The latter appears only to cause process-hangs when attempting to map such
a region, but the former can cause oopses if a get_user_pages() is
triggered at the wrong point.  This patch addresses both bugs.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/powerpc/mm/hugetlbpage.c

@@ -287,15 +287,15 @@ static int open_high_hpage_areas(struct mm_struct *mm, u16 newareas)
 
 int prepare_hugepage_range(unsigned long addr, unsigned long len)
 {
-	int err;
+	int err = 0;
 
 	if ( (addr+len) < addr )
 		return -EINVAL;
 
-	if ((addr + len) < 0x100000000UL)
+	if (addr < 0x100000000UL)
 		err = open_low_hpage_areas(current->mm,
 					  LOW_ESID_MASK(addr, len));
-	else
+	if ((addr + len) >= 0x100000000UL)
 		err = open_high_hpage_areas(current->mm,
 					    HTLB_AREA_MASK(addr, len));
 	if (err) {

include/asm-powerpc/page_64.h

@@ -135,9 +135,9 @@ extern unsigned int HPAGE_SHIFT;
 
 #define in_hugepage_area(context, addr) \
 	(cpu_has_feature(CPU_FTR_16M_PAGE) && \
-	 ( ((1 << GET_HTLB_AREA(addr)) & (context).high_htlb_areas) || \
-	   ( ((addr) < 0x100000000L) && \
-	     ((1 << GET_ESID(addr)) & (context).low_htlb_areas) ) ) )
+	 ( ( (addr) >= 0x100000000UL) \
+	   ? ((1 << GET_HTLB_AREA(addr)) & (context).high_htlb_areas) \
+	   : ((1 << GET_ESID(addr)) & (context).low_htlb_areas) ) )
 
 #else /* !CONFIG_HUGETLB_PAGE */