[PATCH v2] arch : arm : add a criteria for pfn_valid

[Zhaoyang Huang]

From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>

pfn_valid can be wrong when parsing a invalid pfn whose phys address
exceeds BITS_PER_LONG as the MSB will be trimed when shifted.

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
---
v2: use __pfn_to_phys/__phys_to_pfn instead of max_pfn as the criteria
---
 arch/arm/mm/init.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index c2daabb..cc769fa 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -177,6 +177,11 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max_low,
 #ifdef CONFIG_HAVE_ARCH_PFN_VALID
 int pfn_valid(unsigned long pfn)
 {
+	phys_addr_t addr = __pfn_to_phys(pfn);
+
+	if (__phys_to_pfn(addr) != pfn)
+		return 0;
+
 	return memblock_is_map_memory(__pfn_to_phys(pfn));
 }
 EXPORT_SYMBOL(pfn_valid);
-- 
1.9.1