[3.11.y.z extended stable] Patch "ARM: 7840/1: LPAE: don't reject mapping /dev/mem above 4GB" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Mon May 5 10:38:26 UTC 2014

This is a note to let you know that I have just added a patch titled

    ARM: 7840/1: LPAE: don't reject mapping /dev/mem above 4GB

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:


If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see



>From 679e224a76351c3ba4514d9329f8d549a86aebb6 Mon Sep 17 00:00:00 2001
From: Sergey Dyasly <dserrg at gmail.com>
Date: Tue, 24 Sep 2013 16:38:00 +0100
Subject: ARM: 7840/1: LPAE: don't reject mapping /dev/mem above 4GB

commit 3159f372354e8e1f5dee714663d705dd2c7e0759 upstream.

With LPAE enabled, physical address space is larger than 4GB. Allow mapping any
part of it via /dev/mem by using PHYS_MASK to determine valid range.

PHYS_MASK covers 40 bits with LPAE enabled and 32 bits otherwise.

Reported-by: Vassili Karpov <av1474 at comtv.ru>
Signed-off-by: Sergey Dyasly <dserrg at gmail.com>
Acked-by: Catalin Marinas <catalin.marinas at arm.com>
Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
Cc: hujianyang <hujianyang at huawei.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
 arch/arm/mm/mmap.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
index 304661d..5e85ed3 100644
--- a/arch/arm/mm/mmap.c
+++ b/arch/arm/mm/mmap.c
@@ -202,13 +202,11 @@ int valid_phys_addr_range(phys_addr_t addr, size_t size)

- * We don't use supersection mappings for mmap() on /dev/mem, which
- * means that we can't map the memory area above the 4G barrier into
- * userspace.
+ * Do not allow /dev/mem mappings beyond the supported physical range.
 int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
-	return !(pfn + (size >> PAGE_SHIFT) > 0x00100000);
+	return (pfn + (size >> PAGE_SHIFT)) <= (1 + (PHYS_MASK >> PAGE_SHIFT));


More information about the kernel-team mailing list