linux-kernel - [PATCH 3.12 14/50] ARM: 7840/1: LPAE: don't reject mapping /dev/mem above 4GB

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Date:	Mon,  5 May 2014 14:42:56 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Sergey Dyasly <dserrg@...il.com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 14/50] ARM: 7840/1: LPAE: don't reject mapping /dev/mem above 4GB

From: Sergey Dyasly <dserrg@...il.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

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@...tv.ru>
Signed-off-by: Sergey Dyasly <dserrg@...il.com>
Acked-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 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 304661d21369..5e85ed371364 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));
 }
 
 #ifdef CONFIG_STRICT_DEVMEM
-- 
1.9.2

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