linux-kernel - [PATCH 3.10 07/48] ARM: 7840/1: LPAE: dont reject mapping /dev/mem above 4GB

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Message-Id: <20140511191949.129664388@linuxfoundation.org>
Date:	Sun, 11 May 2014 21:19:41 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Vassili Karpov <av1474@...tv.ru>,
	Sergey Dyasly <dserrg@...il.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	hujianyang <hujianyang@...wei.com>
Subject: [PATCH 3.10 07/48] ARM: 7840/1: LPAE: dont reject mapping /dev/mem above 4GB

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

------------------

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

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>
Cc: hujianyang <hujianyang@...wei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm/mm/mmap.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

--- a/arch/arm/mm/mmap.c
+++ b/arch/arm/mm/mmap.c
@@ -204,13 +204,11 @@ int valid_phys_addr_range(phys_addr_t ad
 }
 
 /*
- * 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


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