On 11/19/2015 01:54 PM, Ard Biesheuvel wrote:
On 19 November 2015 at 00:55, Heyi Guo <heyi....@linaro.org> wrote:
On 11/18/2015 04:25 PM, Ard Biesheuvel wrote:
The ARM architecture version 7 and later mandates that device mappings
have the XN (non-executable) bit set, to prevent speculative instruction
fetches from read-sensitive regions. This implies that we should not map
regions as device if we want to execute from them, so the NOR region that
contains our FD image should be mapped as normal memory instead.
The MMU code deals correctly with overlapping ARM_MEMORY_REGION_DESCRIPTOR
entries, and later entries in the array take precedence over earlier ones.
So simply add an entry to the end of the array that overrides the mapping
attributes of the FD image, wherever it resides.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
---
ArmVirtPkg/Library/ArmVirtPlatformLib/VirtMem.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/ArmVirtPkg/Library/ArmVirtPlatformLib/VirtMem.c
b/ArmVirtPkg/Library/ArmVirtPlatformLib/VirtMem.c
index d5d288fb1b48..530f7d608e0b 100644
--- a/ArmVirtPkg/Library/ArmVirtPlatformLib/VirtMem.c
+++ b/ArmVirtPkg/Library/ArmVirtPlatformLib/VirtMem.c
@@ -22,7 +22,7 @@
#include <ArmPlatform.h>
// Number of Virtual Memory Map Descriptors
-#define MAX_VIRTUAL_MEMORY_MAP_DESCRIPTORS 4
+#define MAX_VIRTUAL_MEMORY_MAP_DESCRIPTORS 5
// DDR attributes
#define DDR_ATTRIBUTES_CACHED ARM_MEMORY_REGION_ATTRIBUTE_WRITE_BACK
@@ -100,8 +100,14 @@ ArmPlatformGetVirtualMemoryMap (
VirtualMemoryTable[2].Length = ArmGetPhysAddrTop () -
VirtualMemoryTable[2].PhysicalBase;
VirtualMemoryTable[2].Attributes =
ARM_MEMORY_REGION_ATTRIBUTE_DEVICE;
+ // Remap the FD region as normal executable memory
+ VirtualMemoryTable[3].PhysicalBase = FixedPcdGet64 (PcdFdBaseAddress);
+ VirtualMemoryTable[3].VirtualBase =
VirtualMemoryTable[3].PhysicalBase;
+ VirtualMemoryTable[3].Length = FixedPcdGet32 (PcdFdSize);
+ VirtualMemoryTable[3].Attributes = CacheAttributes;
+
// End of Table
- ZeroMem (&VirtualMemoryTable[3], sizeof
(ARM_MEMORY_REGION_DESCRIPTOR));
+ ZeroMem (&VirtualMemoryTable[4], sizeof
(ARM_MEMORY_REGION_DESCRIPTOR));
Just a minor suggestion: is it better to use
MAX_VIRTUAL_MEMORY_MAP_DESCRIPTORS - 1 instead of 4 to avoid changing two
pieces of code when changing descriptor number?
The end of table entry should follow directly after the last valid
one, while the maximum number of entries could be higher (e.g., I
could have changed it to 8, since we will end up using a single page
anyway).
Got it. Thanks
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