@@ -15,6 +15,9 @@
#include "CpuDxe.h"
+#include <Library/MemoryAllocationLib.h>
+#include <Library/UefiBootServicesTableLib.h>
+
#include <Guid/IdleLoopEvent.h>
@@ -237,6 +240,74 @@ InitializeDma (
CpuArchProtocol->DmaBufferAlignment = ArmCacheWritebackGranule ();
}
+STATIC
+VOID
+RemapAllDataRegionsNonExec (
+ VOID
+ )
+{
+ UINTN MemoryMapSize;
+ UINTN MapKey;
+ UINTN DescriptorSize;
+ UINT32 DescriptorVersion;
+ EFI_MEMORY_DESCRIPTOR *MemoryMap;
+ EFI_MEMORY_DESCRIPTOR *MemoryMapEntry;
+ EFI_MEMORY_DESCRIPTOR *MemoryMapEnd;
+ EFI_STATUS Status;
+
+ //
+ // Iterate over the memory map, and remove execute permissions from all
+ // memory regions that are not BootServiceCode or RuntimeServicesCode.
+ //
+
+ //
+ // Get the EFI memory map.
+ //
+ MemoryMapSize = 0;
+ MemoryMap = NULL;
+
+ Status = gBS->GetMemoryMap (
+ &MemoryMapSize,
+ MemoryMap,
+ &MapKey,
+ &DescriptorSize,
+ &DescriptorVersion
+ );
+ ASSERT (Status == EFI_BUFFER_TOO_SMALL);
+ do {
+ MemoryMap = (EFI_MEMORY_DESCRIPTOR *) AllocatePool (MemoryMapSize);
+ ASSERT (MemoryMap != NULL);
+ Status = gBS->GetMemoryMap (
+ &MemoryMapSize,
+ MemoryMap,
+ &MapKey,
+ &DescriptorSize,
+ &DescriptorVersion
+ );
+ if (EFI_ERROR (Status)) {
+ FreePool (MemoryMap);
+ }
+ } while (Status == EFI_BUFFER_TOO_SMALL);
+ ASSERT_EFI_ERROR (Status);
+
+ MemoryMapEntry = MemoryMap;
+ MemoryMapEnd = (EFI_MEMORY_DESCRIPTOR *) ((UINT8 *) MemoryMap + MemoryMapSize);
+ while ((UINTN) MemoryMapEntry < (UINTN) MemoryMapEnd) {
+ if ((MemoryMapEntry->Type != EfiBootServicesCode) &&
+ (MemoryMapEntry->Type != EfiRuntimeServicesCode)) {
+
+ CpuSetMemoryAttributes (&mCpu, MemoryMapEntry->PhysicalStart,
+ EFI_PAGES_TO_SIZE(MemoryMapEntry->NumberOfPages), EFI_MEMORY_XP);
+ DEBUG((DEBUG_ERROR, "%a: removing exec permissions from 0x%lx - 0x%lx (Type == 0x%x)\n",
+ __FUNCTION__, MemoryMapEntry->PhysicalStart,
+ MemoryMapEntry->PhysicalStart + EFI_PAGES_TO_SIZE(MemoryMapEntry->NumberOfPages) - 1,
+ MemoryMapEntry->Type));
+ }
+ MemoryMapEntry = NEXT_MEMORY_DESCRIPTOR (MemoryMapEntry, DescriptorSize);
+ }
+ FreePool (MemoryMap);
+}
+
EFI_STATUS
CpuDxeInitialize (
IN EFI_HANDLE ImageHandle,
@@ -264,6 +335,11 @@ CpuDxeInitialize (
//
SyncCacheConfig (&mCpu);
+ //
+ // Remap all conventional memory as non-executable.
+ //
+ RemapAllDataRegionsNonExec ();
+
// If the platform is a MPCore system then install the Configuration Table describing the
// secondary core states
if (ArmIsMpCore()) {
When installing the CPU arch protocol, iterate over the UEFI memory map and remove the executable permissions from each encountered non-code region. Those will be re-added later selectively, to the extent required according to the image protection policy and section alignment. With a strict image protection policy in place, this all but eliminates any regions that are mapped both writable and executable, which is an significant improvement in security. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- ArmPkg/Drivers/CpuDxe/CpuDxe.c | 76 ++++++++++++++++++++ 1 file changed, 76 insertions(+) -- 2.7.4 _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel