From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date: Tue, 14 Mar 2017 19:52:11 +0000 (+0000)
Subject: ArmPkg/UncachedMemoryAllocationLib: set XP bit via CPU arch protocol
X-Git-Tag: edk2-stable201903~4394
X-Git-Url: https://git.proxmox.com/?p=mirror_edk2.git;a=commitdiff_plain;h=0985beff2ce5e9f41e39e1900a8d19d22975d733

ArmPkg/UncachedMemoryAllocationLib: set XP bit via CPU arch protocol

Commit e7b24ec9785d ("ArmPkg/UncachedMemoryAllocationLib: map uncached
allocations non-executable") adds code that manipulates the GCD memory
space attributes of a newly allocated uncached region without checking
whether this region expose these attributes in its capabilities mask.

Given that the intent is to remove executable permissions from the region,
this is a fairly pointless exercise to begin with, regardless of whether
it is correct or not. The reason is that RO/XP memory attributes in the
GCD memory space map or the UEFI memory map are completely disconnected
from the actual mapping permissions used in the page tables.

So instead, invoke the CPU arch protocol directly, and add the non-exec
attributes in the page tables directly.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
Tested-by: Ryan Harkin <ryan.harkin@linaro.org>
---

diff --git a/ArmPkg/Library/UncachedMemoryAllocationLib/UncachedMemoryAllocationLib.c b/ArmPkg/Library/UncachedMemoryAllocationLib/UncachedMemoryAllocationLib.c
index b4fbfbcb36..fdaaf2d706 100644
--- a/ArmPkg/Library/UncachedMemoryAllocationLib/UncachedMemoryAllocationLib.c
+++ b/ArmPkg/Library/UncachedMemoryAllocationLib/UncachedMemoryAllocationLib.c
@@ -27,6 +27,10 @@
 #include <Library/DxeServicesTableLib.h>
 #include <Library/CacheMaintenanceLib.h>
 
+#include <Protocol/Cpu.h>
+
+STATIC EFI_CPU_ARCH_PROTOCOL    *mCpu;
+
 VOID *
 UncachedInternalAllocatePages (
   IN EFI_MEMORY_TYPE  MemoryType,
@@ -150,15 +154,25 @@ AllocatePagesFromList (
 
   Status = gDS->GetMemorySpaceDescriptor (Memory, &Descriptor);
   if (EFI_ERROR (Status)) {
-    gBS->FreePages (Memory, Pages);
-    return Status;
+    goto FreePages;
   }
 
   Status = gDS->SetMemorySpaceAttributes (Memory, EFI_PAGES_TO_SIZE (Pages),
-                  EFI_MEMORY_WC | EFI_MEMORY_XP);
+                  EFI_MEMORY_WC);
   if (EFI_ERROR (Status)) {
-    gBS->FreePages (Memory, Pages);
-    return Status;
+    goto FreePages;
+  }
+
+  //
+  // EFI_CPU_ARCH_PROTOCOL::SetMemoryAttributes() will preserve the original
+  // memory type attribute if no memory type is passed. Permission attributes
+  // will be replaced, so EFI_MEMORY_RO will be removed if present (although
+  // it would be a bug if that were the case for an AllocatePages() allocation)
+  //
+  Status = mCpu->SetMemoryAttributes (mCpu, Memory, EFI_PAGES_TO_SIZE (Pages),
+                   EFI_MEMORY_XP);
+  if (EFI_ERROR (Status)) {
+    goto FreePages;
   }
 
   InvalidateDataCacheRange ((VOID *)(UINTN)Memory, EFI_PAGES_TO_SIZE (Pages));
@@ -166,8 +180,8 @@ AllocatePagesFromList (
   NewNode = AllocatePool (sizeof (FREE_PAGE_NODE));
   if (NewNode == NULL) {
     ASSERT (FALSE);
-    gBS->FreePages (Memory, Pages);
-    return EFI_OUT_OF_RESOURCES;
+    Status = EFI_OUT_OF_RESOURCES;
+    goto FreePages;
   }
 
   NewNode->Base       = Memory;
@@ -181,6 +195,10 @@ AllocatePagesFromList (
 
   *Allocation = NewNode->Allocation;
   return EFI_SUCCESS;
+
+FreePages:
+  gBS->FreePages (Memory, Pages);
+  return Status;
 }
 
 /**
@@ -236,6 +254,16 @@ FreePagesFromList (
  * This function is not responsible to free allocated buffer (eg: case of memory leak,
  * runtime allocation).
  */
+EFI_STATUS
+EFIAPI
+UncachedMemoryAllocationLibConstructor (
+  IN EFI_HANDLE        ImageHandle,
+  IN EFI_SYSTEM_TABLE  *SystemTable
+  )
+{
+  return gBS->LocateProtocol (&gEfiCpuArchProtocolGuid, NULL, (VOID **)&mCpu);
+}
+
 EFI_STATUS
 EFIAPI
 UncachedMemoryAllocationLibDestructor (
diff --git a/ArmPkg/Library/UncachedMemoryAllocationLib/UncachedMemoryAllocationLib.inf b/ArmPkg/Library/UncachedMemoryAllocationLib/UncachedMemoryAllocationLib.inf
index d7a0f2f792..c637430c90 100644
--- a/ArmPkg/Library/UncachedMemoryAllocationLib/UncachedMemoryAllocationLib.inf
+++ b/ArmPkg/Library/UncachedMemoryAllocationLib/UncachedMemoryAllocationLib.inf
@@ -22,7 +22,7 @@
   MODULE_TYPE                    = DXE_DRIVER
   VERSION_STRING                 = 1.0
   LIBRARY_CLASS                  = UncachedMemoryAllocationLib
-
+  CONSTRUCTOR                    = UncachedMemoryAllocationLibConstructor
   DESTRUCTOR                     = UncachedMemoryAllocationLibDestructor
 
 [Sources.common]
@@ -42,3 +42,9 @@
 
 [Pcd]
   gArmTokenSpaceGuid.PcdArmFreeUncachedMemorySizeThreshold
+
+[Protocols]
+  gEfiCpuArchProtocolGuid
+
+[Depex]
+  gEfiCpuArchProtocolGuid