ArmPkg/CpuDxe ARM: Fix page-to-section attribute conversion

The section-to-page attribute conversion takes the shareability and
execute-never attributes into account, whereas the page-to-section
counterpart does not. The result is that GetMemoryRegionPage () -which
takes a section attribute argument (via *RegionAttributes) that is
ostensibly based on the first page in the range, but differs from the
actual page attributes when converted back- may return with a
RegionLength of zero. This is incorrect, and confuses code that scans a
region by calling GetMemoryRegion () in sequence.

So fix the conversion, and ASSERT () on a non-zero region length.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/ArmPkg/Drivers/CpuDxe/Arm/Mmu.c b/ArmPkg/Drivers/CpuDxe/Arm/Mmu.c
index ea856f5cdd..8eb1f71395 100644
--- a/ArmPkg/Drivers/CpuDxe/Arm/Mmu.c
+++ b/ArmPkg/Drivers/CpuDxe/Arm/Mmu.c
@@ -480,6 +480,8 @@ GetMemoryRegion (
 

     PageAttributes    = PageTable[PageTableIndex] & TT_DESCRIPTOR_PAGE_ATTRIBUTE_MASK;

     *RegionAttributes = TT_DESCRIPTOR_CONVERT_TO_SECTION_CACHE_POLICY (PageAttributes) |

+                        TT_DESCRIPTOR_CONVERT_TO_SECTION_S (PageAttributes) |

+                        TT_DESCRIPTOR_CONVERT_TO_SECTION_XN (PageAttributes) |

                         TT_DESCRIPTOR_CONVERT_TO_SECTION_AP (PageAttributes);

   }

 

@@ -494,6 +496,7 @@ GetMemoryRegion (
 

       // Scan the page table to find the end of the region.

       Status = GetMemoryRegionPage (PageTable, BaseAddress, RegionLength, RegionAttributes);

+      ASSERT (*RegionLength > 0);

 

       // If we have found the end of the region (Status == EFI_SUCCESS) then we exit the for-loop

       if (Status == EFI_SUCCESS) {