When running the OS with a page size > 4 KB, we need to round up mappings
for regions that are not aligned to the OS's page size. We already avoid
block mappings for EfiRuntimeServicesCode/Data regions for other reasons,
but in the unlikely event that other unaliged regions exists that have the
EFI_MEMORY_RUNTIME attribute set, ensure that unaligned regions are always
mapped down to pages. This way, the overlapping page is guaranteed not to
be covered by a block mapping that needs to be split.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
arch/arm64/kernel/efi.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index 4aef89f37049..ba9bee389fd5 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -65,6 +65,20 @@ int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
bool allow_block_mappings = (md->type != EFI_RUNTIME_SERVICES_CODE &&
md->type != EFI_RUNTIME_SERVICES_DATA);
+ if (!PAGE_ALIGNED(md->phys_addr) ||
+ !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT)) {
+ /*
+ * If the end address of this region is not aligned to page
+ * size, the mapping is rounded up, and may end up sharing a
+ * page frame with the next UEFI memory region. If we create
+ * a block entry now, we may need to split it again when mapping
+ * the next region, and support for that is going to be removed
+ * from the MMU routines. So avoid block mappings altogether in
+ * that case.
+ */
+ allow_block_mappings = false;
+ }
+
create_pgd_mapping(mm, md->phys_addr, md->virt_addr,
md->num_pages << EFI_PAGE_SHIFT,
__pgprot(prot_val | PTE_NG), allow_block_mappings);
--
2.7.4
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