Currently, we infer the UEFI memory region mapping permissions
from the memory region type (i.e., runtime services code are
mapped RWX and runtime services data mapped RW-). This appears to
work fine but is not entirely UEFI spec compliant. So instead, use
the designated permission attributes to decide how these regions
should be mapped.
Since UEFIv2.5 introduces a new EFI_MEMORY_RO permission attribute,
and redefines EFI_MEMORY_WP as a cacheability attribute, use only
the former as a read-only attribute. For setting the PXN bit, the
corresponding EFI_MEMORY_XP attribute is used.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
arch/arm64/kernel/efi.c | 32 +++++++++++++-------
1 file changed, 21 insertions(+), 11 deletions(-)
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index ab21e0d58278..5dcab58d5d30 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -247,20 +247,30 @@ static bool __init efi_virtmap_init(void)
memrange_efi_to_native(&paddr, &npages);
size = npages << PAGE_SHIFT;
- pr_info(" EFI remap 0x%016llx => %p\n",
- md->phys_addr, (void *)md->virt_addr);
-
- /*
- * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
- * executable, everything else can be mapped with the XN bits
- * set.
- */
if (!is_normal_ram(md))
prot = __pgprot(PROT_DEVICE_nGnRE);
- else if (md->type == EFI_RUNTIME_SERVICES_CODE)
- prot = PAGE_KERNEL_EXEC;
else
- prot = PAGE_KERNEL;
+ prot = PAGE_KERNEL_EXEC;
+
+ /*
+ * On 64 KB granule kernels, only use strict permissions when
+ * the region does not share a 64 KB page frame with another
+ * region at either end.
+ */
+ if (!IS_ENABLED(CONFIG_ARM64_64K_PAGES) ||
+ !(md->virt_addr % PAGE_SIZE ||
+ (md->phys_addr + md->num_pages * EFI_PAGE_SIZE) % PAGE_SIZE)) {
+
+ if (md->attribute & EFI_MEMORY_RO)
+ prot |= __pgprot(PTE_RDONLY);
+ if (md->attribute & EFI_MEMORY_XP)
+ prot |= __pgprot(PTE_PXN);
+ }
+
+ pr_info(" EFI remap 0x%016llx => %p (R%c%c)\n",
+ md->phys_addr, (void *)md->virt_addr,
+ prot & __pgprot(PTE_RDONLY) ? '-' : 'W',
+ prot & __pgprot(PTE_PXN) ? '-' : 'X');
create_pgd_mapping(&efi_mm, paddr, md->virt_addr, size, prot);
}
--
1.9.1
--
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