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 <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
