From 1fd55a9a09b0293af95ab4299b108f030fef4464 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Mon, 25 Apr 2016 21:06:43 +0100 Subject: [PATCH] arm64/efi: Apply strict permissions to UEFI Runtime Services regions Recent UEFI versions expose permission attributes for runtime services memory regions, either in the UEFI memory map or in the separate memory attributes table. This allows the kernel to map these regions with stricter permissions, rather than the RWX permissions that are used by default. So wire this up in our mapping routine. Note that in the absence of permission attributes, we still only map regions of type EFI_RUNTIME_SERVICE_CODE with the executable bit set. Also, we base the mapping attributes of EFI_MEMORY_MAPPED_IO on the type directly rather than on the absence of the EFI_MEMORY_WB attribute. This is more correct, but is also required for compatibility with the upcoming support for the Memory Attributes Table, which only carries permission attributes, not memory type attributes. Signed-off-by: Ard Biesheuvel Signed-off-by: Matt Fleming Cc: Borislav Petkov Cc: Catalin Marinas Cc: Leif Lindholm Cc: Mark Rutland Cc: Peter Jones Cc: Peter Zijlstra Cc: Sai Praneeth Prakhya Cc: Thomas Gleixner Cc: Will Deacon Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/1461614832-17633-12-git-send-email-matt@codeblueprint.co.uk Signed-off-by: Ingo Molnar --- arch/arm64/kernel/efi.c | 54 ++++++++++++++++++++++++++++++----------- 1 file changed, 40 insertions(+), 14 deletions(-) diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c index b6abc852f2a1..33a6da160a50 100644 --- a/arch/arm64/kernel/efi.c +++ b/arch/arm64/kernel/efi.c @@ -17,22 +17,48 @@ #include -int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md) +/* + * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be + * executable, everything else can be mapped with the XN bits + * set. Also take the new (optional) RO/XP bits into account. + */ +static __init pteval_t create_mapping_protection(efi_memory_desc_t *md) { - pteval_t prot_val; + u64 attr = md->attribute; + u32 type = md->type; - /* - * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be - * executable, everything else can be mapped with the XN bits - * set. - */ - if ((md->attribute & EFI_MEMORY_WB) == 0) - prot_val = PROT_DEVICE_nGnRE; - else if (md->type == EFI_RUNTIME_SERVICES_CODE || - !PAGE_ALIGNED(md->phys_addr)) - prot_val = pgprot_val(PAGE_KERNEL_EXEC); - else - prot_val = pgprot_val(PAGE_KERNEL); + if (type == EFI_MEMORY_MAPPED_IO) + return PROT_DEVICE_nGnRE; + + if (WARN_ONCE(!PAGE_ALIGNED(md->phys_addr), + "UEFI Runtime regions are not aligned to 64 KB -- buggy firmware?")) + /* + * If the region is not aligned to the page size of the OS, we + * can not use strict permissions, since that would also affect + * the mapping attributes of the adjacent regions. + */ + return pgprot_val(PAGE_KERNEL_EXEC); + + /* R-- */ + if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) == + (EFI_MEMORY_XP | EFI_MEMORY_RO)) + return pgprot_val(PAGE_KERNEL_RO); + + /* R-X */ + if (attr & EFI_MEMORY_RO) + return pgprot_val(PAGE_KERNEL_ROX); + + /* RW- */ + if (attr & EFI_MEMORY_XP || type != EFI_RUNTIME_SERVICES_CODE) + return pgprot_val(PAGE_KERNEL); + + /* RWX */ + return pgprot_val(PAGE_KERNEL_EXEC); +} + +int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md) +{ + pteval_t prot_val = create_mapping_protection(md); create_pgd_mapping(mm, md->phys_addr, md->virt_addr, md->num_pages << EFI_PAGE_SHIFT, -- 2.20.1