diff options
| -rw-r--r-- | drivers/firmware/efi/Kconfig | 12 | ||||
| -rw-r--r-- | drivers/firmware/efi/libstub/x86-stub.c | 110 |
2 files changed, 118 insertions, 4 deletions
diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig index f8ddd2259ba0..4720ba98cec3 100644 --- a/drivers/firmware/efi/Kconfig +++ b/drivers/firmware/efi/Kconfig @@ -91,6 +91,18 @@ config EFI_SOFT_RESERVE If unsure, say Y. +config EFI_DXE_MEM_ATTRIBUTES + bool "Adjust memory attributes in EFISTUB" + depends on EFI && EFI_STUB && X86 + default y + help + UEFI specification does not guarantee all memory to be + accessible for both write and execute as the kernel expects + it to be. + Use DXE services to check and alter memory protection + attributes during boot via EFISTUB to ensure that memory + ranges used by the kernel are writable and executable. + config EFI_PARAMS_FROM_FDT bool help diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c index cda60aba2f12..b14e88ccefca 100644 --- a/drivers/firmware/efi/libstub/x86-stub.c +++ b/drivers/firmware/efi/libstub/x86-stub.c @@ -212,9 +212,110 @@ static void retrieve_apple_device_properties(struct boot_params *boot_params) } } +static void +adjust_memory_range_protection(unsigned long start, unsigned long size) +{ + efi_status_t status; + efi_gcd_memory_space_desc_t desc; + unsigned long end, next; + unsigned long rounded_start, rounded_end; + unsigned long unprotect_start, unprotect_size; + int has_system_memory = 0; + + if (efi_dxe_table == NULL) + return; + + rounded_start = rounddown(start, EFI_PAGE_SIZE); + rounded_end = roundup(start + size, EFI_PAGE_SIZE); + + /* + * Don't modify memory region attributes, they are + * already suitable, to lower the possibility to + * encounter firmware bugs. + */ + + for (end = start + size; start < end; start = next) { + + status = efi_dxe_call(get_memory_space_descriptor, start, &desc); + + if (status != EFI_SUCCESS) + return; + + next = desc.base_address + desc.length; + + /* + * Only system memory is suitable for trampoline/kernel image placement, + * so only this type of memory needs its attributes to be modified. + */ + + if (desc.gcd_memory_type != EfiGcdMemoryTypeSystemMemory || + (desc.attributes & (EFI_MEMORY_RO | EFI_MEMORY_XP)) == 0) + continue; + + unprotect_start = max(rounded_start, (unsigned long)desc.base_address); + unprotect_size = min(rounded_end, next) - unprotect_start; + + status = efi_dxe_call(set_memory_space_attributes, + unprotect_start, unprotect_size, + EFI_MEMORY_WB); + + if (status != EFI_SUCCESS) { + efi_warn("Unable to unprotect memory range [%08lx,%08lx]: %d\n", + unprotect_start, + unprotect_start + unprotect_size, + (int)status); + } + } +} + +/* + * Trampoline takes 2 pages and can be loaded in first megabyte of memory + * with its end placed between 128k and 640k where BIOS might start. + * (see arch/x86/boot/compressed/pgtable_64.c) + * + * We cannot find exact trampoline placement since memory map + * can be modified by UEFI, and it can alter the computed address. + */ + +#define TRAMPOLINE_PLACEMENT_BASE ((128 - 8)*1024) +#define TRAMPOLINE_PLACEMENT_SIZE (640*1024 - (128 - 8)*1024) + +void startup_32(struct boot_params *boot_params); + +static void +setup_memory_protection(unsigned long image_base, unsigned long image_size) +{ + /* + * Allow execution of possible trampoline used + * for switching between 4- and 5-level page tables + * and relocated kernel image. + */ + + adjust_memory_range_protection(TRAMPOLINE_PLACEMENT_BASE, + TRAMPOLINE_PLACEMENT_SIZE); + +#ifdef CONFIG_64BIT + if (image_base != (unsigned long)startup_32) + adjust_memory_range_protection(image_base, image_size); +#else + /* + * Clear protection flags on a whole range of possible + * addresses used for KASLR. We don't need to do that + * on x86_64, since KASLR/extraction is performed after + * dedicated identity page tables are built and we only + * need to remove possible protection on relocated image + * itself disregarding further relocations. + */ + adjust_memory_range_protection(LOAD_PHYSICAL_ADDR, + KERNEL_IMAGE_SIZE - LOAD_PHYSICAL_ADDR); +#endif +} + static const efi_char16_t apple[] = L"Apple"; -static void setup_quirks(struct boot_params *boot_params) +static void setup_quirks(struct boot_params *boot_params, + unsigned long image_base, + unsigned long image_size) { efi_char16_t *fw_vendor = (efi_char16_t *)(unsigned long) efi_table_attr(efi_system_table, fw_vendor); @@ -223,6 +324,9 @@ static void setup_quirks(struct boot_params *boot_params) if (IS_ENABLED(CONFIG_APPLE_PROPERTIES)) retrieve_apple_device_properties(boot_params); } + + if (IS_ENABLED(CONFIG_EFI_DXE_MEM_ATTRIBUTES)) + setup_memory_protection(image_base, image_size); } /* @@ -342,8 +446,6 @@ static void __noreturn efi_exit(efi_handle_t handle, efi_status_t status) asm("hlt"); } -void startup_32(struct boot_params *boot_params); - void __noreturn efi_stub_entry(efi_handle_t handle, efi_system_table_t *sys_table_arg, struct boot_params *boot_params); @@ -798,7 +900,7 @@ unsigned long efi_main(efi_handle_t handle, setup_efi_pci(boot_params); - setup_quirks(boot_params); + setup_quirks(boot_params, bzimage_addr, buffer_end - buffer_start); status = exit_boot(boot_params, handle); if (status != EFI_SUCCESS) { |