From cad27ef27ef7d897893b921c86337a8cc9d0cd0e Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Thu, 23 Mar 2017 19:00:51 +0000 Subject: [PATCH] arm64: efi: split Image code and data into separate PE/COFF sections To prevent unintended modifications to the kernel text (malicious or otherwise) while running the EFI stub, describe the kernel image as two separate sections: a .text section with read-execute permissions, covering .text, .rodata and .init.text, and a .data section with read-write permissions, covering .init.data, .data and .bss. This relies on the firmware to actually take the section permission flags into account, but this is something that is currently being implemented in EDK2, which means we will likely start seeing it in the wild between one and two years from now. Acked-by: Mark Rutland Signed-off-by: Ard Biesheuvel Signed-off-by: Catalin Marinas --- arch/arm64/kernel/efi-header.S | 23 ++++++++++++++++++----- arch/arm64/kernel/vmlinux.lds.S | 2 ++ 2 files changed, 20 insertions(+), 5 deletions(-) diff --git a/arch/arm64/kernel/efi-header.S b/arch/arm64/kernel/efi-header.S index 7637226ea9ca..613fc3000677 100644 --- a/arch/arm64/kernel/efi-header.S +++ b/arch/arm64/kernel/efi-header.S @@ -27,8 +27,8 @@ optional_header: .short PE_OPT_MAGIC_PE32PLUS // PE32+ format .byte 0x02 // MajorLinkerVersion .byte 0x14 // MinorLinkerVersion - .long _end - efi_header_end // SizeOfCode - .long 0 // SizeOfInitializedData + .long __initdata_begin - efi_header_end // SizeOfCode + .long __pecoff_data_size // SizeOfInitializedData .long 0 // SizeOfUninitializedData .long __efistub_entry - _head // AddressOfEntryPoint .long efi_header_end - _head // BaseOfCode @@ -74,9 +74,9 @@ extra_header_fields: // Section table section_table: .ascii ".text\0\0\0" - .long _end - efi_header_end // VirtualSize + .long __initdata_begin - efi_header_end // VirtualSize .long efi_header_end - _head // VirtualAddress - .long _edata - efi_header_end // SizeOfRawData + .long __initdata_begin - efi_header_end // SizeOfRawData .long efi_header_end - _head // PointerToRawData .long 0 // PointerToRelocations @@ -84,7 +84,20 @@ section_table: .short 0 // NumberOfRelocations .short 0 // NumberOfLineNumbers .long IMAGE_SCN_CNT_CODE | \ - IMAGE_SCN_MEM_EXECUTE | \ + IMAGE_SCN_MEM_READ | \ + IMAGE_SCN_MEM_EXECUTE // Characteristics + + .ascii ".data\0\0\0" + .long __pecoff_data_size // VirtualSize + .long __initdata_begin - _head // VirtualAddress + .long __pecoff_data_rawsize // SizeOfRawData + .long __initdata_begin - _head // PointerToRawData + + .long 0 // PointerToRelocations + .long 0 // PointerToLineNumbers + .short 0 // NumberOfRelocations + .short 0 // NumberOfLineNumbers + .long IMAGE_SCN_CNT_INITIALIZED_DATA | \ IMAGE_SCN_MEM_READ | \ IMAGE_SCN_MEM_WRITE // Characteristics diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 2c93d259046c..987a00ee446c 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -213,6 +213,7 @@ SECTIONS } PECOFF_EDATA_PADDING + __pecoff_data_rawsize = ABSOLUTE(. - __initdata_begin); _edata = .; BSS_SECTION(0, 0, 0) @@ -228,6 +229,7 @@ SECTIONS . += RESERVED_TTBR0_SIZE; #endif + __pecoff_data_size = ABSOLUTE(. - __initdata_begin); _end = .; STABS_DEBUG