@@ -38,7 +38,7 @@ pe_header:
.long PE_MAGIC
coff_header:
.short IMAGE_FILE_MACHINE_ARM64 // Machine
- .short 1 // NumberOfSections
+ .short 2 // NumberOfSections
.long 0 // TimeDateStamp
.long 0 // PointerToSymbolTable
.long 0 // NumberOfSymbols
@@ -51,8 +51,8 @@ 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 __pecoff_data_start - efi_header_end // SizeOfCode
+ .long __pecoff_data_size // SizeOfInitializedData
.long 0 // SizeOfUninitializedData
.long __efistub_entry - _head // AddressOfEntryPoint
.long efi_header_end - _head // BaseOfCode
@@ -98,9 +98,9 @@ extra_header_fields:
// Section table
section_table:
.ascii ".text\0\0\0"
- .long _end - efi_header_end // VirtualSize
+ .long __pecoff_data_start - efi_header_end // VirtualSize
.long efi_header_end - _head // VirtualAddress
- .long _edata - efi_header_end // SizeOfRawData
+ .long __pecoff_data_start - efi_header_end // SizeOfRawData
.long efi_header_end - _head // PointerToRawData
.long 0 // PointerToRelocations
@@ -108,7 +108,20 @@ 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 __pecoff_data_start - _head // VirtualAddress
+ .long __pecoff_data_rawsize // SizeOfRawData
+ .long __pecoff_data_start - _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
@@ -149,6 +149,9 @@ SECTIONS
ARM_EXIT_KEEP(EXIT_TEXT)
}
+ . = ALIGN(SZ_4K);
+ __pecoff_data_start = .;
+
.init.data : {
INIT_DATA
INIT_SETUP(16)
@@ -206,6 +209,7 @@ SECTIONS
}
PECOFF_EDATA_PADDING
+ __pecoff_data_rawsize = ABSOLUTE(. - __pecoff_data_start);
_edata = .;
BSS_SECTION(0, 0, 0)
@@ -221,6 +225,7 @@ SECTIONS
. += RESERVED_TTBR0_SIZE;
#endif
+ __pecoff_data_size = ABSOLUTE(. - __pecoff_data_start);
_end = .;
STABS_DEBUG
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. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/arm64/kernel/efi-header.S | 25 +++++++++++++++----- arch/arm64/kernel/vmlinux.lds.S | 5 ++++ 2 files changed, 24 insertions(+), 6 deletions(-)