The IMAGE_DLLCHARACTERISTICS_NX_COMPAT flag marks an EFI binary where the following conditions are met [1]:

* Executable and writable sections are separated. * The application does not run self-modifying code. * The application uses the EFI_MEMORY_ATTRIBUTE_PROTOCOL when loading executable code. * The application does not assume that all memory ranges are usable. * The stack is not expected to be executable.

The only EFI binaries U-Boot provides that do not fulfill these requirements are the EFI app and the EFI payload.

Once we have implemented separation of writable and executable memory in U-Boot we can use the IMAGE_DLLCHARACTERISTICS_NX_COMPAT flag to decide if we will load an EFI binary.

[1] New UEFI CA memory mitigation requirements for signing https://techcommunity.microsoft.com/t5/hardware-dev-center/new-uefi-ca-memor...

Signed-off-by: Heinrich Schuchardt heinrich.schuchardt@canonical.com --- The separation of executable and writable sections for armv7 EFI binaries is provided by

[PATCH 1/1] arm: separate .data and .text sections of EFI binaries https://lore.kernel.org/u-boot/20240214190625.13764-1-heinrich.schuchardt@ca... --- arch/arm/lib/crt0_aarch64_efi.S | 4 ++++ arch/arm/lib/crt0_arm_efi.S | 4 ++++ arch/riscv/lib/crt0_riscv_efi.S | 4 ++++ include/asm-generic/pe.h | 3 +++ 4 files changed, 15 insertions(+)

diff --git a/arch/arm/lib/crt0_aarch64_efi.S b/arch/arm/lib/crt0_aarch64_efi.S index 3c2cef6ec7..fe6eca576e 100644 --- a/arch/arm/lib/crt0_aarch64_efi.S +++ b/arch/arm/lib/crt0_aarch64_efi.S @@ -66,7 +66,11 @@ extra_header_fields: .long _start - ImageBase /* SizeOfHeaders */ .long 0 /* CheckSum */ .short IMAGE_SUBSYSTEM_EFI_APPLICATION /* Subsystem */ +#if CONFIG_VENDOR_EFI .short 0 /* DllCharacteristics */ +#else + .short IMAGE_DLLCHARACTERISTICS_NX_COMPAT +#endif .quad 0 /* SizeOfStackReserve */ .quad 0 /* SizeOfStackCommit */ .quad 0 /* SizeOfHeapReserve */ diff --git a/arch/arm/lib/crt0_arm_efi.S b/arch/arm/lib/crt0_arm_efi.S index ba9fada500..afeff3f3fb 100644 --- a/arch/arm/lib/crt0_arm_efi.S +++ b/arch/arm/lib/crt0_arm_efi.S @@ -65,7 +65,11 @@ extra_header_fields: .long _start - image_base /* SizeOfHeaders */ .long 0 /* CheckSum */ .short IMAGE_SUBSYSTEM_EFI_APPLICATION /* Subsystem */ +#if CONFIG_VENDOR_EFI .short 0 /* DllCharacteristics */ +#else + .short IMAGE_DLLCHARACTERISTICS_NX_COMPAT +#endif .long 0 /* SizeOfStackReserve */ .long 0 /* SizeOfStackCommit */ .long 0 /* SizeOfHeapReserve */ diff --git a/arch/riscv/lib/crt0_riscv_efi.S b/arch/riscv/lib/crt0_riscv_efi.S index 46b0855237..c7a4559eac 100644 --- a/arch/riscv/lib/crt0_riscv_efi.S +++ b/arch/riscv/lib/crt0_riscv_efi.S @@ -96,7 +96,11 @@ extra_header_fields: .long _start - ImageBase /* SizeOfHeaders */ .long 0 /* CheckSum */ .short IMAGE_SUBSYSTEM_EFI_APPLICATION /* Subsystem */ +#if CONFIG_VENDOR_EFI .short 0 /* DllCharacteristics */ +#else + .short IMAGE_DLLCHARACTERISTICS_NX_COMPAT +#endif #if __riscv_xlen == 32 .long 0 /* SizeOfStackReserve */ .long 0 /* SizeOfStackCommit */ diff --git a/include/asm-generic/pe.h b/include/asm-generic/pe.h index b9d674b6da..cd5b6ad62b 100644 --- a/include/asm-generic/pe.h +++ b/include/asm-generic/pe.h @@ -51,6 +51,9 @@ #define IMAGE_SUBSYSTEM_EFI_RUNTIME_DRIVER 12 #define IMAGE_SUBSYSTEM_EFI_ROM 13

+/* DLL characteristics */ +#define IMAGE_DLLCHARACTERISTICS_NX_COMPAT 0x100 + /* Section flags */ #define IMAGE_SCN_CNT_CODE 0x00000020 #define IMAGE_SCN_CNT_INITIALIZED_DATA 0x00000040