[PATCH v2 5/7] arm: efi: split zImage code and data into separate PE/COFF sections
Gregory CLEMENT
gregory.clement at free-electrons.com
Fri Sep 8 06:50:42 PDT 2017
Hi Ard,
On jeu., juin 29 2017, Ard Biesheuvel <ard.biesheuvel at linaro.org> wrote:
> 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, .piggytext and the GOT sections (which the
> stub does not care about anyway), and a .data section with read-write
> permissions, covering .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.
This patch had been merged in mainline yesterday and now prevent the
Marvell Armada 370 and the Armada XP based SoC to boot. I also suspect
that more Socs are impacted because the number of boot fail exploded
according to kci:
https://kernelci.org/boot/all/job/mainline/branch/master/kernel/v4.13-8899-g8dc5b3a6cb2f/
I found this patch after bisecting (I can provide the bisect log if
needed).
The kernel failed to boot only if CONFIG_EFI is enabled so it occurs in
multi_v7_defconfig but not with mvebu_v7_defconfig.
Currently the solution is to revert this patch.
Have you a better option?
Thanks,
Gregory
>
> Cc: Russell King <linux at armlinux.org.uk>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> ---
> arch/arm/boot/compressed/efi-header.S | 32 ++++++++++++++------
> arch/arm/boot/compressed/vmlinux.lds.S | 30 +++++++++++++-----
> 2 files changed, 46 insertions(+), 16 deletions(-)
>
> diff --git a/arch/arm/boot/compressed/efi-header.S b/arch/arm/boot/compressed/efi-header.S
> index 542e1ad432ae..c94a88ae834d 100644
> --- a/arch/arm/boot/compressed/efi-header.S
> +++ b/arch/arm/boot/compressed/efi-header.S
> @@ -54,20 +54,22 @@ coff_header:
> IMAGE_FILE_EXECUTABLE_IMAGE | \
> IMAGE_FILE_LINE_NUMS_STRIPPED @ Characteristics
>
> +#define __pecoff_code_size (__pecoff_data_start - __efi_start)
> +
> optional_header:
> .short PE_OPT_MAGIC_PE32 @ PE32 format
> .byte 0x02 @ MajorLinkerVersion
> .byte 0x14 @ MinorLinkerVersion
> - .long _end - __efi_start @ SizeOfCode
> - .long 0 @ SizeOfInitializedData
> + .long __pecoff_code_size @ SizeOfCode
> + .long __pecoff_data_size @ SizeOfInitializedData
> .long 0 @ SizeOfUninitializedData
> .long efi_stub_entry - start @ AddressOfEntryPoint
> .long start_offset @ BaseOfCode
> - .long 0 @ BaseOfData
> + .long __pecoff_data_start - start @ BaseOfData
>
> extra_header_fields:
> .long 0 @ ImageBase
> - .long SZ_512 @ SectionAlignment
> + .long SZ_4K @ SectionAlignment
> .long SZ_512 @ FileAlignment
> .short 0 @ MajorOsVersion
> .short 0 @ MinorOsVersion
> @@ -77,7 +79,7 @@ extra_header_fields:
> .short 0 @ MinorSubsystemVersion
> .long 0 @ Win32VersionValue
>
> - .long _end - start @ SizeOfImage
> + .long __pecoff_end - start @ SizeOfImage
> .long start_offset @ SizeOfHeaders
> .long 0 @ CheckSum
> .short IMAGE_SUBSYSTEM_EFI_APPLICATION @ Subsystem
> @@ -98,9 +100,9 @@ extra_header_fields:
>
> section_table:
> .ascii ".text\0\0\0"
> - .long _end - __efi_start @ VirtualSize
> + .long __pecoff_code_size @ VirtualSize
> .long __efi_start @ VirtualAddress
> - .long _edata - __efi_start @ SizeOfRawData
> + .long __pecoff_code_size @ SizeOfRawData
> .long __efi_start @ PointerToRawData
> .long 0 @ PointerToRelocations
> .long 0 @ PointerToLineNumbers
> @@ -108,12 +110,24 @@ section_table:
> .short 0 @ NumberOfLineNumbers
> .long IMAGE_SCN_CNT_CODE | \
> IMAGE_SCN_MEM_READ | \
> - IMAGE_SCN_MEM_WRITE | \
> IMAGE_SCN_MEM_EXECUTE @ Characteristics
>
> + .ascii ".data\0\0\0"
> + .long __pecoff_data_size @ VirtualSize
> + .long __pecoff_data_start - start @ VirtualAddress
> + .long __pecoff_data_rawsize @ SizeOfRawData
> + .long __pecoff_data_start - start @ 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
> +
> .set section_count, (. - section_table) / 40
>
> - .align 9
> + .align 12
> __efi_start:
> #endif
> .endm
> diff --git a/arch/arm/boot/compressed/vmlinux.lds.S b/arch/arm/boot/compressed/vmlinux.lds.S
> index 1fa62432e283..dfcc2baa0077 100644
> --- a/arch/arm/boot/compressed/vmlinux.lds.S
> +++ b/arch/arm/boot/compressed/vmlinux.lds.S
> @@ -53,13 +53,6 @@ SECTIONS
> *(.rodata)
> *(.rodata.*)
> }
> - .data : {
> - /*
> - * The EFI stub always executes from RAM, and runs strictly before the
> - * decompressor, so we can make an exception for its r/w data, and keep it
> - */
> - *(.data.efistub)
> - }
> .piggydata : {
> *(.piggydata)
> }
> @@ -75,6 +68,26 @@ SECTIONS
> /* ensure the zImage file size is always a multiple of 64 bits */
> /* (without a dummy byte, ld just ignores the empty section) */
> .pad : { BYTE(0); . = ALIGN(8); }
> +
> +#ifdef CONFIG_EFI_STUB
> + .data : ALIGN(4096) {
> + __pecoff_data_start = .;
> + /*
> + * The EFI stub always executes from RAM, and runs strictly before the
> + * decompressor, so we can make an exception for its r/w data, and keep it
> + */
> + *(.data.efistub)
> + __pecoff_data_end = .;
> +
> + /*
> + * PE/COFF mandates a file size which is a multiple of 512 bytes if the
> + * section size equals or exceeds 4 KB
> + */
> + . = ALIGN(512);
> + }
> + __pecoff_data_rawsize = . - ADDR(.data);
> +#endif
> +
> _edata = .;
>
> _magic_sig = ZIMAGE_MAGIC(0x016f2818);
> @@ -89,6 +102,9 @@ SECTIONS
> . = ALIGN(8); /* the stack must be 64-bit aligned */
> .stack : { *(.stack) }
>
> + PROVIDE(__pecoff_data_size = ALIGN(512) - ADDR(.data));
> + PROVIDE(__pecoff_end = ALIGN(512));
> +
> .stab 0 : { *(.stab) }
> .stabstr 0 : { *(.stabstr) }
> .stab.excl 0 : { *(.stab.excl) }
> --
> 2.9.3
>
>
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--
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
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