[PATCH v2 5/7] arm: efi: split zImage code and data into separate PE/COFF sections

[Gregory CLEMENT]

Hi Ard,
 
 On ven., sept. 08 2017, Ard Biesheuvel <ard.biesheuvel at linaro.org> wrote:

> On 8 September 2017 at 15:33, Gregory CLEMENT
> <gregory.clement at free-electrons.com> wrote:
>> Hi Ard,
>>
>>  On ven., sept. 08 2017, Ard Biesheuvel <ard.biesheuvel at linaro.org> wrote:
>>
>>> On 8 September 2017 at 14:54, Ard Biesheuvel <ard.biesheuvel at linaro.org> wrote:
>>>> On 8 September 2017 at 14:50, Gregory CLEMENT
>>>> <gregory.clement at free-electrons.com> wrote:
>>>>> 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/
>>>>>
>>>>
>>>> Ouch.
>>>>
>>>>> 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?
>>>>>
>>>>
>>>> I will investigate.
>>>
>>> I cannot reproduce this on QEMU or my Beaglebone white. I have tried a
>>> locally built zImage as well as the one built by kernelci.
>>>
>>> Could you please try whether this fixes things? It does not explain
>>> anything but it will help me figure out what is going on (hopefully)
>>
>> I've just tested this change and it didn't fix anything.
>>
>> Gregory
>>
>>>
>>>
>>> diff --git a/arch/arm/boot/compressed/efi-header.S
>>> b/arch/arm/boot/compressed/efi-header.S
>>> index c94a88ae834d..671a6e5b7b99 100644
>>> --- a/arch/arm/boot/compressed/efi-header.S
>>> +++ b/arch/arm/boot/compressed/efi-header.S
>>> @@ -127,7 +127,7 @@ section_table:
>>>
>>>                 .set    section_count, (. - section_table) / 40
>>>
>>> -               .align  12
>>> +               .align  9
>>>  __efi_start:
>>>  #endif
>>>                 .endm
>>
>
>
> How about this?

It fixed the bug! (I tested with and without your previous patch and it
worked in both case)

When you will send your patch, you can add my:
Tested-by: Gregory CLEMENT <gregory.clement at free-electrons.com>

Thanks,

Gregory


>
> diff --git a/arch/arm/boot/compressed/vmlinux.lds.S
> b/arch/arm/boot/compressed/vmlinux.lds.S
> index 7a4c59154361..dfcc2baa0077 100644
> --- a/arch/arm/boot/compressed/vmlinux.lds.S
> +++ b/arch/arm/boot/compressed/vmlinux.lds.S
> @@ -29,6 +29,11 @@ SECTIONS
>       * of the text/got segments.
>       */
>      *(.data)
> +    /*
> +     * C code that is shared with the kernel proper (but rebuilt for the
> +     * decompressor) may contain exports that we have no use for here.
> +     */
> +    *(*ksymtab* *kcrctab*)
>    }
>
>    . = TEXT_START;
>
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-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com