Re: [PATCH modules 0/2] Fix handling of exit unwinding sections (on ARM)

[Jessica Yu <jeyu@kernel.org>]

+++ Matthias Schiffer [06/06/19 10:14 +0200]:
>On Mon, 2019-06-03 at 12:57 +0200, Matthias Schiffer wrote:
>> For some time (050d18d1c651 "ARM: 8650/1: module: handle negative
>> R_ARM_PREL31 addends correctly", v4.11+), building a kernel without
>> CONFIG_MODULE_UNLOAD would lead to module loads failing on ARM
>> systems with
>> certain memory layouts, with messages like:
>>
>>   imx_sdma: section 16 reloc 0 sym '': relocation 42 out of range
>>   (0x7f015260 -> 0xc0f5a5e8)
>>
>> (0x7f015260 is in the module load area, 0xc0f5a5e8 a regular vmalloc
>> address; relocation 42 is R_ARM_PREL31)
>>
>> This is caused by relocatiosn in the .ARM.extab.exit.text and
>> .ARM.exidx.exit.text sections referencing the .exit.text section. As
>> the
>> module loader will omit loading .exit.text without
>> CONFIG_MODULE_UNLOAD,
>> there will be relocations from loaded to unloaded sections; the
>> resulting
>> huge offsets trigger the sanity checks added in 050d18d1c651.
>>
>> IA64 might be affected by a similar issue - sections with names like
>> .IA_64.unwind.exit.text and .IA_64.unwind_info.exit.text appear in
>> the ld
>> script - but I don't know much about that arch.
>>
>> Also, I'm not sure if this is stable-worthy - just enabling
>> CONFIG_MODULE_UNLOAD should be a viable workaround on affected
>> kernels.
>>
>>
>> Kind regards,
>> Matthias
>
>
>Hi,
>any comments on these patches? If not, who is going to take them in
>their tree?

I don't mind either way. I can take the patches through my tree if
Russell ack's the second one (after comments have been addressed).

Thanks!

Jessica