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

[Jessica Yu]

+++ 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