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SubjectRe: [PATCH 7/7] modpost: detect section mismatch for R_ARM_REL32
On Thu, 1 Jun 2023 at 16:36, Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Thu, Jun 1, 2023 at 9:40 PM Ard Biesheuvel <ardb@kernel.org> wrote:
> >
> > On Thu, 1 Jun 2023 at 14:10, Masahiro Yamada <masahiroy@kernel.org> wrote:
> > >
> > > For ARM, modpost fails to detect some types of section mismatches.
> > >
> > > [test code]
> > >
> > > .section .init.data,"aw"
> > > bar:
> > > .long 0
> > >
> > > .section .data,"aw"
> > > .globl foo
> > > foo:
> > > .long bar - .
> > >
> > > It is apparently a bad reference, but modpost does not report anything.
> > >
> > > The test code above produces the following relocations.
> > >
> > > Relocation section '.rel.data' at offset 0xe8 contains 1 entry:
> > > Offset Info Type Sym.Value Sym. Name
> > > 00000000 00000403 R_ARM_REL32 00000000 .init.data
> > >
> > > Currently, R_ARM_REL32 is just skipped.
> > >
> > > Handle it like R_ARM_ABS32.
> >
> > OK, so the reason we can handle these in the same way is because we
> > never calculate the resulting value, right? Because that value would
> > be different for these cases.
>
> Right.
>
> '- loc' is unnecessary here because modpost never calculates the
> resulting instruction.
>
> modpost wants to know the location of the referenced symbol.
> (the offset from the start of the section).
>
> For the same reason, I omitted '- loc' for
> PC-relative ones such as R_ARM_CALL, R_ARM_JUMP24, etc.
>

OK makes sense - I just wanted to double check

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