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Date:   Wed, 21 Nov 2018 16:14:47 -0500
From:   "Liam R. Howlett" <Liam.Howlett@Oracle.com>
To:     Nadav Amit <namit@vmware.com>
Cc:     Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "x86@kernel.org" <x86@kernel.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: Out of tree module build errors since v4.20-rc1
Message-ID: <20181121211447.weqjjk2fwbc27er6@oracle.com>
Mail-Followup-To: Nadav Amit <namit@vmware.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, "x86@kernel.org" <x86@kernel.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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* Nadav Amit <namit@vmware.com> [181121 16:12]:
> > On Nov 21, 2018, at 12:56 PM, Liam R. Howlett <Liam.Howlett@Oracle.com>=
 wrote:
> >=20
> >=20
> > My out of tree driver build is now reporting issues with the jump table:
> >=20
> > ./include/linux/jump_label.h: In function =E2=80=98jump_entry_code=E2=
=80=99:
> > ./include/linux/jump_label.h:153:14: error: dereferencing pointer to in=
complete type =E2=80=98const struct jump_entry=E2=80=99
> >  return entry->code;
> >              ^~
> > ./include/linux/jump_label.h: In function =E2=80=98jump_entry_set_init=
=E2=80=99:
> > ./include/linux/jump_label.h:180:7: error: dereferencing pointer to inc=
omplete type =E2=80=98struct jump_entry=E2=80=99
> >  entry->key |=3D 2;
> >       ^~
> > ./include/linux/jump_label.h: At top level:
> > ./include/linux/jump_label.h:212:26: error: array type has incomplete e=
lement type =E2=80=98struct jump_entry=E2=80=99
> > extern struct jump_entry __start___jump_table[];
> >                          ^~~~~~~~~~~~~~~~~~~~
> > ./include/linux/jump_label.h:213:26: error: array type has incomplete e=
lement type =E2=80=98struct jump_entry=E2=80=99
> > extern struct jump_entry __stop___jump_table[];
> >                          ^~~~~~~~~~~~~~~~~~~
> >=20
> >=20
> > This happens in v4.20-rc3 as well, so I bisected between v4.19 to
> > v4.20-rc1 which resulted in the following commit:
> >=20
> > b34006c4258c9c86597b6b7123d6a9a3513d6cd7 is the first bad commit
> > commit b34006c4258c9c86597b6b7123d6a9a3513d6cd7
> > Author: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > Date:   Tue Sep 18 23:51:41 2018 -0700
> >=20
> >    x86/jump_table: Use relative references
> >=20
> >=20
> >=20
> >=20
> > Initially I assumed this was my own fault, but my module does not have
> > these issues when using v4.19.  Is there anything I should try/change in
> > my module makefile, includes, etc to support this relative reference
> > code?
>=20
> Do you see HAVE_ARCH_JUMP_LABEL_RELATIVE set in your kernel config?
>=20

Yes:
 $ grep HAVE_ARCH_JUMP_LABEL_RELATIVE .config
 CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE=3Dy


I should have mentioned I ran 'make defoldconfig' between each bisect.