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Date:   Wed, 06 Jan 2021 20:08:29 +0000
To:     Thomas Bogendoerfer <tsbogend@alpha.franken.de>
From:   Alexander Lobakin <alobakin@pm.me>
Cc:     Alexander Lobakin <alobakin@pm.me>,
        Nathan Chancellor <natechancellor@gmail.com>,
        Kees Cook <keescook@chromium.org>,
        Fangrui Song <maskray@google.com>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        Alex Smith <alex.smith@imgtec.com>,
        Ralf Baechle <ralf@linux-mips.org>,
        Markos Chandras <markos.chandras@imgtec.com>,
        linux-mips@vger.kernel.org, stable@vger.kernel.org,
        linux-kernel@vger.kernel.org
Reply-To: Alexander Lobakin <alobakin@pm.me>
Subject: [PATCH v2 mips-next 3/4] MIPS: vmlinux.lds.S: catch bad .got, .plt and .rel.dyn at link time
Message-ID: <20210106200801.31993-3-alobakin@pm.me>
In-Reply-To: <20210106200801.31993-1-alobakin@pm.me>
References: <20210106200713.31840-1-alobakin@pm.me> <20210106200801.31993-1-alobakin@pm.me>
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Catch any symbols placed in .got, .got.plt, .plt, .rel.dyn
or .rela.dyn and check for these sections to be zero-sized
at link time.

At least two of them were noticed in real builds:

mips-alpine-linux-musl-ld: warning: orphan section `.rel.dyn'
from `init/main.o' being placed in section `.rel.dyn'

ld.lld: warning: <internal>:(.got) is being placed in '.got'

Adopted from x86/kernel/vmlinux.lds.S.

Reported-by: Nathan Chancellor <natechancellor@gmail.com> # .got
Suggested-by: Fangrui Song <maskray@google.com> # .rel.dyn
Signed-off-by: Alexander Lobakin <alobakin@pm.me>
---
 arch/mips/kernel/vmlinux.lds.S | 35 ++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.=
S
index 5d6563970ab2..05eda9d9a7d5 100644
--- a/arch/mips/kernel/vmlinux.lds.S
+++ b/arch/mips/kernel/vmlinux.lds.S
@@ -227,4 +227,39 @@ SECTIONS
 =09=09*(.pdr)
 =09=09*(.reginfo)
 =09}
+
+=09/*
+=09 * Sections that should stay zero sized, which is safer to
+=09 * explicitly check instead of blindly discarding.
+=09 */
+
+=09.got : {
+=09=09*(.got)
+=09=09*(.igot.*)
+=09}
+=09ASSERT(SIZEOF(.got) =3D=3D 0, "Unexpected GOT entries detected!")
+
+=09.got.plt (INFO) : {
+=09=09*(.got.plt)
+=09}
+=09ASSERT(SIZEOF(.got.plt) =3D=3D 0, "Unexpected GOT/PLT entries detected!=
")
+
+=09.plt : {
+=09=09*(.plt)
+=09=09*(.plt.*)
+=09=09*(.iplt)
+=09}
+=09ASSERT(SIZEOF(.plt) =3D=3D 0, "Unexpected run-time procedure linkages d=
etected!")
+
+=09.rel.dyn : {
+=09=09*(.rel.*)
+=09=09*(.rel_*)
+=09}
+=09ASSERT(SIZEOF(.rel.dyn) =3D=3D 0, "Unexpected run-time relocations (.re=
l) detected!")
+
+=09.rela.dyn : {
+=09=09*(.rela.*)
+=09=09*(.rela_*)
+=09}
+=09ASSERT(SIZEOF(.rela.dyn) =3D=3D 0, "Unexpected run-time relocations (.r=
ela) detected!")
 }
--=20
2.30.0