From: Nathan Chancellor natechancellor@gmail.com Date: Wed, 6 Jan 2021 13:23:24 -0700
On Wed, Jan 06, 2021 at 08:08:29PM +0000, Alexander Lobakin wrote:
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 *(.pdr) *(.reginfo) }
- /*
* Sections that should stay zero sized, which is safer to* explicitly check instead of blindly discarding.*/- .got : {
*(.got)*(.igot.*)- }
- ASSERT(SIZEOF(.got) == 0, "Unexpected GOT entries detected!")
This assertion does trigger now.
$ make -skj"$(nproc)" ARCH=mips CROSS_COMPILE=mipsel-linux-gnu- LLVM=1 \ O=out/mipsel distclean malta_kvm_guest_defconfig all ... ld.lld: error: Unexpected GOT entries detected! ld.lld: error: Unexpected GOT entries detected! ...
Oops. I'll build my kernel with LLVM stack and dig into it deeper tomorrow.
- .got.plt (INFO) : {
*(.got.plt)- }
- ASSERT(SIZEOF(.got.plt) == 0, "Unexpected GOT/PLT entries detected!")
- .plt : {
*(.plt)*(.plt.*)*(.iplt)- }
- ASSERT(SIZEOF(.plt) == 0, "Unexpected run-time procedure linkages detected!")
- .rel.dyn : {
*(.rel.*)*(.rel_*)- }
- ASSERT(SIZEOF(.rel.dyn) == 0, "Unexpected run-time relocations (.rel) detected!")
- .rela.dyn : {
*(.rela.*)*(.rela_*)- }
- ASSERT(SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations (.rela) detected!")
}
2.30.0
Thanks, Al