| Message ID | 20210106200801.31993-3-alobakin@pm.me (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | MIPS: vmlinux.lds.S sections fix & cleanup | expand |
On Wed, Jan 6, 2021 at 12:08 PM Alexander Lobakin <alobakin@pm.me> 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!") > + > + .got.plt (INFO) : { > + *(.got.plt) > + } > + ASSERT(SIZEOF(.got.plt) == 0, "Unexpected GOT/PLT entries detected!") (INFO) drops the SHF_ALLOC flag from the output section (It does not mean "informational"). INFO is not need here. The diff from 815d680771ae09080d2da83dac2647c08cdf99ce "x86/build: Enforce an empty .got.plt section" is not needed. > + .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!") > } x86 has both .rel.dyn and .rela.dyn because i386 psABI uses REL while x86-64 psABI uses RELA, but mips does not need .rela.dyn > -- > 2.30.0 > >
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! ... > + .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 > >
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
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!") + + .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!") }
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(+)