Re: [PATCH v6 13/29] arm64/build: Assert for unwanted sections
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: 2020-10-26 12:29:38
Also in:
linux-arch, linux-efi, linux-renesas-soc, lkml
Hi Kees, On Fri, Aug 21, 2020 at 9:56 PM Kees Cook [off-list ref] wrote:
In preparation for warning on orphan sections, discard unwanted non-zero-sized generated sections, and enforce other expected-to-be-zero-sized sections (since discarding them might hide problems with them suddenly gaining unexpected entries). Suggested-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Kees Cook <redacted>
This is now commit be2881824ae9eb92 ("arm64/build: Assert for unwanted
sections") in v5.10-rc1, and is causing the following error with
renesas_defconfig[1]:
aarch64-linux-gnu-ld: warning: orphan section `.eh_frame' from
`kernel/bpf/core.o' being placed in section `.eh_frame'
aarch64-linux-gnu-ld: Unexpected GOT/PLT entries detected!
aarch64-linux-gnu-ld: Unexpected run-time procedure linkages detected!
I cannot reproduce this with the standard arm64 defconfig.
I bisected the error to the aforementioned commit, but understand this
is not the real reason. If I revert this commit, I still get:
aarch64-linux-gnu-ld: warning: orphan section `.got.plt' from
`arch/arm64/kernel/head.o' being placed in section `.got.plt'
aarch64-linux-gnu-ld: warning: orphan section `.plt' from
`arch/arm64/kernel/head.o' being placed in section `.plt'
aarch64-linux-gnu-ld: warning: orphan section `.data.rel.ro' from
`arch/arm64/kernel/head.o' being placed in section `.data.rel.ro'
aarch64-linux-gnu-ld: warning: orphan section `.eh_frame' from
`kernel/bpf/core.o' being placed in section `.eh_frame'
I.e. including the ".eh_frame" warning. I have tried bisecting that
warning (i.e. with be2881824ae9eb92 reverted), but that leads me to
commit b3e5d80d0c48c0cc ("arm64/build: Warn on orphan section
placement"), which is another red herring.
Note that even on plain be2881824ae9eb92, I get:
aarch64-linux-gnu-ld: Unexpected GOT/PLT entries detected!
aarch64-linux-gnu-ld: Unexpected run-time procedure linkages detected!
The parent commit obviously doesn't show that (but probably still has
the problem).
Do you have a clue!
Thanks!
quoted hunk ↗ jump to hunk
--- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S@@ -121,6 +121,14 @@ SECTIONS *(.got) /* Global offset table */ } + /* + * Make sure that the .got.plt is either completely empty or it + * contains only the lazy dispatch entries. + */ + .got.plt : { *(.got.plt) } + ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, + "Unexpected GOT/PLT entries detected!") + . = ALIGN(SEGMENT_ALIGN); _etext = .; /* End of text section */@@ -243,6 +251,18 @@ SECTIONS ELF_DETAILS HEAD_SYMBOLS + + /* + * Sections that should stay zero sized, which is safer to + * explicitly check instead of blindly discarding. + */ + .plt : { + *(.plt) *(.plt.*) *(.iplt) *(.igot) + } + ASSERT(SIZEOF(.plt) == 0, "Unexpected run-time procedure linkages detected!") + + .data.rel.ro : { *(.data.rel.ro) } + ASSERT(SIZEOF(.data.rel.ro) == 0, "Unexpected RELRO detected!") } #include "image-vars.h"
[1] https://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-devel.git/log/?h=topic/renesas-defconfig Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel