On Wed, Feb 14, 2024 at 01:29:29PM -0800, Fangrui Song wrote:
> A s390 patch modeling its --orphan-handling= after x86 [1] sparked my
> motivation to simplify patterns. Commit 5354e84598f2 ("x86/build: Add
> asserts for unwanted sections") added asserts that certain input
> sections must be absent or empty. The patterns can be simplified.
>
> For dynamic relocations,
>
> *(.rela.*) is sufficient to match all dynamic relocations synthesized by
> GNU ld and LLD. .rela_* is unnecessary. --emit-relocs may create .rela_*
> sections for section names prefixed with _, but they are not matched by
> linker scripts.
>
> .plt instead of .plt.* is sufficient to match synthesized PLT entries.
Do you mean ".plt.foo" matches ".plt" ?
> .igot and .igot.plt are for non-preemptible STT_GNU_IFUNC in GNU ld (LLD
> just uses .got), which the kernel does not use. In addition, if .igot or
> .igot.plt is ever non-empty, there will be .rela.* dynamic relocations
> leading to an assert failure anyway.
I think at the time I was dealing with avoid multiple warnings out of
the linker, as I was getting orphan warnings in addition to the
non-empty warnings.
>
> [1]: https://lore.kernel.org/all/[email protected]/
>
> Signed-off-by: Fangrui Song <[email protected]>
Is anything harmed by leaving all of this as-is?
-Kees
> ---
> arch/x86/boot/compressed/vmlinux.lds.S | 6 +++---
> arch/x86/kernel/vmlinux.lds.S | 8 ++++----
> 2 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
> index 083ec6d7722a..9f288f67972a 100644
> --- a/arch/x86/boot/compressed/vmlinux.lds.S
> +++ b/arch/x86/boot/compressed/vmlinux.lds.S
> @@ -104,17 +104,17 @@ SECTIONS
> ASSERT(SIZEOF(.got) == 0, "Unexpected GOT entries detected!")
>
> .plt : {
> - *(.plt) *(.plt.*)
> + *(.plt)
> }
> ASSERT(SIZEOF(.plt) == 0, "Unexpected run-time procedure linkages detected!")
>
> .rel.dyn : {
> - *(.rel.*) *(.rel_*)
> + *(.rel.*)
> }
> ASSERT(SIZEOF(.rel.dyn) == 0, "Unexpected run-time relocations (.rel) detected!")
>
> .rela.dyn : {
> - *(.rela.*) *(.rela_*)
> + *(.rela.*)
> }
> ASSERT(SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations (.rela) detected!")
> }
> diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
> index a349dbfc6d5a..b3da7b81d2b3 100644
> --- a/arch/x86/kernel/vmlinux.lds.S
> +++ b/arch/x86/kernel/vmlinux.lds.S
> @@ -463,22 +463,22 @@ SECTIONS
> * explicitly check instead of blindly discarding.
> */
> .got : {
> - *(.got) *(.igot.*)
> + *(.got)
> }
> ASSERT(SIZEOF(.got) == 0, "Unexpected GOT entries detected!")
>
> .plt : {
> - *(.plt) *(.plt.*) *(.iplt)
> + *(.plt)
> }
> ASSERT(SIZEOF(.plt) == 0, "Unexpected run-time procedure linkages detected!")
>
> .rel.dyn : {
> - *(.rel.*) *(.rel_*)
> + *(.rel.*)
> }
> ASSERT(SIZEOF(.rel.dyn) == 0, "Unexpected run-time relocations (.rel) detected!")
>
> .rela.dyn : {
> - *(.rela.*) *(.rela_*)
> + *(.rela.*)
> }
> ASSERT(SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations (.rela) detected!")
> }
> --
> 2.43.0.687.g38aa6559b0-goog
>
--
Kees Cook