From: "Fāng-ruì Sòng" <maskray@google.com>
To: Bill Wendling <morbo@google.com>
Cc: Alan Modra <amodra@gmail.com>,
linuxppc-dev@lists.ozlabs.org, Paul Mackerras <paulus@samba.org>
Subject: Re: [PATCH] powerpc/boot: move the .got section to after the .dynamic section
Date: Mon, 19 Oct 2020 16:56:59 -0700 [thread overview]
Message-ID: <CAFP8O3+Mg6B4WnDzAnT43132JTbtKgkK7JFwm8Sqhc1m0CzY1g@mail.gmail.com> (raw)
In-Reply-To: <20201017000151.150788-1-morbo@google.com>
On Fri, Oct 16, 2020 at 5:01 PM Bill Wendling <morbo@google.com> wrote:
>
> Both .dynamic and .got are RELRO sections and should be placed together,
> and LLD emits an error:
>
> ld.lld: error: section: .got is not contiguous with other relro sections
>
> Place them together to avoid this.
>
> Cc: Fangrui Song <maskray@google.com>
> Cc: Alan Modra <amodra@gmail.com>
> Signed-off-by: Bill Wendling <morbo@google.com>
> ---
> arch/powerpc/boot/zImage.lds.S | 21 +++++++++++----------
> 1 file changed, 11 insertions(+), 10 deletions(-)
>
> diff --git a/arch/powerpc/boot/zImage.lds.S b/arch/powerpc/boot/zImage.lds.S
> index a21f3a76e06f..d6f072865627 100644
> --- a/arch/powerpc/boot/zImage.lds.S
> +++ b/arch/powerpc/boot/zImage.lds.S
> @@ -34,6 +34,17 @@ SECTIONS
> __dynamic_start = .;
> *(.dynamic)
> }
> +
> +#ifdef CONFIG_PPC64_BOOT_WRAPPER
> + . = ALIGN(256);
> + .got :
> + {
> + __toc_start = .;
> + *(.got)
> + *(.toc)
> + }
> +#endif
> +
> .hash : { *(.hash) }
> .interp : { *(.interp) }
> .rela.dyn :
> @@ -76,16 +87,6 @@ SECTIONS
> _esm_blob_end = .;
> }
>
> -#ifdef CONFIG_PPC64_BOOT_WRAPPER
> - . = ALIGN(256);
> - .got :
> - {
> - __toc_start = .;
> - *(.got)
> - *(.toc)
> - }
> -#endif
The kernel does not require this but normally all read-only sections
precede SHF_WRITE sections.
.dynamic and .got have the SHF_WRITE flag and should be placed here.
Ideally, the order is: R RX RW(RELRO) RW(non-RELRO) (LLD order)
For comparison:
GNU ld -z separate-code order: R RX R RW(RELRO) RW(non-RELRO) (GNU
ld>=2.31 enables -z separate-code by default for Linux x86)
GNU ld -z noseparate-code order: RX RW(RELRO) RW(non-RELRO)
(AFAIK The only reason .dynamic is writable is due to DT_DEBUG (whose
purpose is questionable nowadays). mips .dynamic is read-only. LLD has
an option -z rodynamic to make .dynamic readonly)
> . = ALIGN(4096);
> .bss :
> {
> --
> 2.29.0.rc1.297.gfa9743e501-goog
>
next prev parent reply other threads:[~2020-10-19 23:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-17 0:01 [PATCH] powerpc/boot: move the .got section to after the .dynamic section Bill Wendling
2020-10-19 23:56 ` Fāng-ruì Sòng [this message]
2020-11-18 22:39 ` [PATCH] powerpc/wrapper: add "-z rodynamic" when using LLD Bill Wendling
2020-11-18 22:55 ` Fangrui Song
2020-12-10 11:30 ` Michael Ellerman
2020-12-10 11:30 ` [PATCH] powerpc/boot: move the .got section to after the .dynamic section Michael Ellerman
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