linux-kernel - Re: [PATCH mips-next 0/4] MIPS: vmlinux.lds.S sections fix & cleanup

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Date:   Mon, 4 Jan 2021 17:09:36 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Alexander Lobakin <alobakin@...me>
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Kees Cook <keescook@...omium.org>,
        Ingo Molnar <mingo@...nel.org>,
        Fangrui Song <maskray@...gle.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Alex Smith <alex.smith@...tec.com>,
        Markos Chandras <markos.chandras@...tec.com>,
        linux-mips@...r.kernel.org, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH mips-next 0/4] MIPS: vmlinux.lds.S sections fix & cleanup

On Mon, Jan 04, 2021 at 12:18:10PM +0000, Alexander Lobakin wrote:
> This series hunts the problems discovered after manual enabling of
> ARCH_WANT_LD_ORPHAN_WARN, notably the missing PAGE_ALIGNED_DATA()
> section affecting VDSO placement (marked for stable).
> 
> Compile and runtime tested on MIPS32R2 CPS board with no issues.
> 
> Alexander Lobakin (4):
>   MIPS: vmlinux.lds.S: add missing PAGE_ALIGNED_DATA() section
>   MIPS: vmlinux.lds.S: add ".rel.dyn" to DISCARDS
>   MIPS: vmlinux.lds.S: add ".gnu.attributes" to DISCARDS
>   MIPS: select ARCH_WANT_LD_ORPHAN_WARN
> 
>  arch/mips/Kconfig              | 1 +
>  arch/mips/kernel/vmlinux.lds.S | 5 ++++-
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> -- 
> 2.30.0
> 

Glad to see ARCH_WANT_LD_ORPHAN_WARN catching on :)

I took this for a spin with clang with malta_kvm_guest_defconfig and I
only see one section unaccounted for:

$ make -skj"$(nproc)" ARCH=mips CROSS_COMPILE=mipsel-linux-gnu- LLVM=1 O=out/mips distclean malta_kvm_guest_defconfig all
...
ld.lld: warning: <internal>:(.got) is being placed in '.got'
ld.lld: warning: <internal>:(.got) is being placed in '.got'
ld.lld: warning: <internal>:(.got) is being placed in '.got'

Looks like most architectures place it in .got (ia64, nios2, powerpc)
or .text (arm64).

Cheers,
Nathan