linux-kernel - Re: [PATCH v2] arm64: Handle .ARM.attributes section in linker scripts

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Message-ID: <20250206135715.GA180182@ax162>
Date: Thu, 6 Feb 2025 06:57:15 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Will Deacon <will@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev, stable@...r.kernel.org
Subject: Re: [PATCH v2] arm64: Handle .ARM.attributes section in linker
 scripts

Hi Will,

On Thu, Feb 06, 2025 at 01:05:26PM +0000, Will Deacon wrote:
> On Tue, Feb 04, 2025 at 10:48:55AM -0700, Nathan Chancellor wrote:
> > A recent LLVM commit [1] started generating an .ARM.attributes section
> > similar to the one that exists for 32-bit, which results in orphan
> > section warnings (or errors if CONFIG_WERROR is enabled) from the linker
> > because it is not handled in the arm64 linker scripts.
> > 
> >   ld.lld: error: arch/arm64/kernel/vdso/vgettimeofday.o:(.ARM.attributes) is being placed in '.ARM.attributes'
> >   ld.lld: error: arch/arm64/kernel/vdso/vgetrandom.o:(.ARM.attributes) is being placed in '.ARM.attributes'
> > 
> >   ld.lld: error: vmlinux.a(lib/vsprintf.o):(.ARM.attributes) is being placed in '.ARM.attributes'
> >   ld.lld: error: vmlinux.a(lib/win_minmax.o):(.ARM.attributes) is being placed in '.ARM.attributes'
> >   ld.lld: error: vmlinux.a(lib/xarray.o):(.ARM.attributes) is being placed in '.ARM.attributes'
> > 
> > Discard the new sections in the necessary linker scripts to resolve the
> > warnings, as the kernel and vDSO do not need to retain it, similar to
> > the .note.gnu.property section.
> > 
> > Cc: stable@...r.kernel.org
> > Fixes: b3e5d80d0c48 ("arm64/build: Warn on orphan section placement")
> > Link: https://github.com/llvm/llvm-project/commit/ee99c4d4845db66c4daa2373352133f4b237c942 [1]
> > Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> > ---
> > Changes in v2:
> > - Discard the section instead of adding it to the final artifacts to
> >   mirror the .note.gnu.property section handling (Will).
> 
> Thanks for the v2. Just a minor nit:
> 
> > - Link to v1: https://lore.kernel.org/r/20250124-arm64-handle-arm-attributes-in-linker-script-v1-1-74135b6cf349@kernel.org
> > ---
> >  arch/arm64/kernel/vdso/vdso.lds.S | 1 +
> >  arch/arm64/kernel/vmlinux.lds.S   | 1 +
> >  2 files changed, 2 insertions(+)
> > 
> > diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S
> > index 4ec32e86a8da..8095fef66209 100644
> > --- a/arch/arm64/kernel/vdso/vdso.lds.S
> > +++ b/arch/arm64/kernel/vdso/vdso.lds.S
> > @@ -80,6 +80,7 @@ SECTIONS
> >  		*(.data .data.* .gnu.linkonce.d.* .sdata*)
> >  		*(.bss .sbss .dynbss .dynsbss)
> >  		*(.eh_frame .eh_frame_hdr)
> > +		*(.ARM.attributes)
> >  	}
> 
> Can we chuck this in the earlier /DISCARD/ section along with
> .note.gnu.property? i.e.

Sure, I don't see why not. Do you want the comment above it updated to
mention this section or should I leave it as is?

> diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S
> index 4ec32e86a8da..47ad6944f9f0 100644
> --- a/arch/arm64/kernel/vdso/vdso.lds.S
> +++ b/arch/arm64/kernel/vdso/vdso.lds.S
> @@ -41,6 +41,7 @@ SECTIONS
>          */
>         /DISCARD/       : {
>                 *(.note.GNU-stack .note.gnu.property)
> +               *(.ARM.attributes)
>         }
>         .note           : { *(.note.*) }                :text   :note
> 
> 
> Will