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

[Nathan Chancellor <nathan@kernel.org>]

On Thu, Feb 06, 2025 at 03:22:47PM +0000, Will Deacon wrote:
> On Thu, Feb 06, 2025 at 06:57:15AM -0700, Nathan Chancellor wrote:
> > 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@vger.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@kernel.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?
> 
> If you can think of something useful to add to the comment, don't let me
> stop you!

Eh, I could not come up with much so I will leave it as is. v3 incoming
shortly.

Cheers,
Nathan