linux-kernel - Re: [PATCH 2/2] arm64: vdso32: Add DWARF

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Date:   Thu, 30 Jun 2022 14:08:34 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Joey Gouly <joey.gouly@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, patches@...ts.linudx.dev
Subject: Re: [PATCH 2/2] arm64: vdso32: Add DWARF_DEBUG

On Thu, Jun 30, 2022 at 8:32 AM Nathan Chancellor <nathan@...nel.org> wrote:
>
> When building the 32-bit vDSO with LLVM 15 and CONFIG_DEBUG_INFO, there
> are the following orphan section warnings:
>
>   ld.lld: warning: arch/arm64/kernel/vdso32/note.o:(.debug_abbrev) is being placed in '.debug_abbrev'
>   ld.lld: warning: arch/arm64/kernel/vdso32/note.o:(.debug_info) is being placed in '.debug_info'
>   ld.lld: warning: arch/arm64/kernel/vdso32/note.o:(.debug_str_offsets) is being placed in '.debug_str_offsets'
>   ld.lld: warning: arch/arm64/kernel/vdso32/note.o:(.debug_str) is being placed in '.debug_str'
>   ld.lld: warning: arch/arm64/kernel/vdso32/note.o:(.debug_addr) is being placed in '.debug_addr'
>   ld.lld: warning: arch/arm64/kernel/vdso32/note.o:(.debug_line) is being placed in '.debug_line'
>   ld.lld: warning: arch/arm64/kernel/vdso32/note.o:(.debug_line_str) is being placed in '.debug_line_str'
>   ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_loclists) is being placed in '.debug_loclists'
>   ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_abbrev) is being placed in '.debug_abbrev'
>   ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_info) is being placed in '.debug_info'
>   ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_rnglists) is being placed in '.debug_rnglists'
>   ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_str_offsets) is being placed in '.debug_str_offsets'
>   ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_str) is being placed in '.debug_str'
>   ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_addr) is being placed in '.debug_addr'
>   ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_frame) is being placed in '.debug_frame'
>   ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_line) is being placed in '.debug_line'
>   ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_line_str) is being placed in '.debug_line_str'
>
> These are DWARF5 sections, as that is the implicit default version for

Most of these are DWARF v5, but some like .debug_info and .debug_line
are DWARF v2; this isn't specifically a DWARF v5 issue, more so just
an issue with CONFIG_DEBUG_INFO.  Not worth a v2 IMO though.  Thanks
for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> clang-14 and newer when just '-g' is used. All DWARF sections are
> handled by the DWARF_DEBUG macro from include/asm-generic/vmlinux.lds.h
> so use that macro here to fix the warnings regardless of DWARF version.
>
> Fixes: 9d4775b332e1 ("arm64: vdso32: enable orphan handling for VDSO")
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
>  arch/arm64/kernel/vdso32/vdso.lds.S | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm64/kernel/vdso32/vdso.lds.S b/arch/arm64/kernel/vdso32/vdso.lds.S
> index c25bed8e6df1..8d95d7d35057 100644
> --- a/arch/arm64/kernel/vdso32/vdso.lds.S
> +++ b/arch/arm64/kernel/vdso32/vdso.lds.S
> @@ -57,6 +57,7 @@ SECTIONS
>         .rel.dyn        : { *(.rel*) }
>
>         .ARM.exidx : { *(.ARM.exidx*) }
> +       DWARF_DEBUG
>         ELF_DETAILS
>         .ARM.attributes 0 : { *(.ARM.attributes) }
>
> --
> 2.37.0
>


-- 
Thanks,
~Nick Desaulniers