linux-kernel - Re: [PATCH] kallsyms: ignore ARMv4 thunks along with others

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Date: Thu, 15 Feb 2024 05:34:11 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>, Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>, 
	Pierre-Clément Tosi <ptosi@...gle.com>, 
	Ard Biesheuvel <ardb@...nel.org>, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kallsyms: ignore ARMv4 thunks along with others

On Thu, Feb 15, 2024 at 3:19 AM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> lld is now able to build ARMv4 and ARMv4T kernels, which means it can generate
> thunks for those that can interfere with kallsyms table generation since
> they do not get ignore like the corresponding ARMv5+ ones are:
>
> Inconsistent kallsyms data
> Try "make KALLSYMS_EXTRA_PASS=1" as a workaround
>
> Add the missing symbols to the list of ignored symbol prefixes.
>
> Fixes: 5eb6e280432d ("ARM: 9289/1: Allow pre-ARMv5 builds with ld.lld 16.0.0 and newer")
> Fixes: efe6e3068067 ("kallsyms: fix nonconverging kallsyms table with lld")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  scripts/mksysmap | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/scripts/mksysmap b/scripts/mksysmap
> index 9ba1c9da0a40..c809bf592790 100755
> --- a/scripts/mksysmap
> +++ b/scripts/mksysmap
> @@ -52,6 +52,8 @@ ${NM} -n ${1} | sed >${2} -e "
>  / __AArch64ADRPThunk_/d
>
>  # arm lld
> +/ __ARMv4PILongThunk_/d
> +/ __ARMv4PILongBXThunk_/d
>  / __ARMV5PILongThunk_/d
>  / __ARMV7PILongThunk_/d
>  / __ThumbV7PILongThunk_/d
> --
> 2.39.2
>



If this is a recurring problem,
maybe is it better to use a regular expression?


Remove these lines:

# arm64 lld
/ __AArch64ADRPThunk_/d

# arm lld
/ __ARMV5PILongThunk_/d
/ __ARMV7PILongThunk_/d
/ __ThumbV7PILongThunk_/d

# mips lld
/ __LA25Thunk_/d
/ __microLA25Thunk_/d





Add this:

# lld
/ __[^[:space:]]*Thunk_/d





This pattern is only used in tooling,
but never in the kernel space.



$ git grep '__[^[:space:]]*Thunk_'
scripts/mksysmap:/ __AArch64ADRPThunk_/d
scripts/mksysmap:/ __ARMV5PILongThunk_/d
scripts/mksysmap:/ __ARMV7PILongThunk_/d
scripts/mksysmap:/ __ThumbV7PILongThunk_/d
scripts/mksysmap:/ __LA25Thunk_/d
scripts/mksysmap:/ __microLA25Thunk_/d
tools/perf/tests/vmlinux-kallsyms.c:            "__AArch64ADRPThunk_",
 /* arm64 lld */
tools/perf/tests/vmlinux-kallsyms.c:            "__ARMV5PILongThunk_",
 /* arm lld */
tools/perf/tests/vmlinux-kallsyms.c:            "__ARMV7PILongThunk_",
tools/perf/tests/vmlinux-kallsyms.c:            "__ThumbV7PILongThunk_",
tools/perf/tests/vmlinux-kallsyms.c:            "__LA25Thunk_",
 /* mips lld */
tools/perf/tests/vmlinux-kallsyms.c:            "__microLA25Thunk_",












-- 
Best Regards
Masahiro Yamada