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From: Masahiro Yamada <masahiroy@kernel.org>
Date: Thu, 15 Feb 2024 05:34:11 +0900
Message-ID: <CAK7LNASQUhJGSdQiyEpc5Rpuk_hJwSCu=W=4JkL-Et_giFNvPg@mail.gmail.com>
Subject: Re: [PATCH] kallsyms: ignore ARMv4 thunks along with others
To: Arnd Bergmann <arnd@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>, Nathan Chancellor <nathan@kernel.org>, Nicolas Schier <nicolas@fjasle.eu>, 
	=?UTF-8?Q?Pierre=2DCl=C3=A9ment_Tosi?= <ptosi@google.com>, 
	Ard Biesheuvel <ardb@kernel.org>, linux-kbuild@vger.kernel.org, 
	linux-kernel@vger.kernel.org
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On Thu, Feb 15, 2024 at 3:19=E2=80=AFAM Arnd Bergmann <arnd@kernel.org> wro=
te:
>
> From: Arnd Bergmann <arnd@arndb.de>
>
> lld is now able to build ARMv4 and ARMv4T kernels, which means it can gen=
erate
> 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=3D1" 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@arndb.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_",


--=20
Best Regards
Masahiro Yamada