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References: <20231002165750.1661-1-will@kernel.org> <20231002165750.1661-3-will@kernel.org>
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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Mon, 2 Oct 2023 10:00:58 -0700
Message-ID: <CAKwvOdmLey43Ng5p7bD2arUY6T=B+y=K-Lo-Qbya540ZUJXU4Q@mail.gmail.com>
Subject: Re: [PATCH v5 2/3] scripts/faddr2line: Use LLVM addr2line and readelf
 if LLVM=1
To:     Will Deacon <will@kernel.org>
Cc:     linux-kernel@vger.kernel.org, kernel-team@android.com,
        Masahiro Yamada <masahiroy@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nicolas Schier <nicolas@fjasle.eu>,
        Josh Poimboeuf <jpoimboe@kernel.org>,
        John Stultz <jstultz@google.com>, linux-kbuild@vger.kernel.org
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On Mon, Oct 2, 2023 at 9:58=E2=80=AFAM Will Deacon <will@kernel.org> wrote:
>
> GNU utilities cannot necessarily parse objects built by LLVM, which can
> result in confusing errors when using 'faddr2line':
>
> $ CROSS_COMPILE=3Daarch64-linux-gnu- ./scripts/faddr2line vmlinux do_one_=
initcall+0xf4/0x260
> aarch64-linux-gnu-addr2line: vmlinux: unknown type [0x13] section `.relr.=
dyn'
> aarch64-linux-gnu-addr2line: DWARF error: invalid or unhandled FORM value=
: 0x25
> do_one_initcall+0xf4/0x260:
> aarch64-linux-gnu-addr2line: vmlinux: unknown type [0x13] section `.relr.=
dyn'
> aarch64-linux-gnu-addr2line: DWARF error: invalid or unhandled FORM value=
: 0x25
> $x.73 at main.c:?
>
> Although this can be worked around by setting CROSS_COMPILE to "llvm=3D-"=
,
> it's cleaner to follow the same syntax as the top-level Makefile and
> accept LLVM=3D as an indication to use the llvm- tools, optionally
> specifying their location or specific version number.
>
> Cc: Josh Poimboeuf <jpoimboe@kernel.org>
> Cc: John Stultz <jstultz@google.com>
> Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
> Signed-off-by: Will Deacon <will@kernel.org>

Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>  scripts/faddr2line | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/scripts/faddr2line b/scripts/faddr2line
> index a35a420d0f26..6b8206802157 100755
> --- a/scripts/faddr2line
> +++ b/scripts/faddr2line
> @@ -58,8 +58,21 @@ die() {
>         exit 1
>  }
>
> -READELF=3D"${CROSS_COMPILE:-}readelf"
> -ADDR2LINE=3D"${CROSS_COMPILE:-}addr2line"
> +UTIL_SUFFIX=3D""
> +if [[ "${LLVM:-}" =3D=3D "" ]]; then
> +       UTIL_PREFIX=3D${CROSS_COMPILE:-}
> +else
> +       UTIL_PREFIX=3Dllvm-
> +
> +       if [[ "${LLVM}" =3D=3D *"/" ]]; then
> +               UTIL_PREFIX=3D${LLVM}${UTIL_PREFIX}
> +       elif [[ "${LLVM}" =3D=3D "-"* ]]; then
> +               UTIL_SUFFIX=3D${LLVM}
> +       fi
> +fi
> +
> +READELF=3D"${UTIL_PREFIX}readelf${UTIL_SUFFIX}"
> +ADDR2LINE=3D"${UTIL_PREFIX}addr2line${UTIL_SUFFIX}"
>  AWK=3D"awk"
>  GREP=3D"grep"
>
> --
> 2.42.0.582.g8ccd20d70d-goog
>


--=20
Thanks,
~Nick Desaulniers