Re: [PATCH v4 2/3] scripts/faddr2line: Use LLVM addr2line and readelf if LLVM=1

From: Nick Desaulniers <ndesaulniers@google.com>
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
Subject: Re: [PATCH v4 2/3] scripts/faddr2line: Use LLVM addr2line and readelf if LLVM=1
Date: Thu, 14 Sep 2023 08:55:03 -0700	[thread overview]
Message-ID: <CAKwvOd=z5pjr2Y=jxYU=Y10EKniWd4w8YV_yhZRvVBoon8TRLQ@mail.gmail.com> (raw)
In-Reply-To: <20230914131225.13415-3-will@kernel.org>

On Thu, Sep 14, 2023 at 6:12 AM 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=aarch64-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=-",
> it's cleaner to follow the same syntax as the top-level Makefile and
> accept LLVM= 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 series!
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="${CROSS_COMPILE:-}readelf"
> -ADDR2LINE="${CROSS_COMPILE:-}addr2line"
> +UTIL_SUFFIX=""
> +if [[ "${LLVM:-}" == "" ]]; then
> +       UTIL_PREFIX=${CROSS_COMPILE:-}
> +else
> +       UTIL_PREFIX=llvm-
> +
> +       if [[ "${LLVM}" == *"/" ]]; then
> +               UTIL_PREFIX=${LLVM}${UTIL_PREFIX}
> +       elif [[ "${LLVM}" == "-"* ]]; then
> +               UTIL_SUFFIX=${LLVM}
> +       fi
> +fi
> +
> +READELF="${UTIL_PREFIX}readelf${UTIL_SUFFIX}"
> +ADDR2LINE="${UTIL_PREFIX}addr2line${UTIL_SUFFIX}"
>  AWK="awk"
>  GREP="grep"
>
> --
> 2.42.0.283.g2d96d420d3-goog
>

-- 
Thanks,
~Nick Desaulniers