netdev - Re: [PATCH net] scripts/pahole-flags.sh: Make sure pahole --version works

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Date:   Wed, 5 Jan 2022 14:14:19 -0800
From:   Saeed Mahameed <saeed@...nel.org>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Saeed Mahameed <saeedm@...dia.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH net] scripts/pahole-flags.sh: Make sure pahole --version
 works

On Wed, Jan 05, 2022 at 02:42:01PM +0100, Daniel Borkmann wrote:
>On 12/31/21 8:56 AM, Saeed Mahameed wrote:
>>From: Saeed Mahameed <saeedm@...dia.com>
>>
>>I had a broken pahole and it's been driving me crazy to see tons of the
>>following error messages on every build.
>>
>>pahole: symbol lookup error: pahole: undefined symbol: btf_gen_floats
>>scripts/pahole-flags.sh: line 12: [: : integer expression expected
>>scripts/pahole-flags.sh: line 16: [: : integer expression expected
>>
>>Address this by redirecting pahole --version stderr to devnull,
>>and validate stdout has a non empty string, otherwise exit silently.
>
>I'll leave this up to Andrii, but broken pahole version sounds like it would
>have been better to fix the local pahole installation instead [rather than the
>kernel having to guard against it, especially if it's driving you crazy]?
>

Already did :)

>I could image that silent exit on empty version string due to broken pahole
>deployment might rather waste developer's time to then go and debug why btf
>wasn't generated..
>

Good point, I was mainly thinking about developers who are not familiar with btf
and who have no time debugging irrelevant build issues, but up to you, I
personally like silent build scripts.

>>Fixes: 9741e07ece7c ("kbuild: Unify options for BTF generation for vmlinux and modules")
>>CC: Andrii Nakryiko <andrii@...nel.org>
>>CC: Jiri Olsa <jolsa@...hat.com>
>>Signed-off-by: Saeed Mahameed <saeedm@...dia.com>
>>---
>>  scripts/pahole-flags.sh | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>>diff --git a/scripts/pahole-flags.sh b/scripts/pahole-flags.sh
>>index e6093adf4c06..b3b53f890d40 100755
>>--- a/scripts/pahole-flags.sh
>>+++ b/scripts/pahole-flags.sh
>>@@ -7,7 +7,8 @@ if ! [ -x "$(command -v ${PAHOLE})" ]; then
>>  	exit 0
>>  fi
>>-pahole_ver=$(${PAHOLE} --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/')
>>+pahole_ver=$(${PAHOLE} --version 2>/dev/null | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/')
>>+[ -z "${pahole_ver}" ] && exit 0
>>  if [ "${pahole_ver}" -ge "118" ] && [ "${pahole_ver}" -le "121" ]; then
>>  	# pahole 1.18 through 1.21 can't handle zero-sized per-CPU vars
>>
>