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

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

[Saeed Mahameed]

From: Saeed Mahameed <saeedm@nvidia.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.

Fixes: 9741e07ece7c ("kbuild: Unify options for BTF generation for vmlinux and modules")
CC: Andrii Nakryiko <andrii@kernel.org>
CC: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.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
-- 
2.33.1

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

[Daniel Borkmann]

On 12/31/21 8:56 AM, Saeed Mahameed wrote:
> From: Saeed Mahameed <saeedm@nvidia.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]?

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..

> Fixes: 9741e07ece7c ("kbuild: Unify options for BTF generation for vmlinux and modules")
> CC: Andrii Nakryiko <andrii@kernel.org>
> CC: Jiri Olsa <jolsa@redhat.com>
> Signed-off-by: Saeed Mahameed <saeedm@nvidia.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
> 

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

[Saeed Mahameed]

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@nvidia.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@kernel.org>
>>CC: Jiri Olsa <jolsa@redhat.com>
>>Signed-off-by: Saeed Mahameed <saeedm@nvidia.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
>>
>

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

[Andrii Nakryiko]

On Wed, Jan 5, 2022 at 2:14 PM Saeed Mahameed <saeed@kernel.org> wrote:
>
> 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@nvidia.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.
>

Sorry, trying to understand. If you didn't use BTF (and thus
CONFIG_DEBUG_INFO_BTF is not set), is pahole still being called? If
yes, we might want to address that, I suppose.

But if you have a broken pahole that emits something to stderr
(undefined symbol in shared library), then I agree with Daniel that we
shouldn't be working around that in Linux build script.

> >>Fixes: 9741e07ece7c ("kbuild: Unify options for BTF generation for vmlinux and modules")
> >>CC: Andrii Nakryiko <andrii@kernel.org>
> >>CC: Jiri Olsa <jolsa@redhat.com>
> >>Signed-off-by: Saeed Mahameed <saeedm@nvidia.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
> >>
> >