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linux/scripts/Makefile.btf

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kbuild: avoid too many execution of scripts/pahole-flags.sh scripts/pahole-flags.sh is executed so many times. You can confirm it, as follows: $ cat <<EOF >> scripts/pahole-flags.sh > echo "scripts/pahole-flags.sh was executed" >&2 > EOF $ make -s scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed [ lots of repeated lines... ] This scripts is executed more than 20 times during the kernel build because PAHOLE_FLAGS is a recursively expanded variable and exported to sub-processes. With GNU Make >= 4.4, it is executed more than 60 times because exported variables are also passed to other $(shell ) invocations. Without careful coding, it is known to cause an exponential fork explosion. [1] The use of $(shell ) in an exported recursive variable is likely wrong because $(shell ) is always evaluated due to the 'export' keyword, and the evaluation can occur multiple times by the nature of recursive variables. Convert the shell script to a Makefile, which is included only when CONFIG_DEBUG_INFO_BTF=y. [1]: https://savannah.gnu.org/bugs/index.php?64746 Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Alan Maguire <alan.maguire@oracle.com> Tested-by: Alan Maguire <alan.maguire@oracle.com> Reviewed-by: Nicolas Schier <n.schier@avm.de> Tested-by: Miguel Ojeda <ojeda@kernel.org> Acked-by: Miguel Ojeda <ojeda@kernel.org> Acked-by: Jiri Olsa <jolsa@kernel.org> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
2023-10-19 00:19:48 +09:00
kbuild,bpf: Switch to using --btf_features for pahole v1.26 and later The btf_features list can be used for pahole v1.26 and later - it is useful because if a feature is not yet implemented it will not exit with a failure message. This will allow us to add feature requests to the pahole options without having to check pahole versions in future; if the version of pahole supports the feature it will be added. Signed-off-by: Alan Maguire <alan.maguire@oracle.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Tested-by: Eduard Zingerman <eddyz87@gmail.com> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20240507135514.490467-1-alan.maguire@oracle.com
2024-05-07 14:55:14 +01:00
kbuild: avoid too many execution of scripts/pahole-flags.sh scripts/pahole-flags.sh is executed so many times. You can confirm it, as follows: $ cat <<EOF >> scripts/pahole-flags.sh > echo "scripts/pahole-flags.sh was executed" >&2 > EOF $ make -s scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed [ lots of repeated lines... ] This scripts is executed more than 20 times during the kernel build because PAHOLE_FLAGS is a recursively expanded variable and exported to sub-processes. With GNU Make >= 4.4, it is executed more than 60 times because exported variables are also passed to other $(shell ) invocations. Without careful coding, it is known to cause an exponential fork explosion. [1] The use of $(shell ) in an exported recursive variable is likely wrong because $(shell ) is always evaluated due to the 'export' keyword, and the evaluation can occur multiple times by the nature of recursive variables. Convert the shell script to a Makefile, which is included only when CONFIG_DEBUG_INFO_BTF=y. [1]: https://savannah.gnu.org/bugs/index.php?64746 Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Alan Maguire <alan.maguire@oracle.com> Tested-by: Alan Maguire <alan.maguire@oracle.com> Reviewed-by: Nicolas Schier <n.schier@avm.de> Tested-by: Miguel Ojeda <ojeda@kernel.org> Acked-by: Miguel Ojeda <ojeda@kernel.org> Acked-by: Jiri Olsa <jolsa@kernel.org> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
2023-10-19 00:19:48 +09:00
kbuild,bpf: Switch to using --btf_features for pahole v1.26 and later The btf_features list can be used for pahole v1.26 and later - it is useful because if a feature is not yet implemented it will not exit with a failure message. This will allow us to add feature requests to the pahole options without having to check pahole versions in future; if the version of pahole supports the feature it will be added. Signed-off-by: Alan Maguire <alan.maguire@oracle.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Tested-by: Eduard Zingerman <eddyz87@gmail.com> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20240507135514.490467-1-alan.maguire@oracle.com
2024-05-07 14:55:14 +01:00
kbuild: avoid too many execution of scripts/pahole-flags.sh scripts/pahole-flags.sh is executed so many times. You can confirm it, as follows: $ cat <<EOF >> scripts/pahole-flags.sh > echo "scripts/pahole-flags.sh was executed" >&2 > EOF $ make -s scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed [ lots of repeated lines... ] This scripts is executed more than 20 times during the kernel build because PAHOLE_FLAGS is a recursively expanded variable and exported to sub-processes. With GNU Make >= 4.4, it is executed more than 60 times because exported variables are also passed to other $(shell ) invocations. Without careful coding, it is known to cause an exponential fork explosion. [1] The use of $(shell ) in an exported recursive variable is likely wrong because $(shell ) is always evaluated due to the 'export' keyword, and the evaluation can occur multiple times by the nature of recursive variables. Convert the shell script to a Makefile, which is included only when CONFIG_DEBUG_INFO_BTF=y. [1]: https://savannah.gnu.org/bugs/index.php?64746 Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Alan Maguire <alan.maguire@oracle.com> Tested-by: Alan Maguire <alan.maguire@oracle.com> Reviewed-by: Nicolas Schier <n.schier@avm.de> Tested-by: Miguel Ojeda <ojeda@kernel.org> Acked-by: Miguel Ojeda <ojeda@kernel.org> Acked-by: Jiri Olsa <jolsa@kernel.org> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
2023-10-19 00:19:48 +09:00
kbuild,bpf: Switch to using --btf_features for pahole v1.26 and later The btf_features list can be used for pahole v1.26 and later - it is useful because if a feature is not yet implemented it will not exit with a failure message. This will allow us to add feature requests to the pahole options without having to check pahole versions in future; if the version of pahole supports the feature it will be added. Signed-off-by: Alan Maguire <alan.maguire@oracle.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Tested-by: Eduard Zingerman <eddyz87@gmail.com> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20240507135514.490467-1-alan.maguire@oracle.com
2024-05-07 14:55:14 +01:00
kbuild: avoid too many execution of scripts/pahole-flags.sh scripts/pahole-flags.sh is executed so many times. You can confirm it, as follows: $ cat <<EOF >> scripts/pahole-flags.sh > echo "scripts/pahole-flags.sh was executed" >&2 > EOF $ make -s scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed [ lots of repeated lines... ] This scripts is executed more than 20 times during the kernel build because PAHOLE_FLAGS is a recursively expanded variable and exported to sub-processes. With GNU Make >= 4.4, it is executed more than 60 times because exported variables are also passed to other $(shell ) invocations. Without careful coding, it is known to cause an exponential fork explosion. [1] The use of $(shell ) in an exported recursive variable is likely wrong because $(shell ) is always evaluated due to the 'export' keyword, and the evaluation can occur multiple times by the nature of recursive variables. Convert the shell script to a Makefile, which is included only when CONFIG_DEBUG_INFO_BTF=y. [1]: https://savannah.gnu.org/bugs/index.php?64746 Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Alan Maguire <alan.maguire@oracle.com> Tested-by: Alan Maguire <alan.maguire@oracle.com> Reviewed-by: Nicolas Schier <n.schier@avm.de> Tested-by: Miguel Ojeda <ojeda@kernel.org> Acked-by: Miguel Ojeda <ojeda@kernel.org> Acked-by: Jiri Olsa <jolsa@kernel.org> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
2023-10-19 00:19:48 +09:00