From: Andrii Nakryiko <andrii@xxxxxxxxxx> Subject: kbuild: skip per-CPU BTF generation for pahole v1.18-v1.21 Commit "mm/page_alloc: convert per-cpu list protection to local_lock" will introduce a zero-sized per-CPU variable, which causes pahole to generate invalid BTF. Only pahole versions 1.18 through 1.21 are impacted, as before 1.18 pahole doesn't know anything about per-CPU variables, and 1.22 contains the proper fix for the issue. Luckily, pahole 1.18 got --skip_encoding_btf_vars option disabling BTF generation for per-CPU variables in anticipation of some unanticipated problems. So use this escape hatch to disable per-CPU var BTF info on those problematic pahole versions. Users relying on availability of per-CPU var BTFs would need to upgrade to pahole 1.22+, but everyone won't notice any regressions. Link: https://lkml.kernel.org/r/20210530002536.3193829-1-andrii@xxxxxxxxxx Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Cc: Hao Luo <haoluo@xxxxxxxxxx> Cc: Michal Suchanek <msuchanek@xxxxxxx> Cc: Jiri Olsa <jolsa@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- scripts/link-vmlinux.sh | 4 ++++ 1 file changed, 4 insertions(+) --- a/scripts/link-vmlinux.sh~kbuild-skip-per-cpu-btf-generation-for-pahole-v118-v121 +++ a/scripts/link-vmlinux.sh @@ -235,6 +235,10 @@ gen_btf() vmlinux_link ${1} + if [ "${pahole_ver}" -ge "118" ] && [ "${pahole_ver}" -le "121" ]; then + # pahole 1.18 through 1.21 can't handle zero-sized per-CPU vars + extra_paholeopt="${extra_paholeopt} --skip_encoding_btf_vars" + fi if [ "${pahole_ver}" -ge "121" ]; then extra_paholeopt="${extra_paholeopt} --btf_gen_floats" fi _
