The patch titled
Subject: kbuild: skip per-CPU BTF generation for pahole v1.18-v1.21
has been added to the -mm tree. Its filename is
kbuild-skip-per-cpu-btf-generation-for-pahole-v118-v121.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/kbuild-skip-per-cpu-btf-generation-for-pahole-v118-v121.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/kbuild-skip-per-cpu-btf-generation-for-pahole-v118-v121.patch
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------------------------------------------------------
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
_
Patches currently in -mm which might be from andrii@xxxxxxxxxx are
kbuild-skip-per-cpu-btf-generation-for-pahole-v118-v121.patch
