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    Subject[PATCH 5.13 266/800] kbuild: skip per-CPU BTF generation for pahole v1.18-v1.21
    Date
    From: Andrii Nakryiko <andrii@kernel.org>

    [ Upstream commit a0b8200d06ad6450c179407baa5f0f52f8cfcc97 ]

    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@kernel.org
    Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
    Acked-by: Mel Gorman <mgorman@techsingularity.net>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Hao Luo <haoluo@google.com>
    Cc: Michal Suchanek <msuchanek@suse.de>
    Cc: Jiri Olsa <jolsa@kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    scripts/link-vmlinux.sh | 4 ++++
    1 file changed, 4 insertions(+)

    diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
    index 0e0f6466b18d..475faa15854e 100755
    --- a/scripts/link-vmlinux.sh
    +++ b/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
    --
    2.30.2


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