kbuild: skip per-CPU BTF generation for pahole v1.18-v1.21

stable inclusion
from stable-v5.10.151
commit f5f413cb3e8af235c5d310bea9942424fb242c2c
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I64L0X

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f5f413cb3e8af235c5d310bea9942424fb242c2c

--------------------------------

commit a0b8200d upstream.

[small context changes due to missing floats support in 5.10]

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.orgSigned-off-by: NAndrii Nakryiko <andrii@kernel.org>
Acked-by: NMel 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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NLipeng Sang <sanglipeng1@jd.com>
(cherry picked from commit 40a0d0a9)

scripts/link-vmlinux.sh

@@ -161,6 +161,11 @@ 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
+
 	info "BTF" ${2}
 	LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${extra_paholeopt} ${1}