From c8c739fb4b6d58d9a72bae03910d9e9ed55c98b2 Mon Sep 17 00:00:00 2001
From: Andrii Nakryiko <andrii@kernel.org>
Date: Mon, 28 Jun 2021 19:41:34 -0700
Subject: [PATCH] kbuild: skip per-CPU BTF generation for pahole v1.18-v1.21
References: jsc#SLE-24559
Patch-mainline: v5.14-rc1
Git-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>
Add boilerplate from commit db16c1fe92d7 ("bpf: Generate BTF_KIND_FLOAT when linking vmlinux")
which is itself not applicable to Linux 5.3 because it does not support
BTF_KIND_FLOAT.
Signed-off-by: Michal Suchanek <msuchanek@suse.de>
---
scripts/link-vmlinux.sh | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 40c2476e38e1..4799108cad51 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -103,6 +103,7 @@ vmlinux_link()
gen_btf()
{
local pahole_ver
+ local extra_paholeopt=
if ! [ -x "$(command -v ${PAHOLE})" ]; then
echo >&2 "BTF: ${1}: pahole (${PAHOLE}) is not available"
@@ -115,9 +116,15 @@ gen_btf()
return 1
fi
- info "BTF" ${2}
vmlinux_link ${1}
- LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1}
+
+ if [ "${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}
# Create ${2} which contains just .BTF section but no symbols. Add
# SHF_ALLOC because .BTF will be part of the vmlinux image. --strip-all
--
2.35.3