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kbuild: Unify options for BTF generation for vmlinux and modules
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Using new PAHOLE_FLAGS variable to pass extra arguments to
pahole for both vmlinux and modules BTF data generation.

Adding new scripts/pahole-flags.sh script that detect and
prints pahole options.

[ fixed issues found by kernel test robot ]

Signed-off-by: Jiri Olsa <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
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Jiri Olsa authored and anakryiko committed Nov 2, 2021
1 parent 0869e50 commit 9741e07
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Showing 4 changed files with 25 additions and 11 deletions.
3 changes: 3 additions & 0 deletions Makefile
Original file line number Diff line number Diff line change
Expand Up @@ -480,6 +480,8 @@ LZ4 = lz4c
XZ = xz
ZSTD = zstd

PAHOLE_FLAGS = $(shell PAHOLE=$(PAHOLE) $(srctree)/scripts/pahole-flags.sh)

CHECKFLAGS := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \
-Wbitwise -Wno-return-void -Wno-unknown-attribute $(CF)
NOSTDINC_FLAGS :=
Expand Down Expand Up @@ -534,6 +536,7 @@ export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE
export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE
export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
export PAHOLE_FLAGS

# Files to ignore in find ... statements

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2 changes: 1 addition & 1 deletion scripts/Makefile.modfinal
Original file line number Diff line number Diff line change
Expand Up @@ -40,7 +40,7 @@ quiet_cmd_ld_ko_o = LD [M] $@
quiet_cmd_btf_ko = BTF [M] $@
cmd_btf_ko = \
if [ -f vmlinux ]; then \
LLVM_OBJCOPY="$(OBJCOPY)" $(PAHOLE) -J --btf_base vmlinux $@; \
LLVM_OBJCOPY="$(OBJCOPY)" $(PAHOLE) -J $(PAHOLE_FLAGS) --btf_base vmlinux $@; \
$(RESOLVE_BTFIDS) -b vmlinux $@; \
else \
printf "Skipping BTF generation for %s due to unavailability of vmlinux\n" $@ 1>&2; \
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11 changes: 1 addition & 10 deletions scripts/link-vmlinux.sh
Original file line number Diff line number Diff line change
Expand Up @@ -205,7 +205,6 @@ 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"
Expand All @@ -220,16 +219,8 @@ 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

info "BTF" ${2}
LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${extra_paholeopt} ${1}
LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${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
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20 changes: 20 additions & 0 deletions scripts/pahole-flags.sh
Original file line number Diff line number Diff line change
@@ -0,0 +1,20 @@
#!/bin/sh
# SPDX-License-Identifier: GPL-2.0

extra_paholeopt=

if ! [ -x "$(command -v ${PAHOLE})" ]; then
return
fi

pahole_ver=$(${PAHOLE} --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/')

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

echo ${extra_paholeopt}

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