Commit 42450f7a authored by Masahiro Yamada's avatar Masahiro Yamada Committed by Alexei Starovoitov
Browse files

btf: move pahole check in scripts/link-vmlinux.sh to lib/Kconfig.debug 

When DEBUG_INFO_DWARF5 is selected, pahole 1.21+ is required to enable
DEBUG_INFO_BTF.

When DEBUG_INFO_DWARF4 or DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT is selected,
DEBUG_INFO_BTF can be enabled without pahole installed, but a build error
will occur in scripts/link-vmlinux.sh:

    LD      .tmp_vmlinux1
  BTF: .tmp_vmlinux1: pahole (pahole) is not available
  Failed to generate BTF for vmlinux
  Try to disable CONFIG_DEBUG_INFO_BTF

We did not guard DEBUG_INFO_BTF by PAHOLE_VERSION when previously
discussed [1].

However, commit 613fe169 ("kbuild: Add CONFIG_PAHOLE_VERSION")
added CONFIG_PAHOLE_VERSION after all. Now several CONFIG options, as
well as the combination of DEBUG_INFO_BTF and DEBUG_INFO_DWARF5, are
guarded by PAHOLE_VERSION.

The remaining compile-time check in scripts/link-vmlinux.sh now appears
to be an awkward inconsistency.

This commit adopts Nathan's original work.

[1]: https://lore.kernel.org/lkml/20210111180609.713998-1-natechancellor@gmail.com/



Signed-off-by: default avatarMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: default avatarAlan Maguire <alan.maguire@oracle.com>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Reviewed-by: default avatarNathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240913173759.1316390-2-masahiroy@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent c980dc9c

lib/Kconfig.debug

+4 −2
Original line number Diff line number Diff line
@@ -379,13 +379,15 @@ config DEBUG_INFO_BTF 
	depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED

	depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST

	depends on BPF_SYSCALL

	depends on PAHOLE_VERSION >= 116

	depends on !DEBUG_INFO_DWARF5 || PAHOLE_VERSION >= 121

	# pahole uses elfutils, which does not have support for Hexagon relocations

	depends on !HEXAGON

	help

	  Generate deduplicated BTF type information from DWARF debug info.

	  Turning this on expects presence of pahole tool, which will convert

	  DWARF type info into equivalent deduplicated BTF type info.

	  Turning this on requires pahole v1.16 or later (v1.21 or later to

	  support DWARF 5), which will convert DWARF type info into equivalent

	  deduplicated BTF type info.



config PAHOLE_HAS_SPLIT_BTF

	def_bool PAHOLE_VERSION >= 119

scripts/link-vmlinux.sh

+0 −12
Original line number Diff line number Diff line
@@ -107,20 +107,8 @@ vmlinux_link() 
# ${1} - vmlinux image

gen_btf()

{

	local pahole_ver

	local btf_data=${1}.btf.o



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

		echo >&2 "BTF: ${1}: pahole (${PAHOLE}) is not available"

		return 1

	fi



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

	if [ "${pahole_ver}" -lt "116" ]; then

		echo >&2 "BTF: ${1}: pahole version $(${PAHOLE} --version) is too old, need at least v1.16"

		return 1

	fi



	info BTF "${btf_data}"

	LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}