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

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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 613fe16923 ("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: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240913173759.1316390-2-masahiroy@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Masahiro Yamada 2024-09-14 02:37:53 +09:00 committed by Alexei Starovoitov
parent c980dc9c67
commit 42450f7a90
2 changed files with 4 additions and 14 deletions
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6
lib/Kconfig.debug
View File

@ -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

12
scripts/link-vmlinux.sh
View File

@ -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}