On Wed, Sep 11, 2024 at 08:03:57PM +0900, Masahiro Yamada wrote:
> 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 613fe1692377 ("kbuild: Add CONFIG_PAHOLE_VERSION")
> added CONFIG_PAHOLE_VERSION at 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@xxxxxxxxx/
>
> Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> ---
>
> lib/Kconfig.debug | 3 ++-
> scripts/link-vmlinux.sh | 12 ------------
> 2 files changed, 2 insertions(+), 13 deletions(-)
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 5e2f30921cb2..eff408a88dfd 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -379,12 +379,13 @@ 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
> + Turning this on requires presence of pahole tool, which will convert
> DWARF type info into equivalent deduplicated BTF type info.
>
> config PAHOLE_HAS_SPLIT_BTF
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index cfffc41e20ed..53bd4b727e21 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -111,20 +111,8 @@ 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}
>
> --
> 2.43.0
>
