On Tue, Aug 20, 2024 at 10:59:50AM +0200, Jiri Slaby (SUSE) wrote:
> From: Jiri Slaby <jslaby@xxxxxxx>
>
> == WARNING ==
> This is only a PoC. There are deficiencies like CROSS_COMPILE or LLVM
> are completely unhandled.
>
> The simple version is just do there:
> ifeq ($(CONFIG_64BIT,y)
> but it has its own deficiencies, of course.
>
> So any ideas, inputs?
> == WARNING ==
>
> When pahole is run with -j on 32bit userspace (32bit pahole in
> particular), it randomly fails with OOM:
> > btf_encoder__tag_kfuncs: Failed to get ELF section(62) data: out of memory.
> > btf_encoder__encode: failed to tag kfuncs!
>
> or simply SIGSEGV (failed to allocate the btf encoder).
>
> It very depends on how many threads are created.
>
> So do not invoke pahole with -j on 32bit.
could you share more details about your setup?
does it need to run on pure 32bit to reproduce? I can't reproduce when
doing cross build and running 32 bit pahole on x86_64.. I do see some
errors though
[667939] STRUCT bpf_prog_aux Error emitting BTF type
Encountered error while encoding BTF.
thanks,
jirka
>
> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
> Fixes: b4f72786429c ("scripts/pahole-flags.sh: Parse DWARF and generate BTF with multithreading.")
> Closes: https://bugzilla.suse.com/show_bug.cgi?id=1229450
> Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
> Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
> Cc: Nicolas Schier <nicolas@xxxxxxxxx>
> Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
> Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
> Cc: Martin KaFai Lau <martin.lau@xxxxxxxxx>
> Cc: Eduard Zingerman <eddyz87@xxxxxxxxx>
> Cc: Song Liu <song@xxxxxxxxxx>
> Cc: Yonghong Song <yonghong.song@xxxxxxxxx>
> Cc: John Fastabend <john.fastabend@xxxxxxxxx>
> Cc: KP Singh <kpsingh@xxxxxxxxxx>
> Cc: Stanislav Fomichev <sdf@xxxxxxxxxxx>
> Cc: Hao Luo <haoluo@xxxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-kbuild@xxxxxxxxxxxxxxx
> Cc: bpf@xxxxxxxxxxxxxxx
> Cc: shung-hsi.yu@xxxxxxxx
> Cc: msuchanek@xxxxxxxx
> ---
> init/Kconfig | 4 ++++
> scripts/Makefile.btf | 2 ++
> scripts/pahole-class.sh | 21 +++++++++++++++++++++
> 3 files changed, 27 insertions(+)
> create mode 100644 scripts/pahole-class.sh
>
> diff --git a/init/Kconfig b/init/Kconfig
> index f36ca8a0e209..f5e80497eef0 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -113,6 +113,10 @@ config PAHOLE_VERSION
> int
> default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
>
> +config PAHOLE_CLASS
> + string
> + default $(shell,$(srctree)/scripts/pahole-class.sh $(PAHOLE))
> +
> config CONSTRUCTORS
> bool
>
> diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
> index b75f09f3f424..f7de8e922bce 100644
> --- a/scripts/Makefile.btf
> +++ b/scripts/Makefile.btf
> @@ -12,7 +12,9 @@ endif
>
> pahole-flags-$(call test-ge, $(pahole-ver), 121) += --btf_gen_floats
>
> +ifeq ($(CONFIG_PAHOLE_CLASS),ELF64)
> pahole-flags-$(call test-ge, $(pahole-ver), 122) += -j
> +endif
>
> pahole-flags-$(call test-ge, $(pahole-ver), 125) += --skip_encoding_btf_inconsistent_proto --btf_gen_optimized
>
> diff --git a/scripts/pahole-class.sh b/scripts/pahole-class.sh
> new file mode 100644
> index 000000000000..d15a92077f76
> --- /dev/null
> +++ b/scripts/pahole-class.sh
> @@ -0,0 +1,21 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# Usage: $ ./pahole-class.sh pahole
> +#
> +# Prints pahole's ELF class, such as ELF64
> +
> +if [ ! -x "$(command -v "$@")" ]; then
> + echo 0
> + exit 1
> +fi
> +
> +PAHOLE="$(which "$@")"
> +CLASS="$(readelf -h "$PAHOLE" 2>/dev/null | sed -n 's/.*Class: *// p')"
> +
> +# Scripts like scripts/dummy-tools/pahole
> +if [ -n "$CLASS" ]; then
> + echo "$CLASS"
> +else
> + echo ELF64
> +fi
> --
> 2.46.0
>
