From patchwork Wed Oct 18 15:19:48 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Masahiro Yamada X-Patchwork-Id: 13427219 X-Patchwork-Delegate: bpf@iogearbox.net Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 694BD20307; Wed, 18 Oct 2023 15:20:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bbbQz7uO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 805DDC433CC; Wed, 18 Oct 2023 15:20:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697642408; bh=lrwp96Hw7hR0NmIZyK9E+Yck2vromf2V4V2XM+YwBrM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bbbQz7uOjLBbcJOU77RCqez7qqCnwfeNfFfIy1x/tmueoX47XKwqdFDKFGTvYpH1t cn0NbHXwsx2nyphvX8w8Q3ImvYRiYty2VZVXAJ1d+XVLtaTlCYYpv4oULvYtcm5Rny /wU0RJWp/c2MLEjUj1y1/Ooz9i8vFL+l4kkNQFpOv0nGdbXt3eVxUAAdpBt/6mBml8 6jjxz3ST6I+tLONlMYb55FbSGWFD8JB+8lpMK2Q4WHdO/HQDj0x3qkKKYqh8Nay62X godcax2rXU8iUZewPbVup/dPB3svnE1h6SKIhYXu/80y5yhoXCsEzb6DGO2feHwxVc B0WAv4z/9WT6A== From: Masahiro Yamada To: linux-kbuild@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Masahiro Yamada , Alan Maguire , Nicolas Schier , Miguel Ojeda , Alex Gaynor , Alexei Starovoitov , Alice Ryhl , Andreas Hindborg , Andrii Nakryiko , Benno Lossin , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Boqun Feng , Daniel Borkmann , Gary Guo , Hao Luo , Jiri Olsa , John Fastabend , KP Singh , Martin KaFai Lau , Nathan Chancellor , Nick Desaulniers , Nicolas Schier , Song Liu , Stanislav Fomichev , Wedson Almeida Filho , Yonghong Song , bpf@vger.kernel.org, rust-for-linux@vger.kernel.org Subject: [bpf-next PATCH v2 2/4] kbuild: avoid too many execution of scripts/pahole-flags.sh Date: Thu, 19 Oct 2023 00:19:48 +0900 Message-Id: <20231018151950.205265-2-masahiroy@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20231018151950.205265-1-masahiroy@kernel.org> References: <20231018151950.205265-1-masahiroy@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net scripts/pahole-flags.sh is executed so many times. You can check how many times it is invoked during the build, as follows: $ cat <> scripts/pahole-flags.sh > echo "scripts/pahole-flags.sh was executed" >&2 > EOF $ make -s scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed scripts/pahole-flags.sh was executed [ lots of repeated lines suppressed... ] This scripts is executed more than 20 times during the kernel build because PAHOLE_FLAGS is a recursively expanded variable and exported to sub-processes. With the GNU Make >= 4.4, it is executed more than 60 times because exported variables are also passed to other $(shell ) invocations. Without careful coding, it is known to cause an exponential fork explosion. [1] The use of $(shell ) in an exported recursive variable is likely wrong because $(shell ) is always evaluated due to the 'export' keyword, and the evaluation can occur multiple times by the nature of recursive variables. Convert the shell script to a Makefile, which is included only when CONFIG_DEBUG_INFO_BTF=y. [1]: https://savannah.gnu.org/bugs/index.php?64746 Signed-off-by: Masahiro Yamada Reviewed-by: Alan Maguire Tested-by: Alan Maguire Reviewed-by: Nicolas Schier Tested-by: Miguel Ojeda Acked-by: Miguel Ojeda Acked-by: Jiri Olsa Reviewed-by: Martin Rodriguez Reboredo --- Changes in v2: - Fix a typo in commit description - Update MAINTAINERS MAINTAINERS | 2 +- Makefile | 4 +--- scripts/Makefile.btf | 19 +++++++++++++++++++ scripts/pahole-flags.sh | 30 ------------------------------ 4 files changed, 21 insertions(+), 34 deletions(-) create mode 100644 scripts/Makefile.btf delete mode 100755 scripts/pahole-flags.sh diff --git a/MAINTAINERS b/MAINTAINERS index 35977b269d5e..a08d558b1aaa 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3742,7 +3742,7 @@ F: net/sched/act_bpf.c F: net/sched/cls_bpf.c F: samples/bpf/ F: scripts/bpf_doc.py -F: scripts/pahole-flags.sh +F: scripts/Makefile.btf F: scripts/pahole-version.sh F: tools/bpf/ F: tools/lib/bpf/ diff --git a/Makefile b/Makefile index fed9a6cc3665..eaddec67e5e1 100644 --- a/Makefile +++ b/Makefile @@ -513,8 +513,6 @@ 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 := @@ -605,7 +603,6 @@ export KBUILD_RUSTFLAGS RUSTFLAGS_KERNEL RUSTFLAGS_MODULE export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_RUSTFLAGS_MODULE KBUILD_LDFLAGS_MODULE export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL KBUILD_RUSTFLAGS_KERNEL -export PAHOLE_FLAGS # Files to ignore in find ... statements @@ -1002,6 +999,7 @@ KBUILD_CPPFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) # include additional Makefiles when needed include-y := scripts/Makefile.extrawarn include-$(CONFIG_DEBUG_INFO) += scripts/Makefile.debug +include-$(CONFIG_DEBUG_INFO_BTF)+= scripts/Makefile.btf include-$(CONFIG_KASAN) += scripts/Makefile.kasan include-$(CONFIG_KCSAN) += scripts/Makefile.kcsan include-$(CONFIG_KMSAN) += scripts/Makefile.kmsan diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf new file mode 100644 index 000000000000..82377e470aed --- /dev/null +++ b/scripts/Makefile.btf @@ -0,0 +1,19 @@ +# SPDX-License-Identifier: GPL-2.0 + +pahole-ver := $(CONFIG_PAHOLE_VERSION) +pahole-flags-y := + +# pahole 1.18 through 1.21 can't handle zero-sized per-CPU vars +ifeq ($(call test-le, $(pahole-ver), 121),y) +pahole-flags-$(call test-ge, $(pahole-ver), 118) += --skip_encoding_btf_vars +endif + +pahole-flags-$(call test-ge, $(pahole-ver), 121) += --btf_gen_floats + +pahole-flags-$(call test-ge, $(pahole-ver), 122) += -j + +pahole-flags-$(CONFIG_PAHOLE_HAS_LANG_EXCLUDE) += --lang_exclude=rust + +pahole-flags-$(call test-ge, $(pahole-ver), 125) += --skip_encoding_btf_inconsistent_proto --btf_gen_optimized + +export PAHOLE_FLAGS := $(pahole-flags-y) diff --git a/scripts/pahole-flags.sh b/scripts/pahole-flags.sh deleted file mode 100755 index 728d55190d97..000000000000 --- a/scripts/pahole-flags.sh +++ /dev/null @@ -1,30 +0,0 @@ -#!/bin/sh -# SPDX-License-Identifier: GPL-2.0 - -extra_paholeopt= - -if ! [ -x "$(command -v ${PAHOLE})" ]; then - exit 0 -fi - -pahole_ver=$($(dirname $0)/pahole-version.sh ${PAHOLE}) - -if [ "${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 -if [ "${pahole_ver}" -ge "122" ]; then - extra_paholeopt="${extra_paholeopt} -j" -fi -if [ "${pahole_ver}" -ge "124" ]; then - # see PAHOLE_HAS_LANG_EXCLUDE - extra_paholeopt="${extra_paholeopt} --lang_exclude=rust" -fi -if [ "${pahole_ver}" -ge "125" ]; then - extra_paholeopt="${extra_paholeopt} --skip_encoding_btf_inconsistent_proto --btf_gen_optimized" -fi - -echo ${extra_paholeopt}