GCC-15 doesn't guarantee that a {0} initializer clears the whole union [1].
This may cause bugs if data is not intialized properly.
The kernel enabld the -fzero-init-padding-bits=all option to tackle the
issue, which was merged in commit dce4aab8441d ("kbuild: Use
-fzero-init-padding-bits=all").
This series propagates the same flag to the tools build. It uses
tools/scripts/Makefile.include as the central place to add the
option to EXTRA_CFLAGS and HOST_EXTRACFLAGS for the CC and HOSTCC
compilers. Each project under tools/ appends the variables as needed.
BPF/bpftool related patches will be sent separately, as maintainers
prefer them to go via the BPF tree.
The changes are organized into three parts:
Patches 01 – 04: Fixes for thermal build.
Patch 05: Propagate -fzero-init-padding-bits=all to
EXTRA_CFLAGS and HOST_EXTRACFLAGS for the
CC and HOSTCC compilers, respectively.
Patches 06 – 24: Apply EXTRA_CFLAGS and HOST_EXTRACFLAGS in
project Makefiles.
The change has been verified:
Test 1: Cross compiling perf
host: gcc 15.2.0 (x86_64), target: aarch64-linux-gnu-gcc
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- LDFLAGS="-static" \
-C tools/perf VF=1 CORESIGHT=1 NO_JEVENTS=1 DEBUG=1
Test 2: Cross compiling selftest bpf and sched_ext
host: gcc 15.2.0 (x86_64), target: aarch64-linux-gnu-gcc
export ARCH=arm64
export CROSS_COMPILE=aarch64-linux-gnu-
make -C tools/testing/selftests/ TARGETS="bpf sched_ext" SKIP_TARGETS=""
Test 3: Native compiling selftest bpf and sched_ext
host: gcc 15.2.0 (x86_64)
make -C tools/testing/selftests/ TARGETS="bpf sched_ext" SKIP_TARGETS=""
Test 4: BPF CI test (with BPF patches sent separately)
https://github.com/kernel-patches/bpf/actions/runs/23439834394
[1] https://gcc.gnu.org/gcc-15/changes.html
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
Changes in v6:
- Gathered Acked tags (thanks Jonathan!)
- Left out bpftool patches and will send together with other BPF patches (Quentin)
- Added back complete info in cover (Peter.Z)
- Link to v5: https://lore.kernel.org/r/20260318-tools_build_fix_zero_init-v5-0-bbeffd8da199@arm.com
Changes in v5:
- Gathered Acked tags (thanks Daniel, Namhyung, Benjamin!)
- Appended HOST_EXTRACFLAGS after KBUILD_HOSTCFLAGS (Ian)
- Appended CFLAGS for libc-test (Thomas)
- Left out BPF patches and will send out separately (Alexei)
- Rebase on v7.0.0-rc4
- Link to v4: https://lore.kernel.org/r/20260311-tools_build_fix_zero_init-v4-0-9e35bdb99cb3@arm.com
---
Leo Yan (24):
tools: lib: thermal: Fix typo
tools/thermal: Fix typo
tools: lib: thermal: Initialize CFLAGS before including Makefile.include
tools/thermal: Initialize CFLAGS before including Makefile.include
tools build: Append -fzero-init-padding-bits=all to extra cflags
perf build: Append extra host flags
tools build: Append extra host cflags
tools: bootconfig: Append extra cflags
tools: counter: Append extra cflags
tools: dma: Append extra cflags
tools: gpio: Append extra cflags
tools: hv: Append extra cflags
tools: iio: Append extra cflags
tools: mm: Append extra cflags
tools: objtool: Append extra host cflags
tools: power: acpi: Append extra cflags
tools: power: x86/intel-speed-select: Append extra cflags
tools: sched_ext: Append extra cflags
tools: spi: Append extra cflags
tools: tracing: Append extra cflags
tools: usb: Append extra cflags
selftests/hid: Append extra cflags
selftests/nolibc: Append extra cflags
selftests/sched_ext: Append extra cflags
tools/bootconfig/Makefile | 1 +
tools/build/Makefile | 6 ++++--
tools/counter/Makefile | 1 +
tools/dma/Makefile | 1 +
tools/gpio/Makefile | 1 +
tools/hv/Makefile | 1 +
tools/iio/Makefile | 1 +
tools/lib/thermal/Makefile | 20 ++++++++++---------
tools/mm/Makefile | 1 +
tools/objtool/Makefile | 2 ++
tools/perf/Makefile.config | 2 +-
tools/power/acpi/Makefile.config | 1 +
tools/power/x86/intel-speed-select/Makefile | 1 +
tools/sched_ext/Makefile | 1 +
tools/scripts/Makefile.include | 30 +++++++++++++++++++++++++++++
tools/spi/Makefile | 1 +
tools/testing/selftests/hid/Makefile | 1 +
tools/testing/selftests/nolibc/Makefile | 7 +++----
tools/testing/selftests/sched_ext/Makefile | 1 +
tools/thermal/lib/Makefile | 20 ++++++++++---------
tools/tracing/latency/Makefile | 1 +
tools/usb/Makefile | 1 +
22 files changed, 77 insertions(+), 25 deletions(-)
---
base-commit: bfec8e88ff6022b056615ec71506703e7e54de82
change-id: 20260224-tools_build_fix_zero_init-dc5261bd8b8b
Best regards,
--
Leo Yan <leo.yan@arm.com>