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: Rename to cross-cc-option so the function name
cc-option can be reserved for using globally.
Patch 06: Propagate -fzero-init-padding-bits=all to
EXTRA_CFLAGS and HOST_EXTRACFLAGS for the
CC and HOSTCC compilers, respectively.
Patches 07 – 23: Apply EXTRA_CFLAGS and HOST_EXTRACFLAGS in
project Makefiles.
The change has been verified:
Test 1: Cross compiling perf (rebased on perf-tools-next)
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: BPF CI test (BPF patches will be sent separately)
https://github.com/kernel-patches/bpf/actions/runs/26815163486
[1] https://gcc.gnu.org/gcc-15/changes.html
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
Changes in v7:
- Appended $(EXTRA_CFLAGS) in tracing/rtla/Makefile.
- Refactored testing/selftests/lib.mk to include Makefile.include, as
the $(EXTRA_CFLAGS) can be applied globally for selftest, dropped the
patches for selftests/hid, selftests/nolibc and selftests/sched_ext.
- Link to v6: https://lore.kernel.org/r/20260323-tools_build_fix_zero_init-v6-0-235858c51af9@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 (23):
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
selftests/nolibc: Use a dedicated cross cc-option helper
tools build: Append -fzero-init-padding-bits=all to extra cflags
perf build: Append extra host flags
tools build: Append extra host CFLAGS for fixdep
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: Include tools Makefile.include
tools/bootconfig/Makefile | 1 +
tools/build/Makefile | 8 ++++---
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/lib.mk | 30 +++++++++++++-------------
tools/testing/selftests/nolibc/Makefile.nolibc | 12 +++++------
tools/thermal/lib/Makefile | 20 +++++++++--------
tools/tracing/latency/Makefile | 1 +
tools/tracing/rtla/Makefile | 1 +
tools/usb/Makefile | 1 +
22 files changed, 95 insertions(+), 43 deletions(-)
---
base-commit: 6f3ed7fec72fc8979b2a8c7219c0a9fcfc8d07b5
change-id: 20260224-tools_build_fix_zero_init-dc5261bd8b8b
Best regards,
--
Leo Yan <leo.yan@arm.com>