[PATCH v7 00/23] tools build: Append -fzero-init-padding-bits=all option

[PATCH v7 00/23] tools build: Append -fzero-init-padding-bits=all option

[Leo Yan]

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>

[PATCH v7 01/23] tools: lib: thermal: Fix typo

[Leo Yan]

s/CFGLAS/CFLAGS

Fixes: 47c4b0de080a ("tools/lib/thermal: Add a thermal library")
Acked-by: Daniel Lezcano <daniel.lezcano@kernel.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/lib/thermal/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/lib/thermal/Makefile b/tools/lib/thermal/Makefile
index 41aa7a324ff4d76351b89d7d7cf382df3fc14052..09d8f4ba6a0ab7ab9c99ac7f64d52d0268bee340 100644
--- a/tools/lib/thermal/Makefile
+++ b/tools/lib/thermal/Makefile
@@ -66,8 +66,8 @@ override CFLAGS += -fPIC
 override CFLAGS += $(NL3_CFLAGS)
 override CFLAGS += $(INCLUDES)
 override CFLAGS += -fvisibility=hidden
-override CFGLAS += -Wl,-L.
-override CFGLAS += -Wl,-lthermal
+override CFLAGS += -Wl,-L.
+override CFLAGS += -Wl,-lthermal
 
 all:
 

-- 
2.34.1

[PATCH v7 02/23] tools/thermal: Fix typo

[Leo Yan]

s/CFGLAS/CFLAGS

Fixes: 3b7c5e8adf9c ("tools/thermal: Add util library")
Acked-by: Daniel Lezcano <daniel.lezcano@kernel.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/thermal/lib/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/thermal/lib/Makefile b/tools/thermal/lib/Makefile
index 056d212f25cf51cd8c02260fbe2ef28dda5e4acb..8c9a37f999b826855dad11c0d9574b41d5b24244 100644
--- a/tools/thermal/lib/Makefile
+++ b/tools/thermal/lib/Makefile
@@ -60,8 +60,8 @@ override CFLAGS += $(EXTRA_WARNINGS)
 override CFLAGS += -Werror -Wall
 override CFLAGS += -fPIC
 override CFLAGS += $(INCLUDES)
-override CFGLAS += -Wl,-L.
-override CFGLAS += -Wl,-lthermal
+override CFLAGS += -Wl,-L.
+override CFLAGS += -Wl,-lthermal
 
 all:
 

-- 
2.34.1

[PATCH v7 03/23] tools: lib: thermal: Initialize CFLAGS before including Makefile.include

[Leo Yan]

tools/scripts/Makefile.include may expand EXTRA_CFLAGS in a future
change.  This could alter the initialization of CFLAGS in the thermal
Makefile, as the default options "-g -Wall" would never be set once
EXTRA_CFLAGS is expanded.

Prepare for this by moving the CFLAGS initialization before including
tools/scripts/Makefile.include, so it is not affected by the extended
EXTRA_CFLAGS.

Append EXTRA_CFLAGS to CFLAGS only after including Makefile.include and
place it last so that the extra flags propagate properly and can
override the default options.

Acked-by: Daniel Lezcano <daniel.lezcano@kernel.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/lib/thermal/Makefile | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/tools/lib/thermal/Makefile b/tools/lib/thermal/Makefile
index 09d8f4ba6a0ab7ab9c99ac7f64d52d0268bee340..b55fa42cefa47628b7f2fac32fc08fcd82580a0e 100644
--- a/tools/lib/thermal/Makefile
+++ b/tools/lib/thermal/Makefile
@@ -23,6 +23,14 @@ INSTALL = install
 DESTDIR ?=
 DESTDIR_SQ = '$(subst ','\'',$(DESTDIR))'
 
+# Defer assigning EXTRA_CFLAGS to CFLAGS until after including
+# tools/scripts/Makefile.include, as it may add flags to EXTRA_CFLAGS.
+ifdef EXTRA_CFLAGS
+  CFLAGS :=
+else
+  CFLAGS := -g -Wall
+endif
+
 include $(srctree)/tools/scripts/Makefile.include
 include $(srctree)/tools/scripts/Makefile.arch
 
@@ -39,13 +47,6 @@ libdir = $(prefix)/$(libdir_relative)
 libdir_SQ = $(subst ','\'',$(libdir))
 libdir_relative_SQ = $(subst ','\'',$(libdir_relative))
 
-# Set compile option CFLAGS
-ifdef EXTRA_CFLAGS
-  CFLAGS := $(EXTRA_CFLAGS)
-else
-  CFLAGS := -g -Wall
-endif
-
 NL3_CFLAGS = $(shell pkg-config --cflags libnl-3.0 2>/dev/null)
 ifeq ($(NL3_CFLAGS),)
 NL3_CFLAGS = -I/usr/include/libnl3
@@ -68,6 +69,7 @@ override CFLAGS += $(INCLUDES)
 override CFLAGS += -fvisibility=hidden
 override CFLAGS += -Wl,-L.
 override CFLAGS += -Wl,-lthermal
+override CFLAGS += $(EXTRA_CFLAGS)
 
 all:
 

-- 
2.34.1

[PATCH v7 04/23] tools/thermal: Initialize CFLAGS before including Makefile.include

[Leo Yan]

tools/scripts/Makefile.include may expand EXTRA_CFLAGS in a future
change.  This could alter the initialization of CFLAGS in the thermal
Makefile, as the default options "-g -Wall" would never be set once
EXTRA_CFLAGS is expanded.

Prepare for this by moving the CFLAGS initialization before including
tools/scripts/Makefile.include, so it is not affected by the extended
EXTRA_CFLAGS.

Append EXTRA_CFLAGS to CFLAGS only after including Makefile.include and
place it last so that the extra flags propagate properly and can
override the default options.

Acked-by: Daniel Lezcano <daniel.lezcano@kernel.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/thermal/lib/Makefile | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/tools/thermal/lib/Makefile b/tools/thermal/lib/Makefile
index 8c9a37f999b826855dad11c0d9574b41d5b24244..333b711bc7f0f9610e165ff7dc72c42980c59c99 100644
--- a/tools/thermal/lib/Makefile
+++ b/tools/thermal/lib/Makefile
@@ -23,6 +23,14 @@ INSTALL = install
 DESTDIR ?=
 DESTDIR_SQ = '$(subst ','\'',$(DESTDIR))'
 
+# Defer assigning EXTRA_CFLAGS to CFLAGS until after including
+# tools/scripts/Makefile.include, as it may add flags to EXTRA_CFLAGS.
+ifdef EXTRA_CFLAGS
+  CFLAGS :=
+else
+  CFLAGS := -g -Wall
+endif
+
 include $(srctree)/tools/scripts/Makefile.include
 include $(srctree)/tools/scripts/Makefile.arch
 
@@ -39,13 +47,6 @@ libdir = $(prefix)/$(libdir_relative)
 libdir_SQ = $(subst ','\'',$(libdir))
 libdir_relative_SQ = $(subst ','\'',$(libdir_relative))
 
-# Set compile option CFLAGS
-ifdef EXTRA_CFLAGS
-  CFLAGS := $(EXTRA_CFLAGS)
-else
-  CFLAGS := -g -Wall
-endif
-
 INCLUDES = \
 -I/usr/include/libnl3 \
 -I$(srctree)/tools/lib/thermal/include \
@@ -62,6 +63,7 @@ override CFLAGS += -fPIC
 override CFLAGS += $(INCLUDES)
 override CFLAGS += -Wl,-L.
 override CFLAGS += -Wl,-lthermal
+override CFLAGS += $(EXTRA_CFLAGS)
 
 all:
 

-- 
2.34.1

[PATCH v7 05/23] selftests/nolibc: Use a dedicated cross cc-option helper

[Leo Yan]

Makefile.nolibc uses cc-option for architecture-specific flag probes
such as -m32, -mmultiple and -mabi=elfv2. These probes need to include
CLANG_CROSS_FLAGS so that Clang tests the option for the selected target
instead of the host.

The file also includes tools/scripts/Makefile.include. In a sequential
change, Makefile.include will define its own cc-option helper.

Rename the nolibc helper to cross-cc-option and use it for the
architecture-specific probes that require CLANG_CROSS_FLAGS. This keeps
the cross-build checks explicit and avoids clashing with the common
tools cc-option helper.

Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/testing/selftests/nolibc/Makefile.nolibc | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/nolibc/Makefile.nolibc b/tools/testing/selftests/nolibc/Makefile.nolibc
index f30bc68470cceec2b61805af0a4a9f2fb2de7c57..e88b1c15445f3c64dd78cc7edef5c9670a389b50 100644
--- a/tools/testing/selftests/nolibc/Makefile.nolibc
+++ b/tools/testing/selftests/nolibc/Makefile.nolibc
@@ -23,7 +23,7 @@ include $(srctree)/scripts/subarch.include
 ARCH = $(SUBARCH)
 endif
 
-cc-option = $(call __cc-option, $(CC),$(CLANG_CROSS_FLAGS),$(1),$(2))
+cross-cc-option = $(call __cc-option, $(CC),$(CLANG_CROSS_FLAGS),$(1),$(2))
 
 # XARCH extends the kernel's ARCH with a few variants of the same
 # architecture that only differ by the configuration, the toolchain
@@ -211,13 +211,13 @@ else
 Q=@
 endif
 
-CFLAGS_i386 = $(call cc-option,-m32)
+CFLAGS_i386 = $(call cross-cc-option,-m32)
 CFLAGS_x32 = -mx32
 CFLAGS_arm = -marm
 CFLAGS_armthumb = -mthumb -march=armv6t2
-CFLAGS_ppc = -m32 -mbig-endian -mno-vsx $(call cc-option,-mmultiple)
-CFLAGS_ppc64 = -m64 -mbig-endian -mno-vsx $(call cc-option,-mmultiple)
-CFLAGS_ppc64le = -m64 -mlittle-endian -mno-vsx $(call cc-option,-mabi=elfv2)
+CFLAGS_ppc = -m32 -mbig-endian -mno-vsx $(call cross-cc-option,-mmultiple)
+CFLAGS_ppc64 = -m64 -mbig-endian -mno-vsx $(call cross-cc-option,-mmultiple)
+CFLAGS_ppc64le = -m64 -mlittle-endian -mno-vsx $(call cross-cc-option,-mabi=elfv2)
 CFLAGS_s390x = -m64
 CFLAGS_mips32le = -EL -mabi=32 -fPIC
 CFLAGS_mips32be = -EB -mabi=32
@@ -226,7 +226,7 @@ CFLAGS_mipsn32be = -EB -mabi=n32 -march=mips64r6
 CFLAGS_mips64le = -EL -mabi=64 -march=mips64r6
 CFLAGS_mips64be = -EB -mabi=64 -march=mips64r2
 CFLAGS_loongarch = $(if $(LLVM),-fuse-ld=lld)
-CFLAGS_sparc32 = $(call cc-option,-m32) -mcpu=v8
+CFLAGS_sparc32 = $(call cross-cc-option,-m32) -mcpu=v8
 CFLAGS_sh4 = -ml -m4
 ifeq ($(origin XARCH),command line)
 CFLAGS_XARCH = $(CFLAGS_$(XARCH))

-- 
2.34.1

[PATCH v7 06/23] tools build: Append -fzero-init-padding-bits=all to extra cflags

[Leo Yan]

GCC-15 release claims [1]:

  {0} initializer in C or C++ for unions no longer guarantees clearing
  of the whole union (except for static storage duration initialization),
  it just initializes the first union member to zero. If initialization
  of the whole union including padding bits is desirable, use {} (valid
  in C23 or C++) or use -fzero-init-padding-bits=unions option to
  restore old GCC behavior.

As a result, this new behaviour might cause unexpected data when we
initialize a union with using the '{ 0 }' initializer.

Since commit dce4aab8441d ("kbuild: Use -fzero-init-padding-bits=all"),
the kernel has enabled -fzero-init-padding-bits=all to zero padding bits
in unions and structures.  This commit applies the same option for tools
building.

The option is not supported by any version older than GCC 15, nor is it
supported by LLVM.  This patch adds the cc-option and host-cc-option
functions to dynamically detect compiler option and append it to the
EXTRA_CFLAGS and HOST_EXTRACFLAGS respectively.

[1] https://gcc.gnu.org/gcc-15/changes.html

Acked-by: Quentin Monnet <qmo@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/scripts/Makefile.include | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index 41971a68972dda218714d6b95b1d9d92349285c3..17d24cf84051ae99eb5b4c4bdfda43cd187891f6 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -139,6 +139,36 @@ else
 EXTRA_WARNINGS += -Wshadow
 endif
 
+# output directory for tests below
+TMPOUT = .tmp_$$$$
+
+# try-run
+# Usage: option = $(call try-run, $(CC)...-o "$$TMP",option-ok,otherwise)
+# Exit code chooses option. "$$TMP" serves as a temporary file and is
+# automatically cleaned up.
+try-run = $(shell set -e;		\
+	TMP=$(TMPOUT)/tmp;		\
+	trap "rm -rf $(TMPOUT)" EXIT;	\
+	mkdir -p $(TMPOUT);		\
+	if ($(1)) >/dev/null 2>&1;	\
+	then echo "$(2)";		\
+	else echo "$(3)";		\
+	fi)
+
+# cc-option
+# Usage: CFLAGS += $(call cc-option,-march=winchip-c6,-march=i586)
+cc-option = $(call try-run, \
+	$(CC) -Werror $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2))
+
+host-cc-option = $(call try-run, \
+	$(HOSTCC) -Werror $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2))
+
+# Explicitly clear padding bits with the initializer '{ 0 }'
+FLAG_ZERO_INIT := $(call cc-option,-fzero-init-padding-bits=all)
+override EXTRA_CFLAGS += $(FLAG_ZERO_INIT)
+HOST_FLAG_ZERO_INIT := $(call host-cc-option,-fzero-init-padding-bits=all)
+override HOST_EXTRACFLAGS += $(HOST_FLAG_ZERO_INIT)
+
 ifneq ($(findstring $(MAKEFLAGS), w),w)
 PRINT_DIR = --no-print-directory
 else

-- 
2.34.1

[PATCH v7 07/23] perf build: Append extra host flags

[Leo Yan]

Append HOST_EXTRACFLAGS to HOST_CFLAGS so that additional flags can be
applied to the host compiler.

Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/perf/Makefile.config | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 333ddd0e4bd814e9b935e9f706e640baccf49b7e..17c27b876551922a537dc0e1000d396c43ff9e12 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -17,7 +17,7 @@ detected     = $(shell echo "$(1)=y"       >> $(OUTPUT).config-detected)
 detected_var = $(shell echo "$(1)=$($(1))" >> $(OUTPUT).config-detected)
 
 CFLAGS := $(EXTRA_CFLAGS) $(filter-out -Wnested-externs,$(EXTRA_WARNINGS))
-HOSTCFLAGS := $(filter-out -Wnested-externs,$(EXTRA_WARNINGS))
+HOSTCFLAGS := $(HOST_EXTRACFLAGS) $(filter-out -Wnested-externs,$(EXTRA_WARNINGS))
 
 # This is required because the kernel is built with this and some of the code
 # borrowed from kernel headers depends on it, e.g. put_unaligned_*().

-- 
2.34.1

[PATCH v7 08/23] tools build: Append extra host CFLAGS for fixdep

[Leo Yan]

tools/scripts/Makefile.include can add host compiler options through
HOST_EXTRACFLAGS. Make sure the tools build uses those flags when building
fixdep.

Create a local HOST_CFLAGS variable from KBUILD_HOSTCFLAGS and
HOST_EXTRACFLAGS, and pass it to the fixdep build.

Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/build/Makefile | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/tools/build/Makefile b/tools/build/Makefile
index 3a5a3808ab2a1dedd40f35ea322913e8a0788130..2761f80df7611c4731ef1d4529cae7dfe279bad0 100644
--- a/tools/build/Makefile
+++ b/tools/build/Makefile
@@ -40,18 +40,20 @@ endif
 FIXDEP		:= $(OUTPUT)fixdep
 FIXDEP_IN	:= $(OUTPUT)fixdep-in.o
 
+HOST_CFLAGS	:= $(KBUILD_HOSTCFLAGS) $(HOST_EXTRACFLAGS)
+
 # To track fixdep's dependencies properly, fixdep needs to run on itself.
 # Build it twice the first time.
 $(FIXDEP_IN): FORCE
 	$(Q)if [ ! -f $(FIXDEP) ]; then						\
-		$(MAKE) $(build)=fixdep HOSTCFLAGS="$(KBUILD_HOSTCFLAGS)";	\
+		$(MAKE) $(build)=fixdep HOSTCFLAGS="$(HOST_CFLAGS)";		\
 		rm -f $(FIXDEP).o;						\
 	fi
-	$(Q)$(MAKE) $(build)=fixdep HOSTCFLAGS="$(KBUILD_HOSTCFLAGS)"
+	$(Q)$(MAKE) $(build)=fixdep HOSTCFLAGS="$(HOST_CFLAGS)"
 
 
 $(FIXDEP): $(FIXDEP_IN)
-	$(QUIET_LINK)$(HOSTCC) $(FIXDEP_IN) $(KBUILD_HOSTLDFLAGS) -o $@
+	$(QUIET_LINK)$(HOSTCC) $(FIXDEP_IN) $(HOST_CFLAGS) -o $@
 
 FORCE:
 

-- 
2.34.1

[PATCH v7 09/23] tools: bootconfig: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/bootconfig/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/bootconfig/Makefile b/tools/bootconfig/Makefile
index 90eb47c9d8de67b0ccc74a8de0af3a7e0b97feeb..4490df707585acf356153b78cb87760f622a6190 100644
--- a/tools/bootconfig/Makefile
+++ b/tools/bootconfig/Makefile
@@ -11,6 +11,7 @@ endif
 
 LIBSRC = $(srctree)/lib/bootconfig.c $(srctree)/include/linux/bootconfig.h
 override CFLAGS += -Wall -g -I$(CURDIR)/include
+override CFLAGS += $(EXTRA_CFLAGS)
 
 ALL_TARGETS := bootconfig
 ALL_PROGRAMS := $(patsubst %,$(OUTPUT)%,$(ALL_TARGETS))

-- 
2.34.1

[PATCH v7 10/23] tools: counter: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/counter/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/counter/Makefile b/tools/counter/Makefile
index d82d35a520f610260abb43f6ae28e56d73268231..1495c0e03d9c00653a24bc92b24d83340dbb4909 100644
--- a/tools/counter/Makefile
+++ b/tools/counter/Makefile
@@ -14,6 +14,7 @@ MAKEFLAGS += -r
 
 override CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include \
 	 -I$(srctree)/tools/include
+override CFLAGS += $(EXTRA_CFLAGS)
 
 ALL_TARGETS := counter_example counter_watch_events
 ALL_PROGRAMS := $(patsubst %,$(OUTPUT)%,$(ALL_TARGETS))

-- 
2.34.1

[PATCH v7 11/23] tools: dma: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

Acked-by: Qinxin Xia <xiaqinxin@huawei.com>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/dma/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/dma/Makefile b/tools/dma/Makefile
index e4abf37bf020ca613b6dca340299198cb887126a..86d3d2e361110b664b885c0e9423660a2d5e8221 100644
--- a/tools/dma/Makefile
+++ b/tools/dma/Makefile
@@ -17,6 +17,7 @@ endif
 MAKEFLAGS += -r
 
 override CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include
+override CFLAGS += $(EXTRA_CFLAGS)
 
 ALL_TARGETS := dma_map_benchmark
 ALL_PROGRAMS := $(patsubst %,$(OUTPUT)%,$(ALL_TARGETS))

-- 
2.34.1

[PATCH v7 12/23] tools: gpio: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

Acked-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/gpio/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/gpio/Makefile b/tools/gpio/Makefile
index 342e056c8c665ac075041ff7c7ca7ba94c691187..05a0057ec361626f41ca87e5295691364f03d2cb 100644
--- a/tools/gpio/Makefile
+++ b/tools/gpio/Makefile
@@ -17,6 +17,7 @@ endif
 MAKEFLAGS += -r
 
 override CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include
+override CFLAGS += $(EXTRA_CFLAGS)
 
 ALL_TARGETS := lsgpio gpio-hammer gpio-event-mon gpio-watch
 ALL_PROGRAMS := $(patsubst %,$(OUTPUT)%,$(ALL_TARGETS))

-- 
2.34.1

[PATCH v7 13/23] tools: hv: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/hv/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/hv/Makefile b/tools/hv/Makefile
index 016753f3dd7f61e88d91dd5dc939ad66f8485acc..9a141d1a80d7b0e2b971d5a4adf67e2e7a65d3f0 100644
--- a/tools/hv/Makefile
+++ b/tools/hv/Makefile
@@ -18,6 +18,7 @@ MAKEFLAGS += -r
 
 override CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include
 override CFLAGS += -Wno-address-of-packed-member
+override CFLAGS += $(EXTRA_CFLAGS)
 
 ALL_TARGETS := hv_kvp_daemon hv_vss_daemon
 ifneq ($(filter x86_64 x86,$(ARCH)),)

-- 
2.34.1

[PATCH v7 14/23] tools: iio: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

Acked-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/iio/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/iio/Makefile b/tools/iio/Makefile
index 3bcce0b7d10f42208765be83dac047faa2e0ceb1..f0428421792d1cbe5ff71b01b67f23eb908fa714 100644
--- a/tools/iio/Makefile
+++ b/tools/iio/Makefile
@@ -13,6 +13,7 @@ endif
 MAKEFLAGS += -r
 
 override CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include
+override CFLAGS += $(EXTRA_CFLAGS)
 
 ALL_TARGETS := iio_event_monitor lsiio iio_generic_buffer
 ALL_PROGRAMS := $(patsubst %,$(OUTPUT)%,$(ALL_TARGETS))

-- 
2.34.1

[PATCH v7 15/23] tools: mm: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/mm/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/mm/Makefile b/tools/mm/Makefile
index f5725b5c23aa261994b5b42f37c443bee2edebf2..d48491da2edc95fca57c0707c42961fde7b02072 100644
--- a/tools/mm/Makefile
+++ b/tools/mm/Makefile
@@ -10,6 +10,7 @@ LIB_DIR = ../lib/api
 LIBS = $(LIB_DIR)/libapi.a
 
 CFLAGS += -Wall -Wextra -I../lib/ -pthread
+CFLAGS += $(EXTRA_CFLAGS)
 LDFLAGS += $(LIBS) -pthread
 
 all: $(BUILD_TARGETS)

-- 
2.34.1

[PATCH v7 16/23] tools: objtool: Append extra host cflags

[Leo Yan]

Append HOST_EXTRACFLAGS to HOSTCFLAGS so that additional flags can be
applied to the host compiler.

Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/objtool/Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index b71d1886022e9b3d9fde52bf73bd502aa20d173e..182d0ab47a6ce8925ec8618f337d2664965b6c9c 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -11,6 +11,8 @@ ifeq ($(SRCARCH),loongarch)
 	BUILD_ORC	   := y
 endif
 
+HOSTCFLAGS += $(HOST_EXTRACFLAGS)
+
 ifeq ($(ARCH_HAS_KLP),y)
 	HAVE_XXHASH = $(shell printf "$(pound)include <xxhash.h>\nXXH3_state_t *state;int main() {}" | \
 		      $(HOSTCC) $(HOSTCFLAGS) -xc - -o /dev/null -lxxhash 2> /dev/null && echo y || echo n)

-- 
2.34.1

[PATCH v7 17/23] tools: power: acpi: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/power/acpi/Makefile.config | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/power/acpi/Makefile.config b/tools/power/acpi/Makefile.config
index cd7106876a5f39dfda38e286c54c3a7c268b34a2..11088deab42ee5a793f978feb9f4f7bb7024c48c 100644
--- a/tools/power/acpi/Makefile.config
+++ b/tools/power/acpi/Makefile.config
@@ -69,6 +69,7 @@ KERNEL_INCLUDE := $(OUTPUT)include
 ACPICA_INCLUDE := $(srctree)/../../../drivers/acpi/acpica
 CFLAGS += -D_LINUX -I$(KERNEL_INCLUDE) -I$(ACPICA_INCLUDE)
 CFLAGS += $(WARNINGS)
+CFLAGS += $(EXTRA_CFLAGS)
 MKDIR = mkdir
 
 ifeq ($(strip $(V)),false)

-- 
2.34.1

[PATCH v7 18/23] tools: power: x86/intel-speed-select: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/power/x86/intel-speed-select/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/power/x86/intel-speed-select/Makefile b/tools/power/x86/intel-speed-select/Makefile
index 6b299aae2ded89c3a70a3649996e258b98001ee7..5947afce9fde7c054647fa3ee0c661b60b863f29 100644
--- a/tools/power/x86/intel-speed-select/Makefile
+++ b/tools/power/x86/intel-speed-select/Makefile
@@ -20,6 +20,7 @@ NL3_CFLAGS = -I/usr/include/libnl3
 endif
 
 override CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include $(NL3_CFLAGS)
+override CFLAGS += $(EXTRA_CFLAGS)
 override LDFLAGS += -lnl-genl-3 -lnl-3
 
 ALL_TARGETS := intel-speed-select

-- 
2.34.1

[PATCH v7 19/23] tools: sched_ext: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/sched_ext/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/sched_ext/Makefile b/tools/sched_ext/Makefile
index 21554f0896923fa9c2e5b98c85d65d964152e592..e0d705b2fe0ca763fece5137ea43ccb776d18012 100644
--- a/tools/sched_ext/Makefile
+++ b/tools/sched_ext/Makefile
@@ -92,6 +92,7 @@ endif
 CFLAGS += -g -O2 -rdynamic -pthread -Wall -Werror $(GENFLAGS)			\
 	  -I$(INCLUDE_DIR) -I$(GENDIR) -I$(LIBDIR)				\
 	  -I$(TOOLSINCDIR) -I$(APIDIR) -I$(CURDIR)/include
+CFLAGS += $(EXTRA_CFLAGS)
 
 # Silence some warnings when compiled with clang
 ifneq ($(LLVM),)

-- 
2.34.1

[PATCH v7 20/23] tools: spi: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/spi/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/spi/Makefile b/tools/spi/Makefile
index 7fccd245a53515ab019529c8e5e91a044eaaa68b..82f9bc6365911b962422633147b108fabc70a2db 100644
--- a/tools/spi/Makefile
+++ b/tools/spi/Makefile
@@ -13,6 +13,7 @@ endif
 MAKEFLAGS += -r
 
 CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include
+CFLAGS += $(EXTRA_CFLAGS)
 
 ALL_TARGETS := spidev_test spidev_fdx
 ALL_PROGRAMS := $(patsubst %,$(OUTPUT)%,$(ALL_TARGETS))

-- 
2.34.1

[PATCH v7 21/23] tools: tracing: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/tracing/latency/Makefile | 1 +
 tools/tracing/rtla/Makefile    | 1 +
 2 files changed, 2 insertions(+)

diff --git a/tools/tracing/latency/Makefile b/tools/tracing/latency/Makefile
index 257a56b1899f23837de533353e9c2cebdb6035bd..d32a6a13753035355f0e3a05bf88870b8aa55f64 100644
--- a/tools/tracing/latency/Makefile
+++ b/tools/tracing/latency/Makefile
@@ -57,6 +57,7 @@ ifeq ($(config),1)
 endif
 
 CFLAGS		+= $(INCLUDES) $(LIB_INCLUDES)
+CFLAGS		+= $(EXTRA_CFLAGS)
 
 export CFLAGS OUTPUT srctree
 
diff --git a/tools/tracing/rtla/Makefile b/tools/tracing/rtla/Makefile
index 45690ee14544dfb9648dbafe5132b8c46a44d3ea..c8df8cb9baa0ce8671d94977e82591cb63d18b67 100644
--- a/tools/tracing/rtla/Makefile
+++ b/tools/tracing/rtla/Makefile
@@ -67,6 +67,7 @@ ifeq ($(config),1)
 endif
 
 CFLAGS		+= $(INCLUDES) $(LIB_INCLUDES)
+CFLAGS		+= $(EXTRA_CFLAGS)
 
 export CFLAGS OUTPUT srctree
 

-- 
2.34.1

[PATCH v7 22/23] tools: usb: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/usb/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/usb/Makefile b/tools/usb/Makefile
index c6235667dd46223b646bbab5c82c810221750182..42362dcdf2743dace62a5385a7d2707c42bdd3c0 100644
--- a/tools/usb/Makefile
+++ b/tools/usb/Makefile
@@ -14,6 +14,7 @@ endif
 MAKEFLAGS += -r
 
 override CFLAGS += -O2 -Wall -Wextra -g -D_GNU_SOURCE -I$(OUTPUT)include -I$(srctree)/tools/include
+override CFLAGS += $(EXTRA_CFLAGS)
 override LDFLAGS += -lpthread
 
 ALL_TARGETS := testusb ffs-test

-- 
2.34.1

[PATCH v7 23/23] selftests: Include tools Makefile.include

[Leo Yan]

selftests/lib.mk has its own compiler setup instead of using the common
tools build helpers. This duplicates part of the LLVM handling prepared
by tools/scripts/Makefile.include.

Include tools/scripts/Makefile.include from selftests/lib.mk so
selftests reuse the LLVM prefix/suffix validation and the provided
CLANG_CROSS_FLAGS. This improves Clang cross builds, especially when
CROSS_COMPILE is set it can derive --prefix, --sysroot and
--gcc-toolchain flags from the GCC cross toolchain.

Keep the $(CLANG_TARGET_FLAGS_$(ARCH)) target flag as a fallback when
CLANG_CROSS_FLAGS is empty, and append EXTRA_CFLAGS to the selftest.

Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/testing/selftests/lib.mk | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk
index f02cc8a2e4ae322d65a031178013270922611c42..e2e2d8aa57280ffd37bced18ecd43e7a5566abae 100644
--- a/tools/testing/selftests/lib.mk
+++ b/tools/testing/selftests/lib.mk
@@ -1,11 +1,17 @@
 # This mimics the top-level Makefile. We do it explicitly here so that this
 # Makefile can operate with or without the kbuild infrastructure.
-ifneq ($(LLVM),)
-ifneq ($(filter %/,$(LLVM)),)
-LLVM_PREFIX := $(LLVM)
-else ifneq ($(filter -%,$(LLVM)),)
-LLVM_SUFFIX := $(LLVM)
+ifeq (0,$(MAKELEVEL))
+    ifeq ($(OUTPUT),)
+	OUTPUT := $(shell pwd)
+	DEFAULT_INSTALL_HDR_PATH := 1
+    endif
 endif
+selfdir = $(realpath $(dir $(filter %/lib.mk,$(MAKEFILE_LIST))))
+top_srcdir = $(selfdir)/../../..
+
+include $(top_srcdir)/tools/scripts/Makefile.include
+
+ifneq ($(LLVM),)
 
 CLANG := $(LLVM_PREFIX)clang$(LLVM_SUFFIX)
 
@@ -35,7 +41,8 @@ else
 CLANG_FLAGS     += --target=$(CLANG_TARGET_FLAGS)
 endif # CLANG_TARGET_FLAGS
 else
-CLANG_FLAGS     += --target=$(notdir $(CROSS_COMPILE:%-=%))
+# CLANG_CROSS_FLAGS comes from Makefile.include
+CLANG_FLAGS     += $(CLANG_CROSS_FLAGS)
 endif # CROSS_COMPILE
 
 # gcc defaults to silence (off) for the following warnings, but clang defaults
@@ -51,15 +58,6 @@ else
 CC := $(CROSS_COMPILE)gcc
 endif # LLVM
 
-ifeq (0,$(MAKELEVEL))
-    ifeq ($(OUTPUT),)
-	OUTPUT := $(shell pwd)
-	DEFAULT_INSTALL_HDR_PATH := 1
-    endif
-endif
-selfdir = $(realpath $(dir $(filter %/lib.mk,$(MAKEFILE_LIST))))
-top_srcdir = $(selfdir)/../../..
-
 # msg: emit succinct information message describing current building step
 # $1 - generic step name (e.g., CC, LINK, etc);
 # $2 - optional "flavor" specifier; if provided, will be emitted as [flavor];
@@ -202,6 +200,8 @@ CFLAGS += -D_GNU_SOURCE=
 # Additional include paths needed by kselftest.h and local headers
 CFLAGS += -I${top_srcdir}/tools/testing/selftests
 
+CFLAGS += $(EXTRA_CFLAGS)
+
 # Enables to extend CFLAGS and LDFLAGS from command line, e.g.
 # make USERCFLAGS=-Werror USERLDFLAGS=-static
 CFLAGS += $(USERCFLAGS)

-- 
2.34.1

Re: [PATCH v7 02/23] tools/thermal: Fix typo

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Fixing the `CFGLAS` typo to `CFLAGS` introduces linker flags (`-Wl,-lthermal` and `-Wl,-L.`) into the C compilation phase (`CFLAGS`). This breaks the build under Clang because the unused linker arguments during the `-c` compilation step trigger a warning that is turned into a fatal error by `-Werror`. Furthermore, these flags are useless because `CFLAGS` is not even passed to the `$(CC) --shared` link step in these Makefiles.
--

commit 93498abb92499dd9b72fc403e55f192942d97b46
Author: Leo Yan <leo.yan@arm.com>

tools/thermal: Fix typo

This commit fixes a typo in the tools/thermal/lib/Makefile, changing CFGLAS
to CFLAGS for the thermal library linker flags.

> diff --git a/tools/thermal/lib/Makefile b/tools/thermal/lib/Makefile
> --- a/tools/thermal/lib/Makefile
> +++ b/tools/thermal/lib/Makefile
> @@ -60,8 +60,8 @@ override CFLAGS += $(EXTRA_WARNINGS)
>  override CFLAGS += -Werror -Wall
>  override CFLAGS += -fPIC
>  override CFLAGS += $(INCLUDES)
> -override CFGLAS += -Wl,-L.
> -override CFGLAS += -Wl,-lthermal
> +override CFLAGS += -Wl,-L.
> +override CFLAGS += -Wl,-lthermal

[Severity: Low]
Does adding these linker flags into the C compilation phase break the build
when compiling with Clang?

Since the Makefile also specifies -Werror, passing -Wl,-lthermal and -Wl,-L.
during the C compilation step might trigger a fatal unused argument warning
under Clang. 

Are these linker flags actually needed in CFLAGS, or should they be added to
LDFLAGS instead, considering CFLAGS doesn't appear to be passed to the shared
link step?

Also, does the prior commit in this series introduce this same behavior in
tools/lib/thermal/Makefile by fixing an identical typo?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260602-tools_build_fix_zero_init-v7-0-631baf679fe7@arm.com?part=2

Re: [PATCH v7 01/23] tools: lib: thermal: Fix typo

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Fixing the 'CFGLAS' typo activates logically incorrect linker flags inside the compiler flags (CFLAGS), injecting them into the object compilation step.
--

commit 783a6df50ce2cf932c85a46af96705ee016835e4
Author: Leo Yan <leo.yan@arm.com>

tools: lib: thermal: Fix typo

This commit fixes a typo in tools/lib/thermal/Makefile by replacing
CFGLAS with CFLAGS for the linker flags.

> diff --git a/tools/lib/thermal/Makefile b/tools/lib/thermal/Makefile
> --- a/tools/lib/thermal/Makefile
> +++ b/tools/lib/thermal/Makefile
> @@ -66,8 +66,8 @@ override CFLAGS += -fPIC
>  override CFLAGS += $(NL3_CFLAGS)
>  override CFLAGS += $(INCLUDES)
>  override CFLAGS += -fvisibility=hidden
> -override CFGLAS += -Wl,-L.
> -override CFGLAS += -Wl,-lthermal
> +override CFLAGS += -Wl,-L.
> +override CFLAGS += -Wl,-lthermal

[Severity: Low]
Does this activate logically incorrect linker flags?

By fixing the typo, the linker flags -Wl,-L. and -Wl,-lthermal are now injected
into CFLAGS. Linker flags do not belong in CFLAGS, which is used for compiling
object files. Furthermore, instructing libthermal to link against itself while
it is being built is conceptually a circular dependency.

While GCC silently ignores these flags during object compilation, their
presence in CFLAGS causes Clang to emit -Wunused-command-line-argument
warnings. Because the Makefile enforces -Werror, this newly introduced logical
error breaks the build for Clang users.

Should these two lines be deleted entirely instead of renaming the variable?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260602-tools_build_fix_zero_init-v7-0-631baf679fe7@arm.com?part=1

Re: [PATCH v7 03/23] tools: lib: thermal: Initialize CFLAGS before including Makefile.include

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] This problem wasn't introduced by this patch, but the fix for the CFLAGS initialization order completely missed `tools/lib/bpf/Makefile`. This leaves it vulnerable to the `EXTRA_CFLAGS` expansion introduced later in the series.
--

commit d569bb22d825610f92ca0c5003854cd0736f3058
Author: Leo Yan <leo.yan@arm.com>

tools: lib: thermal: Initialize CFLAGS before including Makefile.include

This commit prepares the thermal lib Makefile for future changes to
tools/scripts/Makefile.include that may expand EXTRA_CFLAGS. It moves
the CFLAGS initialization before the include to ensure default compiler
options like -g and -Wall are not silently dropped.

> diff --git a/tools/lib/thermal/Makefile b/tools/lib/thermal/Makefile
> index 09d8f4ba6a0ab..b55fa42cefa47 100644
> --- a/tools/lib/thermal/Makefile
> +++ b/tools/lib/thermal/Makefile
> @@ -23,6 +23,14 @@ INSTALL = install
>  DESTDIR ?=
>  DESTDIR_SQ = '$(subst ','\'',$(DESTDIR))'
>  
> +# Defer assigning EXTRA_CFLAGS to CFLAGS until after including
> +# tools/scripts/Makefile.include, as it may add flags to EXTRA_CFLAGS.
> +ifdef EXTRA_CFLAGS
> +  CFLAGS :=
> +else
> +  CFLAGS := -g -Wall
> +endif

[Severity: High]
This is a pre-existing issue, but it looks like this same vulnerable CFLAGS 
initialization order exists in tools/lib/bpf/Makefile.

Since a later patch in this series unconditionally populates EXTRA_CFLAGS 
via Makefile.include, does this mean libbpf will skip its default 
initialization and build without optimizations?

tools/lib/bpf/Makefile:
    ...
    include $(srctree)/tools/scripts/Makefile.include
    ...
    ifdef EXTRA_CFLAGS
      CFLAGS := $(EXTRA_CFLAGS)
    else
      CFLAGS := -g -O2
    endif

Should tools/lib/bpf/Makefile also be updated in this series to prevent 
a performance regression in libbpf?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260602-tools_build_fix_zero_init-v7-0-631baf679fe7@arm.com?part=3

Re: [PATCH v7 08/23] tools build: Append extra host CFLAGS for fixdep

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] The link step for `fixdep` replaces `KBUILD_HOSTLDFLAGS` with `HOST_CFLAGS`, unintentionally dropping all host linker flags.
--

commit fdc8f23a99f210f1577aab161879510c7af15c47
Author: Leo Yan <leo.yan@arm.com>

tools build: Append extra host CFLAGS for fixdep

This commit introduces a local HOST_CFLAGS variable that combines
KBUILD_HOSTCFLAGS and HOST_EXTRACFLAGS, and passes it to the fixdep build
process to ensure host compiler options are included.

> diff --git a/tools/build/Makefile b/tools/build/Makefile
> index 3a5a3808ab2a1..2761f80df7611 100644
> --- a/tools/build/Makefile
> +++ b/tools/build/Makefile

[ ... ]

>  $(FIXDEP): $(FIXDEP_IN)
> -	$(QUIET_LINK)$(HOSTCC) $(FIXDEP_IN) $(KBUILD_HOSTLDFLAGS) -o $@
> +	$(QUIET_LINK)$(HOSTCC) $(FIXDEP_IN) $(HOST_CFLAGS) -o $@

[Severity: Low]
Does this unintentionally drop the host linker flags? 

By replacing KBUILD_HOSTLDFLAGS with HOST_CFLAGS during the link step for
the fixdep executable, we might be missing required linker flags like LFS
options or custom library paths. 

Should this step retain KBUILD_HOSTLDFLAGS instead of or in addition to
HOST_CFLAGS when generating the binary?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260602-tools_build_fix_zero_init-v7-0-631baf679fe7@arm.com?part=8

Re: [PATCH v7 05/23] selftests/nolibc: Use a dedicated cross cc-option helper

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Renaming `cc-option` to `cross-cc-option` in `Makefile.nolibc` breaks compiler flag probing in `Makefile.include` during cross-builds with Clang.
--

commit 2287b14b38d381104f1caab4547ea009ec49cae7
Author: Leo Yan <leo.yan@arm.com>

selftests/nolibc: Use a dedicated cross cc-option helper

This commit renames the nolibc cc-option helper to cross-cc-option to ensure
CLANG_CROSS_FLAGS is used for architecture-specific flag probes. This keeps
cross-build checks explicit and avoids clashing with the common tools helper.

> diff --git a/tools/testing/selftests/nolibc/Makefile.nolibc b/tools/testing/selftests/nolibc/Makefile.nolibc
> --- a/tools/testing/selftests/nolibc/Makefile.nolibc
> +++ b/tools/testing/selftests/nolibc/Makefile.nolibc
> @@ -23,7 +23,7 @@ include $(srctree)/scripts/subarch.include
>  ARCH = $(SUBARCH)
>  endif
>  
> -cc-option = $(call __cc-option, $(CC),$(CLANG_CROSS_FLAGS),$(1),$(2))
> +cross-cc-option = $(call __cc-option, $(CC),$(CLANG_CROSS_FLAGS),$(1),$(2))

[Severity: Medium]
Does this change break compiler flag probing in Makefile.include during
cross-builds with Clang?

Since cc-option is no longer overridden to include $(CLANG_CROSS_FLAGS) here,
uses of cc-option in Makefile.include will fall back to the generic cc-option
defined in scripts/Makefile.compiler.

For example, Makefile.include evaluates:

__CFLAGS_STACKPROTECTOR = $(call cc-option,-fstack-protector-all) \
    $(call cc-option,-mstack-protector-guard=global)

Because CC is left as just clang without any target flags in this context,
the generic cc-option will probe the host compiler instead of the target
compiler. Could this discard valid target flags if the host doesn't support
them, altering test coverage and breaking feature enablement for the nolibc
test suite?

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260602-tools_build_fix_zero_init-v7-0-631baf679fe7@arm.com?part=5

Re: [PATCH v7 06/23] tools build: Append -fzero-init-padding-bits=all to extra cflags

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] The `try-run` macro attempts to create a temporary directory in the source tree, breaking out-of-tree builds on read-only filesystems.
- [High] Unconditionally appending to `EXTRA_CFLAGS` in `Makefile.include` breaks `libbpf`'s default compilation flags, causing it to be built without debug info and optimizations.
--

commit e8ede2fdc1b643da62469cb30003522715558696
Author: Leo Yan <leo.yan@arm.com>
Subject: tools build: Append -fzero-init-padding-bits=all to extra cflags

The kernel has enabled -fzero-init-padding-bits=all to zero padding bits
in unions and structures. This commit applies the same option for tools
building by adding cc-option and host-cc-option to dynamically detect and
append it to EXTRA_CFLAGS and HOST_EXTRACFLAGS.

Link: https://gcc.gnu.org/gcc-15/changes.html

> diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
> index 41971a68972dd..17d24cf84051a 100644
> --- a/tools/scripts/Makefile.include
> +++ b/tools/scripts/Makefile.include
[ ... ]
> @@ -139,6 +139,36 @@ else
>  EXTRA_WARNINGS += -Wshadow
>  endif
>  
> +# output directory for tests below
> +TMPOUT = .tmp_$$$$
> +
> +# try-run
> +# Usage: option = $(call try-run, $(CC)...-o "$$TMP",option-ok,otherwise)
> +# Exit code chooses option. "$$TMP" serves as a temporary file and is
> +# automatically cleaned up.
> +try-run = $(shell set -e;		\
> +	TMP=$(TMPOUT)/tmp;		\
> +	trap "rm -rf $(TMPOUT)" EXIT;	\
> +	mkdir -p $(TMPOUT);		\

[Severity: High]
Does this break out-of-tree builds on read-only filesystems?

Because TMPOUT is hardcoded as .tmp_$$$$ without an $(OUTPUT) prefix,
the mkdir -p command will attempt to write directly to the source directory.

When performing out-of-tree builds (like make O=/path/to/build) on read-only
source trees, this fails with a read-only file system error. Since the
compiler flag uses immediate assignment (:=), this failure might spam the
console and silently drop the option during parsing.

> +	if ($(1)) >/dev/null 2>&1;	\
> +	then echo "$(2)";		\
> +	else echo "$(3)";		\
> +	fi)
> +
[ ... ]
> +host-cc-option = $(call try-run, \
> +	$(HOSTCC) -Werror $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2))
> +
> +# Explicitly clear padding bits with the initializer '{ 0 }'
> +FLAG_ZERO_INIT := $(call cc-option,-fzero-init-padding-bits=all)
> +override EXTRA_CFLAGS += $(FLAG_ZERO_INIT)

[Severity: High]
Will this cause libbpf to lose its default debug and optimization flags?

In tools/lib/bpf/Makefile, there is a conditional block:

ifdef EXTRA_CFLAGS
  CFLAGS := $(EXTRA_CFLAGS)
else
  CFLAGS := -g -O2
endif

Because tools/scripts/Makefile.include is included prior to this check,
EXTRA_CFLAGS will unconditionally contain -fzero-init-padding-bits=all
if supported by the compiler.

This means EXTRA_CFLAGS is always defined, causing libbpf to completely drop
its default -g -O2 flags and compile with only the padding bits flag.

It appears libthermal was fixed to avoid this issue, but is a corresponding
fix needed for libbpf in this patch series?

> +HOST_FLAG_ZERO_INIT := $(call host-cc-option,-fzero-init-padding-bits=all)
> +override HOST_EXTRACFLAGS += $(HOST_FLAG_ZERO_INIT)
> +

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260602-tools_build_fix_zero_init-v7-0-631baf679fe7@arm.com?part=6

Re: [PATCH v7 17/23] tools: power: acpi: Append extra cflags

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] EXTRA_CFLAGS cannot override optimization and debug flags.
--

commit bdc57550350069918185456205e82edb378bafaf
Author: Leo Yan <leo.yan@arm.com>

tools: power: acpi: Append extra cflags

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

> diff --git a/tools/power/acpi/Makefile.config b/tools/power/acpi/Makefile.config
> --- a/tools/power/acpi/Makefile.config
> +++ b/tools/power/acpi/Makefile.config
> @@ -69,6 +69,7 @@ KERNEL_INCLUDE := $(OUTPUT)include
>  ACPICA_INCLUDE := $(srctree)/../../../drivers/acpi/acpica
>  CFLAGS += -D_LINUX -I$(KERNEL_INCLUDE) -I$(ACPICA_INCLUDE)
>  CFLAGS += $(WARNINGS)
> +CFLAGS += $(EXTRA_CFLAGS)

[Severity: Low]
Will appending EXTRA_CFLAGS here prevent it from overriding the default
optimization and debug flags?

Because CFLAGS are evaluated sequentially by the compiler, any flags added
later in the file will override earlier ones. Further down in 
tools/power/acpi/Makefile.config, the optimization flags are appended:

# if DEBUG is enabled, then we do not strip or optimize
ifeq ($(strip $(DEBUG)),true)
	CFLAGS += -O1 -g -DDEBUG
	STRIPCMD = /bin/true -Since_we_are_debugging
else
	CFLAGS += $(OPTIMIZATION) -fomit-frame-pointer
	STRIPCMD = $(STRIP) -s --remove-section=.note --remove-section=.comment
endif

It appears that user-provided optimization overrides (such as passing -O0
in EXTRA_CFLAGS) will be silently overridden by these defaults. Should
EXTRA_CFLAGS be appended after the debug and optimization flags instead?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260602-tools_build_fix_zero_init-v7-0-631baf679fe7@arm.com?part=17

Re: [PATCH v7 23/23] selftests: Include tools Makefile.include

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Including `tools/scripts/Makefile.include` inside `tools/testing/selftests/lib.mk` breaks normal assignments to `EXTRA_CFLAGS` in selftest Makefiles, causing silent loss of compiler flags and test coverage.
--

commit 969534670ab7ca5eb2e61c1ef0a49417bd7e304d
Author: Leo Yan <leo.yan@arm.com>

selftests: Include tools Makefile.include

This commit includes tools/scripts/Makefile.include from selftests/lib.mk
to reuse LLVM cross-build validation and flags. It aims to improve Clang
cross builds by deriving cross-compile options directly from the GCC
cross toolchain.

> diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk
> index f02cc8a2e4ae3..e2e2d8aa57280 100644
> --- a/tools/testing/selftests/lib.mk
> +++ b/tools/testing/selftests/lib.mk
> @@ -1,11 +1,17 @@
[ ... ]
> +selfdir = $(realpath $(dir $(filter %/lib.mk,$(MAKEFILE_LIST))))
> +top_srcdir = $(selfdir)/../../..
> +
> +include $(top_srcdir)/tools/scripts/Makefile.include

[Severity: Medium]
Does including Makefile.include here break EXTRA_CFLAGS assignments in
individual selftest makefiles?

tools/scripts/Makefile.include modifies EXTRA_CFLAGS using the override
directive:

override EXTRA_CFLAGS += $(FLAG_ZERO_INIT)

According to GNU Make semantics, once a variable has been appended using
override, any subsequent normal assignments without override are ignored.

For example, tools/testing/selftests/x86/Makefile attempts to append
flags later:

EXTRA_CFLAGS += -DCAN_BUILD_32

Because of the earlier override, this normal assignment is silently dropped.
Consequently, tests like single_step_syscall.c evaluate #ifdef CAN_BUILD_32
as false in main(), silently skipping 32-bit specific test coverage.

Could this be resolved by either removing the override in Makefile.include
or updating selftest makefiles to also use override for EXTRA_CFLAGS?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260602-tools_build_fix_zero_init-v7-0-631baf679fe7@arm.com?part=23