[PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS

[PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS

[Nathan Chancellor]

Hi all,

Clang can emit a few different warnings when it encounters a flag that it
recognizes but does not support internally. These warnings are elevated to
errors within {as,cc}-option via -Werror to catch unsupported flags that should
not be added to KBUILD_{A,C}FLAGS; see commit c3f0d0bc5b01 ("kbuild, LLVMLinux:
Add -Werror to cc-option to support clang").

If an unsupported flag is unconditionally to KBUILD_{A,C}FLAGS, all subsequent
{as,cc}-option will always fail, preventing supported and even potentially
necessary flags from getting adding to the tool flags.

One would expect these warnings to be visible in the kernel build logs since
they are added to KBUILD_{A,C}FLAGS but unfortunately, these warnings are
hidden with clang's -Qunused-arguments flag, which is added to KBUILD_CPPFLAGS
and used for both compiling and assembling files.

Patches 1-4 address the internal inconsistencies of invoking the assembler
within kbuild by using KBUILD_AFLAGS consistently and using '-x
assembler-with-cpp' over '-x assembler'. This matches how assembly files are
built across the kernel and helps avoid problems in situations where macro
definitions or warning flags are present in KBUILD_AFLAGS, which cause
instances of -Wunused-command-line-argument when the preprocessor is not called
to consume them. There were a couple of places in architecture code where this
change would break things so those are fixed first.

Patches 5-12 clean up warnings that will show up when -Qunused-argument is
dropped. I hope none of these are controversial.

Patch 13 turns two warnings into errors so that the presence of unused flags
cannot be easily ignored.

Patch 14 drops -Qunused-argument. This is done last so that it can be easily
reverted if need be.

This series has seen my personal test framework, which tests several different
configurations and architectures, with LLVM tip of tree (16.0.0). I have done
defconfig, allmodconfig, and allnoconfig builds for arm, arm64, i386, mips,
powerpc, riscv, s390, and x86_64 with GCC 12.2.0 as well but I am hoping the
rest of the test infrastructure will catch any lurking problems.

I would like this series to stay together so that there is no opportunity for
breakage so please consider giving acks so that this can be carried via the
kbuild tree (and many thanks to the people who have already provided such
tags).

---
Changes in v2:
- Pick up tags where provided (thank you everyone!)
- Patch 6 and 9: Clarify that '-s' is a compiler flag that is only relevant to
  the linking phase and remove all mention of the assembler's '-s' flag, as the
  assembler is never directly invoked (Nick, Segher)
- Patch 7: Move '-z noexecstack' into new ldflags-y variable (Nick)
- Patch 8: Reword commit message to explain the problem in a clearer manner
  (Nick)
- Link to v1: https://lore.kernel.org/r/20221228-drop-qunused-arguments-v1-0-658cbc8fc592@kernel.org

---
Nathan Chancellor (12):
      MIPS: Always use -Wa,-msoft-float and eliminate GAS_HAS_SET_HARDFLOAT
      MIPS: Prefer cc-option for additions to cflags
      powerpc: Remove linker flag from KBUILD_AFLAGS
      powerpc/vdso: Remove unused '-s' flag from ASFLAGS
      powerpc/vdso: Improve linker flags
      powerpc/vdso: Remove an unsupported flag from vgettimeofday-32.o with clang
      s390/vdso: Drop unused '-s' flag from KBUILD_AFLAGS_64
      s390/vdso: Drop '-shared' from KBUILD_CFLAGS_64
      s390/purgatory: Remove unused '-MD' and unnecessary '-c' flags
      drm/amd/display: Do not add '-mhard-float' to dml_ccflags for clang
      kbuild: Turn a couple more of clang's unused option warnings into errors
      kbuild: Stop using '-Qunused-arguments' with clang

Nick Desaulniers (2):
      x86/boot/compressed: prefer cc-option for CFLAGS additions
      kbuild: Update assembler calls to use proper flags and language target

 Makefile                                    |  1 -
 arch/mips/Makefile                          | 13 ++-------
 arch/mips/include/asm/asmmacro-32.h         |  4 +--
 arch/mips/include/asm/asmmacro.h            | 42 ++++++++++++++---------------
 arch/mips/include/asm/fpregdef.h            | 14 ----------
 arch/mips/include/asm/mipsregs.h            | 20 +++-----------
 arch/mips/kernel/genex.S                    |  2 +-
 arch/mips/kernel/r2300_fpu.S                |  4 +--
 arch/mips/kernel/r4k_fpu.S                  | 12 ++++-----
 arch/mips/kvm/fpu.S                         |  6 ++---
 arch/mips/loongson2ef/Platform              |  2 +-
 arch/powerpc/Makefile                       |  2 +-
 arch/powerpc/kernel/vdso/Makefile           | 25 +++++++++++------
 arch/s390/kernel/vdso64/Makefile            |  4 +--
 arch/s390/purgatory/Makefile                |  2 +-
 arch/x86/boot/compressed/Makefile           |  2 +-
 drivers/gpu/drm/amd/display/dc/dml/Makefile |  3 ++-
 scripts/Kconfig.include                     |  2 +-
 scripts/Makefile.clang                      |  2 ++
 scripts/Makefile.compiler                   |  8 +++---
 scripts/as-version.sh                       |  2 +-
 21 files changed, 74 insertions(+), 98 deletions(-)
---
base-commit: 88603b6dc419445847923fcb7fe5080067a30f98
change-id: 20221228-drop-qunused-arguments-0c5c7dae54fb

Best regards,
-- 
Nathan Chancellor <nathan@kernel.org>

[PATCH v2 01/14] x86/boot/compressed: prefer cc-option for CFLAGS additions

[Nathan Chancellor]

From: Nick Desaulniers <ndesaulniers@google.com>

as-option tests new options using KBUILD_CFLAGS, which causes problems
when using as-option to update KBUILD_AFLAGS because many compiler
options are not valid assembler options.

This will be fixed in a follow up patch. Before doing so, move the
assembler test for -Wa,-mrelax-relocations=no from using as-option to
cc-option.

Link: https://lore.kernel.org/llvm/CAK7LNATcHt7GcXZ=jMszyH=+M_LC9Qr6yeAGRCBbE6xriLxtUQ@mail.gmail.com/
Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
Cc: tglx@linutronix.de
Cc: mingo@redhat.com
Cc: bp@alien8.de
Cc: dave.hansen@linux.intel.com
Cc: x86@kernel.org
---
 arch/x86/boot/compressed/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 1acff356d97a..6b6cfe607bdb 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -50,7 +50,7 @@ KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
 KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
 KBUILD_CFLAGS += -D__DISABLE_EXPORTS
 # Disable relocation relaxation in case the link is not PIE.
-KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no)
+KBUILD_CFLAGS += $(call cc-option,-Wa$(comma)-mrelax-relocations=no)
 KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
 
 # sev.c indirectly inludes inat-table.h which is generated during

-- 
2.39.0

[PATCH v2 02/14] MIPS: Always use -Wa,-msoft-float and eliminate GAS_HAS_SET_HARDFLOAT

[Nathan Chancellor]

-Wa,-msoft-float is tested with as-option, which will be a problem for
clang with an upcoming change to move as-option to use KBUILD_AFLAGS
instead of KBUILD_CFLAGS due to a lack of '-mno-abicalls' in
KBUILD_AFLAGS at the point that this check occurs; $(cflags-y) is added
to KBUILD_AFLAGS towards the end of this file.

  clang: error: ignoring '-fno-PIE' option as it cannot be used with implicit usage of -mabicalls and the N64 ABI [-Werror,-Woption-ignored]

This could be resolved by switching to a cc-option check but
'$(cflags-y)' would need to be added so that '-mno-abicalls' is present
for the test. However, this check is no longer necessary, as
-msoft-float is supported by all supported assembler versions (GNU as
2.25+ and LLVM 11+). Eliminate GAS_HAS_SET_HARDFLOAT and all of its
uses, inlining SET_HARDFLOAT where necessary.

Link: https://lore.kernel.org/202209101939.bvk64Fok-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
Cc: linux-mips@vger.kernel.org
---
 arch/mips/Makefile                  | 11 +---------
 arch/mips/include/asm/asmmacro-32.h |  4 ++--
 arch/mips/include/asm/asmmacro.h    | 42 ++++++++++++++++++-------------------
 arch/mips/include/asm/fpregdef.h    | 14 -------------
 arch/mips/include/asm/mipsregs.h    | 20 ++++--------------
 arch/mips/kernel/genex.S            |  2 +-
 arch/mips/kernel/r2300_fpu.S        |  4 ++--
 arch/mips/kernel/r4k_fpu.S          | 12 +++++------
 arch/mips/kvm/fpu.S                 |  6 +++---
 9 files changed, 40 insertions(+), 75 deletions(-)

diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index 490dea07d4e0..a00a6d94e16f 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -95,7 +95,7 @@ all-$(CONFIG_SYS_SUPPORTS_ZBOOT)+= vmlinuz
 # crossformat linking we rely on the elf2ecoff tool for format conversion.
 #
 cflags-y			+= -G 0 -mno-abicalls -fno-pic -pipe
-cflags-y			+= -msoft-float
+cflags-y			+= -msoft-float -Wa,-msoft-float
 LDFLAGS_vmlinux			+= -G 0 -static -n -nostdlib
 KBUILD_AFLAGS_MODULE		+= -mlong-calls
 KBUILD_CFLAGS_MODULE		+= -mlong-calls
@@ -104,15 +104,6 @@ ifeq ($(CONFIG_RELOCATABLE),y)
 LDFLAGS_vmlinux			+= --emit-relocs
 endif
 
-#
-# pass -msoft-float to GAS if it supports it.  However on newer binutils
-# (specifically newer than 2.24.51.20140728) we then also need to explicitly
-# set ".set hardfloat" in all files which manipulate floating point registers.
-#
-ifneq ($(call as-option,-Wa$(comma)-msoft-float,),)
-	cflags-y		+= -DGAS_HAS_SET_HARDFLOAT -Wa,-msoft-float
-endif
-
 cflags-y += -ffreestanding
 
 cflags-$(CONFIG_CPU_BIG_ENDIAN)		+= -EB
diff --git a/arch/mips/include/asm/asmmacro-32.h b/arch/mips/include/asm/asmmacro-32.h
index 1c08c1f7903c..83a4940b7c89 100644
--- a/arch/mips/include/asm/asmmacro-32.h
+++ b/arch/mips/include/asm/asmmacro-32.h
@@ -15,7 +15,7 @@
 
 	.macro	fpu_save_single thread tmp=t0
 	.set push
-	SET_HARDFLOAT
+	.set hardfloat
 	cfc1	\tmp,  fcr31
 	s.d	$f0,  THREAD_FPR0(\thread)
 	s.d	$f2,  THREAD_FPR2(\thread)
@@ -39,7 +39,7 @@
 
 	.macro	fpu_restore_single thread tmp=t0
 	.set push
-	SET_HARDFLOAT
+	.set hardfloat
 	lw	\tmp, THREAD_FCR31(\thread)
 	l.d	$f0,  THREAD_FPR0(\thread)
 	l.d	$f2,  THREAD_FPR2(\thread)
diff --git a/arch/mips/include/asm/asmmacro.h b/arch/mips/include/asm/asmmacro.h
index ca83ada7015f..1c4438f3f2ab 100644
--- a/arch/mips/include/asm/asmmacro.h
+++ b/arch/mips/include/asm/asmmacro.h
@@ -83,7 +83,7 @@
 
 	.macro	fpu_save_16even thread tmp=t0
 	.set	push
-	SET_HARDFLOAT
+	.set	hardfloat
 	cfc1	\tmp, fcr31
 	sdc1	$f0,  THREAD_FPR0(\thread)
 	sdc1	$f2,  THREAD_FPR2(\thread)
@@ -109,7 +109,7 @@
 	.set	push
 	.set	mips64r2
 	.set	fp=64
-	SET_HARDFLOAT
+	.set	hardfloat
 	sdc1	$f1,  THREAD_FPR1(\thread)
 	sdc1	$f3,  THREAD_FPR3(\thread)
 	sdc1	$f5,  THREAD_FPR5(\thread)
@@ -142,7 +142,7 @@
 
 	.macro	fpu_restore_16even thread tmp=t0
 	.set	push
-	SET_HARDFLOAT
+	.set	hardfloat
 	lw	\tmp, THREAD_FCR31(\thread)
 	ldc1	$f0,  THREAD_FPR0(\thread)
 	ldc1	$f2,  THREAD_FPR2(\thread)
@@ -168,7 +168,7 @@
 	.set	push
 	.set	mips64r2
 	.set	fp=64
-	SET_HARDFLOAT
+	.set	hardfloat
 	ldc1	$f1,  THREAD_FPR1(\thread)
 	ldc1	$f3,  THREAD_FPR3(\thread)
 	ldc1	$f5,  THREAD_FPR5(\thread)
@@ -373,7 +373,7 @@
 	.macro	_cfcmsa	rd, cs
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	insn_if_mips 0x787e0059 | (\cs << 11)
 	insn32_if_mm 0x587e0056 | (\cs << 11)
 	move	\rd, $1
@@ -383,7 +383,7 @@
 	.macro	_ctcmsa	cd, rs
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	move	$1, \rs
 	insn_if_mips 0x783e0819 | (\cd << 6)
 	insn32_if_mm 0x583e0816 | (\cd << 6)
@@ -393,7 +393,7 @@
 	.macro	ld_b	wd, off, base
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	PTR_ADDU $1, \base, \off
 	insn_if_mips 0x78000820 | (\wd << 6)
 	insn32_if_mm 0x58000807 | (\wd << 6)
@@ -403,7 +403,7 @@
 	.macro	ld_h	wd, off, base
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	PTR_ADDU $1, \base, \off
 	insn_if_mips 0x78000821 | (\wd << 6)
 	insn32_if_mm 0x58000817 | (\wd << 6)
@@ -413,7 +413,7 @@
 	.macro	ld_w	wd, off, base
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	PTR_ADDU $1, \base, \off
 	insn_if_mips 0x78000822 | (\wd << 6)
 	insn32_if_mm 0x58000827 | (\wd << 6)
@@ -423,7 +423,7 @@
 	.macro	ld_d	wd, off, base
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	PTR_ADDU $1, \base, \off
 	insn_if_mips 0x78000823 | (\wd << 6)
 	insn32_if_mm 0x58000837 | (\wd << 6)
@@ -433,7 +433,7 @@
 	.macro	st_b	wd, off, base
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	PTR_ADDU $1, \base, \off
 	insn_if_mips 0x78000824 | (\wd << 6)
 	insn32_if_mm 0x5800080f | (\wd << 6)
@@ -443,7 +443,7 @@
 	.macro	st_h	wd, off, base
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	PTR_ADDU $1, \base, \off
 	insn_if_mips 0x78000825 | (\wd << 6)
 	insn32_if_mm 0x5800081f | (\wd << 6)
@@ -453,7 +453,7 @@
 	.macro	st_w	wd, off, base
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	PTR_ADDU $1, \base, \off
 	insn_if_mips 0x78000826 | (\wd << 6)
 	insn32_if_mm 0x5800082f | (\wd << 6)
@@ -463,7 +463,7 @@
 	.macro	st_d	wd, off, base
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	PTR_ADDU $1, \base, \off
 	insn_if_mips 0x78000827 | (\wd << 6)
 	insn32_if_mm 0x5800083f | (\wd << 6)
@@ -473,7 +473,7 @@
 	.macro	copy_s_w	ws, n
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	insn_if_mips 0x78b00059 | (\n << 16) | (\ws << 11)
 	insn32_if_mm 0x58b00056 | (\n << 16) | (\ws << 11)
 	.set	pop
@@ -482,7 +482,7 @@
 	.macro	copy_s_d	ws, n
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	insn_if_mips 0x78b80059 | (\n << 16) | (\ws << 11)
 	insn32_if_mm 0x58b80056 | (\n << 16) | (\ws << 11)
 	.set	pop
@@ -491,7 +491,7 @@
 	.macro	insert_w	wd, n
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	insn_if_mips 0x79300819 | (\n << 16) | (\wd << 6)
 	insn32_if_mm 0x59300816 | (\n << 16) | (\wd << 6)
 	.set	pop
@@ -500,7 +500,7 @@
 	.macro	insert_d	wd, n
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	insn_if_mips 0x79380819 | (\n << 16) | (\wd << 6)
 	insn32_if_mm 0x59380816 | (\n << 16) | (\wd << 6)
 	.set	pop
@@ -553,7 +553,7 @@
 	st_d	29, THREAD_FPR29 - FPR_BASE_OFFS, FPR_BASE
 	st_d	30, THREAD_FPR30 - FPR_BASE_OFFS, FPR_BASE
 	st_d	31, THREAD_FPR31 - FPR_BASE_OFFS, FPR_BASE
-	SET_HARDFLOAT
+	.set	hardfloat
 	_cfcmsa	$1, MSA_CSR
 	sw	$1, THREAD_MSA_CSR(\thread)
 	.set	pop
@@ -562,7 +562,7 @@
 	.macro	msa_restore_all	thread
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	lw	$1, THREAD_MSA_CSR(\thread)
 	_ctcmsa	MSA_CSR, $1
 #ifdef TOOLCHAIN_SUPPORTS_MSA
@@ -618,7 +618,7 @@
 	.macro	msa_init_all_upper
 	.set	push
 	.set	noat
-	SET_HARDFLOAT
+	.set	hardfloat
 	not	$1, zero
 	msa_init_upper	0
 	msa_init_upper	1
diff --git a/arch/mips/include/asm/fpregdef.h b/arch/mips/include/asm/fpregdef.h
index f184ba088532..429481f9028d 100644
--- a/arch/mips/include/asm/fpregdef.h
+++ b/arch/mips/include/asm/fpregdef.h
@@ -14,20 +14,6 @@
 
 #include <asm/sgidefs.h>
 
-/*
- * starting with binutils 2.24.51.20140729, MIPS binutils warn about mixing
- * hardfloat and softfloat object files.  The kernel build uses soft-float by
- * default, so we also need to pass -msoft-float along to GAS if it supports it.
- * But this in turn causes assembler errors in files which access hardfloat
- * registers.  We detect if GAS supports "-msoft-float" in the Makefile and
- * explicitly put ".set hardfloat" where floating point registers are touched.
- */
-#ifdef GAS_HAS_SET_HARDFLOAT
-#define SET_HARDFLOAT .set hardfloat
-#else
-#define SET_HARDFLOAT
-#endif
-
 #if _MIPS_SIM == _MIPS_SIM_ABI32
 
 /*
diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
index 99eeafe6dcab..2d53704d9f24 100644
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -2367,7 +2367,7 @@ do {									\
 /*
  * Macros to access the floating point coprocessor control registers
  */
-#define _read_32bit_cp1_register(source, gas_hardfloat)			\
+#define read_32bit_cp1_register(source)					\
 ({									\
 	unsigned int __res;						\
 									\
@@ -2377,36 +2377,24 @@ do {									\
 	"	# gas fails to assemble cfc1 for some archs,	\n"	\
 	"	# like Octeon.					\n"	\
 	"	.set	mips1					\n"	\
-	"	"STR(gas_hardfloat)"				\n"	\
+	"	.set hardfloat					\n"	\
 	"	cfc1	%0,"STR(source)"			\n"	\
 	"	.set	pop					\n"	\
 	: "=r" (__res));						\
 	__res;								\
 })
 
-#define _write_32bit_cp1_register(dest, val, gas_hardfloat)		\
+#define write_32bit_cp1_register(dest, val)				\
 do {									\
 	__asm__ __volatile__(						\
 	"	.set	push					\n"	\
 	"	.set	reorder					\n"	\
-	"	"STR(gas_hardfloat)"				\n"	\
+	"	.set hardfloat					\n"	\
 	"	ctc1	%0,"STR(dest)"				\n"	\
 	"	.set	pop					\n"	\
 	: : "r" (val));							\
 } while (0)
 
-#ifdef GAS_HAS_SET_HARDFLOAT
-#define read_32bit_cp1_register(source)					\
-	_read_32bit_cp1_register(source, .set hardfloat)
-#define write_32bit_cp1_register(dest, val)				\
-	_write_32bit_cp1_register(dest, val, .set hardfloat)
-#else
-#define read_32bit_cp1_register(source)					\
-	_read_32bit_cp1_register(source, )
-#define write_32bit_cp1_register(dest, val)				\
-	_write_32bit_cp1_register(dest, val, )
-#endif
-
 #ifdef TOOLCHAIN_SUPPORTS_DSP
 #define rddsp(mask)							\
 ({									\
diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
index 3425df6019c0..b6de8e88c1bd 100644
--- a/arch/mips/kernel/genex.S
+++ b/arch/mips/kernel/genex.S
@@ -480,7 +480,7 @@ NESTED(nmi_handler, PT_SIZE, sp)
 	.set	push
 	/* gas fails to assemble cfc1 for some archs (octeon).*/ \
 	.set	mips1
-	SET_HARDFLOAT
+	.set	hardfloat
 	cfc1	a1, fcr31
 	.set	pop
 	.endm
diff --git a/arch/mips/kernel/r2300_fpu.S b/arch/mips/kernel/r2300_fpu.S
index 2748c55820c2..6c745aa9e825 100644
--- a/arch/mips/kernel/r2300_fpu.S
+++ b/arch/mips/kernel/r2300_fpu.S
@@ -64,7 +64,7 @@ LEAF(_restore_fp)
  */
 LEAF(_save_fp_context)
 	.set	push
-	SET_HARDFLOAT
+	.set	hardfloat
 	li	v0, 0					# assume success
 	cfc1	t1, fcr31
 	EX2(s.d $f0, 0(a0))
@@ -98,7 +98,7 @@ LEAF(_save_fp_context)
  */
 LEAF(_restore_fp_context)
 	.set	push
-	SET_HARDFLOAT
+	.set	hardfloat
 	li	v0, 0					# assume success
 	EX(lw t0, (a1))
 	EX2(l.d $f0, 0(a0))
diff --git a/arch/mips/kernel/r4k_fpu.S b/arch/mips/kernel/r4k_fpu.S
index 2e687c60bc4f..4e8c98517d9d 100644
--- a/arch/mips/kernel/r4k_fpu.S
+++ b/arch/mips/kernel/r4k_fpu.S
@@ -26,7 +26,7 @@
 
 	.macro	EX insn, reg, src
 	.set	push
-	SET_HARDFLOAT
+	.set	hardfloat
 	.set	nomacro
 .ex\@:	\insn	\reg, \src
 	.set	pop
@@ -98,14 +98,14 @@ LEAF(_init_msa_upper)
  */
 LEAF(_save_fp_context)
 	.set	push
-	SET_HARDFLOAT
+	.set	hardfloat
 	cfc1	t1, fcr31
 	.set	pop
 
 #if defined(CONFIG_64BIT) || defined(CONFIG_CPU_MIPSR2) || \
     defined(CONFIG_CPU_MIPSR5) || defined(CONFIG_CPU_MIPSR6)
 	.set	push
-	SET_HARDFLOAT
+	.set	hardfloat
 #if defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_CPU_MIPSR5)
 	.set	mips32r2
 	.set	fp=64
@@ -135,7 +135,7 @@ LEAF(_save_fp_context)
 #endif
 
 	.set push
-	SET_HARDFLOAT
+	.set	hardfloat
 	/* Store the 16 even double precision registers */
 	EX	sdc1 $f0, 0(a0)
 	EX	sdc1 $f2, 16(a0)
@@ -173,7 +173,7 @@ LEAF(_restore_fp_context)
 #if defined(CONFIG_64BIT) || defined(CONFIG_CPU_MIPSR2) || \
     defined(CONFIG_CPU_MIPSR5) || defined(CONFIG_CPU_MIPSR6)
 	.set	push
-	SET_HARDFLOAT
+	.set	hardfloat
 #if defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_CPU_MIPSR5)
 	.set	mips32r2
 	.set	fp=64
@@ -201,7 +201,7 @@ LEAF(_restore_fp_context)
 1:	.set pop
 #endif
 	.set push
-	SET_HARDFLOAT
+	.set hardfloat
 	EX	ldc1 $f0, 0(a0)
 	EX	ldc1 $f2, 16(a0)
 	EX	ldc1 $f4, 32(a0)
diff --git a/arch/mips/kvm/fpu.S b/arch/mips/kvm/fpu.S
index 16f17c6390dd..eb2e8cc3532f 100644
--- a/arch/mips/kvm/fpu.S
+++ b/arch/mips/kvm/fpu.S
@@ -22,7 +22,7 @@
 
 LEAF(__kvm_save_fpu)
 	.set	push
-	SET_HARDFLOAT
+	.set	hardfloat
 	.set	fp=64
 	mfc0	t0, CP0_STATUS
 	sll     t0, t0, 5			# is Status.FR set?
@@ -66,7 +66,7 @@ LEAF(__kvm_save_fpu)
 
 LEAF(__kvm_restore_fpu)
 	.set	push
-	SET_HARDFLOAT
+	.set	hardfloat
 	.set	fp=64
 	mfc0	t0, CP0_STATUS
 	sll     t0, t0, 5			# is Status.FR set?
@@ -110,7 +110,7 @@ LEAF(__kvm_restore_fpu)
 
 LEAF(__kvm_restore_fcsr)
 	.set	push
-	SET_HARDFLOAT
+	.set	hardfloat
 	lw	t0, VCPU_FCR31(a0)
 	/*
 	 * The ctc1 must stay at this offset in __kvm_restore_fcsr.

-- 
2.39.0

[PATCH v2 03/14] MIPS: Prefer cc-option for additions to cflags

[Nathan Chancellor]

A future change will switch as-option to use KBUILD_AFLAGS instead of
KBUILD_CFLAGS to allow clang to drop -Qunused-arguments, which may cause
issues if the flag being tested requires a flag previously added to
KBUILD_CFLAGS but not KBUILD_AFLAGS. Use cc-option for cflags additions
so that the flags are tested properly.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
Cc: linux-mips@vger.kernel.org
---
 arch/mips/Makefile             | 2 +-
 arch/mips/loongson2ef/Platform | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index a00a6d94e16f..04e46ec24319 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -143,7 +143,7 @@ cflags-y += -fno-stack-check
 #
 # Avoid this by explicitly disabling that assembler behaviour.
 #
-cflags-y += $(call as-option,-Wa$(comma)-mno-fix-loongson3-llsc,)
+cflags-y += $(call cc-option,-Wa$(comma)-mno-fix-loongson3-llsc,)
 
 #
 # CPU-dependent compiler/assembler options for optimization.
diff --git a/arch/mips/loongson2ef/Platform b/arch/mips/loongson2ef/Platform
index eebabf9df6ac..c6f7a4b95997 100644
--- a/arch/mips/loongson2ef/Platform
+++ b/arch/mips/loongson2ef/Platform
@@ -25,7 +25,7 @@ cflags-$(CONFIG_CPU_LOONGSON2F) += -march=loongson2f
 # binutils does not merge support for the flag then we can revisit & remove
 # this later - for now it ensures vendor toolchains don't cause problems.
 #
-cflags-$(CONFIG_CPU_LOONGSON2EF)	+= $(call as-option,-Wa$(comma)-mno-fix-loongson3-llsc,)
+cflags-$(CONFIG_CPU_LOONGSON2EF)	+= $(call cc-option,-Wa$(comma)-mno-fix-loongson3-llsc,)
 
 # Enable the workarounds for Loongson2f
 ifdef CONFIG_CPU_LOONGSON2F_WORKAROUNDS

-- 
2.39.0

[PATCH v2 04/14] kbuild: Update assembler calls to use proper flags and language target

[Nathan Chancellor]

From: Nick Desaulniers <ndesaulniers@google.com>

as-instr uses KBUILD_AFLAGS, but as-option uses KBUILD_CFLAGS. This can
cause as-option to fail unexpectedly when CONFIG_WERROR is set, because
clang will emit -Werror,-Wunused-command-line-argument for various -m
and -f flags in KBUILD_CFLAGS for assembler sources.

Callers of as-option and as-instr should be adding flags to
KBUILD_AFLAGS / aflags-y, not KBUILD_CFLAGS / cflags-y. Use
KBUILD_AFLAGS in all macros to clear up the initial problem.

Unfortunately, -Wunused-command-line-argument can still be triggered
with clang by the presence of warning flags or macro definitions because
'-x assembler' is used, instead of '-x assembler-with-cpp', which will
consume these flags. Switch to '-x assembler-with-cpp' in places where
'-x assembler' is used, as the compiler is always used as the driver for
out of line assembler sources in the kernel.

Finally, add -Werror to these macros so that they behave consistently
whether or not CONFIG_WERROR is set.

Link: https://github.com/ClangBuiltLinux/linux/issues/1699
Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
[nathan: Reworded and expanded on problems in commit message
         Use '-x assembler-with-cpp' in a couple more places]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
Benchmarking '-x assembler' vs. '-x assembler-with-cpp' does show that
invoking the preprocessor incurs some overhead but my kernel builds do
not show any noticeable slowdowns due to how infrequently these macros
are used.

$ hyperfine -L lang assembler,assembler-with-cpp -N -w 5 "/usr/bin/gcc -x {lang} -c -o /dev/null /dev/null"
Benchmark 1: /usr/bin/gcc -x assembler -c -o /dev/null /dev/null
  Time (mean ± σ):       5.5 ms ±   0.5 ms    [User: 4.1 ms, System: 1.3 ms]
  Range (min … max):     4.3 ms …   6.3 ms    472 runs

Benchmark 2: /usr/bin/gcc -x assembler-with-cpp -c -o /dev/null /dev/null
  Time (mean ± σ):      12.7 ms ±   1.0 ms    [User: 9.1 ms, System: 3.6 ms]
  Range (min … max):     9.6 ms …  14.2 ms    225 runs

Summary
  '/usr/bin/gcc -x assembler -c -o /dev/null /dev/null' ran
    2.29 ± 0.28 times faster than '/usr/bin/gcc -x assembler-with-cpp -c -o /dev/null /dev/null'

$ hyperfine -L lang assembler,assembler-with-cpp -N -w 5 "/usr/bin/clang -x {lang} -c -o /dev/null /dev/null"
Benchmark 1: /usr/bin/clang -x assembler -c -o /dev/null /dev/null
  Time (mean ± σ):      21.0 ms ±   1.1 ms    [User: 9.6 ms, System: 11.1 ms]
  Range (min … max):    13.9 ms …  22.0 ms    138 runs

Benchmark 2: /usr/bin/clang -x assembler-with-cpp -c -o /dev/null /dev/null
  Time (mean ± σ):      56.9 ms ±   3.2 ms    [User: 27.2 ms, System: 29.5 ms]
  Range (min … max):    53.9 ms …  62.1 ms    48 runs

Summary
  '/usr/bin/clang -x assembler -c -o /dev/null /dev/null' ran
    2.71 ± 0.20 times faster than '/usr/bin/clang -x assembler-with-cpp -c -o /dev/null /dev/null'
---
 scripts/Kconfig.include   | 2 +-
 scripts/Makefile.compiler | 8 ++++----
 scripts/as-version.sh     | 2 +-
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index 274125307ebd..5a84b6443875 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -33,7 +33,7 @@ ld-option = $(success,$(LD) -v $(1))
 
 # $(as-instr,<instr>)
 # Return y if the assembler supports <instr>, n otherwise
-as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler -o /dev/null -)
+as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler-with-cpp -o /dev/null -)
 
 # check if $(CC) and $(LD) exist
 $(error-if,$(failure,command -v $(CC)),C compiler '$(CC)' not found)
diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
index 3d8adfd34af1..7aa1fbc4aafe 100644
--- a/scripts/Makefile.compiler
+++ b/scripts/Makefile.compiler
@@ -29,16 +29,16 @@ try-run = $(shell set -e;		\
 	fi)
 
 # as-option
-# Usage: cflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
+# Usage: aflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
 
 as-option = $(call try-run,\
-	$(CC) $(KBUILD_CFLAGS) $(1) -c -x assembler /dev/null -o "$$TMP",$(1),$(2))
+	$(CC) -Werror $(KBUILD_AFLAGS) $(1) -c -x assembler-with-cpp /dev/null -o "$$TMP",$(1),$(2))
 
 # as-instr
-# Usage: cflags-y += $(call as-instr,instr,option1,option2)
+# Usage: aflags-y += $(call as-instr,instr,option1,option2)
 
 as-instr = $(call try-run,\
-	printf "%b\n" "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3))
+	printf "%b\n" "$(1)" | $(CC) -Werror $(KBUILD_AFLAGS) -c -x assembler-with-cpp -o "$$TMP" -,$(2),$(3))
 
 # __cc-option
 # Usage: MY_CFLAGS += $(call __cc-option,$(CC),$(MY_CFLAGS),-march=winchip-c6,-march=i586)
diff --git a/scripts/as-version.sh b/scripts/as-version.sh
index 1a21495e9ff0..af717476152d 100755
--- a/scripts/as-version.sh
+++ b/scripts/as-version.sh
@@ -45,7 +45,7 @@ orig_args="$@"
 # Get the first line of the --version output.
 IFS='
 '
-set -- $(LC_ALL=C "$@" -Wa,--version -c -x assembler /dev/null -o /dev/null 2>/dev/null)
+set -- $(LC_ALL=C "$@" -Wa,--version -c -x assembler-with-cpp /dev/null -o /dev/null 2>/dev/null)
 
 # Split the line on spaces.
 IFS=' '

-- 
2.39.0

[PATCH v2 05/14] powerpc: Remove linker flag from KBUILD_AFLAGS

[Nathan Chancellor]

When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
points out that KBUILD_AFLAGS contains a linker flag, which will be
used:

  clang: error: -Wl,-a32: 'linker' input unused [-Werror,-Wunused-command-line-argument]

This was likely supposed to be '-Wa,-a$(BITS)'. However, this change is
unnecessary, as all supported versions of clang and gcc will pass '-a64'
or '-a32' to GNU as based on the value of '-m'; the behavior of the
latest stable release of the oldest supported major version of each
compiler is shown below and each compiler's latest release exhibits the
same behavior (GCC 12.2.0 and Clang 15.0.6).

  $ powerpc64-linux-gcc --version | head -1
  powerpc64-linux-gcc (GCC) 5.5.0

  $ powerpc64-linux-gcc -m64 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
  .../as -a64 -mppc64 -many -mbig -o /dev/null /tmp/cctwuBzZ.s

  $ powerpc64-linux-gcc -m32 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
  .../as -a32 -mppc -many -mbig -o /dev/null /tmp/ccaZP4mF.sg

  $ clang --version | head -1
  Ubuntu clang version 11.1.0-++20211011094159+1fdec59bffc1-1~exp1~20211011214622.5

  $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
    -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
   "/usr/bin/powerpc64-linux-gnu-as" "-a64" "-mppc64" "-many" "-o" "/dev/null" "/tmp/null-80267c.s"

  $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
    -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
   "/usr/bin/powerpc64-linux-gnu-as" "-a32" "-mppc" "-many" "-o" "/dev/null" "/tmp/null-ab8f8d.s"

Remove this flag altogether to avoid future issues.

Fixes: 1421dc6d4829 ("powerpc/kbuild: Use flags variables rather than overriding LD/CC/AS")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---
Cc: mpe@ellerman.id.au
Cc: npiggin@gmail.com
Cc: christophe.leroy@csgroup.eu
Cc: linuxppc-dev@lists.ozlabs.org
---
 arch/powerpc/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index dc4cbf0a5ca9..4fd630efe39d 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -90,7 +90,7 @@ aflags-$(CONFIG_CPU_LITTLE_ENDIAN)	+= -mlittle-endian
 
 ifeq ($(HAS_BIARCH),y)
 KBUILD_CFLAGS	+= -m$(BITS)
-KBUILD_AFLAGS	+= -m$(BITS) -Wl,-a$(BITS)
+KBUILD_AFLAGS	+= -m$(BITS)
 KBUILD_LDFLAGS	+= -m elf$(BITS)$(LDEMULATION)
 endif
 

-- 
2.39.0

[PATCH v2 06/14] powerpc/vdso: Remove unused '-s' flag from ASFLAGS

[Nathan Chancellor]

When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
warns:

  clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]

The compiler's '-s' flag is a linking option (it is passed along to the
linker directly), which means it does nothing when the linker is not
invoked by the compiler. The kernel builds all .o files with '-c', which
stops the compilation pipeline before linking, so '-s' can be safely
dropped from ASFLAGS.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
---
Cc: mpe@ellerman.id.au
Cc: npiggin@gmail.com
Cc: christophe.leroy@csgroup.eu
Cc: linuxppc-dev@lists.ozlabs.org

As I mentioned before, it is possible that we should add '-s' to
ldflags-y in the following patch but I assume someone would have noticed
by now if that was a problem.
---
 arch/powerpc/kernel/vdso/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
index 6a977b0d8ffc..45c0cc5d34b6 100644
--- a/arch/powerpc/kernel/vdso/Makefile
+++ b/arch/powerpc/kernel/vdso/Makefile
@@ -51,10 +51,10 @@ ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
 ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
 
 CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
-AS32FLAGS := -D__VDSO32__ -s
+AS32FLAGS := -D__VDSO32__
 
 CC64FLAGS := -Wl,-soname=linux-vdso64.so.1
-AS64FLAGS := -D__VDSO64__ -s
+AS64FLAGS := -D__VDSO64__
 
 targets += vdso32.lds
 CPPFLAGS_vdso32.lds += -P -C -Upowerpc

-- 
2.39.0

[PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Nathan Chancellor]

When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
are several warnings in the PowerPC vDSO:

  clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
  clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
  clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]

  clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
  clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]

The first group of warnings point out that linker flags were being added
to all invocations of $(CC), even though they will only be used during
the final vDSO link. Move those flags to ldflags-y.

The second group of warnings are compiler or assembler flags that will
be unused during linking. Filter them out from KBUILD_CFLAGS so that
they are not used during linking.

Additionally, '-z noexecstack' was added directly to the ld_and_check
rule in commit 1d53c0192b15 ("powerpc/vdso: link with -z noexecstack")
but now that there is a common ldflags variable, it can be moved there.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---
Cc: mpe@ellerman.id.au
Cc: npiggin@gmail.com
Cc: christophe.leroy@csgroup.eu
Cc: linuxppc-dev@lists.ozlabs.org
---
 arch/powerpc/kernel/vdso/Makefile | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
index 45c0cc5d34b6..4337b3aa9171 100644
--- a/arch/powerpc/kernel/vdso/Makefile
+++ b/arch/powerpc/kernel/vdso/Makefile
@@ -47,13 +47,17 @@ KCOV_INSTRUMENT := n
 UBSAN_SANITIZE := n
 KASAN_SANITIZE := n
 
-ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
-ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
-
-CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
+ccflags-y := -fno-common -fno-builtin
+ldflags-y := -Wl,--hash-style=both -nostdlib -shared -z noexecstack
+ldflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
+# Filter flags that clang will warn are unused for linking
+ldflags-y += $(filter-out $(CC_FLAGS_FTRACE) -Wa$(comma)%, $(KBUILD_CFLAGS))
+
+CC32FLAGS := -m32
+LD32FLAGS := -Wl,-soname=linux-vdso32.so.1
 AS32FLAGS := -D__VDSO32__
 
-CC64FLAGS := -Wl,-soname=linux-vdso64.so.1
+LD64FLAGS := -Wl,-soname=linux-vdso64.so.1
 AS64FLAGS := -D__VDSO64__
 
 targets += vdso32.lds
@@ -92,14 +96,14 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
 
 # actual build commands
 quiet_cmd_vdso32ld_and_check = VDSO32L $@
-      cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
+      cmd_vdso32ld_and_check = $(VDSOCC) $(ldflags-y) $(CC32FLAGS) $(LD32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
 quiet_cmd_vdso32as = VDSO32A $@
       cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<
 quiet_cmd_vdso32cc = VDSO32C $@
       cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $<
 
 quiet_cmd_vdso64ld_and_check = VDSO64L $@
-      cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
+      cmd_vdso64ld_and_check = $(VDSOCC) $(ldflags-y) $(CC64FLAGS) $(LD64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
 quiet_cmd_vdso64as = VDSO64A $@
       cmd_vdso64as = $(VDSOCC) $(a_flags) $(CC64FLAGS) $(AS64FLAGS) -c -o $@ $<
 

-- 
2.39.0

[PATCH v2 08/14] powerpc/vdso: Remove an unsupported flag from vgettimeofday-32.o with clang

[Nathan Chancellor]

When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
warns:

  clang-16: error: argument unused during compilation: '-fno-stack-clash-protection' [-Werror,-Wunused-command-line-argument]

This warning happens because vgettimeofday-32.c gets its base CFLAGS
from the main kernel, which may contain flags that are only supported on
a 64-bit target but not a 32-bit one, which is the case here.
-fstack-clash-protection and its negation are only suppported by the
64-bit powerpc target but that flag is included in an invocation for a
32-bit powerpc target, so clang points out that while the flag is one
that it recognizes, it is not actually used by this compiler job.

To eliminate the warning, remove -fno-stack-clash-protection from
vgettimeofday-32.c's CFLAGS when using clang, as has been done for other
flags previously.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---
Cc: mpe@ellerman.id.au
Cc: npiggin@gmail.com
Cc: christophe.leroy@csgroup.eu
Cc: linuxppc-dev@lists.ozlabs.org
---
 arch/powerpc/kernel/vdso/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
index 4337b3aa9171..e78a57e0a6c0 100644
--- a/arch/powerpc/kernel/vdso/Makefile
+++ b/arch/powerpc/kernel/vdso/Makefile
@@ -16,6 +16,11 @@ ifneq ($(c-gettimeofday-y),)
   CFLAGS_vgettimeofday-32.o += -ffreestanding -fasynchronous-unwind-tables
   CFLAGS_REMOVE_vgettimeofday-32.o = $(CC_FLAGS_FTRACE)
   CFLAGS_REMOVE_vgettimeofday-32.o += -mcmodel=medium -mabi=elfv1 -mabi=elfv2 -mcall-aixdesc
+  # This flag is supported by clang for 64-bit but not 32-bit so it will cause
+  # an unused command line flag warning for this file.
+  ifdef CONFIG_CC_IS_CLANG
+  CFLAGS_REMOVE_vgettimeofday-32.o += -fno-stack-clash-protection
+  endif
   CFLAGS_vgettimeofday-64.o += -include $(c-gettimeofday-y)
   CFLAGS_vgettimeofday-64.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
   CFLAGS_vgettimeofday-64.o += $(call cc-option, -fno-stack-protector)

-- 
2.39.0

[PATCH v2 09/14] s390/vdso: Drop unused '-s' flag from KBUILD_AFLAGS_64

[Nathan Chancellor]

When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
warns:

  clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]

The compiler's '-s' flag is a linking option (it is passed along to the
linker directly), which means it does nothing when the linker is not
invoked by the compiler. The kernel builds all .o files with '-c', which
stops the compilation pipeline before linking, so '-s' can be safely
dropped from KBUILD_AFLAGS_64.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
---
Cc: linux-s390@vger.kernel.org
---
 arch/s390/kernel/vdso64/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/kernel/vdso64/Makefile b/arch/s390/kernel/vdso64/Makefile
index 9e2b95a222a9..a2fe9383d452 100644
--- a/arch/s390/kernel/vdso64/Makefile
+++ b/arch/s390/kernel/vdso64/Makefile
@@ -22,7 +22,7 @@ KBUILD_AFLAGS += -DBUILD_VDSO
 KBUILD_CFLAGS += -DBUILD_VDSO -DDISABLE_BRANCH_PROFILING
 
 KBUILD_AFLAGS_64 := $(filter-out -m64,$(KBUILD_AFLAGS))
-KBUILD_AFLAGS_64 += -m64 -s
+KBUILD_AFLAGS_64 += -m64
 
 KBUILD_CFLAGS_64 := $(filter-out -m64,$(KBUILD_CFLAGS))
 KBUILD_CFLAGS_64 += -m64 -fPIC -shared -fno-common -fno-builtin

-- 
2.39.0

[PATCH v2 10/14] s390/vdso: Drop '-shared' from KBUILD_CFLAGS_64

[Nathan Chancellor]

When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
points out that there is a linking phase flag added to CFLAGS, which
will only be used for compiling

  clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]

'-shared' is already present in ldflags-y so it can just be dropped.

Fixes: 2b2a25845d53 ("s390/vdso: Use $(LD) instead of $(CC) to link vDSO")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
---
Cc: linux-s390@vger.kernel.org
---
 arch/s390/kernel/vdso64/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/kernel/vdso64/Makefile b/arch/s390/kernel/vdso64/Makefile
index a2fe9383d452..34f9542636e9 100644
--- a/arch/s390/kernel/vdso64/Makefile
+++ b/arch/s390/kernel/vdso64/Makefile
@@ -25,7 +25,7 @@ KBUILD_AFLAGS_64 := $(filter-out -m64,$(KBUILD_AFLAGS))
 KBUILD_AFLAGS_64 += -m64
 
 KBUILD_CFLAGS_64 := $(filter-out -m64,$(KBUILD_CFLAGS))
-KBUILD_CFLAGS_64 += -m64 -fPIC -shared -fno-common -fno-builtin
+KBUILD_CFLAGS_64 += -m64 -fPIC -fno-common -fno-builtin
 ldflags-y := -fPIC -shared -soname=linux-vdso64.so.1 \
 	     --hash-style=both --build-id=sha1 -T
 

-- 
2.39.0

[PATCH v2 11/14] s390/purgatory: Remove unused '-MD' and unnecessary '-c' flags

[Nathan Chancellor]

When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
warns while building objects in the purgatory folder:

  clang-16: error: argument unused during compilation: '-MD' [-Werror,-Wunused-command-line-argument]

'-MMD' is always passed to the preprocessor via c_flags, even when
KBUILD_CFLAGS is overridden in a folder, so clang complains the addition
of '-MD' will be unused. Remove '-MD' to clear up this warning, as it is
unnecessary with '-MMD'.

Additionally, '-c' is also unnecessary, remove it while in the area.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
---
Cc: linux-s390@vger.kernel.org
---
 arch/s390/purgatory/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/purgatory/Makefile b/arch/s390/purgatory/Makefile
index d237bc6841cb..32573b4f9bd2 100644
--- a/arch/s390/purgatory/Makefile
+++ b/arch/s390/purgatory/Makefile
@@ -24,7 +24,7 @@ KCSAN_SANITIZE := n
 KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes
 KBUILD_CFLAGS += -Wno-pointer-sign -Wno-sign-compare
 KBUILD_CFLAGS += -fno-zero-initialized-in-bss -fno-builtin -ffreestanding
-KBUILD_CFLAGS += -c -MD -Os -m64 -msoft-float -fno-common
+KBUILD_CFLAGS += -Os -m64 -msoft-float -fno-common
 KBUILD_CFLAGS += -fno-stack-protector
 KBUILD_CFLAGS += $(CLANG_FLAGS)
 KBUILD_CFLAGS += $(call cc-option,-fno-PIE)

-- 
2.39.0

[PATCH v2 12/14] drm/amd/display: Do not add '-mhard-float' to dml_ccflags for clang

[Nathan Chancellor]

When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
warns:

  clang-16: error: argument unused during compilation: '-mhard-float' [-Werror,-Wunused-command-line-argument]

Similar to commit 84edc2eff827 ("selftest/fpu: avoid clang warning"),
just add this flag to GCC builds. Commit 0f0727d971f6 ("drm/amd/display:
readd -msse2 to prevent Clang from emitting libcalls to undefined SW FP
routines") added '-msse2' to prevent clang from emitting software
floating point routines.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
---
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
---
 drivers/gpu/drm/amd/display/dc/dml/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dml/Makefile b/drivers/gpu/drm/amd/display/dc/dml/Makefile
index 0ecea87cf48f..9d0f79dff2e3 100644
--- a/drivers/gpu/drm/amd/display/dc/dml/Makefile
+++ b/drivers/gpu/drm/amd/display/dc/dml/Makefile
@@ -26,7 +26,8 @@
 # subcomponents.
 
 ifdef CONFIG_X86
-dml_ccflags := -mhard-float -msse
+dml_ccflags-$(CONFIG_CC_IS_GCC) := -mhard-float
+dml_ccflags := $(dml_ccflags-y) -msse
 endif
 
 ifdef CONFIG_PPC64

-- 
2.39.0

[PATCH v2 13/14] kbuild: Turn a couple more of clang's unused option warnings into errors

[Nathan Chancellor]

Currently, these warnings are hidden with -Qunused-arguments in
KBUILD_CPPFLAGS. Once that option is removed, these warnings should be
turned into hard errors to make unconditionally added but unsupported
flags for the current compilation mode or target obvious due to a failed
build; otherwise, the warnings might just be ignored if the build log is
not checked.

Link: https://github.com/ClangBuiltLinux/linux/issues/1587
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---
 scripts/Makefile.clang | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang
index 87285b76adb2..70b354fa1cb4 100644
--- a/scripts/Makefile.clang
+++ b/scripts/Makefile.clang
@@ -36,6 +36,8 @@ endif
 # so they can be implemented or wrapped in cc-option.
 CLANG_FLAGS	+= -Werror=unknown-warning-option
 CLANG_FLAGS	+= -Werror=ignored-optimization-argument
+CLANG_FLAGS	+= -Werror=option-ignored
+CLANG_FLAGS	+= -Werror=unused-command-line-argument
 KBUILD_CFLAGS	+= $(CLANG_FLAGS)
 KBUILD_AFLAGS	+= $(CLANG_FLAGS)
 export CLANG_FLAGS

-- 
2.39.0

[PATCH v2 14/14] kbuild: Stop using '-Qunused-arguments' with clang

[Nathan Chancellor]

This option masks all unused command line argument warnings, which can
hide potential issues, such as an architecture Makefile adding an
unsupported flag to KBUILD_AFLAGS or KBUILD_CFLAGS, which will cause all
as-option and cc-options to silently fail due to -Werror with no
indication as to why in the main kernel build.

Remove this flag so that warnings of this nature can be caught early and
obviously in a build.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---
 Makefile | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Makefile b/Makefile
index c05b4fb7121e..4bc79d2a42f2 100644
--- a/Makefile
+++ b/Makefile
@@ -878,7 +878,6 @@ KBUILD_RUSTFLAGS-$(CONFIG_WERROR) += -Dwarnings
 KBUILD_RUSTFLAGS += $(KBUILD_RUSTFLAGS-y)
 
 ifdef CONFIG_CC_IS_CLANG
-KBUILD_CPPFLAGS += -Qunused-arguments
 # The kernel builds with '-std=gnu11' so use of GNU extensions is acceptable.
 KBUILD_CFLAGS += -Wno-gnu
 else

-- 
2.39.0

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Sedat Dilek]

On Thu, Jan 12, 2023 at 4:06 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
> are several warnings in the PowerPC vDSO:
>
>   clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
>   clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
>   clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]
>
>   clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
>   clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]
>
> The first group of warnings point out that linker flags were being added
> to all invocations of $(CC), even though they will only be used during
> the final vDSO link. Move those flags to ldflags-y.
>
> The second group of warnings are compiler or assembler flags that will
> be unused during linking. Filter them out from KBUILD_CFLAGS so that
> they are not used during linking.
>
> Additionally, '-z noexecstack' was added directly to the ld_and_check
> rule in commit 1d53c0192b15 ("powerpc/vdso: link with -z noexecstack")
> but now that there is a common ldflags variable, it can be moved there.
>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> Cc: mpe@ellerman.id.au
> Cc: npiggin@gmail.com
> Cc: christophe.leroy@csgroup.eu
> Cc: linuxppc-dev@lists.ozlabs.org
> ---
>  arch/powerpc/kernel/vdso/Makefile | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
> index 45c0cc5d34b6..4337b3aa9171 100644
> --- a/arch/powerpc/kernel/vdso/Makefile
> +++ b/arch/powerpc/kernel/vdso/Makefile
> @@ -47,13 +47,17 @@ KCOV_INSTRUMENT := n
>  UBSAN_SANITIZE := n
>  KASAN_SANITIZE := n
>
> -ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
> -ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> -
> -CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
> +ccflags-y := -fno-common -fno-builtin
> +ldflags-y := -Wl,--hash-style=both -nostdlib -shared -z noexecstack
> +ldflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> +# Filter flags that clang will warn are unused for linking
> +ldflags-y += $(filter-out $(CC_FLAGS_FTRACE) -Wa$(comma)%, $(KBUILD_CFLAGS))
> +
> +CC32FLAGS := -m32
> +LD32FLAGS := -Wl,-soname=linux-vdso32.so.1
>  AS32FLAGS := -D__VDSO32__
>
> -CC64FLAGS := -Wl,-soname=linux-vdso64.so.1

Set CC64FLAGS := -m64 ?

> +LD64FLAGS := -Wl,-soname=linux-vdso64.so.1
>  AS64FLAGS := -D__VDSO64__
>
>  targets += vdso32.lds
> @@ -92,14 +96,14 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
>
>  # actual build commands
>  quiet_cmd_vdso32ld_and_check = VDSO32L $@
> -      cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> +      cmd_vdso32ld_and_check = $(VDSOCC) $(ldflags-y) $(CC32FLAGS) $(LD32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
>  quiet_cmd_vdso32as = VDSO32A $@
>        cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<
>  quiet_cmd_vdso32cc = VDSO32C $@
>        cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $<
>
>  quiet_cmd_vdso64ld_and_check = VDSO64L $@
> -      cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> +      cmd_vdso64ld_and_check = $(VDSOCC) $(ldflags-y) $(CC64FLAGS) $(LD64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)

If no CC64FLAGS := xxx is set, this can go?

-Sedat-

>  quiet_cmd_vdso64as = VDSO64A $@
>        cmd_vdso64as = $(VDSOCC) $(a_flags) $(CC64FLAGS) $(AS64FLAGS) -c -o $@ $<
>
>
> --
> 2.39.0
>

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Nathan Chancellor]

Hi Sedat,

On Thu, Jan 12, 2023 at 07:02:30PM +0100, Sedat Dilek wrote:
> On Thu, Jan 12, 2023 at 4:06 AM Nathan Chancellor <nathan@kernel.org> wrote:
> >
> > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
> > are several warnings in the PowerPC vDSO:
> >
> >   clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> >   clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> >   clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]
> >
> >   clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
> >   clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]
> >
> > The first group of warnings point out that linker flags were being added
> > to all invocations of $(CC), even though they will only be used during
> > the final vDSO link. Move those flags to ldflags-y.
> >
> > The second group of warnings are compiler or assembler flags that will
> > be unused during linking. Filter them out from KBUILD_CFLAGS so that
> > they are not used during linking.
> >
> > Additionally, '-z noexecstack' was added directly to the ld_and_check
> > rule in commit 1d53c0192b15 ("powerpc/vdso: link with -z noexecstack")
> > but now that there is a common ldflags variable, it can be moved there.
> >
> > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > ---
> > Cc: mpe@ellerman.id.au
> > Cc: npiggin@gmail.com
> > Cc: christophe.leroy@csgroup.eu
> > Cc: linuxppc-dev@lists.ozlabs.org
> > ---
> >  arch/powerpc/kernel/vdso/Makefile | 18 +++++++++++-------
> >  1 file changed, 11 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
> > index 45c0cc5d34b6..4337b3aa9171 100644
> > --- a/arch/powerpc/kernel/vdso/Makefile
> > +++ b/arch/powerpc/kernel/vdso/Makefile
> > @@ -47,13 +47,17 @@ KCOV_INSTRUMENT := n
> >  UBSAN_SANITIZE := n
> >  KASAN_SANITIZE := n
> >
> > -ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
> > -ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > -
> > -CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
> > +ccflags-y := -fno-common -fno-builtin
> > +ldflags-y := -Wl,--hash-style=both -nostdlib -shared -z noexecstack
> > +ldflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > +# Filter flags that clang will warn are unused for linking
> > +ldflags-y += $(filter-out $(CC_FLAGS_FTRACE) -Wa$(comma)%, $(KBUILD_CFLAGS))
> > +
> > +CC32FLAGS := -m32
> > +LD32FLAGS := -Wl,-soname=linux-vdso32.so.1
> >  AS32FLAGS := -D__VDSO32__
> >
> > -CC64FLAGS := -Wl,-soname=linux-vdso64.so.1
> 
> Set CC64FLAGS := -m64 ?

I do not think it is necessary. ldflags-y is filtered from
KBUILD_CFLAGS, which should already include '-m64' (search for
'HAS_BIARCH' in arch/powerpc/Makefile). We would have seen a problem
with this already if a 32-bit target (powerpc-linux-gnu-) CROSS_COMPILE
value since $(c_flags) uses the main kernel's CROSS_COMPILE value.

> > +LD64FLAGS := -Wl,-soname=linux-vdso64.so.1
> >  AS64FLAGS := -D__VDSO64__
> >
> >  targets += vdso32.lds
> > @@ -92,14 +96,14 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
> >
> >  # actual build commands
> >  quiet_cmd_vdso32ld_and_check = VDSO32L $@
> > -      cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > +      cmd_vdso32ld_and_check = $(VDSOCC) $(ldflags-y) $(CC32FLAGS) $(LD32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> >  quiet_cmd_vdso32as = VDSO32A $@
> >        cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<
> >  quiet_cmd_vdso32cc = VDSO32C $@
> >        cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $<
> >
> >  quiet_cmd_vdso64ld_and_check = VDSO64L $@
> > -      cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > +      cmd_vdso64ld_and_check = $(VDSOCC) $(ldflags-y) $(CC64FLAGS) $(LD64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> 
> If no CC64FLAGS := xxx is set, this can go?

Good catch! CC64FLAGS can be removed. Masahiro, I am happy to send a v3
when I am back online next week but if you are able to fix it up during
application, please feel free to do so (once the PowerPC folks give
their Acks of course).

> >  quiet_cmd_vdso64as = VDSO64A $@
> >        cmd_vdso64as = $(VDSOCC) $(a_flags) $(CC64FLAGS) $(AS64FLAGS) -c -o $@ $<
> >
> >
> > --
> > 2.39.0
> >

Thanks for the review, cheers!
Nathan

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Sedat Dilek]

On Thu, Jan 12, 2023 at 7:21 PM Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi Sedat,
>
> On Thu, Jan 12, 2023 at 07:02:30PM +0100, Sedat Dilek wrote:
> > On Thu, Jan 12, 2023 at 4:06 AM Nathan Chancellor <nathan@kernel.org> wrote:
> > >
> > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
> > > are several warnings in the PowerPC vDSO:
> > >
> > >   clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> > >   clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> > >   clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]
> > >
> > >   clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
> > >   clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]
> > >
> > > The first group of warnings point out that linker flags were being added
> > > to all invocations of $(CC), even though they will only be used during
> > > the final vDSO link. Move those flags to ldflags-y.
> > >
> > > The second group of warnings are compiler or assembler flags that will
> > > be unused during linking. Filter them out from KBUILD_CFLAGS so that
> > > they are not used during linking.
> > >
> > > Additionally, '-z noexecstack' was added directly to the ld_and_check
> > > rule in commit 1d53c0192b15 ("powerpc/vdso: link with -z noexecstack")
> > > but now that there is a common ldflags variable, it can be moved there.
> > >
> > > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > > ---
> > > Cc: mpe@ellerman.id.au
> > > Cc: npiggin@gmail.com
> > > Cc: christophe.leroy@csgroup.eu
> > > Cc: linuxppc-dev@lists.ozlabs.org
> > > ---
> > >  arch/powerpc/kernel/vdso/Makefile | 18 +++++++++++-------
> > >  1 file changed, 11 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
> > > index 45c0cc5d34b6..4337b3aa9171 100644
> > > --- a/arch/powerpc/kernel/vdso/Makefile
> > > +++ b/arch/powerpc/kernel/vdso/Makefile
> > > @@ -47,13 +47,17 @@ KCOV_INSTRUMENT := n
> > >  UBSAN_SANITIZE := n
> > >  KASAN_SANITIZE := n
> > >
> > > -ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
> > > -ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > > -
> > > -CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
> > > +ccflags-y := -fno-common -fno-builtin
> > > +ldflags-y := -Wl,--hash-style=both -nostdlib -shared -z noexecstack
> > > +ldflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > > +# Filter flags that clang will warn are unused for linking
> > > +ldflags-y += $(filter-out $(CC_FLAGS_FTRACE) -Wa$(comma)%, $(KBUILD_CFLAGS))
> > > +
> > > +CC32FLAGS := -m32
> > > +LD32FLAGS := -Wl,-soname=linux-vdso32.so.1
> > >  AS32FLAGS := -D__VDSO32__
> > >
> > > -CC64FLAGS := -Wl,-soname=linux-vdso64.so.1
> >
> > Set CC64FLAGS := -m64 ?
>
> I do not think it is necessary. ldflags-y is filtered from
> KBUILD_CFLAGS, which should already include '-m64' (search for
> 'HAS_BIARCH' in arch/powerpc/Makefile). We would have seen a problem
> with this already if a 32-bit target (powerpc-linux-gnu-) CROSS_COMPILE
> value since $(c_flags) uses the main kernel's CROSS_COMPILE value.
>

Happy new 2023 Nathan,

that vdso Makefiles are hard to read.

Looks like x86/vdso explicitly sets -m32 and filter-out -m64 for the
32-bit case.

Best regards,
-Sedat-

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/entry/vdso/Makefile

> > > +LD64FLAGS := -Wl,-soname=linux-vdso64.so.1
> > >  AS64FLAGS := -D__VDSO64__
> > >
> > >  targets += vdso32.lds
> > > @@ -92,14 +96,14 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
> > >
> > >  # actual build commands
> > >  quiet_cmd_vdso32ld_and_check = VDSO32L $@
> > > -      cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > > +      cmd_vdso32ld_and_check = $(VDSOCC) $(ldflags-y) $(CC32FLAGS) $(LD32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> > >  quiet_cmd_vdso32as = VDSO32A $@
> > >        cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<
> > >  quiet_cmd_vdso32cc = VDSO32C $@
> > >        cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $<
> > >
> > >  quiet_cmd_vdso64ld_and_check = VDSO64L $@
> > > -      cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > > +      cmd_vdso64ld_and_check = $(VDSOCC) $(ldflags-y) $(CC64FLAGS) $(LD64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> >
> > If no CC64FLAGS := xxx is set, this can go?
>
> Good catch! CC64FLAGS can be removed. Masahiro, I am happy to send a v3
> when I am back online next week but if you are able to fix it up during
> application, please feel free to do so (once the PowerPC folks give
> their Acks of course).
>
> > >  quiet_cmd_vdso64as = VDSO64A $@
> > >        cmd_vdso64as = $(VDSOCC) $(a_flags) $(CC64FLAGS) $(AS64FLAGS) -c -o $@ $<
> > >
> > >
> > > --
> > > 2.39.0
> > >
>
> Thanks for the review, cheers!
> Nathan

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Masahiro Yamada]

On Fri, Jan 13, 2023 at 3:21 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi Sedat,
>
> On Thu, Jan 12, 2023 at 07:02:30PM +0100, Sedat Dilek wrote:
> > On Thu, Jan 12, 2023 at 4:06 AM Nathan Chancellor <nathan@kernel.org> wrote:
> > >
> > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
> > > are several warnings in the PowerPC vDSO:
> > >
> > >   clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> > >   clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> > >   clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]
> > >
> > >   clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
> > >   clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]
> > >
> > > The first group of warnings point out that linker flags were being added
> > > to all invocations of $(CC), even though they will only be used during
> > > the final vDSO link. Move those flags to ldflags-y.
> > >
> > > The second group of warnings are compiler or assembler flags that will
> > > be unused during linking. Filter them out from KBUILD_CFLAGS so that
> > > they are not used during linking.
> > >
> > > Additionally, '-z noexecstack' was added directly to the ld_and_check
> > > rule in commit 1d53c0192b15 ("powerpc/vdso: link with -z noexecstack")
> > > but now that there is a common ldflags variable, it can be moved there.
> > >
> > > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > > ---
> > > Cc: mpe@ellerman.id.au
> > > Cc: npiggin@gmail.com
> > > Cc: christophe.leroy@csgroup.eu
> > > Cc: linuxppc-dev@lists.ozlabs.org
> > > ---
> > >  arch/powerpc/kernel/vdso/Makefile | 18 +++++++++++-------
> > >  1 file changed, 11 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
> > > index 45c0cc5d34b6..4337b3aa9171 100644
> > > --- a/arch/powerpc/kernel/vdso/Makefile
> > > +++ b/arch/powerpc/kernel/vdso/Makefile
> > > @@ -47,13 +47,17 @@ KCOV_INSTRUMENT := n
> > >  UBSAN_SANITIZE := n
> > >  KASAN_SANITIZE := n
> > >
> > > -ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
> > > -ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > > -
> > > -CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
> > > +ccflags-y := -fno-common -fno-builtin
> > > +ldflags-y := -Wl,--hash-style=both -nostdlib -shared -z noexecstack
> > > +ldflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > > +# Filter flags that clang will warn are unused for linking
> > > +ldflags-y += $(filter-out $(CC_FLAGS_FTRACE) -Wa$(comma)%, $(KBUILD_CFLAGS))
> > > +
> > > +CC32FLAGS := -m32
> > > +LD32FLAGS := -Wl,-soname=linux-vdso32.so.1
> > >  AS32FLAGS := -D__VDSO32__
> > >
> > > -CC64FLAGS := -Wl,-soname=linux-vdso64.so.1
> >
> > Set CC64FLAGS := -m64 ?
>
> I do not think it is necessary. ldflags-y is filtered from
> KBUILD_CFLAGS, which should already include '-m64' (search for
> 'HAS_BIARCH' in arch/powerpc/Makefile). We would have seen a problem
> with this already if a 32-bit target (powerpc-linux-gnu-) CROSS_COMPILE
> value since $(c_flags) uses the main kernel's CROSS_COMPILE value.
>
> > > +LD64FLAGS := -Wl,-soname=linux-vdso64.so.1
> > >  AS64FLAGS := -D__VDSO64__
> > >
> > >  targets += vdso32.lds
> > > @@ -92,14 +96,14 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
> > >
> > >  # actual build commands
> > >  quiet_cmd_vdso32ld_and_check = VDSO32L $@
> > > -      cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > > +      cmd_vdso32ld_and_check = $(VDSOCC) $(ldflags-y) $(CC32FLAGS) $(LD32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> > >  quiet_cmd_vdso32as = VDSO32A $@
> > >        cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<
> > >  quiet_cmd_vdso32cc = VDSO32C $@
> > >        cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $<
> > >
> > >  quiet_cmd_vdso64ld_and_check = VDSO64L $@
> > > -      cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > > +      cmd_vdso64ld_and_check = $(VDSOCC) $(ldflags-y) $(CC64FLAGS) $(LD64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> >
> > If no CC64FLAGS := xxx is set, this can go?
>
> Good catch! CC64FLAGS can be removed. Masahiro, I am happy to send a v3
> when I am back online next week but if you are able to fix it up during
> application, please feel free to do so (once the PowerPC folks give
> their Acks of course).




I removed CC64FLAGS locally.




Just two comments.

- Is 7f3d349065d0c643f7f7013fbf9bc9f2c90b675f
  applicable to powerpc too?

  Maybe, as a follow-up cleanup, use $(LD)
  and remove -Wl, prefixes.


- ldflags-y still pulls $(KBUILD_CFLAGS).
  Potentially, a new flag addition to KBUILD_CFLAGS
  may trigger a new -Wunused-command-line-argument warning.

  I hope somebody takes a closer look at which flags
  are really needed for the linker.







> > >  quiet_cmd_vdso64as = VDSO64A $@
> > >        cmd_vdso64as = $(VDSOCC) $(a_flags) $(CC64FLAGS) $(AS64FLAGS) -c -o $@ $<
> > >
> > >
> > > --
> > > 2.39.0
> > >
>
> Thanks for the review, cheers!
> Nathan



-- 
Best Regards
Masahiro Yamada

Re: [PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS

[Masahiro Yamada]

On Thu, Jan 12, 2023 at 12:05 PM Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi all,
>
> Clang can emit a few different warnings when it encounters a flag that it
> recognizes but does not support internally. These warnings are elevated to
> errors within {as,cc}-option via -Werror to catch unsupported flags that should
> not be added to KBUILD_{A,C}FLAGS; see commit c3f0d0bc5b01 ("kbuild, LLVMLinux:
> Add -Werror to cc-option to support clang").
>
> If an unsupported flag is unconditionally to KBUILD_{A,C}FLAGS, all subsequent
> {as,cc}-option will always fail, preventing supported and even potentially
> necessary flags from getting adding to the tool flags.
>
> One would expect these warnings to be visible in the kernel build logs since
> they are added to KBUILD_{A,C}FLAGS but unfortunately, these warnings are
> hidden with clang's -Qunused-arguments flag, which is added to KBUILD_CPPFLAGS
> and used for both compiling and assembling files.
>
> Patches 1-4 address the internal inconsistencies of invoking the assembler
> within kbuild by using KBUILD_AFLAGS consistently and using '-x
> assembler-with-cpp' over '-x assembler'. This matches how assembly files are
> built across the kernel and helps avoid problems in situations where macro
> definitions or warning flags are present in KBUILD_AFLAGS, which cause
> instances of -Wunused-command-line-argument when the preprocessor is not called
> to consume them. There were a couple of places in architecture code where this
> change would break things so those are fixed first.
>
> Patches 5-12 clean up warnings that will show up when -Qunused-argument is
> dropped. I hope none of these are controversial.
>
> Patch 13 turns two warnings into errors so that the presence of unused flags
> cannot be easily ignored.
>
> Patch 14 drops -Qunused-argument. This is done last so that it can be easily
> reverted if need be.
>
> This series has seen my personal test framework, which tests several different
> configurations and architectures, with LLVM tip of tree (16.0.0). I have done
> defconfig, allmodconfig, and allnoconfig builds for arm, arm64, i386, mips,
> powerpc, riscv, s390, and x86_64 with GCC 12.2.0 as well but I am hoping the
> rest of the test infrastructure will catch any lurking problems.
>
> I would like this series to stay together so that there is no opportunity for
> breakage so please consider giving acks so that this can be carried via the
> kbuild tree (and many thanks to the people who have already provided such
> tags).


All applied to linux-kbuild. Thanks.

I left small comments in 07/14.








> ---
> Changes in v2:
> - Pick up tags where provided (thank you everyone!)
> - Patch 6 and 9: Clarify that '-s' is a compiler flag that is only relevant to
>   the linking phase and remove all mention of the assembler's '-s' flag, as the
>   assembler is never directly invoked (Nick, Segher)
> - Patch 7: Move '-z noexecstack' into new ldflags-y variable (Nick)
> - Patch 8: Reword commit message to explain the problem in a clearer manner
>   (Nick)
> - Link to v1: https://lore.kernel.org/r/20221228-drop-qunused-arguments-v1-0-658cbc8fc592@kernel.org
>
> ---
> Nathan Chancellor (12):
>       MIPS: Always use -Wa,-msoft-float and eliminate GAS_HAS_SET_HARDFLOAT
>       MIPS: Prefer cc-option for additions to cflags
>       powerpc: Remove linker flag from KBUILD_AFLAGS
>       powerpc/vdso: Remove unused '-s' flag from ASFLAGS
>       powerpc/vdso: Improve linker flags
>       powerpc/vdso: Remove an unsupported flag from vgettimeofday-32.o with clang
>       s390/vdso: Drop unused '-s' flag from KBUILD_AFLAGS_64
>       s390/vdso: Drop '-shared' from KBUILD_CFLAGS_64
>       s390/purgatory: Remove unused '-MD' and unnecessary '-c' flags
>       drm/amd/display: Do not add '-mhard-float' to dml_ccflags for clang
>       kbuild: Turn a couple more of clang's unused option warnings into errors
>       kbuild: Stop using '-Qunused-arguments' with clang
>
> Nick Desaulniers (2):
>       x86/boot/compressed: prefer cc-option for CFLAGS additions
>       kbuild: Update assembler calls to use proper flags and language target
>
>  Makefile                                    |  1 -
>  arch/mips/Makefile                          | 13 ++-------
>  arch/mips/include/asm/asmmacro-32.h         |  4 +--
>  arch/mips/include/asm/asmmacro.h            | 42 ++++++++++++++---------------
>  arch/mips/include/asm/fpregdef.h            | 14 ----------
>  arch/mips/include/asm/mipsregs.h            | 20 +++-----------
>  arch/mips/kernel/genex.S                    |  2 +-
>  arch/mips/kernel/r2300_fpu.S                |  4 +--
>  arch/mips/kernel/r4k_fpu.S                  | 12 ++++-----
>  arch/mips/kvm/fpu.S                         |  6 ++---
>  arch/mips/loongson2ef/Platform              |  2 +-
>  arch/powerpc/Makefile                       |  2 +-
>  arch/powerpc/kernel/vdso/Makefile           | 25 +++++++++++------
>  arch/s390/kernel/vdso64/Makefile            |  4 +--
>  arch/s390/purgatory/Makefile                |  2 +-
>  arch/x86/boot/compressed/Makefile           |  2 +-
>  drivers/gpu/drm/amd/display/dc/dml/Makefile |  3 ++-
>  scripts/Kconfig.include                     |  2 +-
>  scripts/Makefile.clang                      |  2 ++
>  scripts/Makefile.compiler                   |  8 +++---
>  scripts/as-version.sh                       |  2 +-
>  21 files changed, 74 insertions(+), 98 deletions(-)
> ---
> base-commit: 88603b6dc419445847923fcb7fe5080067a30f98
> change-id: 20221228-drop-qunused-arguments-0c5c7dae54fb
>
> Best regards,
> --
> Nathan Chancellor <nathan@kernel.org>
>


--
Best Regards
Masahiro Yamada

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Nathan Chancellor]

On Mon, Jan 23, 2023 at 02:27:51AM +0900, Masahiro Yamada wrote:
> On Fri, Jan 13, 2023 at 3:21 AM Nathan Chancellor <nathan@kernel.org> wrote:
> >
> > Hi Sedat,
> >
> > On Thu, Jan 12, 2023 at 07:02:30PM +0100, Sedat Dilek wrote:
> > > On Thu, Jan 12, 2023 at 4:06 AM Nathan Chancellor <nathan@kernel.org> wrote:
> > > >
> > > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
> > > > are several warnings in the PowerPC vDSO:
> > > >
> > > >   clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> > > >   clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> > > >   clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]
> > > >
> > > >   clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
> > > >   clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]
> > > >
> > > > The first group of warnings point out that linker flags were being added
> > > > to all invocations of $(CC), even though they will only be used during
> > > > the final vDSO link. Move those flags to ldflags-y.
> > > >
> > > > The second group of warnings are compiler or assembler flags that will
> > > > be unused during linking. Filter them out from KBUILD_CFLAGS so that
> > > > they are not used during linking.
> > > >
> > > > Additionally, '-z noexecstack' was added directly to the ld_and_check
> > > > rule in commit 1d53c0192b15 ("powerpc/vdso: link with -z noexecstack")
> > > > but now that there is a common ldflags variable, it can be moved there.
> > > >
> > > > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > > > ---
> > > > Cc: mpe@ellerman.id.au
> > > > Cc: npiggin@gmail.com
> > > > Cc: christophe.leroy@csgroup.eu
> > > > Cc: linuxppc-dev@lists.ozlabs.org
> > > > ---
> > > >  arch/powerpc/kernel/vdso/Makefile | 18 +++++++++++-------
> > > >  1 file changed, 11 insertions(+), 7 deletions(-)
> > > >
> > > > diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
> > > > index 45c0cc5d34b6..4337b3aa9171 100644
> > > > --- a/arch/powerpc/kernel/vdso/Makefile
> > > > +++ b/arch/powerpc/kernel/vdso/Makefile
> > > > @@ -47,13 +47,17 @@ KCOV_INSTRUMENT := n
> > > >  UBSAN_SANITIZE := n
> > > >  KASAN_SANITIZE := n
> > > >
> > > > -ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both
> > > > -ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > > > -
> > > > -CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32
> > > > +ccflags-y := -fno-common -fno-builtin
> > > > +ldflags-y := -Wl,--hash-style=both -nostdlib -shared -z noexecstack
> > > > +ldflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
> > > > +# Filter flags that clang will warn are unused for linking
> > > > +ldflags-y += $(filter-out $(CC_FLAGS_FTRACE) -Wa$(comma)%, $(KBUILD_CFLAGS))
> > > > +
> > > > +CC32FLAGS := -m32
> > > > +LD32FLAGS := -Wl,-soname=linux-vdso32.so.1
> > > >  AS32FLAGS := -D__VDSO32__
> > > >
> > > > -CC64FLAGS := -Wl,-soname=linux-vdso64.so.1
> > >
> > > Set CC64FLAGS := -m64 ?
> >
> > I do not think it is necessary. ldflags-y is filtered from
> > KBUILD_CFLAGS, which should already include '-m64' (search for
> > 'HAS_BIARCH' in arch/powerpc/Makefile). We would have seen a problem
> > with this already if a 32-bit target (powerpc-linux-gnu-) CROSS_COMPILE
> > value since $(c_flags) uses the main kernel's CROSS_COMPILE value.
> >
> > > > +LD64FLAGS := -Wl,-soname=linux-vdso64.so.1
> > > >  AS64FLAGS := -D__VDSO64__
> > > >
> > > >  targets += vdso32.lds
> > > > @@ -92,14 +96,14 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
> > > >
> > > >  # actual build commands
> > > >  quiet_cmd_vdso32ld_and_check = VDSO32L $@
> > > > -      cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > > > +      cmd_vdso32ld_and_check = $(VDSOCC) $(ldflags-y) $(CC32FLAGS) $(LD32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> > > >  quiet_cmd_vdso32as = VDSO32A $@
> > > >        cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<
> > > >  quiet_cmd_vdso32cc = VDSO32C $@
> > > >        cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $<
> > > >
> > > >  quiet_cmd_vdso64ld_and_check = VDSO64L $@
> > > > -      cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check)
> > > > +      cmd_vdso64ld_and_check = $(VDSOCC) $(ldflags-y) $(CC64FLAGS) $(LD64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
> > >
> > > If no CC64FLAGS := xxx is set, this can go?
> >
> > Good catch! CC64FLAGS can be removed. Masahiro, I am happy to send a v3
> > when I am back online next week but if you are able to fix it up during
> > application, please feel free to do so (once the PowerPC folks give
> > their Acks of course).
> 
> I removed CC64FLAGS locally.

Thank you!

> Just two comments.
> 
> - Is 7f3d349065d0c643f7f7013fbf9bc9f2c90b675f
>   applicable to powerpc too?
> 
>   Maybe, as a follow-up cleanup, use $(LD)
>   and remove -Wl, prefixes.

Yes, that should be possible to do here as well. Nick attempted it some
time ago but there was some complications with older tools, so we
decided to use ld.lld via the compiler in commit 4406b12214f6
("powerpc/vdso: Link with ld.lld when requested").

> - ldflags-y still pulls $(KBUILD_CFLAGS).
>   Potentially, a new flag addition to KBUILD_CFLAGS
>   may trigger a new -Wunused-command-line-argument warning.

Right, this is certainly possible. Hopefully it will not happen
frequently enough to be problematic.

>   I hope somebody takes a closer look at which flags
>   are really needed for the linker.

This is definitely not a bad idea.

Cheers,
Nathan

Re: [PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS

[Naresh Kamboju]

Hi Nathan,

On Thu, 12 Jan 2023 at 08:35, Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi all,
>
> Clang can emit a few different warnings when it encounters a flag that it
> recognizes but does not support internally. These warnings are elevated to
> errors within {as,cc}-option via -Werror to catch unsupported flags that should
> not be added to KBUILD_{A,C}FLAGS; see commit c3f0d0bc5b01 ("kbuild, LLVMLinux:
> Add -Werror to cc-option to support clang").
>
> If an unsupported flag is unconditionally to KBUILD_{A,C}FLAGS, all subsequent
> {as,cc}-option will always fail, preventing supported and even potentially
> necessary flags from getting adding to the tool flags.
>
> One would expect these warnings to be visible in the kernel build logs since
> they are added to KBUILD_{A,C}FLAGS but unfortunately, these warnings are
> hidden with clang's -Qunused-arguments flag, which is added to KBUILD_CPPFLAGS
> and used for both compiling and assembling files.
>
> Patches 1-4 address the internal inconsistencies of invoking the assembler
> within kbuild by using KBUILD_AFLAGS consistently and using '-x
> assembler-with-cpp' over '-x assembler'. This matches how assembly files are
> built across the kernel and helps avoid problems in situations where macro
> definitions or warning flags are present in KBUILD_AFLAGS, which cause
> instances of -Wunused-command-line-argument when the preprocessor is not called
> to consume them. There were a couple of places in architecture code where this
> change would break things so those are fixed first.
>
> Patches 5-12 clean up warnings that will show up when -Qunused-argument is
> dropped. I hope none of these are controversial.
>
> Patch 13 turns two warnings into errors so that the presence of unused flags
> cannot be easily ignored.
>
> Patch 14 drops -Qunused-argument. This is done last so that it can be easily
> reverted if need be.
>
> This series has seen my personal test framework, which tests several different
> configurations and architectures, with LLVM tip of tree (16.0.0). I have done
> defconfig, allmodconfig, and allnoconfig builds for arm, arm64, i386, mips,
> powerpc, riscv, s390, and x86_64 with GCC 12.2.0 as well but I am hoping the
> rest of the test infrastructure will catch any lurking problems.
>
> I would like this series to stay together so that there is no opportunity for
> breakage so please consider giving acks so that this can be carried via the
> kbuild tree (and many thanks to the people who have already provided such
> tags).
>
> ---
> Changes in v2:
> - Pick up tags where provided (thank you everyone!)
> - Patch 6 and 9: Clarify that '-s' is a compiler flag that is only relevant to
>   the linking phase and remove all mention of the assembler's '-s' flag, as the
>   assembler is never directly invoked (Nick, Segher)
> - Patch 7: Move '-z noexecstack' into new ldflags-y variable (Nick)
> - Patch 8: Reword commit message to explain the problem in a clearer manner
>   (Nick)
> - Link to v1: https://lore.kernel.org/r/20221228-drop-qunused-arguments-v1-0-658cbc8fc592@kernel.org
>
> ---
> Nathan Chancellor (12):
>       MIPS: Always use -Wa,-msoft-float and eliminate GAS_HAS_SET_HARDFLOAT
>       MIPS: Prefer cc-option for additions to cflags
>       powerpc: Remove linker flag from KBUILD_AFLAGS
>       powerpc/vdso: Remove unused '-s' flag from ASFLAGS
>       powerpc/vdso: Improve linker flags
>       powerpc/vdso: Remove an unsupported flag from vgettimeofday-32.o with clang
>       s390/vdso: Drop unused '-s' flag from KBUILD_AFLAGS_64
>       s390/vdso: Drop '-shared' from KBUILD_CFLAGS_64
>       s390/purgatory: Remove unused '-MD' and unnecessary '-c' flags
>       drm/amd/display: Do not add '-mhard-float' to dml_ccflags for clang
>       kbuild: Turn a couple more of clang's unused option warnings into errors
>       kbuild: Stop using '-Qunused-arguments' with clang
>
> Nick Desaulniers (2):
>       x86/boot/compressed: prefer cc-option for CFLAGS additions
>       kbuild: Update assembler calls to use proper flags and language target
>
>  Makefile                                    |  1 -
>  arch/mips/Makefile                          | 13 ++-------
>  arch/mips/include/asm/asmmacro-32.h         |  4 +--
>  arch/mips/include/asm/asmmacro.h            | 42 ++++++++++++++---------------
>  arch/mips/include/asm/fpregdef.h            | 14 ----------
>  arch/mips/include/asm/mipsregs.h            | 20 +++-----------
>  arch/mips/kernel/genex.S                    |  2 +-
>  arch/mips/kernel/r2300_fpu.S                |  4 +--
>  arch/mips/kernel/r4k_fpu.S                  | 12 ++++-----
>  arch/mips/kvm/fpu.S                         |  6 ++---
>  arch/mips/loongson2ef/Platform              |  2 +-
>  arch/powerpc/Makefile                       |  2 +-
>  arch/powerpc/kernel/vdso/Makefile           | 25 +++++++++++------
>  arch/s390/kernel/vdso64/Makefile            |  4 +--
>  arch/s390/purgatory/Makefile                |  2 +-
>  arch/x86/boot/compressed/Makefile           |  2 +-
>  drivers/gpu/drm/amd/display/dc/dml/Makefile |  3 ++-
>  scripts/Kconfig.include                     |  2 +-
>  scripts/Makefile.clang                      |  2 ++
>  scripts/Makefile.compiler                   |  8 +++---
>  scripts/as-version.sh                       |  2 +-
>  21 files changed, 74 insertions(+), 98 deletions(-)


FYI,
[ please provide comments, feedback and improvements on build/ ltp smoke tests ]

LKFT test farm have fetched your patch series [1]
[PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS
 [1] https://lore.kernel.org/llvm/20221228-drop-qunused-arguments-v2-0-9adbddd20d86@kernel.org/

Following build warnings and errors reported.

sh:
gcc-11-defconfig — FAIL
gcc-11-shx3_defconfig — FAIL
https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/https___lore_kernel_org_llvm_20221228-drop-qunused-arguments-v2-1-9adbddd20d86_kernel_org/testrun/14221835/suite/build/tests/

mainline getting passed.
https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14298156/suite/build/test/gcc-11-defconfig/history/
https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14298156/suite/build/test/gcc-11-shx3_defconfig/history/

Build error:
In function 'follow_pmd_mask',
    inlined from 'follow_pud_mask' at /builds/linux/mm/gup.c:735:9,
    inlined from 'follow_p4d_mask' at /builds/linux/mm/gup.c:752:9,
    inlined from 'follow_page_mask' at /builds/linux/mm/gup.c:809:9:
/builds/linux/include/linux/compiler_types.h:358:45: error: call to
'__compiletime_assert_263' declared with attribute error: Unsupported
access size for {READ,WRITE}_ONCE().
  358 |         _compiletime_assert(condition, msg,
__compiletime_assert_, __COUNTER__)


s390:
clang-15-defconfig — FAIL
https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/https___lore_kernel_org_llvm_20221228-drop-qunused-arguments-v2-1-9adbddd20d86_kernel_org/testrun/14221913/suite/build/tests/

mainline getting passed.
https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14300495/suite/build/test/clang-15-defconfig/history/

Build error:
make --silent --keep-going --jobs=8
O=/home/tuxbuild/.cache/tuxmake/builds/1/build LLVM_IAS=0 ARCH=s390
CROSS_COMPILE=s390x-linux-gnu- 'HOSTCC=sccache clang' 'CC=sccache
clang'
`.exit.text' referenced in section `__jump_table' of fs/fuse/inode.o:
defined in discarded section `.exit.text' of fs/fuse/inode.o
`.exit.text' referenced in section `__jump_table' of fs/fuse/inode.o:
defined in discarded section `.exit.text' of fs/fuse/inode.o
`.exit.text' referenced in section `__bug_table' of crypto/algboss.o:
defined in discarded section `.exit.text' of crypto/algboss.o
`.exit.text' referenced in section `__bug_table' of drivers/scsi/sd.o:
defined in discarded section `.exit.text' of drivers/scsi/sd.o
`.exit.text' referenced in section `__jump_table' of drivers/md/md.o:
defined in discarded section `.exit.text' of drivers/md/md.o
`.exit.text' referenced in section `__jump_table' of drivers/md/md.o:
defined in discarded section `.exit.text' of drivers/md/md.o
`.exit.text' referenced in section `.altinstructions' of
drivers/md/md.o: defined in discarded section `.exit.text' of
drivers/md/md.o
`.exit.text' referenced in section `.altinstructions' of
drivers/md/md.o: defined in discarded section `.exit.text' of
drivers/md/md.o
`.exit.text' referenced in section `.altinstructions' of
net/iucv/iucv.o: defined in discarded section `.exit.text' of
net/iucv/iucv.o
`.exit.text' referenced in section `__bug_table' of
drivers/s390/cio/qdio_thinint.o: defined in discarded section
`.exit.text' of drivers/s390/cio/qdio_thinint.o
`.exit.text' referenced in section `__bug_table' of
drivers/s390/net/qeth_l3_main.o: defined in discarded section
`.exit.text' of drivers/s390/net/qeth_l3_main.o
`.exit.text' referenced in section `__bug_table' of
drivers/s390/net/qeth_l3_main.o: defined in discarded section
`.exit.text' of drivers/s390/net/qeth_l3_main.o
s390x-linux-gnu-ld: BFD (GNU Binutils for Debian) 2.35.2 assertion
fail ../../bfd/elf64-s390.c:3349
make[2]: *** [/builds/linux/scripts/Makefile.vmlinux:34: vmlinux] Error 1

But,
Build and boot pass on arm64, arm, x86_64 and i386.
Build test performed for mips, parisc, riscv, s390, sh, sparc and
powerpc (known build errors for maple_defconfig and cell_defconfig),

Please refer following link for detailed build, boot, LTP smoketest.
https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/https___lore_kernel_org_llvm_20221228-drop-qunused-arguments-v2-1-9adbddd20d86_kernel_org/?failures_only=false&results_layout=table#!#test-results

Best regards
Naresh Kamboju

--
Linaro LKFT
https://lkft.linaro.org

> ---
> base-commit: 88603b6dc419445847923fcb7fe5080067a30f98
> change-id: 20221228-drop-qunused-arguments-0c5c7dae54fb
>
> Best regards,
> --
> Nathan Chancellor <nathan@kernel.org>
>
>

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Segher Boessenkool]

Hi!

On Wed, Jan 11, 2023 at 08:05:04PM -0700, Nathan Chancellor wrote:
> When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
> are several warnings in the PowerPC vDSO:
> 
>   clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
>   clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
>   clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]
> 
>   clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
>   clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]

There is nothing wrong with the warnings, but as usual, -Werror is very
counterproductive.

> The first group of warnings point out that linker flags were being added
> to all invocations of $(CC), even though they will only be used during
> the final vDSO link. Move those flags to ldflags-y.

Which is explicitly allowed, and won't do anything, so nothing harmful
either.  It is not a bad idea to avoid this if that is trivial to do,
of course.

> The second group of warnings are compiler or assembler flags that will
> be unused during linking. Filter them out from KBUILD_CFLAGS so that
> they are not used during linking.

And here it is even more obviously fine.  If you need obfuscation like
in your patch, it is better not to do this imo.

The warning text "linker input unused" is misleading btw.  It would be
good to warn about that, if it was true: very likely the user didn't
intend what he wrote.  But a linker input is an object file, or perhaps
a linker script.  These things are just compiler flags.


Segher

Re: [PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS

[Nathan Chancellor]

Hi Naresh,

On Mon, Jan 23, 2023 at 07:28:10PM +0530, Naresh Kamboju wrote:
> FYI,
> [ please provide comments, feedback and improvements on build/ ltp smoke tests ]
> 
> LKFT test farm have fetched your patch series [1]
> [PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS
>  [1] https://lore.kernel.org/llvm/20221228-drop-qunused-arguments-v2-0-9adbddd20d86@kernel.org/

Thank you a lot for testing this series, it is much appreciated!

It looks like this was applied on top of 6.2-rc3 if I am reading your
logs right but your mainline testing is recent, 6.2-rc5. I think the
errors you are seeing here are just existing mainline regressions that
were later fixed.

> Following build warnings and errors reported.
> 
> sh:
> gcc-11-defconfig — FAIL
> gcc-11-shx3_defconfig — FAIL
> https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/https___lore_kernel_org_llvm_20221228-drop-qunused-arguments-v2-1-9adbddd20d86_kernel_org/testrun/14221835/suite/build/tests/
> 
> mainline getting passed.
> https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14298156/suite/build/test/gcc-11-defconfig/history/
> https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14298156/suite/build/test/gcc-11-shx3_defconfig/history/
> 
> Build error:
> In function 'follow_pmd_mask',
>     inlined from 'follow_pud_mask' at /builds/linux/mm/gup.c:735:9,
>     inlined from 'follow_p4d_mask' at /builds/linux/mm/gup.c:752:9,
>     inlined from 'follow_page_mask' at /builds/linux/mm/gup.c:809:9:
> /builds/linux/include/linux/compiler_types.h:358:45: error: call to
> '__compiletime_assert_263' declared with attribute error: Unsupported
> access size for {READ,WRITE}_ONCE().
>   358 |         _compiletime_assert(condition, msg,
> __compiletime_assert_, __COUNTER__)

I think this was fixed with mainline commit 526970be53d5 ("sh/mm: Fix
pmd_t for real"), released in 6.2-rc4. You can see a previous build
failing in the same manner:

https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc3-9-g5a41237ad1d4/testrun/14056384/suite/build/tests/

> s390:
> clang-15-defconfig — FAIL
> https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/https___lore_kernel_org_llvm_20221228-drop-qunused-arguments-v2-1-9adbddd20d86_kernel_org/testrun/14221913/suite/build/tests/
> 
> mainline getting passed.
> https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14300495/suite/build/test/clang-15-defconfig/history/
> 
> Build error:
> make --silent --keep-going --jobs=8
> O=/home/tuxbuild/.cache/tuxmake/builds/1/build LLVM_IAS=0 ARCH=s390
> CROSS_COMPILE=s390x-linux-gnu- 'HOSTCC=sccache clang' 'CC=sccache
> clang'
> `.exit.text' referenced in section `__jump_table' of fs/fuse/inode.o:
> defined in discarded section `.exit.text' of fs/fuse/inode.o
> `.exit.text' referenced in section `__jump_table' of fs/fuse/inode.o:
> defined in discarded section `.exit.text' of fs/fuse/inode.o
> `.exit.text' referenced in section `__bug_table' of crypto/algboss.o:
> defined in discarded section `.exit.text' of crypto/algboss.o
> `.exit.text' referenced in section `__bug_table' of drivers/scsi/sd.o:
> defined in discarded section `.exit.text' of drivers/scsi/sd.o
> `.exit.text' referenced in section `__jump_table' of drivers/md/md.o:
> defined in discarded section `.exit.text' of drivers/md/md.o
> `.exit.text' referenced in section `__jump_table' of drivers/md/md.o:
> defined in discarded section `.exit.text' of drivers/md/md.o
> `.exit.text' referenced in section `.altinstructions' of
> drivers/md/md.o: defined in discarded section `.exit.text' of
> drivers/md/md.o
> `.exit.text' referenced in section `.altinstructions' of
> drivers/md/md.o: defined in discarded section `.exit.text' of
> drivers/md/md.o
> `.exit.text' referenced in section `.altinstructions' of
> net/iucv/iucv.o: defined in discarded section `.exit.text' of
> net/iucv/iucv.o
> `.exit.text' referenced in section `__bug_table' of
> drivers/s390/cio/qdio_thinint.o: defined in discarded section
> `.exit.text' of drivers/s390/cio/qdio_thinint.o
> `.exit.text' referenced in section `__bug_table' of
> drivers/s390/net/qeth_l3_main.o: defined in discarded section
> `.exit.text' of drivers/s390/net/qeth_l3_main.o
> `.exit.text' referenced in section `__bug_table' of
> drivers/s390/net/qeth_l3_main.o: defined in discarded section
> `.exit.text' of drivers/s390/net/qeth_l3_main.o
> s390x-linux-gnu-ld: BFD (GNU Binutils for Debian) 2.35.2 assertion
> fail ../../bfd/elf64-s390.c:3349
> make[2]: *** [/builds/linux/scripts/Makefile.vmlinux:34: vmlinux] Error 1

This should be fixed with mainline commit a494398bde27 ("s390: define
RUNTIME_DISCARD_EXIT to fix link error with GNU ld < 2.36"), released in
6.2-rc4 as well. Same as before, visible in mainline at one point
without this series:

https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc3-9-g5a41237ad1d4/testrun/14057142/suite/build/tests/

> But,
> Build and boot pass on arm64, arm, x86_64 and i386.
> Build test performed for mips, parisc, riscv, s390, sh, sparc and
> powerpc (known build errors for maple_defconfig and cell_defconfig),

Good to hear!

Please consider retesting this series on top of 6.2-rc5 or testing the
current kbuild tree, which has this series applied in it:

https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/log/?h=for-next

Cheers,
Nathan

Re: [PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS

[Naresh Kamboju]

Hi Nathan,

On Mon, 23 Jan 2023 at 21:41, Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi Naresh,
>
> On Mon, Jan 23, 2023 at 07:28:10PM +0530, Naresh Kamboju wrote:
> > FYI,
> > [ please provide comments, feedback and improvements on build/ ltp smoke tests ]
> >
> > LKFT test farm have fetched your patch series [1]
> > [PATCH v2 00/14] Remove clang's -Qunused-arguments from KBUILD_CPPFLAGS
> >  [1] https://lore.kernel.org/llvm/20221228-drop-qunused-arguments-v2-0-9adbddd20d86@kernel.org/
>
> Thank you a lot for testing this series, it is much appreciated!
>
> It looks like this was applied on top of 6.2-rc3 if I am reading your
> logs right but your mainline testing is recent, 6.2-rc5. I think the
> errors you are seeing here are just existing mainline regressions that
> were later fixed.
>
> > Following build warnings and errors reported.
> >
> > sh:
> > gcc-11-defconfig — FAIL
> > gcc-11-shx3_defconfig — FAIL
> > https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/https___lore_kernel_org_llvm_20221228-drop-qunused-arguments-v2-1-9adbddd20d86_kernel_org/testrun/14221835/suite/build/tests/
> >
> > mainline getting passed.
> > https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14298156/suite/build/test/gcc-11-defconfig/history/
> > https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14298156/suite/build/test/gcc-11-shx3_defconfig/history/
> >
> > Build error:
> > In function 'follow_pmd_mask',
> >     inlined from 'follow_pud_mask' at /builds/linux/mm/gup.c:735:9,
> >     inlined from 'follow_p4d_mask' at /builds/linux/mm/gup.c:752:9,
> >     inlined from 'follow_page_mask' at /builds/linux/mm/gup.c:809:9:
> > /builds/linux/include/linux/compiler_types.h:358:45: error: call to
> > '__compiletime_assert_263' declared with attribute error: Unsupported
> > access size for {READ,WRITE}_ONCE().
> >   358 |         _compiletime_assert(condition, msg,
> > __compiletime_assert_, __COUNTER__)
>
> I think this was fixed with mainline commit 526970be53d5 ("sh/mm: Fix
> pmd_t for real"), released in 6.2-rc4. You can see a previous build
> failing in the same manner:
>
> https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc3-9-g5a41237ad1d4/testrun/14056384/suite/build/tests/
>
> > s390:
> > clang-15-defconfig — FAIL
> > https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/https___lore_kernel_org_llvm_20221228-drop-qunused-arguments-v2-1-9adbddd20d86_kernel_org/testrun/14221913/suite/build/tests/
> >
> > mainline getting passed.
> > https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc5/testrun/14300495/suite/build/test/clang-15-defconfig/history/
> >
> > Build error:
> > make --silent --keep-going --jobs=8
> > O=/home/tuxbuild/.cache/tuxmake/builds/1/build LLVM_IAS=0 ARCH=s390
> > CROSS_COMPILE=s390x-linux-gnu- 'HOSTCC=sccache clang' 'CC=sccache
> > clang'
> > `.exit.text' referenced in section `__jump_table' of fs/fuse/inode.o:
> > defined in discarded section `.exit.text' of fs/fuse/inode.o
> > `.exit.text' referenced in section `__jump_table' of fs/fuse/inode.o:
> > defined in discarded section `.exit.text' of fs/fuse/inode.o
> > `.exit.text' referenced in section `__bug_table' of crypto/algboss.o:
> > defined in discarded section `.exit.text' of crypto/algboss.o
> > `.exit.text' referenced in section `__bug_table' of drivers/scsi/sd.o:
> > defined in discarded section `.exit.text' of drivers/scsi/sd.o
> > `.exit.text' referenced in section `__jump_table' of drivers/md/md.o:
> > defined in discarded section `.exit.text' of drivers/md/md.o
> > `.exit.text' referenced in section `__jump_table' of drivers/md/md.o:
> > defined in discarded section `.exit.text' of drivers/md/md.o
> > `.exit.text' referenced in section `.altinstructions' of
> > drivers/md/md.o: defined in discarded section `.exit.text' of
> > drivers/md/md.o
> > `.exit.text' referenced in section `.altinstructions' of
> > drivers/md/md.o: defined in discarded section `.exit.text' of
> > drivers/md/md.o
> > `.exit.text' referenced in section `.altinstructions' of
> > net/iucv/iucv.o: defined in discarded section `.exit.text' of
> > net/iucv/iucv.o
> > `.exit.text' referenced in section `__bug_table' of
> > drivers/s390/cio/qdio_thinint.o: defined in discarded section
> > `.exit.text' of drivers/s390/cio/qdio_thinint.o
> > `.exit.text' referenced in section `__bug_table' of
> > drivers/s390/net/qeth_l3_main.o: defined in discarded section
> > `.exit.text' of drivers/s390/net/qeth_l3_main.o
> > `.exit.text' referenced in section `__bug_table' of
> > drivers/s390/net/qeth_l3_main.o: defined in discarded section
> > `.exit.text' of drivers/s390/net/qeth_l3_main.o
> > s390x-linux-gnu-ld: BFD (GNU Binutils for Debian) 2.35.2 assertion
> > fail ../../bfd/elf64-s390.c:3349
> > make[2]: *** [/builds/linux/scripts/Makefile.vmlinux:34: vmlinux] Error 1
>
> This should be fixed with mainline commit a494398bde27 ("s390: define
> RUNTIME_DISCARD_EXIT to fix link error with GNU ld < 2.36"), released in
> 6.2-rc4 as well. Same as before, visible in mainline at one point
> without this series:
>
> https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2-rc3-9-g5a41237ad1d4/testrun/14057142/suite/build/tests/
>
> > But,
> > Build and boot pass on arm64, arm, x86_64 and i386.
> > Build test performed for mips, parisc, riscv, s390, sh, sparc and
> > powerpc (known build errors for maple_defconfig and cell_defconfig),
>
> Good to hear!
>
> Please consider retesting this series on top of 6.2-rc5 or testing the
> current kbuild tree, which has this series applied in it:

This is the perfect place to test.

> https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/log/?h=for-next

Build test pass on arm, arm64, i386, mips, parisc, powerpc, riscv, s390, sh,
sparc and x86_64.
Boot and LTP smoke pass on qemu-arm64, qemu-armv7, qemu-i386 and qemu-x86_64.

  Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
  Tested-by: Anders Roxell <anders.roxell@linaro.org>

Please refer to the following link for details of testing.
  https://qa-reports.linaro.org/~anders.roxell/linux-mainline-patches/build/linux-kbuild_masahiroy-branch-kbuild-20230124/?failures_only=false&results_layout=table#!#test-results

metadata:
  git_describe : v6.2-rc5-46-ga778c9dd138b
  git_repo : https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git
  git_sha : a778c9dd138b4f4410779705b444d58ce6f8fc44
  git_short_log : a778c9dd138b ("builddeb: clean generated package content")

--
Linaro LKFT
https://lkft.linaro.org

>
> Cheers,
> Nathan

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Nathan Chancellor]

On Mon, Jan 23, 2023 at 09:07:16AM -0600, Segher Boessenkool wrote:
> Hi!
> 
> On Wed, Jan 11, 2023 at 08:05:04PM -0700, Nathan Chancellor wrote:
> > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there
> > are several warnings in the PowerPC vDSO:
> > 
> >   clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> >   clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> >   clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument]
> > 
> >   clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument]
> >   clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument]
> 
> There is nothing wrong with the warnings, but as usual, -Werror is very
> counterproductive.
> 
> > The first group of warnings point out that linker flags were being added
> > to all invocations of $(CC), even though they will only be used during
> > the final vDSO link. Move those flags to ldflags-y.
> 
> Which is explicitly allowed, and won't do anything, so nothing harmful
> either.  It is not a bad idea to avoid this if that is trivial to do,
> of course.

I think this patch shows that it is trivial to do this, the primary core
of the diff is only a few lines.

> > The second group of warnings are compiler or assembler flags that will
> > be unused during linking. Filter them out from KBUILD_CFLAGS so that
> > they are not used during linking.
> 
> And here it is even more obviously fine.  If you need obfuscation like
> in your patch, it is better not to do this imo.

I do not think this patch really obfuscates anything? The filtering is
pretty clear to me.

If this is a real objection to the patch, I suppose we could just
localize '-Qunused-arguments' to this Makefile and be done with it but I
do not think this change is a bad solution to the problem either.

Cheers,
Nathan

Re: [PATCH v2 07/14] powerpc/vdso: Improve linker flags

[Segher Boessenkool]

On Tue, Jan 24, 2023 at 09:14:52AM -0700, Nathan Chancellor wrote:
> On Mon, Jan 23, 2023 at 09:07:16AM -0600, Segher Boessenkool wrote:
> > And here it is even more obviously fine.  If you need obfuscation like
> > in your patch, it is better not to do this imo.
> 
> I do not think this patch really obfuscates anything? The filtering is
> pretty clear to me.

And not having such filtering is more obvious and more clear.

It doesn't matter much for just this patch of course, but it will make
the code significantly harder to read (and deal with in other ways) if
this continues.

> If this is a real objection to the patch, I suppose we could just
> localize '-Qunused-arguments' to this Makefile and be done with it but I
> do not think this change is a bad solution to the problem either.

It is a comment about the direction this patch is moving us in.  I don't
think it is a good idea at all to try to avoid all warnings, and even
more so it is a bad idea to make objectively worse source code just to
appease a trigger-happy and questionable warning.

As I said, you can often avoid warnings by writing better code, like
part of the patch did.  That is a good reaction to warnings.  Making
worse code to avoid warnings is not a good idea normally.

Just don't use -Werror by default, and don't make other people suffer
its yoke!


Segher

Re: [PATCH v2 05/14] powerpc: Remove linker flag from KBUILD_AFLAGS

[Michael Ellerman]

Nathan Chancellor <nathan@kernel.org> writes:
> When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> points out that KBUILD_AFLAGS contains a linker flag, which will be
> used:

Should that say "unused" ?

>   clang: error: -Wl,-a32: 'linker' input unused [-Werror,-Wunused-command-line-argument]
>
> This was likely supposed to be '-Wa,-a$(BITS)'. However, this change is
> unnecessary, as all supported versions of clang and gcc will pass '-a64'
> or '-a32' to GNU as based on the value of '-m'; the behavior of the
> latest stable release of the oldest supported major version of each
> compiler is shown below and each compiler's latest release exhibits the
> same behavior (GCC 12.2.0 and Clang 15.0.6).
>
>   $ powerpc64-linux-gcc --version | head -1
>   powerpc64-linux-gcc (GCC) 5.5.0
>
>   $ powerpc64-linux-gcc -m64 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
>   .../as -a64 -mppc64 -many -mbig -o /dev/null /tmp/cctwuBzZ.s
>
>   $ powerpc64-linux-gcc -m32 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
>   .../as -a32 -mppc -many -mbig -o /dev/null /tmp/ccaZP4mF.sg
>
>   $ clang --version | head -1
>   Ubuntu clang version 11.1.0-++20211011094159+1fdec59bffc1-1~exp1~20211011214622.5
>
>   $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
>     -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
>    "/usr/bin/powerpc64-linux-gnu-as" "-a64" "-mppc64" "-many" "-o" "/dev/null" "/tmp/null-80267c.s"
>
>   $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
>     -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
>    "/usr/bin/powerpc64-linux-gnu-as" "-a32" "-mppc" "-many" "-o" "/dev/null" "/tmp/null-ab8f8d.s"
>
> Remove this flag altogether to avoid future issues.
>
> Fixes: 1421dc6d4829 ("powerpc/kbuild: Use flags variables rather than overriding LD/CC/AS")
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> Cc: mpe@ellerman.id.au

Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

cheers

Re: [PATCH v2 06/14] powerpc/vdso: Remove unused '-s' flag from ASFLAGS

[Michael Ellerman]

Nathan Chancellor <nathan@kernel.org> writes:
> When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> warns:
>
>   clang-16: error: argument unused during compilation: '-s' [-Werror,-Wunused-command-line-argument]
>
> The compiler's '-s' flag is a linking option (it is passed along to the
> linker directly), which means it does nothing when the linker is not
> invoked by the compiler. The kernel builds all .o files with '-c', which
> stops the compilation pipeline before linking, so '-s' can be safely
> dropped from ASFLAGS.
>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
> ---
> Cc: mpe@ellerman.id.au

Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

cheers

Re: [PATCH v2 05/14] powerpc: Remove linker flag from KBUILD_AFLAGS

[Masahiro Yamada]

On Wed, Jan 25, 2023 at 1:11 PM Michael Ellerman <mpe@ellerman.id.au> wrote:
>
> Nathan Chancellor <nathan@kernel.org> writes:
> > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> > points out that KBUILD_AFLAGS contains a linker flag, which will be
> > used:
>
> Should that say "unused" ?



Nathan, shall I fix it up locally?
(it will change the commit hash, though.)





>
> >   clang: error: -Wl,-a32: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> >
> > This was likely supposed to be '-Wa,-a$(BITS)'. However, this change is
> > unnecessary, as all supported versions of clang and gcc will pass '-a64'
> > or '-a32' to GNU as based on the value of '-m'; the behavior of the
> > latest stable release of the oldest supported major version of each
> > compiler is shown below and each compiler's latest release exhibits the
> > same behavior (GCC 12.2.0 and Clang 15.0.6).
> >
> >   $ powerpc64-linux-gcc --version | head -1
> >   powerpc64-linux-gcc (GCC) 5.5.0
> >
> >   $ powerpc64-linux-gcc -m64 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
> >   .../as -a64 -mppc64 -many -mbig -o /dev/null /tmp/cctwuBzZ.s
> >
> >   $ powerpc64-linux-gcc -m32 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
> >   .../as -a32 -mppc -many -mbig -o /dev/null /tmp/ccaZP4mF.sg
> >
> >   $ clang --version | head -1
> >   Ubuntu clang version 11.1.0-++20211011094159+1fdec59bffc1-1~exp1~20211011214622.5
> >
> >   $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
> >     -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
> >    "/usr/bin/powerpc64-linux-gnu-as" "-a64" "-mppc64" "-many" "-o" "/dev/null" "/tmp/null-80267c.s"
> >
> >   $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
> >     -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
> >    "/usr/bin/powerpc64-linux-gnu-as" "-a32" "-mppc" "-many" "-o" "/dev/null" "/tmp/null-ab8f8d.s"
> >
> > Remove this flag altogether to avoid future issues.
> >
> > Fixes: 1421dc6d4829 ("powerpc/kbuild: Use flags variables rather than overriding LD/CC/AS")
> > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > ---
> > Cc: mpe@ellerman.id.au
>
> Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
>
> cheers



-- 
Best Regards
Masahiro Yamada

Re: [PATCH v2 05/14] powerpc: Remove linker flag from KBUILD_AFLAGS

[Nathan Chancellor]

On Thu, Jan 26, 2023 at 10:29:54AM +0900, Masahiro Yamada wrote:
> On Wed, Jan 25, 2023 at 1:11 PM Michael Ellerman <mpe@ellerman.id.au> wrote:
> >
> > Nathan Chancellor <nathan@kernel.org> writes:
> > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> > > points out that KBUILD_AFLAGS contains a linker flag, which will be
> > > used:
> >
> > Should that say "unused" ?
> 
> 
> 
> Nathan, shall I fix it up locally?
> (it will change the commit hash, though.)

Yes please, if you would not mind. Sorry about that and thank you for
spotting it Michael!

Since you have to rebase to fix it, you can include Michael's acks?

Cheers,
Nathan

> > >   clang: error: -Wl,-a32: 'linker' input unused [-Werror,-Wunused-command-line-argument]
> > >
> > > This was likely supposed to be '-Wa,-a$(BITS)'. However, this change is
> > > unnecessary, as all supported versions of clang and gcc will pass '-a64'
> > > or '-a32' to GNU as based on the value of '-m'; the behavior of the
> > > latest stable release of the oldest supported major version of each
> > > compiler is shown below and each compiler's latest release exhibits the
> > > same behavior (GCC 12.2.0 and Clang 15.0.6).
> > >
> > >   $ powerpc64-linux-gcc --version | head -1
> > >   powerpc64-linux-gcc (GCC) 5.5.0
> > >
> > >   $ powerpc64-linux-gcc -m64 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
> > >   .../as -a64 -mppc64 -many -mbig -o /dev/null /tmp/cctwuBzZ.s
> > >
> > >   $ powerpc64-linux-gcc -m32 -### -x assembler-with-cpp -c -o /dev/null /dev/null &| grep 'as '
> > >   .../as -a32 -mppc -many -mbig -o /dev/null /tmp/ccaZP4mF.sg
> > >
> > >   $ clang --version | head -1
> > >   Ubuntu clang version 11.1.0-++20211011094159+1fdec59bffc1-1~exp1~20211011214622.5
> > >
> > >   $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
> > >     -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
> > >    "/usr/bin/powerpc64-linux-gnu-as" "-a64" "-mppc64" "-many" "-o" "/dev/null" "/tmp/null-80267c.s"
> > >
> > >   $ clang --target=powerpc64-linux-gnu -fno-integrated-as -m64 -### \
> > >     -x assembler-with-cpp -c -o /dev/null /dev/null &| grep gnu-as
> > >    "/usr/bin/powerpc64-linux-gnu-as" "-a32" "-mppc" "-many" "-o" "/dev/null" "/tmp/null-ab8f8d.s"
> > >
> > > Remove this flag altogether to avoid future issues.
> > >
> > > Fixes: 1421dc6d4829 ("powerpc/kbuild: Use flags variables rather than overriding LD/CC/AS")
> > > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > > ---
> > > Cc: mpe@ellerman.id.au
> >
> > Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
> >
> > cheers
> 
> 
> 
> -- 
> Best Regards
> Masahiro Yamada

Re: [PATCH v2 05/14] powerpc: Remove linker flag from KBUILD_AFLAGS

[Masahiro Yamada]

On Thu, Jan 26, 2023 at 11:07 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> On Thu, Jan 26, 2023 at 10:29:54AM +0900, Masahiro Yamada wrote:
> > On Wed, Jan 25, 2023 at 1:11 PM Michael Ellerman <mpe@ellerman.id.au> wrote:
> > >
> > > Nathan Chancellor <nathan@kernel.org> writes:
> > > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> > > > points out that KBUILD_AFLAGS contains a linker flag, which will be
> > > > used:
> > >
> > > Should that say "unused" ?
> >
> >
> >
> > Nathan, shall I fix it up locally?
> > (it will change the commit hash, though.)
>
> Yes please, if you would not mind. Sorry about that and thank you for
> spotting it Michael!
>
> Since you have to rebase to fix it, you can include Michael's acks?
>
> Cheers,
> Nathan



Done.








-- 
Best Regards
Masahiro Yamada

Re: [PATCH v2 05/14] powerpc: Remove linker flag from KBUILD_AFLAGS

[Michael Ellerman]

Masahiro Yamada <masahiroy@kernel.org> writes:
> On Thu, Jan 26, 2023 at 11:07 AM Nathan Chancellor <nathan@kernel.org> wrote:
>>
>> On Thu, Jan 26, 2023 at 10:29:54AM +0900, Masahiro Yamada wrote:
>> > On Wed, Jan 25, 2023 at 1:11 PM Michael Ellerman <mpe@ellerman.id.au> wrote:
>> > >
>> > > Nathan Chancellor <nathan@kernel.org> writes:
>> > > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
>> > > > points out that KBUILD_AFLAGS contains a linker flag, which will be
>> > > > used:
>> > >
>> > > Should that say "unused" ?
>> >
>> >
>> >
>> > Nathan, shall I fix it up locally?
>> > (it will change the commit hash, though.)
>>
>> Yes please, if you would not mind. Sorry about that and thank you for
>> spotting it Michael!
>>
>> Since you have to rebase to fix it, you can include Michael's acks?
>>
>> Cheers,
>> Nathan
>
> Done.

Thanks.

cheers