[PATCH v2 0/2] arm64: Simplify gas LSE support detection

[PATCH v2 0/2] arm64: Simplify gas LSE support detection

[Catalin Marinas]

Version two of the patch series moving the LSE assembler support
detection from Makefile to Kconfig.

Changes since v1 [1]:

- Re-introduce the Makefile warning if the .config contains
  CONFIG_ARM64_USE_LSE_ATOMICS but the assembler does not support the
  feature, disabling CONFIG_ARM64_LSE_ATOMICS.

[1] http://lkml.kernel.org/r/20200109174948.48211-1-catalin.marinas@arm.com

Catalin Marinas (2):
  kbuild: Add support for 'as-instr' to be used in Kconfig files
  arm64: Move the LSE gas support detection to Kconfig

 arch/arm64/Kconfig                    |  5 +++++
 arch/arm64/Makefile                   | 11 ++++-------
 arch/arm64/include/asm/atomic_ll_sc.h |  2 +-
 arch/arm64/include/asm/lse.h          |  6 +++---
 arch/arm64/kernel/cpufeature.c        |  4 ++--
 scripts/Kconfig.include               |  4 ++++
 6 files changed, 19 insertions(+), 13 deletions(-)


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[PATCH v2 1/2] kbuild: Add support for 'as-instr' to be used in Kconfig files

[Catalin Marinas]

Similar to 'cc-option' or 'ld-option', it is occasionally necessary to
check whether the assembler supports certain ISA extensions. In the
arm64 code we currently do this in Makefile with an additional define:

lseinstr := $(call as-instr,.arch_extension lse,-DCONFIG_AS_LSE=1)

Add the 'as-instr' option so that it can be used in Kconfig directly:

	def_bool $(as-instr,.arch_extension lse)

Acked-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---
 scripts/Kconfig.include | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index d4adfbe42690..9d07e59cbdf7 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -31,6 +31,10 @@ cc-option = $(success,$(CC) -Werror $(CLANG_FLAGS) $(1) -E -x c /dev/null -o /de
 # Return y if the linker supports <flag>, n otherwise
 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 -)
+
 # check if $(CC) and $(LD) exist
 $(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
 $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)

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[PATCH v2 2/2] arm64: Move the LSE gas support detection to Kconfig

[Catalin Marinas]

As the Kconfig syntax gained support for $(as-instr) tests, move the LSE
gas support detection from Makefile to the main arm64 Kconfig and remove
the additional CONFIG_AS_LSE definition and check.

Cc: Will Deacon <will@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---

Notes:
    v2:
    - Re-introduce build-time warning if .config wants LSE atomics but gas
      does not support it
    - Given that the patch was modified, I have not added Vladimir's
      reviewed-by tag on v1

 arch/arm64/Kconfig                    |  5 +++++
 arch/arm64/Makefile                   | 11 ++++-------
 arch/arm64/include/asm/atomic_ll_sc.h |  2 +-
 arch/arm64/include/asm/lse.h          |  6 +++---
 arch/arm64/kernel/cpufeature.c        |  4 ++--
 5 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index b1b4476ddb83..cf3b6d2a67cf 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1363,6 +1363,11 @@ config ARM64_PAN
 	 instruction if the cpu does not implement the feature.
 
 config ARM64_LSE_ATOMICS
+	bool
+	default ARM64_USE_LSE_ATOMICS
+	depends on $(as-instr,.arch_extension lse)
+
+config ARM64_USE_LSE_ATOMICS
 	bool "Atomic instructions"
 	depends on JUMP_LABEL
 	default y
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 1fbe24d4fdb6..6dd8ecacc428 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -30,11 +30,8 @@ LDFLAGS_vmlinux	+= --fix-cortex-a53-843419
   endif
 endif
 
-# Check for binutils support for specific extensions
-lseinstr := $(call as-instr,.arch_extension lse,-DCONFIG_AS_LSE=1)
-
-ifeq ($(CONFIG_ARM64_LSE_ATOMICS), y)
-  ifeq ($(lseinstr),)
+ifeq ($(CONFIG_ARM64_USE_LSE_ATOMICS), y)
+  ifneq ($(CONFIG_ARM64_LSE_ATOMICS), y)
 $(warning LSE atomics not supported by binutils)
   endif
 endif
@@ -53,11 +50,11 @@ $(warning Detected assembler with broken .inst; disassembly will be unreliable)
   endif
 endif
 
-KBUILD_CFLAGS	+= -mgeneral-regs-only $(lseinstr) $(brokengasinst)	\
+KBUILD_CFLAGS	+= -mgeneral-regs-only $(brokengasinst)	\
 		   $(compat_vdso) $(cc_has_k_constraint)
 KBUILD_CFLAGS	+= -fno-asynchronous-unwind-tables
 KBUILD_CFLAGS	+= $(call cc-disable-warning, psabi)
-KBUILD_AFLAGS	+= $(lseinstr) $(brokengasinst) $(compat_vdso)
+KBUILD_AFLAGS	+= $(brokengasinst) $(compat_vdso)
 
 KBUILD_CFLAGS	+= $(call cc-option,-mabi=lp64)
 KBUILD_AFLAGS	+= $(call cc-option,-mabi=lp64)
diff --git a/arch/arm64/include/asm/atomic_ll_sc.h b/arch/arm64/include/asm/atomic_ll_sc.h
index 7b012148bfd6..13869b76b58c 100644
--- a/arch/arm64/include/asm/atomic_ll_sc.h
+++ b/arch/arm64/include/asm/atomic_ll_sc.h
@@ -12,7 +12,7 @@
 
 #include <linux/stringify.h>
 
-#if IS_ENABLED(CONFIG_ARM64_LSE_ATOMICS) && IS_ENABLED(CONFIG_AS_LSE)
+#ifdef CONFIG_ARM64_LSE_ATOMICS
 #define __LL_SC_FALLBACK(asm_ops)					\
 "	b	3f\n"							\
 "	.subsection	1\n"						\
diff --git a/arch/arm64/include/asm/lse.h b/arch/arm64/include/asm/lse.h
index 80b388278149..4e1009fff686 100644
--- a/arch/arm64/include/asm/lse.h
+++ b/arch/arm64/include/asm/lse.h
@@ -4,7 +4,7 @@
 
 #include <asm/atomic_ll_sc.h>
 
-#if defined(CONFIG_AS_LSE) && defined(CONFIG_ARM64_LSE_ATOMICS)
+#ifdef CONFIG_ARM64_LSE_ATOMICS
 
 #include <linux/compiler_types.h>
 #include <linux/export.h>
@@ -36,7 +36,7 @@ static inline bool system_uses_lse_atomics(void)
 #define ARM64_LSE_ATOMIC_INSN(llsc, lse)				\
 	ALTERNATIVE(llsc, lse, ARM64_HAS_LSE_ATOMICS)
 
-#else	/* CONFIG_AS_LSE && CONFIG_ARM64_LSE_ATOMICS */
+#else	/* CONFIG_ARM64_LSE_ATOMICS */
 
 static inline bool system_uses_lse_atomics(void) { return false; }
 
@@ -44,5 +44,5 @@ static inline bool system_uses_lse_atomics(void) { return false; }
 
 #define ARM64_LSE_ATOMIC_INSN(llsc, lse)	llsc
 
-#endif	/* CONFIG_AS_LSE && CONFIG_ARM64_LSE_ATOMICS */
+#endif	/* CONFIG_ARM64_LSE_ATOMICS */
 #endif	/* __ASM_LSE_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 04cf64e9f0c9..2595c2886d3f 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1291,7 +1291,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.cpu_enable = cpu_enable_pan,
 	},
 #endif /* CONFIG_ARM64_PAN */
-#if defined(CONFIG_AS_LSE) && defined(CONFIG_ARM64_LSE_ATOMICS)
+#ifdef CONFIG_ARM64_LSE_ATOMICS
 	{
 		.desc = "LSE atomic instructions",
 		.capability = ARM64_HAS_LSE_ATOMICS,
@@ -1302,7 +1302,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.sign = FTR_UNSIGNED,
 		.min_field_value = 2,
 	},
-#endif /* CONFIG_AS_LSE && CONFIG_ARM64_LSE_ATOMICS */
+#endif /* CONFIG_ARM64_LSE_ATOMICS */
 	{
 		.desc = "Software prefetching using PRFM",
 		.capability = ARM64_HAS_NO_HW_PREFETCH,

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Re: [PATCH v2 0/2] arm64: Simplify gas LSE support detection

[Vladimir Murzin]

On 1/15/20 11:30 AM, Catalin Marinas wrote:
> Version two of the patch series moving the LSE assembler support
> detection from Makefile to Kconfig.
> 
> Changes since v1 [1]:
> 
> - Re-introduce the Makefile warning if the .config contains
>   CONFIG_ARM64_USE_LSE_ATOMICS but the assembler does not support the
>   feature, disabling CONFIG_ARM64_LSE_ATOMICS.
> 
> [1] http://lkml.kernel.org/r/20200109174948.48211-1-catalin.marinas@arm.com
> 
> Catalin Marinas (2):
>   kbuild: Add support for 'as-instr' to be used in Kconfig files
>   arm64: Move the LSE gas support detection to Kconfig
> 
>  arch/arm64/Kconfig                    |  5 +++++
>  arch/arm64/Makefile                   | 11 ++++-------
>  arch/arm64/include/asm/atomic_ll_sc.h |  2 +-
>  arch/arm64/include/asm/lse.h          |  6 +++---
>  arch/arm64/kernel/cpufeature.c        |  4 ++--
>  scripts/Kconfig.include               |  4 ++++
>  6 files changed, 19 insertions(+), 13 deletions(-)
> 
> 

with

aarch64-linux-gnu-gcc (crosstool-NG linaro-1.13.1-4.9-2014.09 - Linaro GCC 4.9-2014.09) 4.9.2 20140904 (prerelease)

I see (among other warnings)

    arch/arm64/Makefile:35: LSE atomics not supported by binutils

while with

aarch64-none-linux-gnu-gcc (GNU Toolchain for the A-profile Architecture 9.2-2019.12 (arm-9.10)) 9.2.1 20191025

warning disappears.


FWIW:

Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com>


Thanks
Vladimir

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Re: [PATCH v2 0/2] arm64: Simplify gas LSE support detection

[Will Deacon]

On Wed, Jan 15, 2020 at 12:49:17PM +0000, Vladimir Murzin wrote:
> On 1/15/20 11:30 AM, Catalin Marinas wrote:
> > Version two of the patch series moving the LSE assembler support
> > detection from Makefile to Kconfig.
> > 
> > Changes since v1 [1]:
> > 
> > - Re-introduce the Makefile warning if the .config contains
> >   CONFIG_ARM64_USE_LSE_ATOMICS but the assembler does not support the
> >   feature, disabling CONFIG_ARM64_LSE_ATOMICS.
> > 
> > [1] http://lkml.kernel.org/r/20200109174948.48211-1-catalin.marinas@arm.com
> > 
> > Catalin Marinas (2):
> >   kbuild: Add support for 'as-instr' to be used in Kconfig files
> >   arm64: Move the LSE gas support detection to Kconfig
> > 
> >  arch/arm64/Kconfig                    |  5 +++++
> >  arch/arm64/Makefile                   | 11 ++++-------
> >  arch/arm64/include/asm/atomic_ll_sc.h |  2 +-
> >  arch/arm64/include/asm/lse.h          |  6 +++---
> >  arch/arm64/kernel/cpufeature.c        |  4 ++--
> >  scripts/Kconfig.include               |  4 ++++
> >  6 files changed, 19 insertions(+), 13 deletions(-)
> > 
> > 
> 
> with
> 
> aarch64-linux-gnu-gcc (crosstool-NG linaro-1.13.1-4.9-2014.09 - Linaro GCC 4.9-2014.09) 4.9.2 20140904 (prerelease)
> 
> I see (among other warnings)
> 
>     arch/arm64/Makefile:35: LSE atomics not supported by binutils
> 
> while with
> 
> aarch64-none-linux-gnu-gcc (GNU Toolchain for the A-profile Architecture 9.2-2019.12 (arm-9.10)) 9.2.1 20191025
> 
> warning disappears.
> 
> 
> FWIW:
> 
> Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
> Tested-by: Vladimir Murzin <vladimir.murzin@arm.com>

Cheers, I've queued the patches with your tags.

Will

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Re: [PATCH v2 0/2] arm64: Simplify gas LSE support detection

[Vladimir Murzin]

On 1/15/20 12:51 PM, Will Deacon wrote:
> On Wed, Jan 15, 2020 at 12:49:17PM +0000, Vladimir Murzin wrote:
>> On 1/15/20 11:30 AM, Catalin Marinas wrote:
>>> Version two of the patch series moving the LSE assembler support
>>> detection from Makefile to Kconfig.
>>>
>>> Changes since v1 [1]:
>>>
>>> - Re-introduce the Makefile warning if the .config contains
>>>   CONFIG_ARM64_USE_LSE_ATOMICS but the assembler does not support the
>>>   feature, disabling CONFIG_ARM64_LSE_ATOMICS.
>>>
>>> [1] http://lkml.kernel.org/r/20200109174948.48211-1-catalin.marinas@arm.com
>>>
>>> Catalin Marinas (2):
>>>   kbuild: Add support for 'as-instr' to be used in Kconfig files
>>>   arm64: Move the LSE gas support detection to Kconfig
>>>
>>>  arch/arm64/Kconfig                    |  5 +++++
>>>  arch/arm64/Makefile                   | 11 ++++-------
>>>  arch/arm64/include/asm/atomic_ll_sc.h |  2 +-
>>>  arch/arm64/include/asm/lse.h          |  6 +++---
>>>  arch/arm64/kernel/cpufeature.c        |  4 ++--
>>>  scripts/Kconfig.include               |  4 ++++
>>>  6 files changed, 19 insertions(+), 13 deletions(-)
>>>
>>>
>>
>> with
>>
>> aarch64-linux-gnu-gcc (crosstool-NG linaro-1.13.1-4.9-2014.09 - Linaro GCC 4.9-2014.09) 4.9.2 20140904 (prerelease)
>>
>> I see (among other warnings)
>>
>>     arch/arm64/Makefile:35: LSE atomics not supported by binutils
>>
>> while with
>>
>> aarch64-none-linux-gnu-gcc (GNU Toolchain for the A-profile Architecture 9.2-2019.12 (arm-9.10)) 9.2.1 20191025
>>
>> warning disappears.
>>
>>
>> FWIW:
>>
>> Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
>> Tested-by: Vladimir Murzin <vladimir.murzin@arm.com>
> 
> Cheers, I've queued the patches with your tags.

Would you mind if I send follow-up patch for BROKEN_GAS_INST conversion (it depends on as-inst)?

Vladimir

> 
> Will
> 


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Re: [PATCH v2 0/2] arm64: Simplify gas LSE support detection

[Will Deacon]

On Wed, Jan 15, 2020 at 12:59:00PM +0000, Vladimir Murzin wrote:
> On 1/15/20 12:51 PM, Will Deacon wrote:
> > On Wed, Jan 15, 2020 at 12:49:17PM +0000, Vladimir Murzin wrote:
> >> On 1/15/20 11:30 AM, Catalin Marinas wrote:
> >>> Version two of the patch series moving the LSE assembler support
> >>> detection from Makefile to Kconfig.
> >>>
> >>> Changes since v1 [1]:
> >>>
> >>> - Re-introduce the Makefile warning if the .config contains
> >>>   CONFIG_ARM64_USE_LSE_ATOMICS but the assembler does not support the
> >>>   feature, disabling CONFIG_ARM64_LSE_ATOMICS.
> >>>
> >>> [1] http://lkml.kernel.org/r/20200109174948.48211-1-catalin.marinas@arm.com
> >>>
> >>> Catalin Marinas (2):
> >>>   kbuild: Add support for 'as-instr' to be used in Kconfig files
> >>>   arm64: Move the LSE gas support detection to Kconfig
> >>>
> >>>  arch/arm64/Kconfig                    |  5 +++++
> >>>  arch/arm64/Makefile                   | 11 ++++-------
> >>>  arch/arm64/include/asm/atomic_ll_sc.h |  2 +-
> >>>  arch/arm64/include/asm/lse.h          |  6 +++---
> >>>  arch/arm64/kernel/cpufeature.c        |  4 ++--
> >>>  scripts/Kconfig.include               |  4 ++++
> >>>  6 files changed, 19 insertions(+), 13 deletions(-)
> >>>
> >>>
> >>
> >> with
> >>
> >> aarch64-linux-gnu-gcc (crosstool-NG linaro-1.13.1-4.9-2014.09 - Linaro GCC 4.9-2014.09) 4.9.2 20140904 (prerelease)
> >>
> >> I see (among other warnings)
> >>
> >>     arch/arm64/Makefile:35: LSE atomics not supported by binutils
> >>
> >> while with
> >>
> >> aarch64-none-linux-gnu-gcc (GNU Toolchain for the A-profile Architecture 9.2-2019.12 (arm-9.10)) 9.2.1 20191025
> >>
> >> warning disappears.
> >>
> >>
> >> FWIW:
> >>
> >> Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
> >> Tested-by: Vladimir Murzin <vladimir.murzin@arm.com>
> > 
> > Cheers, I've queued the patches with your tags.
> 
> Would you mind if I send follow-up patch for BROKEN_GAS_INST conversion
> (it depends on as-inst)?

Sure, you can send whatever you like!

Will

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