Commit a0a12c3e authored by Nick Desaulniers's avatar Nick Desaulniers Committed by Linus Torvalds
Browse files

asm goto: eradicate CC_HAS_ASM_GOTO 

GCC has supported asm goto since 4.5, and Clang has since version 9.0.0.
The minimum supported versions of these tools for the build according to
Documentation/process/changes.rst are 5.1 and 11.0.0 respectively.

Remove the feature detection script, Kconfig option, and clean up some
fallback code that is no longer supported.

The removed script was also testing for a GCC specific bug that was
fixed in the 4.7 release.

Also remove workarounds for bpftrace using clang older than 9.0.0, since
other BPF backend fixes are required at this point.

Link: https://lore.kernel.org/lkml/CAK7LNATSr=BXKfkdW8f-H5VT_w=xBpT2ZQcZ7rm6JfkdE+QnmA@mail.gmail.com/
Link: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48637


Acked-by: default avatarBorislav Petkov <bp@suse.de>
Suggested-by: default avatarMasahiro Yamada <masahiroy@kernel.org>
Suggested-by: default avatarAlexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Reviewed-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarNathan Chancellor <nathan@kernel.org>
Reviewed-by: default avatarAlexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 15b3f48a

Documentation/kbuild/kconfig-language.rst

+2 −2
Original line number Diff line number Diff line
@@ -525,8 +525,8 @@ followed by a test macro:: 
If you need to expose a compiler capability to makefiles and/or C source files,

`CC_HAS_` is the recommended prefix for the config option::



  config CC_HAS_ASM_GOTO

	def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))

  config CC_HAS_FOO

	def_bool $(success,$(srctree)/scripts/cc-check-foo.sh $(CC))



Build as module only

~~~~~~~~~~~~~~~~~~~~

arch/Kconfig

+1 −2
Original line number Diff line number Diff line
@@ -53,7 +53,6 @@ config KPROBES 
config JUMP_LABEL

	bool "Optimize very unlikely/likely branches"

	depends on HAVE_ARCH_JUMP_LABEL

	depends on CC_HAS_ASM_GOTO

	select OBJTOOL if HAVE_JUMP_LABEL_HACK

	help

	 This option enables a transparent branch optimization that
@@ -1361,7 +1360,7 @@ config HAVE_PREEMPT_DYNAMIC_CALL 


config HAVE_PREEMPT_DYNAMIC_KEY

	bool

	depends on HAVE_ARCH_JUMP_LABEL && CC_HAS_ASM_GOTO

	depends on HAVE_ARCH_JUMP_LABEL

	select HAVE_PREEMPT_DYNAMIC

	help

	   An architecture should select this if it can handle the preemption

arch/um/include/asm/cpufeature.h

+0 −15
Original line number Diff line number Diff line
@@ -65,20 +65,6 @@ extern void setup_clear_cpu_cap(unsigned int bit); 


#define setup_force_cpu_bug(bit) setup_force_cpu_cap(bit)



#if defined(__clang__) && !defined(CONFIG_CC_HAS_ASM_GOTO)



/*

 * Workaround for the sake of BPF compilation which utilizes kernel

 * headers, but clang does not support ASM GOTO and fails the build.

 */

#ifndef __BPF_TRACING__

#warning "Compiler lacks ASM_GOTO support. Add -D __BPF_TRACING__ to your compiler arguments"

#endif



#define static_cpu_has(bit)            boot_cpu_has(bit)



#else



/*

 * Static testing of CPU features. Used the same as boot_cpu_has(). It

 * statically patches the target code for additional performance. Use
@@ -137,7 +123,6 @@ static __always_inline bool _static_cpu_has(u16 bit) 
		boot_cpu_has(bit) :				\

		_static_cpu_has(bit)				\

)

#endif



#define cpu_has_bug(c, bit)		cpu_has(c, (bit))

#define set_cpu_bug(c, bit)		set_cpu_cap(c, (bit))

arch/x86/Makefile

+0 −4
Original line number Diff line number Diff line
@@ -286,10 +286,6 @@ vdso_install: 


archprepare: checkbin

checkbin:

ifndef CONFIG_CC_HAS_ASM_GOTO

	@echo Compiler lacks asm-goto support.

	@exit 1

endif

ifdef CONFIG_RETPOLINE

ifeq ($(RETPOLINE_CFLAGS),)

	@echo "You are building kernel with non-retpoline compiler." >&2

arch/x86/include/asm/cpufeature.h

+0 −15
Original line number Diff line number Diff line
@@ -155,20 +155,6 @@ extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit); 


#define setup_force_cpu_bug(bit) setup_force_cpu_cap(bit)



#if defined(__clang__) && !defined(CONFIG_CC_HAS_ASM_GOTO)



/*

 * Workaround for the sake of BPF compilation which utilizes kernel

 * headers, but clang does not support ASM GOTO and fails the build.

 */

#ifndef __BPF_TRACING__

#warning "Compiler lacks ASM_GOTO support. Add -D __BPF_TRACING__ to your compiler arguments"

#endif



#define static_cpu_has(bit)            boot_cpu_has(bit)



#else



/*

 * Static testing of CPU features. Used the same as boot_cpu_has(). It

 * statically patches the target code for additional performance. Use
@@ -208,7 +194,6 @@ static __always_inline bool _static_cpu_has(u16 bit) 
		boot_cpu_has(bit) :				\

		_static_cpu_has(bit)				\

)

#endif



#define cpu_has_bug(c, bit)		cpu_has(c, (bit))

#define set_cpu_bug(c, bit)		set_cpu_cap(c, (bit))