jump_label: move 'asm goto' support test to Kconfig

Currently, CONFIG_JUMP_LABEL just means "I _want_ to use jump label".

The jump label is controlled by HAVE_JUMP_LABEL, which is defined
like this:

  #if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL)
  # define HAVE_JUMP_LABEL
  #endif

We can improve this by testing 'asm goto' support in Kconfig, then
make JUMP_LABEL depend on CC_HAS_ASM_GOTO.

Ugly #ifdef HAVE_JUMP_LABEL will go away, and CONFIG_JUMP_LABEL will
match to the real kernel capability.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>

Makefile

@@ -514,13 +514,6 @@ RETPOLINE_VDSO_CFLAGS := $(call cc-option,$(RETPOLINE_VDSO_CFLAGS_GCC),$(call cc
 export RETPOLINE_CFLAGS
 export RETPOLINE_VDSO_CFLAGS
 
-# check for 'asm goto'
-ifeq ($(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-goto.sh $(CC) $(KBUILD_CFLAGS)), y)
-  CC_HAVE_ASM_GOTO := 1
-  KBUILD_CFLAGS += -DCC_HAVE_ASM_GOTO
-  KBUILD_AFLAGS += -DCC_HAVE_ASM_GOTO
-endif
-
 # The expansion should be delayed until arch/$(SRCARCH)/Makefile is included.
 # Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile.
 # CC_VERSION_TEXT is referenced from Kconfig (so it needs export),

arch/Kconfig

@@ -71,6 +71,7 @@ config KPROBES
 config JUMP_LABEL
        bool "Optimize very unlikely/likely branches"
        depends on HAVE_ARCH_JUMP_LABEL
+       depends on CC_HAS_ASM_GOTO
        help
          This option enables a transparent branch optimization that
 	 makes certain almost-always-true or almost-always-false branch

arch/arm/kernel/jump_label.c

@@ -4,8 +4,6 @@
 #include <asm/patch.h>
 #include <asm/insn.h>
 
-#ifdef HAVE_JUMP_LABEL
-
 static void __arch_jump_label_transform(struct jump_entry *entry,
 					enum jump_label_type type,
 					bool is_static)
@@ -35,5 +33,3 @@ void arch_jump_label_transform_static(struct jump_entry *entry,
 {
 	__arch_jump_label_transform(entry, type, true);
 }
-
-#endif

arch/arm64/kernel/jump_label.c

@@ -20,8 +20,6 @@
 #include <linux/jump_label.h>
 #include <asm/insn.h>
 
-#ifdef HAVE_JUMP_LABEL
-
 void arch_jump_label_transform(struct jump_entry *entry,
 			       enum jump_label_type type)
 {
@@ -49,5 +47,3 @@ void arch_jump_label_transform_static(struct jump_entry *entry,
 	 * NOP needs to be replaced by a branch.
 	 */
 }
-
-#endif	/* HAVE_JUMP_LABEL */

arch/mips/kernel/jump_label.c

@@ -16,8 +16,6 @@
 #include <asm/cacheflush.h>
 #include <asm/inst.h>
 
-#ifdef HAVE_JUMP_LABEL
-
 /*
  * Define parameters for the standard MIPS and the microMIPS jump
  * instruction encoding respectively:
@@ -70,5 +68,3 @@ void arch_jump_label_transform(struct jump_entry *e,
 
 	mutex_unlock(&text_mutex);
 }
-
-#endif /* HAVE_JUMP_LABEL */

arch/powerpc/include/asm/asm-prototypes.h

@@ -38,7 +38,7 @@ extern struct static_key hcall_tracepoint_key;
 void __trace_hcall_entry(unsigned long opcode, unsigned long *args);
 void __trace_hcall_exit(long opcode, long retval, unsigned long *retbuf);
 /* OPAL tracing */
-#ifdef HAVE_JUMP_LABEL
+#ifdef CONFIG_JUMP_LABEL
 extern struct static_key opal_tracepoint_key;
 #endif
 

arch/powerpc/kernel/jump_label.c

@@ -11,7 +11,6 @@
 #include <linux/jump_label.h>
 #include <asm/code-patching.h>
 
-#ifdef HAVE_JUMP_LABEL
 void arch_jump_label_transform(struct jump_entry *entry,
 			       enum jump_label_type type)
 {
@@ -22,4 +21,3 @@ void arch_jump_label_transform(struct jump_entry *entry,
 	else
 		patch_instruction(addr, PPC_INST_NOP);
 }
-#endif

arch/powerpc/platforms/powernv/opal-tracepoints.c

@@ -4,7 +4,7 @@
 #include <asm/trace.h>
 #include <asm/asm-prototypes.h>
 
-#ifdef HAVE_JUMP_LABEL
+#ifdef CONFIG_JUMP_LABEL
 struct static_key opal_tracepoint_key = STATIC_KEY_INIT;
 
 int opal_tracepoint_regfunc(void)

arch/powerpc/platforms/powernv/opal-wrappers.S

@@ -20,7 +20,7 @@
 	.section	".text"
 
 #ifdef CONFIG_TRACEPOINTS
-#ifdef HAVE_JUMP_LABEL
+#ifdef CONFIG_JUMP_LABEL
 #define OPAL_BRANCH(LABEL)					\
 	ARCH_STATIC_BRANCH(LABEL, opal_tracepoint_key)
 #else

arch/powerpc/platforms/pseries/hvCall.S

@@ -19,7 +19,7 @@
 	
 #ifdef CONFIG_TRACEPOINTS
 
-#ifndef HAVE_JUMP_LABEL
+#ifndef CONFIG_JUMP_LABEL
 	.section	".toc","aw"
 
 	.globl hcall_tracepoint_refcount
@@ -79,7 +79,7 @@ hcall_tracepoint_refcount:
 	mr	r5,BUFREG;					\
 	__HCALL_INST_POSTCALL
 
-#ifdef HAVE_JUMP_LABEL
+#ifdef CONFIG_JUMP_LABEL
 #define HCALL_BRANCH(LABEL)					\
 	ARCH_STATIC_BRANCH(LABEL, hcall_tracepoint_key)
 #else

arch/powerpc/platforms/pseries/lpar.c

@@ -1040,7 +1040,7 @@ EXPORT_SYMBOL(arch_free_page);
 #endif /* CONFIG_PPC_BOOK3S_64 */
 
 #ifdef CONFIG_TRACEPOINTS
-#ifdef HAVE_JUMP_LABEL
+#ifdef CONFIG_JUMP_LABEL
 struct static_key hcall_tracepoint_key = STATIC_KEY_INIT;
 
 int hcall_tracepoint_regfunc(void)

arch/s390/kernel/Makefile

@@ -48,7 +48,7 @@ CFLAGS_ptrace.o		+= -DUTS_MACHINE='"$(UTS_MACHINE)"'
 obj-y	:= traps.o time.o process.o base.o early.o setup.o idle.o vtime.o
 obj-y	+= processor.o sys_s390.o ptrace.o signal.o cpcmd.o ebcdic.o nmi.o
 obj-y	+= debug.o irq.o ipl.o dis.o diag.o vdso.o early_nobss.o
-obj-y	+= sysinfo.o jump_label.o lgr.o os_info.o machine_kexec.o pgm_check.o
+obj-y	+= sysinfo.o lgr.o os_info.o machine_kexec.o pgm_check.o
 obj-y	+= runtime_instr.o cache.o fpu.o dumpstack.o guarded_storage.o sthyi.o
 obj-y	+= entry.o reipl.o relocate_kernel.o kdebugfs.o alternative.o
 obj-y	+= nospec-branch.o ipl_vmparm.o
@@ -72,6 +72,7 @@ obj-$(CONFIG_KPROBES)		+= kprobes.o
 obj-$(CONFIG_FUNCTION_TRACER)	+= mcount.o ftrace.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 obj-$(CONFIG_UPROBES)		+= uprobes.o
+obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o
 
 obj-$(CONFIG_KEXEC_FILE)	+= machine_kexec_file.o kexec_image.o
 obj-$(CONFIG_KEXEC_FILE)	+= kexec_elf.o

arch/s390/kernel/jump_label.c

@@ -10,8 +10,6 @@
 #include <linux/jump_label.h>
 #include <asm/ipl.h>
 
-#ifdef HAVE_JUMP_LABEL
-
 struct insn {
 	u16 opcode;
 	s32 offset;
@@ -103,5 +101,3 @@ void arch_jump_label_transform_static(struct jump_entry *entry,
 {
 	__jump_label_transform(entry, type, 1);
 }
-
-#endif

arch/sparc/kernel/Makefile

@@ -118,4 +118,4 @@ pc--$(CONFIG_PERF_EVENTS) := perf_event.o
 obj-$(CONFIG_SPARC64)	+= $(pc--y)
 
 obj-$(CONFIG_UPROBES)	+= uprobes.o
-obj-$(CONFIG_SPARC64)	+= jump_label.o
+obj-$(CONFIG_JUMP_LABEL) += jump_label.o

arch/sparc/kernel/jump_label.c

@@ -9,8 +9,6 @@
 
 #include <asm/cacheflush.h>
 
-#ifdef HAVE_JUMP_LABEL
-
 void arch_jump_label_transform(struct jump_entry *entry,
 			       enum jump_label_type type)
 {
@@ -47,5 +45,3 @@ void arch_jump_label_transform(struct jump_entry *entry,
 	flushi(insn);
 	mutex_unlock(&text_mutex);
 }
-
-#endif

arch/x86/Makefile

@@ -289,7 +289,7 @@ vdso_install:
 
 archprepare: checkbin
 checkbin:
-ifndef CC_HAVE_ASM_GOTO
+ifndef CONFIG_CC_HAS_ASM_GOTO
 	@echo Compiler lacks asm-goto support.
 	@exit 1
 endif

arch/x86/entry/calling.h

@@ -351,7 +351,7 @@ For 32-bit we have the following conventions - kernel is built with
  */
 .macro CALL_enter_from_user_mode
 #ifdef CONFIG_CONTEXT_TRACKING
-#ifdef HAVE_JUMP_LABEL
+#ifdef CONFIG_JUMP_LABEL
 	STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0
 #endif
 	call enter_from_user_mode

arch/x86/include/asm/cpufeature.h

@@ -140,7 +140,7 @@ 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(CC_HAVE_ASM_GOTO)
+#if defined(__clang__) && !defined(CONFIG_CC_HAS_ASM_GOTO)
 
 /*
  * Workaround for the sake of BPF compilation which utilizes kernel

arch/x86/include/asm/jump_label.h

@@ -2,19 +2,6 @@
 #ifndef _ASM_X86_JUMP_LABEL_H
 #define _ASM_X86_JUMP_LABEL_H
 
-#ifndef HAVE_JUMP_LABEL
-/*
- * For better or for worse, if jump labels (the gcc extension) are missing,
- * then the entire static branch patching infrastructure is compiled out.
- * If that happens, the code in here will malfunction.  Raise a compiler
- * error instead.
- *
- * In theory, jump labels and the static branch patching infrastructure
- * could be decoupled to fix this.
- */
-#error asm/jump_label.h included on a non-jump-label kernel
-#endif
-
 #define JUMP_LABEL_NOP_SIZE 5
 
 #ifdef CONFIG_X86_64

arch/x86/include/asm/rmwcc.h

@@ -11,7 +11,7 @@
 
 #define __CLOBBERS_MEM(clb...)	"memory", ## clb
 
-#if !defined(__GCC_ASM_FLAG_OUTPUTS__) && defined(CC_HAVE_ASM_GOTO)
+#if !defined(__GCC_ASM_FLAG_OUTPUTS__) && defined(CONFIG_CC_HAS_ASM_GOTO)
 
 /* Use asm goto */
 
@@ -27,7 +27,7 @@ cc_label:	c = true;						\
 	c;								\
 })
 
-#else /* defined(__GCC_ASM_FLAG_OUTPUTS__) || !defined(CC_HAVE_ASM_GOTO) */
+#else /* defined(__GCC_ASM_FLAG_OUTPUTS__) || !defined(CONFIG_CC_HAS_ASM_GOTO) */
 
 /* Use flags output or a set instruction */
 
@@ -40,7 +40,7 @@ cc_label:	c = true;						\
 	c;								\
 })
 
-#endif /* defined(__GCC_ASM_FLAG_OUTPUTS__) || !defined(CC_HAVE_ASM_GOTO) */
+#endif /* defined(__GCC_ASM_FLAG_OUTPUTS__) || !defined(CONFIG_CC_HAS_ASM_GOTO) */
 
 #define GEN_UNARY_RMWcc_4(op, var, cc, arg0)				\
 	__GEN_RMWcc(op " " arg0, var, cc, __CLOBBERS_MEM())