On 19/08/2022 10:00:53-0700, Nick Desaulniers wrote: > 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. > > The script was also not portable; users of Dash shell reported errors > when it was invoked. > To be clear, the script was portable, what is not working with dash is the current detection of CC_HAS_ASM_GOTO_TIED_OUTPUT. I'll try the other suggestion from Masahiro. > Link: https://lore.kernel.org/lkml/CAK7LNATSr=BXKfkdW8f-H5VT_w=xBpT2ZQcZ7rm6JfkdE+QnmA@xxxxxxxxxxxxxx/ > Link: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48637 > Reported-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx> > Suggested-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> > Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > --- > Documentation/kbuild/kconfig-language.rst | 4 ++-- > arch/Kconfig | 3 +-- > arch/um/include/asm/cpufeature.h | 4 ++-- > arch/x86/Makefile | 4 ---- > arch/x86/include/asm/cpufeature.h | 4 ++-- > arch/x86/include/asm/rmwcc.h | 19 +------------------ > arch/x86/kvm/emulate.c | 2 +- > init/Kconfig | 4 ---- > scripts/gcc-goto.sh | 22 ---------------------- > tools/arch/x86/include/asm/rmwcc.h | 21 --------------------- > 10 files changed, 9 insertions(+), 78 deletions(-) > delete mode 100755 scripts/gcc-goto.sh > > diff --git a/Documentation/kbuild/kconfig-language.rst b/Documentation/kbuild/kconfig-language.rst > index 7fb398649f51..858ed5d80def 100644 > --- a/Documentation/kbuild/kconfig-language.rst > +++ b/Documentation/kbuild/kconfig-language.rst > @@ -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 $(CC)) > > Build as module only > ~~~~~~~~~~~~~~~~~~~~ > diff --git a/arch/Kconfig b/arch/Kconfig > index f330410da63a..5dbf11a5ba4e 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -53,7 +53,6 @@ config KPROBES > config JUMP_LABEL > bool "Optimize very unlikely/likely branches" > depends on HAVE_ARCH_JUMP_LABEL > - depends on CC_HAS_ASM_GOTO > select OBJTOOL if HAVE_JUMP_LABEL_HACK > help > This option enables a transparent branch optimization that > @@ -1361,7 +1360,7 @@ config HAVE_PREEMPT_DYNAMIC_CALL > > config HAVE_PREEMPT_DYNAMIC_KEY > bool > - depends on HAVE_ARCH_JUMP_LABEL && CC_HAS_ASM_GOTO > + depends on HAVE_ARCH_JUMP_LABEL > select HAVE_PREEMPT_DYNAMIC > help > An architecture should select this if it can handle the preemption > diff --git a/arch/um/include/asm/cpufeature.h b/arch/um/include/asm/cpufeature.h > index 19cd7ed6ec3c..94ff93ce20de 100644 > --- a/arch/um/include/asm/cpufeature.h > +++ b/arch/um/include/asm/cpufeature.h > @@ -65,11 +65,11 @@ extern void setup_clear_cpu_cap(unsigned int bit); > > #define setup_force_cpu_bug(bit) setup_force_cpu_cap(bit) > > -#if defined(__clang__) && !defined(CONFIG_CC_HAS_ASM_GOTO) > +#if defined(__clang__) && __clang_major__ < 9 > > /* > * Workaround for the sake of BPF compilation which utilizes kernel > - * headers, but clang does not support ASM GOTO and fails the build. > + * headers, but clang < 9 does not support ASM GOTO and fails the build. > */ > #ifndef __BPF_TRACING__ > #warning "Compiler lacks ASM_GOTO support. Add -D __BPF_TRACING__ to your compiler arguments" > diff --git a/arch/x86/Makefile b/arch/x86/Makefile > index 7854685c5f25..bafbd905e6e7 100644 > --- a/arch/x86/Makefile > +++ b/arch/x86/Makefile > @@ -286,10 +286,6 @@ vdso_install: > > archprepare: checkbin > checkbin: > -ifndef CONFIG_CC_HAS_ASM_GOTO > - @echo Compiler lacks asm-goto support. > - @exit 1 > -endif > ifdef CONFIG_RETPOLINE > ifeq ($(RETPOLINE_CFLAGS),) > @echo "You are building kernel with non-retpoline compiler." >&2 > diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h > index ea34cc31b047..29951da819ca 100644 > --- a/arch/x86/include/asm/cpufeature.h > +++ b/arch/x86/include/asm/cpufeature.h > @@ -155,11 +155,11 @@ 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) > +#if defined(__clang__) && __clang_major__ < 9 Shouldn't we simply mandates clang >= 9 and drop the whole section? This is what you do later on. > > /* > * Workaround for the sake of BPF compilation which utilizes kernel > - * headers, but clang does not support ASM GOTO and fails the build. > + * headers, but clang < 9 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" > diff --git a/arch/x86/include/asm/rmwcc.h b/arch/x86/include/asm/rmwcc.h > index 8a9eba191516..c82f1b334207 100644 > --- a/arch/x86/include/asm/rmwcc.h > +++ b/arch/x86/include/asm/rmwcc.h > @@ -11,9 +11,7 @@ > > #define __CLOBBERS_MEM(clb...) "memory", ## clb > > -#if !defined(__GCC_ASM_FLAG_OUTPUTS__) && defined(CONFIG_CC_HAS_ASM_GOTO) > - > -/* Use asm goto */ > +#ifndef __GCC_ASM_FLAG_OUTPUTS__ > > #define __GEN_RMWcc(fullop, _var, cc, clobbers, ...) \ > ({ \ > @@ -27,21 +25,6 @@ cc_label: c = true; \ > c; \ > }) > > -#else /* defined(__GCC_ASM_FLAG_OUTPUTS__) || !defined(CONFIG_CC_HAS_ASM_GOTO) */ > - > -/* Use flags output or a set instruction */ > - > -#define __GEN_RMWcc(fullop, _var, cc, clobbers, ...) \ > -({ \ > - bool c; \ > - asm volatile (fullop CC_SET(cc) \ > - : [var] "+m" (_var), CC_OUT(cc) (c) \ > - : __VA_ARGS__ : clobbers); \ > - c; \ > -}) > - > -#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()) > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index b4eeb7c75dfa..08613c65138d 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -493,7 +493,7 @@ FOP_END; > > /* > * XXX: inoutclob user must know where the argument is being expanded. > - * Relying on CONFIG_CC_HAS_ASM_GOTO would allow us to remove _fault. > + * Using asm goto would allow us to remove _fault. > */ > #define asm_safe(insn, inoutclob...) \ > ({ \ > diff --git a/init/Kconfig b/init/Kconfig > index 80fe60fa77fb..532362fcfe31 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -70,11 +70,7 @@ config CC_CAN_LINK_STATIC > default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT > default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static) > > -config CC_HAS_ASM_GOTO > - def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) > - > config CC_HAS_ASM_GOTO_OUTPUT > - depends on CC_HAS_ASM_GOTO > def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null) > > config CC_HAS_ASM_GOTO_TIED_OUTPUT > diff --git a/scripts/gcc-goto.sh b/scripts/gcc-goto.sh > deleted file mode 100755 > index 8b980fb2270a..000000000000 > --- a/scripts/gcc-goto.sh > +++ /dev/null > @@ -1,22 +0,0 @@ > -#!/bin/sh > -# SPDX-License-Identifier: GPL-2.0 > -# Test for gcc 'asm goto' support > -# Copyright (C) 2010, Jason Baron <jbaron@xxxxxxxxxx> > - > -cat << "END" | $@ -x c - -fno-PIE -c -o /dev/null > -int main(void) > -{ > -#if defined(__arm__) || defined(__aarch64__) > - /* > - * Not related to asm goto, but used by jump label > - * and broken on some ARM GCC versions (see GCC Bug 48637). > - */ > - static struct { int dummy; int state; } tp; > - asm (".long %c0" :: "i" (&tp.state)); > -#endif > - > -entry: > - asm goto ("" :::: entry); > - return 0; > -} > -END > diff --git a/tools/arch/x86/include/asm/rmwcc.h b/tools/arch/x86/include/asm/rmwcc.h > index fee7983a90b4..11ff975242ca 100644 > --- a/tools/arch/x86/include/asm/rmwcc.h > +++ b/tools/arch/x86/include/asm/rmwcc.h > @@ -2,8 +2,6 @@ > #ifndef _TOOLS_LINUX_ASM_X86_RMWcc > #define _TOOLS_LINUX_ASM_X86_RMWcc > > -#ifdef CONFIG_CC_HAS_ASM_GOTO > - > #define __GEN_RMWcc(fullop, var, cc, ...) \ > do { \ > asm_volatile_goto (fullop "; j" cc " %l[cc_label]" \ > @@ -20,23 +18,4 @@ cc_label: \ > #define GEN_BINARY_RMWcc(op, var, vcon, val, arg0, cc) \ > __GEN_RMWcc(op " %1, " arg0, var, cc, vcon (val)) > > -#else /* !CONFIG_CC_HAS_ASM_GOTO */ > - > -#define __GEN_RMWcc(fullop, var, cc, ...) \ > -do { \ > - char c; \ > - asm volatile (fullop "; set" cc " %1" \ > - : "+m" (var), "=qm" (c) \ > - : __VA_ARGS__ : "memory"); \ > - return c != 0; \ > -} while (0) > - > -#define GEN_UNARY_RMWcc(op, var, arg0, cc) \ > - __GEN_RMWcc(op " " arg0, var, cc) > - > -#define GEN_BINARY_RMWcc(op, var, vcon, val, arg0, cc) \ > - __GEN_RMWcc(op " %2, " arg0, var, cc, vcon (val)) > - > -#endif /* CONFIG_CC_HAS_ASM_GOTO */ > - > #endif /* _TOOLS_LINUX_ASM_X86_RMWcc */ > -- > 2.37.1.595.g718a3a8f04-goog > -- Alexandre Belloni, co-owner and COO, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
