| Message ID | 20220819170053.2686006-1-ndesaulniers@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Kconfig: eradicate CC_HAS_ASM_GOTO | expand |
On Fri, Aug 19, 2022 at 10:00:53AM -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. > > 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 > Reported-by: Alexandre Belloni <alexandre.belloni@bootlin.com> > Suggested-by: Masahiro Yamada <masahiroy@kernel.org> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> > --- > 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 Nice and good riddance. Acked-by: Borislav Petkov <bp@suse.de>
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@mail.gmail.com/ > Link: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48637 > Reported-by: Alexandre Belloni <alexandre.belloni@bootlin.com> > Suggested-by: Masahiro Yamada <masahiroy@kernel.org> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> > --- > 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@redhat.com> > - > -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 >
On Fri, Aug 19, 2022 at 10:16 AM Alexandre Belloni <alexandre.belloni@bootlin.com> wrote: > > 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. Ah, that was his point about echo; that makes more sense. Unless a v2 is required, perhaps Masahiro would be kind enough to drop this sentence from the commit message when applying? > > > --- 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. I considered it, but I don't think it would be safe to do so in this header. If you look at the comment block below it, it mentions that these kernel headers are being sucked into UAPI headers that are used outside of the kernel builds, such as when building eBPF programs. So we don't know what userspace tools might be consuming these headers. The original intent of the guard was to not break eBPF compilation with older clang releases, so I've retained. that functionality. + Alexei to review (author of commit b1ae32dbab50 ("x86/cpufeature: Guard asm_volatile_goto usage for BPF compilation") ).
On Sat, Aug 20, 2022 at 2:28 AM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Fri, Aug 19, 2022 at 10:16 AM Alexandre Belloni > <alexandre.belloni@bootlin.com> wrote: > > > > 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. > > Ah, that was his point about echo; that makes more sense. > > Unless a v2 is required, perhaps Masahiro would be kind enough to drop > this sentence from the commit message when applying? I can if there is nothing else to fix. And, Alexandre's Reported-by is irrelevant. As for the subject prefix "Kconfig:", I prefer something else, for example, "asm goto:" or "jump label:". I want to reserve "Kconfig:" for changes in scripts/kconfig/. > > > > > > --- 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. > > I considered it, but I don't think it would be safe to do so in this > header. If you look at the comment block below it, it mentions that > these kernel headers are being sucked into UAPI headers that are used > outside of the kernel builds, such as when building eBPF programs. So > we don't know what userspace tools might be consuming these headers. > The original intent of the guard was to not break eBPF compilation > with older clang releases, so I've retained. that functionality. > > + Alexei to review > (author of > commit b1ae32dbab50 ("x86/cpufeature: Guard asm_volatile_goto usage > for BPF compilation") I am not sure at this point. Wait for the input from Alexei. > ). > -- > Thanks, > ~Nick Desaulniers
On Fri, Aug 19, 2022 at 10:42 AM Masahiro Yamada <masahiroy@kernel.org> wrote: > > On Sat, Aug 20, 2022 at 2:28 AM Nick Desaulniers > <ndesaulniers@google.com> wrote: > > > > On Fri, Aug 19, 2022 at 10:16 AM Alexandre Belloni > > <alexandre.belloni@bootlin.com> wrote: > > > > > > 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. > > > > Ah, that was his point about echo; that makes more sense. > > > > Unless a v2 is required, perhaps Masahiro would be kind enough to drop > > this sentence from the commit message when applying? > > I can if there is nothing else to fix. > > > And, Alexandre's Reported-by is irrelevant. > > As for the subject prefix "Kconfig:", > I prefer something else, for example, > "asm goto:" or "jump label:". > > I want to reserve "Kconfig:" for changes in scripts/kconfig/. > > > > > > > > > > > --- 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. > > > > I considered it, but I don't think it would be safe to do so in this > > header. If you look at the comment block below it, it mentions that > > these kernel headers are being sucked into UAPI headers that are used > > outside of the kernel builds, such as when building eBPF programs. So > > we don't know what userspace tools might be consuming these headers. > > The original intent of the guard was to not break eBPF compilation > > with older clang releases, so I've retained. that functionality. > > > > + Alexei to review > > (author of > > commit b1ae32dbab50 ("x86/cpufeature: Guard asm_volatile_goto usage > > for BPF compilation") > > > I am not sure at this point. > Wait for the input from Alexei. It's probably best to remove this old workaround. bpftrace still has code that does: cflags.push_back("-D__BPF_TRACING__"); and bpftrace sort-of works with llvm 6+, but they need to move to a newer clang for tons of other reasons including lots of fixes in the clang bpf backend that were added over the years. So just nuke this old hack.
On Fri, Aug 19, 2022 at 10:01 AM Nick Desaulniers <ndesaulniers@google.com> wrote: > > 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) */ > - ^ probably don't want to remove the terminal endif. Will respin based on feedback from Masahiro + Alexei.
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 /* * 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@redhat.com> - -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 */
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. 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 Reported-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> --- 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