On Thu, May 03, 2018 at 08:31:19PM -0700, Yonghong Song wrote: > This approach is preferred since the already deployed bcc scripts, or > any other bpf applicaitons utilizing LLVM JIT compilation functionality, > will continue work with the new kernel without re-compilation and > re-deployment.
So I really hate this and would much rather see the BPF build environment changed. It not consistenyly having __BPF__ defined really smells like a bug on your end. Sometimes you just need to update tools... Is it really too hard to do -D__BPF__ in the bpf build process that we need to mollest the kernel for it? > Note that this is a hack in the kernel to workaround bpf compilation issue. > The hack will be removed once clang starts to support asm goto. Note that that ^^ already mandates people re-deploy their bpf tools, so why is llvm supporting asm-goto a better point to re-deploy than fixing a consistent __BPF__ define for the bpf build environment? > diff --git a/Makefile b/Makefile > index 83b6c54..cfd8759 100644 > --- a/Makefile > +++ b/Makefile > @@ -504,6 +504,7 @@ export RETPOLINE_CFLAGS > ifeq ($(call shell-cached,$(CONFIG_SHELL) $(srctree)/scripts/gcc-goto.sh > $(CC) $(KBUILD_CFLAGS)), y) > CC_HAVE_ASM_GOTO := 1 > KBUILD_CFLAGS += -DCC_HAVE_ASM_GOTO > + KBUILD_CFLAGS += -D__NO_CLANG_BPF_HACK > KBUILD_AFLAGS += -DCC_HAVE_ASM_GOTO > endif I really think this is the wrong thing to do; but if the x86 maintainers are willing to take this, I'll grudingly shut up. Ingo, Thomas? > diff --git a/arch/x86/include/asm/cpufeature.h > b/arch/x86/include/asm/cpufeature.h > index b27da96..42edd5d 100644 > --- a/arch/x86/include/asm/cpufeature.h > +++ b/arch/x86/include/asm/cpufeature.h > @@ -140,6 +140,8 @@ extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned > int bit); > > #define setup_force_cpu_bug(bit) setup_force_cpu_cap(bit) > > +/* this macro is a temporary hack for bpf until clang gains asm-goto support > */ > +#ifdef __NO_CLANG_BPF_HACK > /* > * Static testing of CPU features. Used the same as boot_cpu_has(). > * These will statically patch the target code for additional > @@ -195,6 +197,9 @@ static __always_inline __pure bool _static_cpu_has(u16 > bit) > boot_cpu_has(bit) : \ > _static_cpu_has(bit) \ > ) > +#else > +#define static_cpu_has(bit) boot_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)) > -- > 2.9.5 >
