Messages in this thread | | | Date | Thu, 10 May 2018 12:49:08 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH bpf v3] x86/cpufeature: bpf hack for clang not supporting asm goto |
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On Thu, May 03, 2018 at 08:31:19PM -0700, Yonghong Song wrote: > Commit d0266046ad54 ("x86: Remove FAST_FEATURE_TESTS") > removed X86_FAST_FEATURE_TESTS and make macro static_cpu_has() always > use __always_inline function _static_cpu_has() funciton. > The static_cpu_has() uses gcc feature asm goto construct, > which is not supported by clang. > > Issues > ====== > > Currently, for BPF programs written in C, the only widely-supported > compiler is clang. Because of clang lacking support > of asm goto construct, if you try to compile > bpf programs under samples/bpf/, > $ make -j20 && make headers_install && make samples/bpf/ > you will see a lot of failures like below: > > clang -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/7/include \ > -I/home/yhs/work/bpf-next/arch/x86/include \ > -I./arch/x86/include/generated -I/home/yhs/work/bpf-next/include \ > -I./include -I/home/yhs/work/bpf-next/arch/x86/include/uapi \ > -I./arch/x86/include/generated/uapi \ > -I/home/yhs/work/bpf-next/include/uapi -I./include/generated/uapi \ > -include /home/yhs/work/bpf-next/include/linux/kconfig.h > -Isamples/bpf \ > -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf/ \ > -D__KERNEL__ -Wno-unused-value -Wno-pointer-sign \ > -D__TARGET_ARCH_x86 -Wno-compare-distinct-pointer-types \ > -Wno-gnu-variable-sized-type-not-at-end \ > -Wno-address-of-packed-member -Wno-tautological-compare \ > -Wno-unknown-warning-option \ > -O2 -emit-llvm -c /home/yhs/work/bpf-next/samples/bpf/xdp_redirect_cpu_kern.c \ > -o -| llc -march=bpf -filetype=obj -o samples/bpf/xdp_redirect_cpu_kern.o > In file included from /home/yhs/work/bpf-next/samples/bpf/xdp_redirect_cpu_kern.c:10:
This is not the kernel's problem.
Fix the samples to build successfully like the rest of the things in tools/ use kernel machinery and undefine/redefine stuff so that it builds. For example, tools/include/asm/alternative-asm.h redefines two macros. So do something along those lines.
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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