编译 linux kernel (4.4) bpf samples with -O0 导致错误

Question

如果我从 linux 内核编译 samples/bpf/ 并将优化更改为 -O0，我会收到以下错误。尽管使用 -O2（Makefile 中的默认设置）工作正常。

谁能解释一下这里出了什么问题。

$ make samples/bpf/

[...]

clang  -nostdinc -isystem /usr/lib/gcc/x86_64-linux-gnu/4.9/include -I./arch/x86/include -Iarch/x86/include/generated/uapi -Iarch/x86/include/generated  -Iinclude -I./arch/x86/include/uapi -Iarch/x86/include/generated/uapi -I./include/uapi -Iinclude/generated/uapi -include ./include/linux/kconfig.h  \
    -D__KERNEL__ -Wno-unused-value -Wno-pointer-sign \
    -O0 -emit-llvm -c samples/bpf/tracex1_kern.c -o -| /home/ravi/bin/llc -march=bpf -filetype=obj -o samples/bpf/tracex1_kern.o
LLVM ERROR: Cannot select: t12: ch,glue = BPFISD::CALL t11, t6, Register:i64 %R1, t11:1
  t6: i64,ch = load<LD8[getelementptr inbounds (%struct.smp_ops, %struct.smp_ops* @smp_ops, i32 0, i32 3)]> t0, t3, undef:i64
    t3: i64 = add t16, Constant:i64<24>
      t16: i64 = BPFISD::Wrapper TargetGlobalAddress:i64<%struct.smp_ops* @smp_ops> 0
        t15: i64 = TargetGlobalAddress<%struct.smp_ops* @smp_ops> 0
      t2: i64 = Constant<24>
    t5: i64 = undef
  t10: i64 = Register %R1
  t11: ch,glue = CopyToReg t9, Register:i64 %R1, Constant:i64<0>
    t10: i64 = Register %R1
    t4: i64 = Constant<0>
In function: smp_send_stop
samples/bpf/Makefile:66: recipe for target 'samples/bpf/tracex1_kern.o' failed
make[1]: *** [samples/bpf/tracex1_kern.o] Error 1
Makefile:1544: recipe for target 'samples/bpf/' failed
make: *** [samples/bpf/] Error 2

Answer 1

这是 BPF 端口中的错误。请在 llvm.org 提交错误并附上复制说明。谢谢！

编译 linux kernel (4.4) bpf samples with -O0 导致错误

Compiling linux kernel (4.4) bpf samples with -O0 results in error

linux

linux-kernel

clang

llvm-clang