With latest llvm trunk, bpf programs under samples/bpf directory, if using CORE, may experience the following errors: LLVM ERROR: Cannot select: intrinsic %llvm.preserve.struct.access.index PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace. Stack dump: 0. Program arguments: llc -march=bpf -filetype=obj -o samples/bpf/test_probe_write_user_kern.o 1. Running pass 'Function Pass Manager' on module '<stdin>'. 2. Running pass 'BPF DAG->DAG Pattern Instruction Selection' on function '@bpf_prog1' #0 0x000000000183c26c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x183c26c) ... #7 0x00000000017c375e (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x17c375e) #8 0x00000000016a75c5 llvm::SelectionDAGISel::CannotYetSelect(llvm::SDNode*) (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x16a75c5) #9 0x00000000016ab4f8 llvm::SelectionDAGISel::SelectCodeCommon(llvm::SDNode*, unsigned char const*, unsigned int) (/data/users/yhs/work/llvm-project/llvm/build.cur/install/bin/llc+0x16ab4f8) ... Aborted (core dumped) | llc -march=bpf -filetype=obj -o samples/bpf/test_probe_write_user_kern.o The reason is due to llvm change https://reviews.llvm.org/D87153 where the CORE relocation global generation is moved from the beginning of target dependent optimization (llc) to the beginning of target independent optimization (opt). Since samples/bpf programs did not use vmlinux.h and its clang compilation uses native architecture, we need to adjust arch triple at opt level to do CORE relocation global generation properly. Otherwise, the above error will appear. This patch fixed the issue by introduce opt and llvm-dis to compilation chain, which will do proper CORE relocation global generation as well as O2 level optimization. Tested with llvm10, llvm11 and trunk/llvm12. Signed-off-by: Yonghong Song <yhs@xxxxxx> --- samples/bpf/Makefile | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile index 4f1ed0e3cf9f..79c5fdea63d2 100644 --- a/samples/bpf/Makefile +++ b/samples/bpf/Makefile @@ -211,6 +211,8 @@ TPROGLDLIBS_xsk_fwd += -pthread # make M=samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang LLC ?= llc CLANG ?= clang +OPT ?= opt +LLVM_DIS ?= llvm-dis LLVM_OBJCOPY ?= llvm-objcopy BTF_PAHOLE ?= pahole @@ -314,7 +316,9 @@ $(obj)/%.o: $(src)/%.c -Wno-address-of-packed-member -Wno-tautological-compare \ -Wno-unknown-warning-option $(CLANG_ARCH_ARGS) \ -I$(srctree)/samples/bpf/ -include asm_goto_workaround.h \ - -O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@ + -O2 -emit-llvm -Xclang -disable-llvm-passes -c $< -o - | \ + $(OPT) -O2 -mtriple=bpf-pc-linux | $(LLVM_DIS) | \ + $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@ ifeq ($(DWARF2BTF),y) $(BTF_PAHOLE) -J $@ endif -- 2.24.1
