path: root/samples/bpf
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authorYonghong Song <yhs@fb.com>2020-10-05 21:34:26 -0700
committerAlexei Starovoitov <ast@kernel.org>2020-10-06 11:45:03 -0700
commit9618bde489b2d23779b1e2d04c10983da21f3818 (patch)
tree34986d2beaaf84168577146cf139d40ed52b2320 /samples/bpf
parent8cee9107e72c93a52a7f2c58658c99887bdb05e0 (diff)
samples/bpf: Change Makefile to cope with latest llvm
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@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Andrii Nakryiko <andriin@fb.com> Link: https://lore.kernel.org/bpf/20201006043427.1891742-1-yhs@fb.com
Diffstat (limited to 'samples/bpf')
1 files changed, 10 insertions, 1 deletions
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 4f1ed0e3cf9f..e29b1e89dd3e 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
@@ -303,6 +305,11 @@ $(obj)/hbm_edt_kern.o: $(src)/hbm.h $(src)/hbm_kern.h
# asm/sysreg.h - inline assembly used by it is incompatible with llvm.
# But, there is no easy way to fix it, so just exclude it since it is
# useless for BPF samples.
+# below we use long chain of commands, clang | opt | llvm-dis | llc,
+# to generate final object file. 'clang' compiles the source into IR
+# with native target, e.g., x64, arm64, etc. 'opt' does bpf CORE IR builtin
+# processing (llvm12) and IR optimizations. 'llvm-dis' converts
+# 'opt' output to IR, and finally 'llc' generates bpf byte code.
$(obj)/%.o: $(src)/%.c
@echo " CLANG-bpf " $@
@@ -314,7 +321,9 @@ $(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)