I ran into problems trying to use the JIT support and display source-level information. Basically, there was no dwarf debug info generated in the jitted-XX.so files, yet I had libdw-dev installed.
Turns out that the feature test build for test-dwarf.bin was broken for me. It would fail for the wrong reason: /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/libdw.so: undefined reference to `elf_compress@ELFUTILS_1.7' In other words, libdw has a dependency on libelf which the Makefile was not accounting for. Thus, perf was not compiled with HAVE_DWARF_SUPPORT and the code in genelf.c was not compiled in. This patch fixes the issue by adding -lelf to the build rule for test-dwarf.c. I wasted quite some time trying to debug this, so I have added a warning in builtin-inject.c so that the user is warned that in case dwarf support is disabled, no source line information will be generated in the output .so files from the jitted code. Signed-off-by: Stephane Eranian <eran...@google.com> --- tools/build/feature/Makefile | 8 +++++++- tools/perf/builtin-inject.c | 3 +++ 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile index cff38f342283..3242e11784e0 100644 --- a/tools/build/feature/Makefile +++ b/tools/build/feature/Makefile @@ -104,12 +104,18 @@ __BUILDXX = $(CXX) $(CXXFLAGS) -MD -Wall -Werror -o $@ $(patsubst %.bin,%.cpp,$( $(OUTPUT)test-setns.bin: $(BUILD) -DWARFLIBS := -ldw +# +# there may be a dependency between libdw and libelf such as +# /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/libdw.so: undefined reference to `elf_compress@ELFUTILS_1.7' +# so force linking with libelf +# +DWARFLIBS := -ldw -lelf ifeq ($(findstring -static,${LDFLAGS}),-static) DWARFLIBS += -lelf -lebl -lz -llzma -lbz2 endif $(OUTPUT)test-dwarf.bin: + echo DWARF=$(DWARFLIBS) $(BUILD) $(DWARFLIBS) $(OUTPUT)test-dwarf_getlocations.bin: diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c index 16a28547ca86..524255ed9a39 100644 --- a/tools/perf/builtin-inject.c +++ b/tools/perf/builtin-inject.c @@ -856,6 +856,9 @@ int cmd_inject(int argc, const char **argv) } #ifdef HAVE_JITDUMP if (inject.jit_mode) { +#ifndef HAVE_DWARF_SUPPORT + pr_warning("perf tool compiled without dwarf, no source line information will be generated\n"); +#endif inject.tool.mmap2 = perf_event__jit_repipe_mmap2; inject.tool.mmap = perf_event__jit_repipe_mmap; inject.tool.ordered_events = true; -- 2.7.4