Messages in this thread | | | Date | Mon, 18 Dec 2017 04:05:10 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH v2] tools/perf/inject: fix dwarf support detection |
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On Fri, Dec 08, 2017 at 09:02:18AM -0800, Stephane Eranian wrote: > 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 die 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, the 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. > > In v2, we removed the extraneaous echo in the make target. > > Signed-off-by: Stephane Eranian <eranian@google.com> > --- > tools/build/feature/Makefile | 7 ++++++- > tools/perf/builtin-inject.c | 3 +++ > 2 files changed, 9 insertions(+), 1 deletion(-) > > diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile > index cff38f342283..be5679707aa0 100644 > --- a/tools/build/feature/Makefile > +++ b/tools/build/feature/Makefile > @@ -104,7 +104,12 @@ __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
you can remove '-lelf' from above line then (again)
jirka
> endif > 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 >
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