Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933961AbdLRSNW (ORCPT ); Mon, 18 Dec 2017 13:13:22 -0500 Received: from mail-wm0-f50.google.com ([74.125.82.50]:42995 "EHLO mail-wm0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933736AbdLRSNS (ORCPT ); Mon, 18 Dec 2017 13:13:18 -0500 X-Google-Smtp-Source: ACJfBotOyr6C/zwqs7JvBC31v86bauUwHd5lJM7fGA8zWyOT76y6pwuoiOl94aCyPJPJ+t4s6pxwQw== From: Stephane Eranian To: linux-kernel@vger.kernel.org Cc: acme@redhat.com, peterz@infradead.org, mingo@elte.hu, jolsa@redhat.com Subject: [PATCH v3] tools/perf/inject: fix dwarf support detection Date: Mon, 18 Dec 2017 10:13:00 -0800 Message-Id: <1513620780-30770-1-git-send-email-eranian@google.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2620 Lines: 67 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. In v3, we removed the superfluous -lelf from the static build DWARFLIBS. Signed-off-by: Stephane Eranian --- tools/build/feature/Makefile | 9 +++++++-- tools/perf/builtin-inject.c | 3 +++ 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile index cff38f342283..6fd6f3174c61 100644 --- a/tools/build/feature/Makefile +++ b/tools/build/feature/Makefile @@ -104,9 +104,14 @@ __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 +DWARFLIBS += -lebl -lz -llzma -lbz2 endif $(OUTPUT)test-dwarf.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