Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753237AbdLHRCZ (ORCPT ); Fri, 8 Dec 2017 12:02:25 -0500 Received: from mail-pf0-f180.google.com ([209.85.192.180]:43264 "EHLO mail-pf0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752484AbdLHRCW (ORCPT ); Fri, 8 Dec 2017 12:02:22 -0500 X-Google-Smtp-Source: AGs4zMakWX8Wuj2f3ru6Ky0Nzhg5dLk5O7ctEjTR+za3v6SypC+LR0KGrr0UqBKB3ZAcUAutZ8z+bg== From: Stephane Eranian To: linux-kernel@vger.kernel.org Cc: acme@redhat.com, peterz@infradead.org, mingo@elte.hu, jolsa@redhat.com Subject: [PATCH v2] tools/perf/inject: fix dwarf support detection Date: Fri, 8 Dec 2017 09:02:18 -0800 Message-Id: <1512752538-10230-1-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: 2478 Lines: 63 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 --- 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 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