From ba3068eb1a349ec4ed8b7ccdae76450f0c315be9 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Thu, 19 Nov 2020 17:23:11 -0500 Subject: [PATCH 18/18] trace: use STAP_SDT_V2 to work around symbol visibility MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Stefan Hajnoczi Message-id: <20201119172311.942629-2-stefanha@redhat.com> Patchwork-id: 99779 O-Subject: [RHEL-8.4.0 qemu-kvm PATCH 1/1] trace: use STAP_SDT_V2 to work around symbol visibility Bugzilla: 1898700 RH-Acked-by: Miroslav Rezanina RH-Acked-by: Gerd Hoffmann RH-Acked-by: Philippe Mathieu-Daudé QEMU binaries no longer launch successfully with recent SystemTap releases. This is because modular QEMU builds link the sdt semaphores into the main binary instead of into the shared objects where they are used. The symbol visibility of semaphores is 'hidden' and the dynamic linker prints an error during module loading: $ ./configure --enable-trace-backends=dtrace --enable-modules ... ... Failed to open module: /builddir/build/BUILD/qemu-4.2.0/s390x-softmmu/../block-curl.so: undefined symbol: qemu_curl_close_semaphore The long-term solution is to generate per-module dtrace .o files and link them into the module instead of the main binary. In the short term we can define STAP_SDT_V2 so dtrace(1) produces a .o file with 'default' symbol visibility instead of 'hidden'. This workaround is small and easier to merge for QEMU 5.2 and downstream backports. Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1898700 Cc: wcohen@redhat.com Cc: fche@redhat.com Cc: kraxel@redhat.com Cc: rjones@redhat.com Cc: ddepaula@redhat.com Signed-off-by: Stefan Hajnoczi Reviewed-by: Daniel P. Berrangé Reviewed-by: Philippe Mathieu-Daudé Reviewed-by: Miroslav Rezanina (cherry picked from commit 4b265c79a85bb35abe19aacea6954c1616521639) Signed-off-by: Stefan Hajnoczi Conflicts: trace/meson.build Downstream uses makefiles, so move the dtrace invocation changes to rules.mak and Makefile. Signed-off-by: Danilo C. L. de Paula --- Makefile | 4 ++-- configure | 7 +++++++ rules.mak | 2 +- 3 files changed, 10 insertions(+), 3 deletions(-) diff --git a/Makefile b/Makefile index ff05c309497..29b01a13ee3 100644 --- a/Makefile +++ b/Makefile @@ -198,7 +198,7 @@ tracetool-y += $(shell find $(SRC_PATH)/scripts/tracetool -name "*.py") $< > $@,"GEN","$(@:%-timestamp=%)") %/trace-dtrace.h: %/trace-dtrace.dtrace $(tracetool-y) - $(call quiet-command,dtrace -o $@ -h -s $<, "GEN","$@") + $(call quiet-command,dtrace -o $@ -DSTAP_SDT_V2 -h -s $<, "GEN","$@") %/trace-dtrace.o: %/trace-dtrace.dtrace $(tracetool-y) @@ -258,7 +258,7 @@ trace-dtrace-root.dtrace-timestamp: $(SRC_PATH)/trace-events $(BUILD_DIR)/config $< > $@,"GEN","$(@:%-timestamp=%)") trace-dtrace-root.h: trace-dtrace-root.dtrace - $(call quiet-command,dtrace -o $@ -h -s $<, "GEN","$@") + $(call quiet-command,dtrace -o $@ -DSTAP_SDT_V2 -h -s $<, "GEN","$@") trace-dtrace-root.o: trace-dtrace-root.dtrace diff --git a/configure b/configure index 5120c1409a7..c62b61403f6 100755 --- a/configure +++ b/configure @@ -5275,6 +5275,13 @@ if have_backend "dtrace"; then trace_backend_stap="no" if has 'stap' ; then trace_backend_stap="yes" + + # Workaround to avoid dtrace(1) producing a file with 'hidden' symbol + # visibility. Define STAP_SDT_V2 to produce 'default' symbol visibility + # instead. QEMU --enable-modules depends on this because the SystemTap + # semaphores are linked into the main binary and not the module's shared + # object. + QEMU_CFLAGS="$QEMU_CFLAGS -DSTAP_SDT_V2" fi fi diff --git a/rules.mak b/rules.mak index 967295dd2b6..bdfc223a5a1 100644 --- a/rules.mak +++ b/rules.mak @@ -101,7 +101,7 @@ LINK = $(call quiet-command, $(LINKPROG) $(QEMU_LDFLAGS) $(QEMU_CFLAGS) $(CFLAGS -c -o $@ $<,"OBJC","$(TARGET_DIR)$@") %.o: %.dtrace - $(call quiet-command,dtrace -o $@ -G -s $<,"GEN","$(TARGET_DIR)$@") + $(call quiet-command,dtrace -o $@ -DSTAP_SDT_V2 -G -s $<,"GEN","$(TARGET_DIR)$@") DSO_OBJ_CFLAGS := -fPIC -DBUILD_DSO module-common.o: CFLAGS += $(DSO_OBJ_CFLAGS) -- 2.27.0