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