From 4b265c79a85bb35abe19aacea6954c1616521639 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Thu, 19 Nov 2020 14:14:57 +0000 Subject: [PATCH] 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 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 Message-id: 20201119141457.844452-1-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi --- configure | 7 +++++++ trace/meson.build | 4 ++-- 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/configure b/configure index 714e75b5d8..796cec14de 100755 --- a/configure +++ b/configure @@ -4832,6 +4832,13 @@ 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/trace/meson.build b/trace/meson.build index d5fc45c628..843ea14495 100644 --- a/trace/meson.build +++ b/trace/meson.build @@ -38,13 +38,13 @@ foreach dir : [ '.' ] + trace_events_subdirs trace_dtrace_h = custom_target(fmt.format('trace-dtrace', 'h'), output: fmt.format('trace-dtrace', 'h'), input: trace_dtrace, - command: [ 'dtrace', '-o', '@OUTPUT@', '-h', '-s', '@INPUT@' ]) + command: [ 'dtrace', '-DSTAP_SDT_V2', '-o', '@OUTPUT@', '-h', '-s', '@INPUT@' ]) trace_ss.add(trace_dtrace_h) if host_machine.system() != 'darwin' trace_dtrace_o = custom_target(fmt.format('trace-dtrace', 'o'), output: fmt.format('trace-dtrace', 'o'), input: trace_dtrace, - command: [ 'dtrace', '-o', '@OUTPUT@', '-G', '-s', '@INPUT@' ]) + command: [ 'dtrace', '-DSTAP_SDT_V2', '-o', '@OUTPUT@', '-G', '-s', '@INPUT@' ]) trace_ss.add(trace_dtrace_o) endif