trace: use STAP_SDT_V2 to work around symbol visibility
authorStefan Hajnoczi <stefanha@redhat.com>
Thu, 19 Nov 2020 14:14:57 +0000 (14:14 +0000)
committerStefan Hajnoczi <stefanha@redhat.com>
Thu, 19 Nov 2020 16:41:09 +0000 (16:41 +0000)
commit4b265c79a85bb35abe19aacea6954c1616521639
treefdd78ee2f1785fb77e98d6d911cdb20b47dc70a5
parentff85db769ffd431f86d263d5e954e809a83be92f
trace: use STAP_SDT_V2 to work around symbol visibility

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 <stefanha@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Miroslav Rezanina <mrezanin@redhat.com>
Message-id: 20201119141457.844452-1-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
configure
trace/meson.build