From 0e330ca9023487b3635cdcee1b7ef03266ea9068 Mon Sep 17 00:00:00 2001

From: Stefan Hajnoczi <stefanha@redhat.com>

Date: Thu, 19 Nov 2020 11:27:04 +0000

Subject: [PATCH] trace: use STAP_SDT_V2 to work around symbol visibility

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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.

Cc: Daniel P. Berrangé <berrange@redhat.com>

Cc: wcohen@redhat.com

Cc: fche@redhat.com

Cc: kraxel@redhat.com

Cc: rjones@redhat.com

Cc: mrezanin@redhat.com

Cc: ddepaula@redhat.com

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

---

 configure         | 1 +

 trace/meson.build | 4 ++--

 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/configure b/configure

index 714e75b5d8..5d91d49c7b 100755

--- a/configure

+++ b/configure

@@ -4832,6 +4832,7 @@ if have_backend "dtrace"; then

   trace_backend_stap="no"

   if has 'stap' ; then

     trace_backend_stap="yes"

+    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

-- 

2.28.0