[Qemu-devel] [PATCH for-2.0 v2] configure: add workaround for SystemTap PR13296

[Stefan Hajnoczi]

SystemTap sdt.h sometimes results in compiled probes without sufficient
information to extract arguments.  See code comment for details on this
workaround.

This patch fixes the apic_reset_irq_delivered() trace event on Fedora 20
with gcc-4.8.2-7.fc20 and systemtap-sdt-devel-2.4-2.fc20 on x86_64.

Signed-off-by: Stefan Hajnoczi <address@hidden>
---
 configure | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/configure b/configure
index aae617e..6c86431 100755
--- a/configure
+++ b/configure
@@ -3635,6 +3635,22 @@ if test "$trace_backend" = "dtrace"; then
   trace_backend_stap="no"
   if has 'stap' ; then
     trace_backend_stap="yes"
+
+    # Sometimes sdt.h probes produce insufficient information to access probe
+    # arguments.  The compiler can be forced to place probe arguments in
+    # registers to avoid the issue.  This workaround has a performance cost so
+    # it should be dropped if SystemTap is able to resolve the underlying
+    # issue.
+    #
+    # On host architectures that are starved for registers, it may not be
+    # possible to force arguments into registers and this causes a compiler
+    # error.  Only apply this workaround on x86_64 where the problem has been
+    # observed.
+    #
+    # https://sourceware.org/bugzilla/show_bug.cgi?id=13296
+    if test "$ARCH" = "x86_64"; then
+      QEMU_CFLAGS="-DSTAP_SDT_ARG_CONSTRAINT=r $QEMU_CFLAGS"
+    fi
   fi
 fi
 
-- 
1.8.5.3