qemu-iotests: Fix core dump suppression in test 039

The shell script attempts to suppress core dumps like this:

    old_ulimit=$(ulimit -c)
    ulimit -c 0
    $QEMU_IO arg...
    ulimit -c "$old_ulimit"

This breaks the test hard unless the limit was zero to begin with!
ulimit sets both hard and soft limit by default, and (re-)raising the
hard limit requires privileges.  Broken since it was added in commit
dc68afe.

Could be fixed by adding -S to set only the soft limit, but I'm not
sure how portable that is in practice.  Simply do it in a subshell
instead, like this:

    (ulimit -c 0; exec $QEMU_IO arg...)

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/039

@@ -47,6 +47,11 @@ _supported_os Linux
 _default_cache_mode "writethrough"
 _supported_cache_modes "writethrough"
 
+_no_dump_exec()
+{
+    (ulimit -c 0; exec "$@")
+}
+
 size=128M
 
 echo
@@ -67,10 +72,7 @@ echo "== Creating a dirty image file =="
 IMGOPTS="compat=1.1,lazy_refcounts=on"
 _make_test_img $size
 
-old_ulimit=$(ulimit -c)
-ulimit -c 0 # do not produce a core dump on abort(3)
-$QEMU_IO -c "write -P 0x5a 0 512" -c "abort" "$TEST_IMG" | _filter_qemu_io
-ulimit -c "$old_ulimit"
+_no_dump_exec $QEMU_IO -c "write -P 0x5a 0 512" -c "abort" "$TEST_IMG" 2>&1 | _filter_qemu_io
 
 # The dirty bit must be set
 ./qcow2.py "$TEST_IMG" dump-header | grep incompatible_features
@@ -103,10 +105,7 @@ echo "== Opening a dirty image read/write should repair it =="
 IMGOPTS="compat=1.1,lazy_refcounts=on"
 _make_test_img $size
 
-old_ulimit=$(ulimit -c)
-ulimit -c 0 # do not produce a core dump on abort(3)
-$QEMU_IO -c "write -P 0x5a 0 512" -c "abort" "$TEST_IMG" | _filter_qemu_io
-ulimit -c "$old_ulimit"
+_no_dump_exec $QEMU_IO -c "write -P 0x5a 0 512" -c "abort" "$TEST_IMG" 2>&1 | _filter_qemu_io
 
 # The dirty bit must be set
 ./qcow2.py "$TEST_IMG" dump-header | grep incompatible_features
@@ -122,10 +121,7 @@ echo "== Creating an image file with lazy_refcounts=off =="
 IMGOPTS="compat=1.1,lazy_refcounts=off"
 _make_test_img $size
 
-old_ulimit=$(ulimit -c)
-ulimit -c 0 # do not produce a core dump on abort(3)
-$QEMU_IO -c "write -P 0x5a 0 512" -c "abort" "$TEST_IMG" | _filter_qemu_io
-ulimit -c "$old_ulimit"
+_no_dump_exec $QEMU_IO -c "write -P 0x5a 0 512" -c "abort" "$TEST_IMG" 2>&1 | _filter_qemu_io
 
 # The dirty bit must not be set since lazy_refcounts=off
 ./qcow2.py "$TEST_IMG" dump-header | grep incompatible_features

tests/qemu-iotests/039.out

@@ -11,6 +11,7 @@ No errors were found on the image.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 
 wrote 512/512 bytes at offset 0
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+./039: Aborted                 ( ulimit -c 0; exec "$@" )
 incompatible_features     0x1
 ERROR cluster 5 refcount=0 reference=1
 ERROR OFLAG_COPIED data cluster: l2_entry=8000000000050000 refcount=0
@@ -42,6 +43,7 @@ read 512/512 bytes at offset 0
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 
 wrote 512/512 bytes at offset 0
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+./039: Aborted                 ( ulimit -c 0; exec "$@" )
 incompatible_features     0x1
 Repairing cluster 5 refcount=0 reference=1
 wrote 512/512 bytes at offset 0
@@ -52,6 +54,7 @@ incompatible_features     0x0
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 
 wrote 512/512 bytes at offset 0
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+./039: Aborted                 ( ulimit -c 0; exec "$@" )
 incompatible_features     0x0
 No errors were found on the image.
 

tests/qemu-iotests/common.filter

@@ -150,6 +150,7 @@ _filter_win32()
 _filter_qemu_io()
 {
     _filter_win32 | sed -e "s/[0-9]* ops\; [0-9/:. sec]* ([0-9/.inf]* [EPTGMKiBbytes]*\/sec and [0-9/.inf]* ops\/sec)/X ops\; XX:XX:XX.X (XXX YYY\/sec and XXX ops\/sec)/" \
+        -e "s/: line [0-9][0-9]*:  *[0-9][0-9]*\( Aborted\)/:\1/" \
         -e "s/qemu-io> //g"
 }