[RFC PATCH 2/3] qemu-iotests: add option to attach gdbserver

[Emanuele Giuseppe Esposito]

Add -gdb flag and GDB_QEMU environmental variable
to python tests to attach a gdbserver to each qemu_system instance.
The GDB_QEMU will just contain the options to provide to gdbserver,
if empty and -gdb is set it will default to "localhost:12345".

The gdb option is provided to python/qemu/machine.py through
the "wrapper" parameter, currently unused by qemu-iotests.

Attaching a gdbserver implies that the qmp socket
should wait indefinitely for an answer from QEMU, otherwise
the connection will drop after 15 seconds.

if -gdb is not provided but $GDB_QEMU is set, the script will ignore the
environmental variable.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 python/qemu/machine.py        |  4 +++-
 python/qemu/qtest.py          |  4 +++-
 tests/qemu-iotests/check      |  5 ++++-
 tests/qemu-iotests/iotests.py |  7 ++++++-
 tests/qemu-iotests/testenv.py | 15 +++++++++++++--
 5 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/python/qemu/machine.py b/python/qemu/machine.py
index c721e07d63..d7fca6b3c1 100644
--- a/python/qemu/machine.py
+++ b/python/qemu/machine.py
@@ -408,7 +408,9 @@ def _launch(self) -> None:
                                        stderr=subprocess.STDOUT,
                                        shell=False,
                                        close_fds=False)
-        self._post_launch()
+
+        timer = None if 'gdbserver' in self._wrapper else 15.0
+        self._post_launch(timer)
 
     def _early_cleanup(self) -> None:
         """
diff --git a/python/qemu/qtest.py b/python/qemu/qtest.py
index 0d01715086..4c90daf430 100644
--- a/python/qemu/qtest.py
+++ b/python/qemu/qtest.py
@@ -111,6 +111,7 @@ class QEMUQtestMachine(QEMUMachine):
     def __init__(self,
                  binary: str,
                  args: Sequence[str] = (),
+                 wrapper: Sequence[str] = (),
                  name: Optional[str] = None,
                  test_dir: str = "/var/tmp",
                  socket_scm_helper: Optional[str] = None,
@@ -119,7 +120,8 @@ def __init__(self,
             name = "qemu-%d" % os.getpid()
         if sock_dir is None:
             sock_dir = test_dir
-        super().__init__(binary, args, name=name, test_dir=test_dir,
+        super().__init__(binary, args, wrapper=wrapper, name=name,
+                         test_dir=test_dir,
                          socket_scm_helper=socket_scm_helper,
                          sock_dir=sock_dir)
         self._qtest: Optional[QEMUQtestProtocol] = None
diff --git a/tests/qemu-iotests/check b/tests/qemu-iotests/check
index df9fd733ff..5a1d0518f1 100755
--- a/tests/qemu-iotests/check
+++ b/tests/qemu-iotests/check
@@ -36,6 +36,8 @@ def make_argparser() -> argparse.ArgumentParser:
                    help='pretty print output for make check')
 
     p.add_argument('-d', dest='debug', action='store_true', help='debug')
+    p.add_argument('-gdb', action='store_true',
+                   help="start gdb server on localhost. Default port is 12345")
     p.add_argument('-misalign', action='store_true',
                    help='misalign memory allocations')
     p.add_argument('--color', choices=['on', 'off', 'auto'],
@@ -115,7 +117,8 @@ if __name__ == '__main__':
     env = TestEnv(imgfmt=args.imgfmt, imgproto=args.imgproto,
                   aiomode=args.aiomode, cachemode=args.cachemode,
                   imgopts=args.imgopts, misalign=args.misalign,
-                  debug=args.debug, valgrind=args.valgrind)
+                  debug=args.debug, valgrind=args.valgrind,
+                  gdb=args.gdb)
 
     if len(sys.argv) > 1 and sys.argv[-len(args.tests)-1] == '--':
         if not args.tests:
diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 2a34eef601..138cf135ea 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -74,6 +74,10 @@
 qemu_prog = os.environ.get('QEMU_PROG', 'qemu')
 qemu_opts = os.environ.get('QEMU_OPTIONS', '').strip().split(' ')
 
+qemu_gdb = []
+if os.environ.get('GDB_QEMU'):
+    qemu_gdb = ['gdbserver'] + os.environ.get('GDB_QEMU').strip().split(' ')
+
 imgfmt = os.environ.get('IMGFMT', 'raw')
 imgproto = os.environ.get('IMGPROTO', 'file')
 output_dir = os.environ.get('OUTPUT_DIR', '.')
@@ -574,7 +578,8 @@ class VM(qtest.QEMUQtestMachine):
 
     def __init__(self, path_suffix=''):
         name = "qemu%s-%d" % (path_suffix, os.getpid())
-        super().__init__(qemu_prog, qemu_opts, name=name,
+        super().__init__(qemu_prog, qemu_opts, wrapper=qemu_gdb,
+                         name=name,
                          test_dir=test_dir,
                          socket_scm_helper=socket_scm_helper,
                          sock_dir=sock_dir)
diff --git a/tests/qemu-iotests/testenv.py b/tests/qemu-iotests/testenv.py
index 169268f61a..62749becbd 100644
--- a/tests/qemu-iotests/testenv.py
+++ b/tests/qemu-iotests/testenv.py
@@ -72,7 +72,8 @@ class TestEnv(ContextManager['TestEnv']):
                      'QEMU_NBD_OPTIONS', 'IMGOPTS', 'IMGFMT', 'IMGPROTO',
                      'AIOMODE', 'CACHEMODE', 'VALGRIND_QEMU',
                      'CACHEMODE_IS_DEFAULT', 'IMGFMT_GENERIC', 'IMGOPTSSYNTAX',
-                     'IMGKEYSECRET', 'QEMU_DEFAULT_MACHINE', 'MALLOC_PERTURB_']
+                     'IMGKEYSECRET', 'QEMU_DEFAULT_MACHINE', 'MALLOC_PERTURB_',
+                     'GDB_QEMU']
 
     def prepare_subprocess(self, args: List[str]) -> Dict[str, str]:
         if self.debug:
@@ -178,7 +179,8 @@ def __init__(self, imgfmt: str, imgproto: str, aiomode: str,
                  imgopts: Optional[str] = None,
                  misalign: bool = False,
                  debug: bool = False,
-                 valgrind: bool = False) -> None:
+                 valgrind: bool = False,
+                 gdb: bool = False) -> None:
         self.imgfmt = imgfmt
         self.imgproto = imgproto
         self.aiomode = aiomode
@@ -186,6 +188,14 @@ def __init__(self, imgfmt: str, imgproto: str, aiomode: 
str,
         self.misalign = misalign
         self.debug = debug
 
+        self.gdb_qemu = os.getenv('GDB_QEMU')
+
+        if gdb and not self.gdb_qemu:
+            self.gdb_qemu = 'localhost:12345'
+        elif self.gdb_qemu and not gdb:
+            del self.gdb_qemu
+            del os.environ['GDB_QEMU']
+
         if valgrind:
             self.valgrind_qemu = 'y'
 
@@ -284,6 +294,7 @@ def print_env(self) -> None:
 TEST_DIR      -- {TEST_DIR}
 SOCK_DIR      -- {SOCK_DIR}
 SOCKET_SCM_HELPER -- {SOCKET_SCM_HELPER}
+GDB_QEMU      -- "{GDB_QEMU}"
 """
 
         args = collections.defaultdict(str, self.get_env())
-- 
2.30.2