Re: [PATCH 0/2] tests/qtest/fuzz: Avoid QTest serialization

[Alexander Bulekov]

On 200526 1725, Philippe Mathieu-Daudé wrote:
> On 5/26/20 4:56 PM, Alexander Bulekov wrote:
> > On 200526 1105, Philippe Mathieu-Daudé wrote:
> >> On 5/26/20 10:56 AM, Stefan Hajnoczi wrote:
> >>> On Tue, May 26, 2020 at 07:58:18AM +0200, Philippe Mathieu-Daudé wrote:
> >>>> Hi Alexander,
> >>>>
> >>>> I forgot to share these 2 patches wrote before
> >>>> the direct MemoryRegion fuzzer sent yesterday.
> >>>>
> >>>> Regards,
> >>>>
> >>>> Phil.
> >>>>
> >>>> Philippe Mathieu-Daudé (2):
> >>>>   tests/qtest/fuzz: Avoid QTest ioport serialization
> >>>>   tests/qtest/fuzz: Avoid QTest mmio serialization
> >>>>
> >>>>  tests/qtest/fuzz/i440fx_fuzz.c      | 19 +++++++++++++------
> >>>>  tests/qtest/fuzz/virtio_net_fuzz.c  |  6 ++++--
> >>>>  tests/qtest/fuzz/virtio_scsi_fuzz.c |  6 +++++-
> >>>>  3 files changed, 22 insertions(+), 9 deletions(-)
> >>>
> >>> Will it still be possible to print qtest reproducer commands when a
> >>> crash is found?
> >>
> >> Yes, there is no change in the corpus format.
> > 
> > Yes, though with these patches, the qtest-based code will be gone.
> > Should there be some option to switch between the two modes?
> 
> How so?
> 
> How do you generate your reproducers?

Right now basically with this:

--- a/qtest.c
+++ b/qtest.c
@@ -808,6 +808,8 @@ bool qtest_driver(void)

 void qtest_server_inproc_recv(void *dummy, const char *buf)
 {
+    // It would be nice to add support for qtest's built in qtest_log_fp.
+    printf(">>> %s\n", buf);
     static GString *gstr;
     if (!gstr) {
         gstr = g_string_new(NULL);
--

It would be nice to add support for qtest's built in qtest_log_fp.
Unless I'm missing something, these address_space_writes completely
bypass qtest, so there has to be some additional step to build
reproducers(eg running against the QTest-based version, or adding some
way to spit out corresponding qtest commands for the
address_space_writes).

> > 
> >>>
> >>> Other than this concern, higher fuzzing rates would be great.
> >>
> >> Thanks,
> >>
> >> Phil.
> >