Re: [Qemu-devel] [PATCH] tests: set MALLOC_PERTURB_ to expose memory bugs

[Lucas Meneghel Rodrigues <lmr@redhat.com>]

On 17/05/13 08:15 AM, Stefan Hajnoczi wrote:
> On Fri, May 17, 2013 at 11:54 AM, Markus Armbruster <armbru@redhat.com> wrote:
>> Stefan Hajnoczi <stefanha@redhat.com> writes:
>>
>>> glibc wipes malloc(3) memory when the MALLOC_PERTURB_ environment
>>> variable is set.  The value of the environment variable determines the
>>> bit pattern used to wipe memory.  For more information, see
>>> http://udrepper.livejournal.com/11429.html.
>>>
>>> Set MALLOC_PERTURB_ for gtester and qemu-iotests.  Note we always set
>>> the environment variable to 1 so the test is deterministic.  Setting a
>>> random variable might expose more bugs but would be harder to reproduce.
>>>
>>> Both make check and qemu-iotests pass with MALLOC_PERTURB_ enabled.
>>>
>>> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
>>> ---
>>> Lucas noticed KVM autotest failures when enabling MALLOC_PERTURB_.  By enabling
>>> it for in-tree test suites we can detect memory management errors earlier.
>>>
>>>   tests/Makefile           | 4 +++-
>>>   tests/qemu-iotests/check | 2 +-
>>>   2 files changed, 4 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/tests/Makefile b/tests/Makefile
>>> index a307d5a..25f6d28 100644
>>> --- a/tests/Makefile
>>> +++ b/tests/Makefile
>>> @@ -171,6 +171,7 @@ GCOV_OPTIONS = -n $(if $(V),-f,)
>>>   $(patsubst %, check-qtest-%, $(QTEST_TARGETS)): check-qtest-%: $(check-qtest-y)
>>>        $(if $(CONFIG_GCOV),@rm -f *.gcda */*.gcda */*/*.gcda */*/*/*.gcda,)
>>>        $(call quiet-command,QTEST_QEMU_BINARY=$*-softmmu/qemu-system-$* \
>>> +             MALLOC_PERTURB_=1 \
>>>                gtester $(GTESTER_OPTIONS) -m=$(SPEED) $(check-qtest-$*-y),"GTESTER $@")
>>>        $(if $(CONFIG_GCOV),@for f in $(gcov-files-$*-y); do \
>>>          echo Gcov report for $$f:;\
>>
>> If you want punishment, why not go for extra punishment?
>>
>> MALLOC_PERTURB_=$(($RANDOM % 255 + 1))
>
> Covered in the commit description:
> "Note we always set
> the environment variable to 1 so the test is deterministic.  Setting a
> random variable might expose more bugs but would be harder to reproduce."
>
> I didn't want to clutter output with "MALLOC_PERTURB_=123" on every
> run.  AFAIK we have no log where this can be silently stashed.  I
> guess we could write it to a file and add that to .gitignore.

Yes, you could consider to have a debug log or something similar.