llvm dev - Sep 2014 - [LLVMdev] Address sanitizer regression test failures for PPC64 targets

Hi all,

I have been experiencing the failure of the address sanitizer regression
tests for a PPC64 target (Power7 machine). My understanding is that most of
the failures are related with the fact the stack is not being dumped.

I tried to understand what might be wrong and started by looking into the
null_deref.cc test as it hangs during the test run.  I observe that after
the detection of the faulty memory access it receives a SEGV after entering
ReportSIGSEGV() more precisely when it gets to the __intercept_strlen() and
tries to access  flags()->replace_str. The caller of __intercept_strlen()
is get_cie_encoding() from libgcc (version 4.8.2 in my system).

As I am not familiar with the sanitizer implementation, I was wondering if
this is an expected failure for PPC targets due to some incomplete
implementation, an unexpected bug, or due to some misconfiguration in the
Clang/LLVM build for PPC targets.

Has anyone experienced a similar issue?

Thanks in advance!
Samuel
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+Bill Schmidt

On Thu, Sep 4, 2014 at 5:39 PM, Samuel F Antao <sfantao at us.ibm.com>
wrote:
> Hi all,
>
> I have been experiencing the failure of the address sanitizer regression
> tests for a PPC64 target (Power7 machine). My understanding is that most of
> the failures are related with the fact the stack is not being dumped.
>
> I tried to understand what might be wrong and started by looking into the
> null_deref.cc test as it hangs during the test run.  I observe that after
> the detection of the faulty memory access it receives a SEGV after entering
> ReportSIGSEGV() more precisely when it gets to the __intercept_strlen() and
> tries to access  flags()->replace_str. The caller of
__intercept_strlen()
> is get_cie_encoding() from libgcc (version 4.8.2 in my system).
>
> As I am not familiar with the sanitizer implementation, I was wondering if
> this is an expected failure for PPC targets due to some incomplete
> implementation, an unexpected bug, or due to some misconfiguration in the
> Clang/LLVM build for PPC targets.
>
> Has anyone experienced a similar issue?
>
Sanitizer used to work on PPC at some point, but currently it fails on most
of the tests from "check-asan" test suite on the PowerPC buildbot (
http://lab.llvm.org:8011/builders/sanitizer-ppc64-linux1).
I can't really diagnose the issue from your description. flags() is just a
pointer to a global variable, so I don't see why access to
flags()->replace_str
will segfault.

>
>
> Thanks in advance!
> Samuel
>
> _______________________________________________
> cfe-dev mailing list
> cfe-dev at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>
>

-- 
Alexey Samsonov
vonosmas at gmail.com
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Note that I've set the SA_NODEFER flag for the SEGV handler in the
ASan runtime only a couple of days ago.
Not sure that could've affected this test though; without that flag
the second SEGV would've simply crashed the program. But you can try
removing the flag from
compiler-rt/trunk/lib/sanitizer_common/sanitizer_posix_libcdep.cc and
see if that makes any difference.

HTH,
Alex

On Fri, Sep 5, 2014 at 5:26 AM, Alexey Samsonov <vonosmas at gmail.com>
wrote:
> +Bill Schmidt
>
> On Thu, Sep 4, 2014 at 5:39 PM, Samuel F Antao <sfantao at
us.ibm.com> wrote:
>>
>> Hi all,
>>
>> I have been experiencing the failure of the address sanitizer
regression
>> tests for a PPC64 target (Power7 machine). My understanding is that
most of
>> the failures are related with the fact the stack is not being dumped.
>>
>> I tried to understand what might be wrong and started by looking into
the
>> null_deref.cc test as it hangs during the test run.  I observe that
after
>> the detection of the faulty memory access it receives a SEGV after
entering
>> ReportSIGSEGV() more precisely when it gets to the __intercept_strlen()
and
>> tries to access  flags()->replace_str. The caller of
__intercept_strlen() is
>> get_cie_encoding() from libgcc (version 4.8.2 in my system).
>>
>> As I am not familiar with the sanitizer implementation, I was wondering
if
>> this is an expected failure for PPC targets due to some incomplete
>> implementation, an unexpected bug, or due to some misconfiguration in
the
>> Clang/LLVM build for PPC targets.
>>
>> Has anyone experienced a similar issue?
>
>
> Sanitizer used to work on PPC at some point, but currently it fails on most
> of the tests from "check-asan" test suite on the PowerPC buildbot
> (http://lab.llvm.org:8011/builders/sanitizer-ppc64-linux1).
> I can't really diagnose the issue from your description. flags() is
just a
> pointer to a global variable, so I don't see why access to
> flags()->replace_str will segfault.
>
>>
>>
>>
>> Thanks in advance!
>> Samuel
>>
>>
>> _______________________________________________
>> cfe-dev mailing list
>> cfe-dev at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>>
>
>
>
> --
> Alexey Samsonov
> vonosmas at gmail.com
>
> _______________________________________________
> cfe-dev mailing list
> cfe-dev at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>


-- 
Alexander Potapenko
Software Engineer
Google Moscow