libsanitizer merge from upstream r208536

[Konstantin Serebryany]

Yuri, this comes from yours
http://llvm.org/viewvc/llvm-project?view=revision&revision=205308
Could you please take a look?

On Thu, May 22, 2014 at 11:54 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Thu, May 22, 2014 at 09:43:01PM +0200, Paolo Carlini wrote:
>> Hi,
>>
>> On 05/22/2014 09:15 PM, Jakub Jelinek wrote:
>> >Do you have LD_PRELOAD set in the environment?
>> I don't.
>> >If not, can you cut'n'paste the large-func-test-1.exe command line
>> >and run it with the given LD_LIBRARY_PATH under ldd? Jakub
>> Sure. This is what I get:
>>
>>         linux-vdso.so.1 (0x00007fffee578000)
>>         libasan.so.1 => /home/paolo/Gcc/svn-dirs/trunk-build/x86_64-unknown-linux-gnu/./libsanitizer/asan/.libs/libasan.so.1
>> (0x00007f41610c7000)
>>         libstdc++.so.6 => /home/paolo/Gcc/svn-dirs/trunk-build/x86_64-unknown-linux-gnu/./libstdc++-v3/src/.libs/libstdc++.so.6
>> (0x00007f4160db6000)
>>         libm.so.6 => /lib64/libm.so.6 (0x00007f4160ab3000)
>>         libgcc_s.so.1 =>
>> /home/paolo/Gcc/svn-dirs/trunk-build/gcc/libgcc_s.so.1
>> (0x00007f416089c000)
>>         libc.so.6 => /lib64/libc.so.6 (0x00007f41604ed000)
>>         libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f41602cf000)
>>         libdl.so.2 => /lib64/libdl.so.2 (0x00007f41600cb000)
>>         /lib64/ld-linux-x86-64.so.2 (0x00007f4161ff3000)
>
> Kostya, guess you should ignore the vDSO.
>
> I'd say the test is useless anyway, if you really want to do some
> quick sanity check, much better would be just dlsym a couple of
> interesting symbols to verify that libasan.so.1 is ahead
> of libc.so.6, libstdc++.so.6, libpthread.so.0 (whatever else
> you want to override).  Otherwise libasan apps will simply stop
> working altogether if LD_PRELOAD is set, to whatever library,
> even if it doesn't define any symbols you care about.
> I'd verify that malloc, memcpy, pthread_create, operator new
> all resolve to the libasan.so.1 copy (if all those have local aliases,
> just compare what dlsym returns with those local aliases).
> Typically people in LD_PRELOAD override malloc (which we want to diagnose),
> or far more rarely stringops (e.g. memstomp, also undesirable).
>
>         Jakub