[cfe-dev] i386 -faddress-sanitizer

[Alexander Potapenko]

You have two issues here then.
First, for some reason the linker doesn't like the unresolved calls to
ASan runtime in your shared object. Can you please attach the full
command line used to invoke the linker (feel free to obfuscate the
file names if needed, but please keep the flags).
Second, you're going to have problems with unresolved symbols once you
load your shared object into a non-instrumented executable.
The only way to detect any errors in a shared library so far is to
rebuild the executable loading that library with ASan.
Please don't link libasan.a with the .so anyway, because you're likely
to have problems with the initialization order. ASan runtime needs to
be initialized at program startup.

On Thu, Oct 18, 2012 at 7:22 PM, Carsten Mattner
<carstenmattner at gmail.com> wrote:
> On Thu, Oct 18, 2012 at 5:18 PM, Kostya Serebryany <kcc at google.com> wrote:
>>
>>
>> On Thu, Oct 18, 2012 at 7:00 PM, Carsten Mattner <carstenmattner at gmail.com>
>> wrote:
>>>
>>> On Thu, Oct 18, 2012 at 4:49 PM, Kostya Serebryany <kcc at google.com> wrote:
>>> > You are linking a shared object, asan.a should not be linked to it.
>>>
>>> What should happen instead?
>>
>>
>> nothing. asan.a should be linked only to the main executable.
>
> I don't build an executable. This is a shared object which gets
> loaded at runtime. Specifically it's a .so implementing a native
> interface binding used with the Erlang runtime.
>
>>> > Are these all the flags passed to ld?
>>>
>>> Yes it's all minus project-specific -l and *.a and *.o args
>>> I have omitted for the email.
>>
>>
>> don't you have something like -Wl,-z,defs ?
>> The problem you describe was seen before in the presence of -Wl,-z,defs,
>> which forces the definitions of all symbols in .so (and __asan* symbols are
>> not defined).
>> The solution was to remove -Wl,-z,defs.
>
> I can't find any of that in the verbose clang linker call's logs.
>
>>> > On Thu, Oct 18, 2012 at 6:23 PM, Carsten Mattner
>>> > <carstenmattner at gmail.com>
>>> > wrote:
>>> >>
>>> >> On Thu, Oct 18, 2012 at 3:36 PM, Alexander Potapenko
>>> >> <glider at google.com>
>>> >> wrote:
>>> >> > Can you append -v at the place it's being invoked to check whether
>>> >> > the
>>> >> > contents of LDFLAGS are being actually passed?
>>> >>
>>> >> $ clang <INPUT_OBJECTS> -lstdc++ -v -faddress-sanitizer -shared
>>> >> <PROJECT_FLAGS> -o <SO_FILE>
>>> >> clang
>>> >> version 3.2 (http://llvm.org/git/clang.git
>>> >> 278eafa2cd8296f8128d13c6466a0ace3d03a872)
>>> >> (http://llvm.org/git/llvm.git
>>> >> 2360b7ad99eedecaae512373e7be49c2143550cf)
>>> >> Target: i386-pc-linux-gnu
>>> >> Thread model: posix
>>> >>
>>> >> "/usr/bin/ld" --eh-frame-hdr -m elf_i386 -shared -o <SO_FILE>
>>> >> /usr/lib/gcc/i686-pc-linux-gnu/4.7.2/../../../crti.o
>>> >> /usr/lib/gcc/i686-pc-linux-gnu/4.7.2/crtbeginS.o
>>> >> -L/usr/lib/gcc/i686-pc-linux-gnu/4.7.2
>>> >> -L/usr/lib/gcc/i686-pc-linux-gnu/4.7.2/../../.. -L/lib -L/usr/lib
>>> >> <INPUT_OBJECTS> -lstdc++ -lgcc --as-needed -lgcc_s --no-as-needed -lc
>>> >> -lgcc --as-needed -lgcc_s --no-as-needed
>>> >> /usr/lib/gcc/i686-pc-linux-gnu/4.7.2/crtendS.o
>>> >> /usr/lib/gcc/i686-pc-linux-gnu/4.7.2/../../../crtn.o
>>> >>
>>> >> I guess the libasan archive should be part of the above call to ld.
>>> >>
>>> >> > On Thu, Oct 18, 2012 at 5:33 PM, Carsten Mattner
>>> >> > <carstenmattner at gmail.com> wrote:
>>> >> >> On Thu, Oct 18, 2012 at 3:29 PM, Alexander Potapenko wrote:
>>> >> >>> Are you linking with ld or clang?
>>> >> >>> -faddress-sanitizer is a Clang flag, so if you're running `ld
>>> >> >>> $LDFLAGS
>>> >> >>> ...` to link your program, it won't work.
>>> >> >>
>>> >> >> clang.
>>> >> >>
>>> >> >>> On Thu, Oct 18, 2012 at 5:12 PM, Carsten Mattner
>>> >> >>> <carstenmattner at gmail.com> wrote:
>>> >> >>>> On Thu, Oct 18, 2012 at 12:27 AM, Eli Friedman wrote:
>>> >> >>>>> On Wed, Oct 17, 2012 at 1:43 PM, Carsten Mattner
>>> >> >>>>> <carstenmattner at gmail.com> wrote:
>>> >> >>>>>> Is it expected that -faddress-sanitizer  does not work on i386
>>> >> >>>>>> and
>>> >> >>>>>> fails
>>> >> >>>>>> to properly link resulting in errors like 'undefined symbol:
>>> >> >>>>>> __asan_init'
>>> >> >>>>>> at runtime?
>>> >> >>>>>>
>>> >> >>>>>> I have ./lib/clang/3.2/lib/linux/libclang_rt.asan-i386.a in
>>> >> >>>>>> llvm's
>>> >> >>>>>> installation,
>>> >> >>>>>> but it doesn't look like it's linked automatically into the
>>> >> >>>>>> executable.
>>> >> >>>>>>
>>> >> >>>>>> CFLAGS:
>>> >> >>>>>> -faddress-sanitizer -O1 -fno-omit-frame-pointer -g
>>> >> >>>>>> $PROJECT_FLAGS
>>> >> >>>>>
>>> >> >>>>> You need to pass in -faddress-sanitizer both when compiling and
>>> >> >>>>> when
>>> >> >>>>> linking an application.  Try something like
>>> >> >>>>> "LDFLAGS=-faddress-sanitizer".
>>> >> >>>>
>>> >> >>>> Oh that makes a lot of sense and is kind of obvious in hindsight.
>>> >> >>>> Yet it didn't work in a quick test. Any options I flags to pass
>>> >> >>>> for
>>> >> >>>> verbose printfs to see what's happening you can suggest?
>>> >> >>>> In the next test I'll also try to explicitly link the libasan
>>> >> >>>> archive
>>> >> >>>> manually for ruling out issues with that archive.
>>> >> >>>> _______________________________________________
>>> >> >>>> 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
>>> >> >
>>> >> >
>>> >> >
>>> >> > --
>>> >> > Alexander Potapenko
>>> >> > Software Engineer
>>> >> > Google Moscow
>>> >> _______________________________________________
>>> >> 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