This is the mail archive of the mailing list for the GCC project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [PATCH][Revised] Enable libsanitizer on darwin

On Wed, Nov 14, 2012 at 07:56:18PM +0400, Alexander Potapenko wrote:
> Hi Rainer,
> The quick answer is no, although the expansion into GCC world may
> require such a guideline.
> We've initially implemented ASan on Linux and then ported it to
> Android (which is very similar to Linux) and Mac (which is very
> different), so we have little experience with porting yet.
> I've summarized the differences between Linux and Mac here:
> The core things to pay attention at are function wrapping (e.g. dlsym
> on Linux, mach_override on Mac), hooking the allocations/deallocations
> in the program, stack unwinding (already done for x86 and ARM), thread
> creation, early initialization, debug info and symbolization. Maybe
> something else. In fact if any of these points work on your platform
> differently than they do on Linux/Mac, you'll have to re-implement
> those.
> Regarding mach_override, it's a Mac OS-specific thing that we use
> because dlsym doesn't reliably override functions (keywords: two-level
> namespace)
> This only works on x86/x86_64 and is just a bunch of ad-hoc hacks to
> hot-patch the library code.
> Extending the instruction table in mach_override.c is irrelevant to
> porting, it's just a mean of making it work with some newer libraries
> provided by Apple.
> It won't work on any other OS (well, without some refactoring; in fact
> it's possible to use it on Linux) or any other arch (one could rewrite
> mach_override.c for ARM, but iOS doesn't allow code patching).
> I'm working on a replacement for mach_override, which will compile
> libasan as a dynamic library on Mac OS and preload it before running
> the program.
> It's not ready yet, so the easiest thing for GCC will be to add some
> more instructions to mach_override and stick to it for now.

   Please see...

So far for all the test cases that I have looked at, the problem
seems to be when mach_overrride.c hits the opcodes...

48 8d 5 

Can you suggest a patch for that one? It may be the only blocker to
asan support on darwin (for x86_64 anyway).

> Alex
> On Wed, Nov 14, 2012 at 7:08 PM, Rainer Orth
> <> wrote:
> > Hi Alex,
> >
> >> most certainly the functionality of asan is not intact.
> >> The error messages denote that mach_override couldn't parse some of
> >> the function prologues, which means some of ASan interceptors just
> >> won't work.
> >> In order to fix this you need to change the DEBUG definition in
> >> mach_override.c, look at the bytes being parsed and fix the
> >> instruction table in mach_override.c
> >
> > is there some guideline how to port asan to a new OS or CPU?  That would
> > certainly be easier than figuring things out on your own one by one.  I
> > guess several target and os port maintainers would want to do so in GCC.
> >
> > Thanks.
> >         Rainer
> >
> > --
> > -----------------------------------------------------------------------------
> > Rainer Orth, Center for Biotechnology, Bielefeld University
> -- 
> Alexander Potapenko
> Software Engineer
> Google Moscow

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]