Re: [PATCH, RFC] Enable libsanitizer on powerpc{,64}

[Konstantin Serebryany <konstantin dot s dot serebryany at gmail dot com>]

On Tue, Nov 20, 2012 at 6:18 PM, Evgeniy Stepanov
<eugeni.stepanov@gmail.com> wrote:
> On Tue, Nov 20, 2012 at 5:52 PM, Konstantin Serebryany
> <konstantin.s.serebryany@gmail.com> wrote:
>>
>> On Tue, Nov 20, 2012 at 5:41 PM, Peter Bergner <bergner@vnet.ibm.com>
>> wrote:
>> > On Tue, 2012-11-20 at 11:07 +0400, Konstantin Serebryany wrote:
>> >> I've applied your patch (with minor style and comment changes)
>> >> upstream:
>> >> http://llvm.org/viewvc/llvm-project?view=rev&revision=168356
>> >> I did not have any way to test it though. Also, gmail does something
>> >> horrible with patches inlined in a message, so I might have missed
>> >> something.
>> >
>> > Doing a quick peruse through your LLVM commit, I see you grabbed the
>> > PopStackFrames() addition, but the asan_linux.cc changes do not include
>> > the call to PopStackFrames() after the _Unwind_Backtrace() call.
>> > Specifically, the following patch hunk:
>> >
>> >>      _Unwind_Backtrace(Unwind_Trace, stack);
>> >> > +    // Pop off the two ASAN functions from the backtrace.
>> >> > +    stack->PopStackFrames(2);
>
>
> I wonder if under some conditions we may get a different number of extra
> frames (inlining comes to mind). What do you think of removing any number of
> frames that belong to the runtime library - we have memory layout info for
> that?

Bad idea, imho.
Hard to implement, slower to run (remember, this *is* a hotspot).
The frames in question are in our run-time and we can fully control inlining.
What is the current number of redundant frames on ARM?

--kcc


>
>
>>
>>
>> Ah, indeed, I missed that.
>> Since the patch also affects ARM, I'd like to hear from Evgeniy Stepanov
>> (or we may decouple powerpc from arm)
>>
>> --kcc
>> >
>> > I'll scan the reset of your commit looking for anything else that
>> > is missing.
>> >
>> >
>> >> Soon I hope to learn how to pull the upstream changes to gcc tree and
>> >> do it myself.
>> >> (http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55376)
>> >> In the meantime, you are welcome to apply the same patch to gcc
>> >> manually.
>> >> Same for the gcc-specific parts of you patch.
>> >
>> > I'll grab your changes from the LLVM tree so as to pick up your
>> > style changes and add anything you inadvertently dropped and
>> > commit it.  Thanks.
>> >
>> > Peter
>> >
>> >
>
>